WEBVTT 00:00:01.000 --> 00:00:07.000 All right, hi everyone! It's now 1PM, so we're gonna go ahead and get started. 00:00:07.000 --> 00:00:17.000 On behalf of the Interstate Technology and Regulatory Council, welcome to today's training, ITRC 1,4-Dioxane, Science Characterization and Analysis and Remediation. 00:00:17.000 --> 00:00:21.000 My name is Taylor Vogel, and I will be your moderator for the training today. 00:00:21.000 --> 00:00:28.000 This training is an introduction to the ITRC online guidance document that was produced by ITRC in 2020. 00:00:28.000 --> 00:00:36.000 I will post the link to the guidance document, as well as the link to the Cluin page for today's training in the chat. 00:00:36.000 --> 00:00:46.000 So let's get into some quick housekeeping rules before we jump into the training. Today's training is being recorded and will be offered on demand through Cluin for those who are not able to join us during our live sessions. 00:00:46.000 --> 00:00:50.000 The clue and Training page also has the slides available for download. 00:00:50.000 --> 00:01:02.000 While on Zoom, you have access to the Q&A window. Please use the Q&A box to ask questions, make comments, or report technical problems at any time during today's training. We will attempt to get to as many questions as we can. 00:01:02.000 --> 00:01:09.000 For those interested in receiving Certificates of completion, they are available at the end of the training by completing the feedback form. 00:01:09.000 --> 00:01:22.000 The feedback form for all ITRC courses are located on the Cluin Training page for each specific course. The Cluin page used to access today's training also contains the feedback form. 00:01:22.000 --> 00:01:27.000 The Interstate Technology and Regulatory Council is a program of the Environmental Council of the States. 00:01:27.000 --> 00:01:42.000 Itrc is a state-led organization composed of over 1,000 members from state agencies, federal government, the private sector, academia, and community stakeholders. Itrc members participate in technical teams, which produce tools, resources, and training courses. 00:01:42.000 --> 00:01:46.000 Training courses, such as the one you are participating in today. 00:01:46.000 --> 00:01:52.000 Please visit the ITRC website if you're interested in becoming an active member or need to view the full ITRC disclaimer. 00:01:52.000 --> 00:02:00.000 If you plan to use ITRC materials, we ask that you review those terms and conditions in detail, and be sure to credit ITRC. 00:02:00.000 --> 00:02:09.000 Itrc is partially funded by the U.S. Government. Icrc nor the U.S. Government warranty the material, nor endorse any specific products. 00:02:09.000 --> 00:02:26.000 Before we start, just a quick note, some links presented today may be broken or out of date, but if you run into any issues accessing a link, you can always navigate directly to the main guidance document and use the table of contents to find the specific sections that are referenced. 00:02:26.000 --> 00:02:36.000 I now have the pleasure of introducing Lauren Larkin from the Minnesota Pollution Control Agency, and she will start off today's training. 00:02:36.000 --> 00:02:45.000 Hi, everybody! Thanks for joining us today. Um, today's training is based on the ITRC 1,4-dioxane team products. 00:02:45.000 --> 00:02:53.000 We developed six fact sheets, as well as the 2021 guidance document, so these are going to be referred to during the training. 00:02:53.000 --> 00:03:02.000 And they're all available on ITRC's 1,4-dioxane website. Uh, our training modules today are based on. 00:03:02.000 --> 00:03:06.000 Let's see, there we go. They're based on the fact sheets. 00:03:06.000 --> 00:03:16.000 And the corresponding sections of the guidance document. So, this training is a six-part modular series focused on history of use and potential sources. 00:03:16.000 --> 00:03:22.000 Regulatory framework. Environmental Fate, transport, and investigation strategies. 00:03:22.000 --> 00:03:29.000 Sampling and toxicity… or sampling and analysis. Toxicity and risk assessment. 00:03:29.000 --> 00:03:45.000 And remediation treatment technologies. So, if you would like to refer back to this training later, you can find a recording of this training and the slides on the Cluin webpage referenced at the bottom of this slide here. 00:03:45.000 --> 00:03:54.000 So, as I mentioned, ITRC has a 1,4-dioxane website. Uh, the link to that website is available at the bottom of this slide. 00:03:54.000 --> 00:03:59.000 So this is where you'll find the fact sheets and the guidance document. 00:03:59.000 --> 00:04:06.000 So our team has developed the fact sheets and guidance document to address questions and guide practitioners in best management practices. 00:04:06.000 --> 00:04:14.000 When managing sites where 1,4-dioxane is present. We've developed these tools for multiple user groups, including the public. 00:04:14.000 --> 00:04:21.000 And in particular, this toxicity and risk assessment fact sheet was created to address common questions the public has. 00:04:21.000 --> 00:04:30.000 About 1,4-dioxane and its risks. Itrc initiated the 1,4-dioxane team in 2018. 00:04:30.000 --> 00:04:42.000 To review the information and science of 1,4-Dioxane. Um, and I just want to take a quick minute to just thank all those folks that helped us to write these documents, including the training, uh. 00:04:42.000 --> 00:04:45.000 Trainers and the weaning organizers who are on the call today. 00:04:45.000 --> 00:04:56.000 Um, they're just, like, all exceptional. Um, you know, leaders in their fields, and they've just really, uh, generously shared their time and the wealth of their experiences, um. 00:04:56.000 --> 00:05:02.000 For many years now, so… Um, okay, so as a little background, just to get us started. 00:05:02.000 --> 00:05:08.000 Uh, one for dioxane has been used as a solvent stabilizer since the 1950s. 00:05:08.000 --> 00:05:16.000 Uh, these solvents were widely used throughout the 80s. Um, would suggest its presence at thousands of solvent sites in the U.S. 00:05:16.000 --> 00:05:26.000 However, it hasn't always been… a standard compound in the typical analytical suites, so it's been overlooked, uh, in the past. 00:05:26.000 --> 00:05:36.000 So, why do we care about 1,4-dioxane? Well. The EPA has classified 1,4-dioxane as likely to be carcinogenic to humans. 00:05:36.000 --> 00:05:42.000 Some states have devised standards or regulatory guidelines for drinking water and groundwater. 00:05:42.000 --> 00:05:49.000 And those are often sub-part-per-billion values. These low values present challenges for analysis. 00:05:49.000 --> 00:05:57.000 Characterization and remediation of 1,4-dioxine. So, our team has created multiple tools and documents. 00:05:57.000 --> 00:06:04.000 That will provide information to assist all interested stakeholders to understand this contaminant and to make informed, educated decisions. 00:06:04.000 --> 00:06:09.000 So we encourage you to use the ITRC14 dioxane products, and these training modules. 00:06:09.000 --> 00:06:14.000 Learn about 1,4-axine and how you can apply these best practices at your sites. 00:06:14.000 --> 00:06:20.000 Um, and just as a reminder, as Taylor noted, if you have questions, please place those in the Q&A box. 00:06:20.000 --> 00:06:28.000 And, um, we'll discuss some of those during the question and answer session that we'll have midway through, and then again at the end of the training. 00:06:28.000 --> 00:06:34.000 Um, and if we don't have time to get to all of those, we'll try and respond within the Q&A box. 00:06:34.000 --> 00:06:43.000 So, with that, I'm going to dive… into our first module, History of Use and Potential Sources. 00:06:43.000 --> 00:06:50.000 Alright. Sorry, too many click-ins. Okay. 00:06:50.000 --> 00:06:55.000 All right, so in this section, I'm going to share information. 00:06:55.000 --> 00:07:05.000 Um, towards a couple of specific learning objectives. So I'm going to provide a high-level overview of the variety of uses for 1,4-dioxane. 00:07:05.000 --> 00:07:11.000 I'll provide an understanding of the history of 1,4-dioxane manufacture and usage. 00:07:11.000 --> 00:07:18.000 And I'll present a brief case study showing the relationship between 1,4-dioxane and chlorinated solvents at site. 00:07:18.000 --> 00:07:24.000 So, what… is 1,4-dioxane used for? 00:07:24.000 --> 00:07:28.000 A short list of some of those uses are included here. 00:07:28.000 --> 00:07:36.000 Um, but there are hundreds of different applications for 1,4-dioxane. For a more comprehensive list, you can see section 1.2. 00:07:36.000 --> 00:07:46.000 Of the ITRC guidance document. Uh, as well as the… there's a comprehensive compilation of uses in, um, Tom Moore's 1,4-Dioxane book. 00:07:46.000 --> 00:07:52.000 So the primary application of 1,4-dioxane was in stabilizing chlorinated solvents. 00:07:52.000 --> 00:08:03.000 Especially 111 trichloroethane, or TCA. Uh, so the history of 1,4-dioxane is intertwined with the history of TCA usage in the U.S. 00:08:03.000 --> 00:08:12.000 So understanding that key relationship helps in identifying of potential 1,4-dioxane release locations. 00:08:12.000 --> 00:08:20.000 So, one question you might ask is, why is 1,4-dioxane needed to stabilize solvents? 00:08:20.000 --> 00:08:26.000 Well, when chlorinated solvents break down during vapor degreaser operations used in metal plating. 00:08:26.000 --> 00:08:31.000 Various assets are formed, which are detrimental to the metal plating process. 00:08:31.000 --> 00:08:39.000 Stabilizers address these acids one of three ways. Acid inhibitors, which prevent formation of acids. 00:08:39.000 --> 00:08:53.000 Acid acceptors, which neutralize the acids after they form. And metal inhibitors, which deactivate the properties of metal surfaces that make them susceptible to acid impacts. And it's this last one. 00:08:53.000 --> 00:09:02.000 A metal inhibitor, um, that is 1,4-dioxine. So, another question that comes up frequently. 00:09:02.000 --> 00:09:09.000 Is whether 1,4-dioxane was a stabilizer. For trichloroethane, or TCE. 00:09:09.000 --> 00:09:20.000 Um, while there is evidence that TCE was stabilized. 1,4-dioxane has not been identified in any documentation as that stabilizing agent. 00:09:20.000 --> 00:09:27.000 On the other hand, there is extensive evidence of 1,4-dioxane being a stabilizer in TCA. 00:09:27.000 --> 00:09:31.000 But Tom Moore, in his decades of searching patents and other literature. 00:09:31.000 --> 00:09:44.000 Didn't find any documentation of 1,4-dioxin in TCE. Uh, it is possible that 1,4-dioxin was used in early TCE formulations, but the early patent literature is vague. 00:09:44.000 --> 00:09:52.000 Um, lastly, since TCE is more stable and less susceptible to degradation during usage than TCA. 00:09:52.000 --> 00:10:01.000 Uh, one for Daxane might not have been needed. Um, but regardless, there is an empirical association between TCE and 1,4-dioxine. 00:10:01.000 --> 00:10:10.000 As will be detailed in the Fate and transport module. Um, so it might not matter whether 1,4-dioxane was in the TCE itself. 00:10:10.000 --> 00:10:16.000 Tce presence is still a good indicator of the possibility of 1,4-dioxane. 00:10:16.000 --> 00:10:23.000 Being present. All right. Okay, so now we want to talk about. 00:10:23.000 --> 00:10:33.000 The history of production of 1,4-dioxane in the U.S. And especially in relation to production history of chlorinated solvents, specifically TCA. 00:10:33.000 --> 00:10:39.000 Uh, so we're gonna zoom in on this timeline to cover that history in three big. 00:10:39.000 --> 00:10:50.000 Time blocks. So, before I dive in, I just want to note that the blue on this graph is going to represent 1,4-dioxane. 00:10:50.000 --> 00:10:57.000 And the green is for chlorinated solvents. So, we'll start with discussing 1,4-dioxin. 00:10:57.000 --> 00:11:00.000 So, this first block is going to take us into the 1970s. 00:11:00.000 --> 00:11:12.000 And begins when 1,4-dioxin was first synthesized in 1863. Um, but was not put into production until 1929, and even then, it was limited. 00:11:12.000 --> 00:11:20.000 Commercial-scale production began in 1951. And ramped up through the 50s, 60s, and 70s. 00:11:20.000 --> 00:11:26.000 All right, so now we're going to talk about… the chlorinated solvents. 00:11:26.000 --> 00:11:37.000 So, chlorinated solvent manufacturer began in 1921. And the first documented evidence of 1,4-dioxane use in TCA was in the late 1950s. 00:11:37.000 --> 00:11:45.000 Chlorinated solvent use in the U.S. Also ramped up dramatically. Um, sorry, I just lost my spot. 00:11:45.000 --> 00:11:50.000 Um. But, um… 00:11:50.000 --> 00:11:55.000 Uh, sorry, chlorinated solvent used in the U.S. Also ramped up dramatically in the 50s, 60s, and 70s. 00:11:55.000 --> 00:12:06.000 Uh, and in the late 1960s and early 70s. Awareness of toxic effects of exposure to CCE caused some users to switch from TCE to TCA. 00:12:06.000 --> 00:12:12.000 Because the latter was thought to be less toxic. All right, so moving on to the second time block. 00:12:12.000 --> 00:12:20.000 During the 1970s and 1980s. 1,4-dioxane usage increased with the increase in TCA usage. 00:12:20.000 --> 00:12:26.000 Although these data suggests there's some variability over that time period. 00:12:26.000 --> 00:12:36.000 Uh, so one data point that's important is that in 1985, U.S. 1.4-dioxane production reached a peak of 25 million pounds per year. 00:12:36.000 --> 00:12:45.000 With 90% of that going into TCA. Whose production also peaked in 1985 at almost 900 million pounds. 00:12:45.000 --> 00:12:54.000 Annually. 1,4-dioxane production declined steadily in the 90s, aughts, and 2010s. 00:12:54.000 --> 00:13:02.000 To less than a million pounds per year. Most of this decline was driven by awareness and regulation of the hazards of TCA. 00:13:02.000 --> 00:13:08.000 Which was designated an ozone depleter in 1995. And in 2004. 00:13:08.000 --> 00:13:15.000 The ATSDR suggested that TCA usage be limited to only essential applications. 00:13:15.000 --> 00:13:20.000 U.s. Epa published a Drinking Water Health Advisory for 1,4-dioxane in 2012. 00:13:20.000 --> 00:13:30.000 Around the same time that they required sampling and drinking water supplies across the U.S. As part of the unregulated Contaminant monitoring rule, the UCMR3. 00:13:30.000 --> 00:13:41.000 All right, so now that we've gone through the history, we'll briefly go through a case study with a fairly typical pattern of chlorinated solvent and 1,4 dioxane usage. 00:13:41.000 --> 00:13:48.000 Um, in this case for Air Force Plant 44, which is part of the Tuscan International Airport Area Superfund site. 00:13:48.000 --> 00:13:59.000 And I'm filling in for our regular presenter today, so I might not be able to answer all your detailed questions about the site specifics, just to let you know, but we will do our best if you want to type those into the Q&A. 00:13:59.000 --> 00:14:05.000 Um, this was a missile manufacturing plant. Uh, with TCE used from the 1950s through today. 00:14:05.000 --> 00:14:14.000 Albeit at minor levels since the 1980s. In 1974, there was a documented switch from TCE to TCA. 00:14:14.000 --> 00:14:21.000 And vapor degreasers used to support the metal plating operations. Uh, two sites of interest for evaluating. 00:14:21.000 --> 00:14:31.000 1,4-dioxane, um, site 3, which was an unlined solvent waste lagoon that operated from 1966 through 1977. 00:14:31.000 --> 00:14:40.000 And sleep 5, which was a metal plane, wastewater and sludge disposal area that operated from the early 1960s through 1977. 00:14:40.000 --> 00:14:45.000 But groundwater extraction and re-injection system has operated since the late. 00:14:45.000 --> 00:14:55.000 1980s to treat the chlorinated solvent plume. So, looking at the 1,4-dioxane plume confirms the relationship. 00:14:55.000 --> 00:15:01.000 Between the chlorinated solvents and the 1,4 dioxane, so… The red on this map is the TCE plume. 00:15:01.000 --> 00:15:11.000 And you can see that the plume represents a number of sources beyond the Air Force Plant 44, which is located down towards the bottom of the map. 00:15:11.000 --> 00:15:21.000 Um, the main TCE plume is discontinuous. Due to 40 years of pumping at a couple of key locations. 00:15:21.000 --> 00:15:28.000 Um, but the purple 1,4-dioxane plume is co-located with the TCE plume for the most part. 00:15:28.000 --> 00:15:36.000 Uh, the 1,4-dioxane plume was wider at the time of discovery because the groundwater system extracted from the center of the plume. 00:15:36.000 --> 00:15:43.000 Was treated to remove TCE with an air stripper, and then re-injected without removing the 1,4-dioxane. 00:15:43.000 --> 00:15:53.000 Um, onto the outside of the plume. So, at the time of its discovery in groundwater, 1,4-dioxane was being injected at about 10 micrograms per liter. 00:15:53.000 --> 00:16:05.000 So, subsequently, the plume has narrowed dramatically, uh, since the re-injection was changed to be upgradient of the plume, rather than cross-gradient. 00:16:05.000 --> 00:16:13.000 So, to wrap up, um, the takeaways from this discussion are that 1,4-dioxane is widely used in a variety of industries. 00:16:13.000 --> 00:16:23.000 Uh, but the primary use was in TCA. One for dioxane manufacturer over time is tied to the manufacture and use of TCA. 00:16:23.000 --> 00:16:35.000 And 1,4-dioxane may have been present in TCE. Uh, there's little direct evidence of this. However, it doesn't really matter, because the empirical association exists between. 00:16:35.000 --> 00:16:43.000 Tce and 1,4 dioxane, and is well documented. Uh, and lastly, uh, 1,4-dioxane is found co-located. 00:16:43.000 --> 00:16:47.000 With chlorinated solvents at many sites, and at about the same order of magnitude. 00:16:47.000 --> 00:16:55.000 So, with that… I'm gonna hand off the presentation of our next module on regulatory framework to Dr. Janet Anderson. 00:16:55.000 --> 00:17:02.000 Who's a principal toxicologist with over 15 years of experience providing toxicology and risk management strategies. 00:17:02.000 --> 00:17:14.000 Um, and a specialization in communicating the key findings from toxicology studies used to inform state and federal regulatory policy and public health decisions. So, thanks so much, Janet. 00:17:14.000 --> 00:17:19.000 Thanks, Lauren. Hi, everybody, and welcome to the second module. I'll talk about 1,4-doxins. 00:17:19.000 --> 00:17:27.000 Regulatory framework. Um… let's see, for an emerging contaminant, see if I can get these… 00:17:27.000 --> 00:17:33.000 Slides to advance, there we go. Um, we're gonna talk about how 1,4-doxane is, um. 00:17:33.000 --> 00:17:46.000 Regulated across various state and U.S. Programs. And we're going to focus a little bit in, um, on some of the environmental exposures and the regulatory programs and guidance values that we have for when production, and. 00:17:46.000 --> 00:17:55.000 Groundwater, drinking water, soil, and air. Um, what's interesting is that even the 1.4 doxane is often called an emerging contaminant, it is actually regulated across. 00:17:55.000 --> 00:18:10.000 A wide array of programs, both at the federal and state level. Many of them are shown here. I'm not going to get into a lot of detail of these, but, um, more details can be found in Section 2 of the guidance document that Lauren referenced in the beginning that's available online. 00:18:10.000 --> 00:18:16.000 And, um, even though it's a little bit old now, it pretty much is still up to date with regard to regulations. 00:18:16.000 --> 00:18:21.000 Of course, go to the authoritative agency and the regulation to confirm. 00:18:21.000 --> 00:18:28.000 But we're going to highlight a few of these in the training today. We're going to start at the beginning. 00:18:28.000 --> 00:18:33.000 Um, in the United States. The EPA Toxic Substances Control Act. 00:18:33.000 --> 00:18:42.000 Regulates, um… chemical manufacturing, uh, processing, distribution, use, and disposal. 00:18:42.000 --> 00:18:49.000 The TSCA program was amended in 2016, and at that time, Oneford vaccine was identified as one of the top 10 priority chemicals. 00:18:49.000 --> 00:18:56.000 Under the amended program. So EPA began their risk evaluation process for Winfrodoxin. 00:18:56.000 --> 00:19:05.000 Issuing their first draft risk assessment in 2019. Um, that draft assessment, though, really just considered evaluation of risk to workers, both. 00:19:05.000 --> 00:19:11.000 Manufacturers and occupational non-users during the industrial and commercial conditions of use. 00:19:11.000 --> 00:19:20.000 It did not include any other risk pathways. Um, since then, though, things have changed and been updated a little bit. 00:19:20.000 --> 00:19:32.000 That initial risk, um, evaluation was finalized in December of 2020, so just in time to be incorporated into the technical guidance document that we wrote for ITRC. 00:19:32.000 --> 00:19:41.000 Um, it did include a supplemental risk evaluation that looked at general, um, public risk as a byproduct to certain consumer products. 00:19:41.000 --> 00:19:51.000 And it looked at, um, surface water exposures to the general public, um, from either swimming or fish consumption via release from manufacturing plants. So any kind of. 00:19:51.000 --> 00:20:01.000 Direct industry releases to super, um, to surface water. But it did not evaluate risk from drinking water exposures or a wider range of consumer products. 00:20:01.000 --> 00:20:17.000 So again, this risk evaluation was finalized in December of 2020, um, but things have changed since then. So these, uh, information on this slide is not included in our technical guidance document, so I'm just including this for informational purposes. 00:20:17.000 --> 00:20:24.000 Um, the final, uh, risk conclusion from EPA was released in November of 2024. 00:20:24.000 --> 00:20:28.000 It included a draft supplement of risk evaluation that was released. 00:20:28.000 --> 00:20:36.000 Uh, about a year and a half prior to that for public review and comment, and included consideration of air and water exposure pathways. 00:20:36.000 --> 00:20:44.000 Um, and so these additional, uh, evaluations and additional data were incorporated by EPA. 00:20:44.000 --> 00:20:49.000 Their final conclusion was that 1,4-doxane presents an unreasonable risk to human health. 00:20:49.000 --> 00:20:57.000 When we break that down by their, um, specific conditions of use, they found no unreasonable risk to occupational workers still. 00:20:57.000 --> 00:21:05.000 And no unreasonable risk to the general public from those direct exposures to consumer products, to include detergents and cleaning agents this time. 00:21:05.000 --> 00:21:10.000 But they did find an unreasonable risk to workers in the direct manufacturing. 00:21:10.000 --> 00:21:15.000 Locations, unreasonable risk to communities that may be exposed to the surface water. 00:21:15.000 --> 00:21:20.000 Um, releases if that surface water was used as a drinking water source. 00:21:20.000 --> 00:21:26.000 Um, and also unreasonable risk to the general public from down-the-drain disposal of consumer products. 00:21:26.000 --> 00:21:32.000 Um, if that down drain disposal got released to surface water, and that surface water was a drinking water source. 00:21:32.000 --> 00:21:39.000 So I encourage you to look at EPA's most updated risk evaluation there for more information. 00:21:39.000 --> 00:21:44.000 Um, so EPA did, as I said, find unreasonable risk to workers. Well, what are our worker standards? 00:21:44.000 --> 00:21:50.000 We do have, um, some regulations in the occupational setting for 1,4 vaccine. 00:21:50.000 --> 00:22:01.000 These are relatively outdated air exposure guidelines. The American Conference of Governmental Industrial Hygienists, or ACGIH, has a threshold… an hour threshold limit. 00:22:01.000 --> 00:22:07.000 And California OSHA also has a much lower 8-hour time-weighted average, um. 00:22:07.000 --> 00:22:16.000 Exposure for workers. Niosh also, in addition to those 8 hours worker exposures, has a ceiling limit. 00:22:16.000 --> 00:22:28.000 And a immediately dangerous to life and health limit. So again, these are for workers in the occupational setting, and are really all related to potential air exposure. 00:22:28.000 --> 00:22:34.000 What about, um, moving to consumer products, specifically in cosmetics and pharmaceuticals? 00:22:34.000 --> 00:22:42.000 Um, we currently regulate both cosmetics and pharmaceuticals under the U.S. Food and Drug Administration. 00:22:42.000 --> 00:22:51.000 There currently are no real limits specific to one 4-noxine, but the FDA has a recommended maximum of 10,000 microgram per limit in any one product. 00:22:51.000 --> 00:22:57.000 Specific to cosmetics. And oneford octane is classified as a Class II solvent. 00:22:57.000 --> 00:23:03.000 And just under that generic solvent classification, there's the daily exposure recommendation. 00:23:03.000 --> 00:23:10.000 Um, not to exceed in pharmaceuticals. What about personal care products? So, um… 00:23:10.000 --> 00:23:16.000 Recall that EPA determined there was currently no unreasonable risk to the general public associated with 14D. 00:23:16.000 --> 00:23:20.000 In personal care products from the direct use of those products. 00:23:20.000 --> 00:23:27.000 Um, so that was consistent in their release, um, risk determination all the way back from December. 00:23:27.000 --> 00:23:33.000 But several states, um, do have some product labeling and consumer product laws related to lymphrodoxin. 00:23:33.000 --> 00:23:39.000 So, for example, Prop 65, or the California Safe Drinking Water and Toxic Enforcement Act. 00:23:39.000 --> 00:23:45.000 Uh, does have one for doxane listed as a chemical known to cause cancer to the state of California? 00:23:45.000 --> 00:23:52.000 Which requires manufacturers and distributors and retailers to provide that warning label, um, on products that contain. 00:23:52.000 --> 00:23:57.000 Um, any amount of one production that would result in an exposure greater than 30 micrograms per day. 00:23:57.000 --> 00:24:05.000 Under California's, uh, cleaning products, Right to Know Act, there's also a disclosure of ingredient requirement. 00:24:05.000 --> 00:24:18.000 A few other states as well. Um, New York, um, passed some cleaning and personal care product regulations related to oneford vaccine with various threshold limits. It started at 2 ppm, um, in the product itself. 00:24:18.000 --> 00:24:23.000 And then that level was reduced to 1 ppm in December of 2023. 00:24:23.000 --> 00:24:36.000 Um, Oregon, Vermont, Washington, they also have various, uh. Disclosure recommendations and disclosure laws for products that contain 1,4-doxane. 00:24:36.000 --> 00:24:42.000 All right, well, surface water was also mentioned by EPA as a potential source of unreasonable risk. 00:24:42.000 --> 00:24:47.000 If one protaxine is in surface water that's used as a drinking water source. 00:24:47.000 --> 00:24:56.000 Currently, well, in the US, EPA regulates surface water under our Clean Water Act, and there are currently no surface water quality criteria. 00:24:56.000 --> 00:25:03.000 For one for a doxane. We are seeing numerous, um, national pollutant discharge elimination System, or MPDES, permits. 00:25:03.000 --> 00:25:11.000 That have monitoring requirements, and those. Um, I've seen that number kind of increase over the years, but again, no exact criteria. 00:25:11.000 --> 00:25:18.000 Several states do, however, have surface water quality standards on their regulatory books. For example, Colorado and Michigan. 00:25:18.000 --> 00:25:26.000 And several states also have specific wastewater discharge requirements. Alright, how about environmental cleanup? 00:25:26.000 --> 00:25:31.000 So 1 Protoxane is listed as a hazardous substance under both CERCLA and RICRA. 00:25:31.000 --> 00:25:42.000 Under CERCLA, we have regional screening levels, those RSLs. That are used to screen and inform potential next steps for any kind of remediation and cleanup goals. 00:25:42.000 --> 00:25:47.000 So those RSLs are listed here at the conservative 10 to the minus 6. 00:25:47.000 --> 00:25:58.000 Cancer risk level for residential exposure. Um, and as you can see, we've got numbers for groundwater, soil, and air. 00:25:58.000 --> 00:26:07.000 Um, our guidance document online has a really handy, I think it's handy, um, map. This is interactive. You can click on any state. 00:26:07.000 --> 00:26:17.000 And at least as of a few years ago, the hyperlinks were all working, and it would take you directly to the state, um, program and the regulations specific to one for doxane. 00:26:17.000 --> 00:26:23.000 Again, please always go to the actual authoritative reference to confirm that the number is still accurate. 00:26:23.000 --> 00:26:31.000 But as far as cleanup standards or guidance values here, if you look at these states, any state that we have shown here in green. 00:26:31.000 --> 00:26:36.000 Yellow or orange. Those are the states that have some sort of guidance or standard value. 00:26:36.000 --> 00:26:47.000 Related to 1Fortoxane. Cleanup programs. And as you can see, the values range from about 0.3 part per billion to 200 part per billion. 00:26:47.000 --> 00:26:55.000 Uh, really, some of the more recent promulgated standards fall in the single-digit part per billion, so 4 to 9. 00:26:55.000 --> 00:26:58.000 And that reflects the 10 to the minus 5 risk level. 00:26:58.000 --> 00:27:02.000 Um, but again, you can click on each one of these states to get more information. 00:27:02.000 --> 00:27:11.000 Um, as mentioned on the previous slide, uh. One for a vaccine is not regulated, or is not regulated at the federal level, um, for… 00:27:11.000 --> 00:27:15.000 Cleanup programs, so we've got screening levels, and so the difference is largely. 00:27:15.000 --> 00:27:22.000 Um, the conservative nature of what risk threshold were the screening levels set. 00:27:22.000 --> 00:27:35.000 All right, how about drinking water? So, in the U.S, drinking water is regulated under the Safe Drinking Water Act at the federal level by EPA. We currently have no maximum contaminant level, or no MCL. 00:27:35.000 --> 00:27:41.000 So, um, 1,4-doxane has been identified as a candidate contaminant list. 00:27:41.000 --> 00:27:47.000 Compound since 2008. So it's been on that CCL list, uh, for many, many years. 00:27:47.000 --> 00:27:57.000 But, um, EPA has not yet determined whether there's a meaningful opportunity for public health risk reduction. So that's the latest statement from EPA. 00:27:57.000 --> 00:28:11.000 Concerning setting a federal drinking water. Determination for one Ford vaccine. So it's still on the list, and they're still evaluating it, um, but I think they've had other priorities, and they have not yet determined. 00:28:11.000 --> 00:28:19.000 Whether they need to set an MCL. But we do have a health advisory for drinking water, or guidance. 00:28:19.000 --> 00:28:33.000 So, since 2012, uh, 1,4DOXIN has been listed in EPA's drinking water standards and health advisory document with a guidance level of 35 part per billion, or 35 micrograms per liter. 00:28:33.000 --> 00:28:39.000 That represents the 10 to the minus 4 cancer risk, which is what EPA uses for their health advisories. 00:28:39.000 --> 00:28:47.000 For carcinogens. Um, again, this is a guidance value, so it's not an enforceable drinking water standard. 00:28:47.000 --> 00:28:56.000 Um, also on our map, though, those blue states are states that they, um, have either drinking water standard, regulatory promulgated level. 00:28:56.000 --> 00:29:09.000 Or some sort of guidance value. So again, EPA's Lifetime Cancer Risk Level is 35. New York is the only state with a full promulgated drinking water value, um, issued in 2020. 00:29:09.000 --> 00:29:19.000 At 1 part per billion. New Jersey has a number proposed, they still haven't passed it or finalized it. Um, Health Canada also, just for context, and I'll talk about it later. 00:29:19.000 --> 00:29:25.000 Has their equivalent of an MCL, they call it a maximum allowable concentration at 50 parts per billion. 00:29:25.000 --> 00:29:38.000 And, um, we're watching closely California. We anticipate a draft public health goal, which is the state's first step in setting an MCL, hopefully within the next month or so. 00:29:38.000 --> 00:29:43.000 All right, so that concludes our Whirlwind tour of the regulatory framework. To summarize. 00:29:43.000 --> 00:29:48.000 Oneford vaccine is regulated across a variety of state and federal programs. 00:29:48.000 --> 00:29:53.000 The Tosca evaluation suggests that there is concern for certain exposure pathways and some. 00:29:53.000 --> 00:30:01.000 Receptors. States in particular have more advanced reporting requirements, labeling requirements, and limits in personal care products. 00:30:01.000 --> 00:30:10.000 We're watching closely some of the state drinking water standards. We can screen for and assess risk in the environment for risk assessment at environmental sites. 00:30:10.000 --> 00:30:19.000 Using those RSLs. And although not yet regulated at the federal level, there's actually a range of drinking water guidance levels and or standards. 00:30:19.000 --> 00:30:27.000 That are available to guide risk management decisions. All right, and those are the numbers. So, with that… 00:30:27.000 --> 00:30:35.000 I turn it over to my friends. David and Monica to talk about the environmental fate, transport, and investigation strategies. 00:30:35.000 --> 00:30:44.000 All right, uh, thanks, Janet. Yeah, this is Dave Adamson, Module 3, and I'll start off and then pass it on to Monica. 00:30:44.000 --> 00:30:50.000 But when we talk about bait and transport, conceptual site models, see if I can get the slides working. 00:30:50.000 --> 00:30:56.000 Here we go with our learning objectives, so these are the roadmap for what we're going to talk about. 00:30:56.000 --> 00:31:04.000 First, we want to understand the key, uh, physical chemical properties of 1,4-dioxane, particularly related to those things that might also be present with. 00:31:04.000 --> 00:31:13.000 Identify the real relevant transport processes, use those to develop a general conceptual site model for wind-free dioxane. 00:31:13.000 --> 00:31:20.000 And then, you know, pull that all together and use that to establish an informed site assessment strategy. 00:31:20.000 --> 00:31:26.000 Okay, so when we talk about bait and transport, uh, what are we talking about? We're really talking about how that. 00:31:26.000 --> 00:31:34.000 Compound moves once it's in the environment. And what happens to it while it's moving. This provides us with a technical basis for. 00:31:34.000 --> 00:31:41.000 Making decisions about 1,4-dioxane, like where to look for it when we're doing a site assessment, how to evaluate for the potential for risk. 00:31:41.000 --> 00:31:51.000 And the basis for making treatment decisions. Um, my last point, uh, Fritz and Francisco are going to talk about more in the remediation treatment training module. 00:31:51.000 --> 00:32:01.000 When we talk about the characteristics, we can sort of put them into two broad categories. We've got the physical chemical properties of one protaxine itself, so things like solubility or. 00:32:01.000 --> 00:32:17.000 Or, uh, uh, uh… It's partition coefficient, and then we've got the characteristics of the site where it may have been released. So maybe the groundwater velocity, or the dissolved oxygen levels. So these are our components for building our conceptual site model. 00:32:17.000 --> 00:32:34.000 I will point out that we've learned a lot about OneFridoxine faint transport in the last few years. What we've shown here captures what was known at the time that this document was developed, with the understanding that our knowledge about this particular compound is definitely still evolving. 00:32:34.000 --> 00:32:44.000 Okay, so in terms of our critical characteristics for fate and transport, these are the sort of things that, if you remember anything, you're going to want to remember, and we'll talk about these in the next couple slides. 00:32:44.000 --> 00:32:53.000 But really, one for dioxane, that molecule there on the right, it's got a low organic carbon partitioning coefficient, so it doesn't bind strongly to soils. 00:32:53.000 --> 00:32:59.000 It readily… wants to readily leach into groundwater. In part, that's because it's… it's missile. 00:32:59.000 --> 00:33:08.000 The bullet essentially wants to dissolve completely. Uh, as Lauren mentioned, it's a common co-contaminant with chlorinated solvents. 00:33:08.000 --> 00:33:21.000 Uh, it's got a low Henry's constant relative to common cold contaminants, so it's not very volatile. And then, as Monica will talk about, it's known degradation pathways involve oxidation. 00:33:21.000 --> 00:33:34.000 Another way to look at this is to think about this in sort of a tabular form, and look at these characteristics of 1.4 dioxane, and that's what's highlighted there in red, relative to these other common groundwater. 00:33:34.000 --> 00:33:53.000 Contaminants, and so each of these rows is an individual. Physical character, or physical chemical parameter. Um, so, for example, one for doxanne's emissible compound, so in that first row of the water solubility, that translates to 1,000 grams per liter, a value that's about 3 orders of magnitude. 00:33:53.000 --> 00:33:57.000 And a lot of those other compounds that are listed in other columns. 00:33:57.000 --> 00:34:01.000 Similarly, if you look at that row with the Henry's Law constant. 00:34:01.000 --> 00:34:06.000 That describes the tendency to partition the air after it's dissolved into water. 00:34:06.000 --> 00:34:17.000 It's generally about 3 orders of magnitude less than some of these other compounds. Vapor pressure, on the other hand, actually not all that different. We'll talk about this more in a few slides when we discuss volumization. 00:34:17.000 --> 00:34:22.000 It's also worth then looking at that KOC value, and again, this is a log KOC value. 00:34:22.000 --> 00:34:30.000 Um, so the KOC value for .54 for 1-4 dioxane means it's about an order of magnitude, or maybe even a little more. 00:34:30.000 --> 00:34:36.000 Less prone to partition to organic carbon than some of these other compounds. 00:34:36.000 --> 00:34:45.000 And again, this value, this low value, is just another reflection of how much 1-4 dioxane wants to be associated with water. 00:34:45.000 --> 00:35:04.000 All right, next up is our conceptual site model for wind oxane. So, this is sort of a good jumping-off point for then looking at the individual fate and transport processes. This doesn't necessarily include everything, but when we were developing this as part of the ITRC guidance document, again, it's Figure 3.3, as you can see. 00:35:04.000 --> 00:35:11.000 This is what we really wanted to highlight as really the things that are most important for what happens when production at. 00:35:11.000 --> 00:35:21.000 These sorts of contaminated sites. So first, we're going to start with vitalization. That's just the transfer of a contaminant from a liquid phase to a gas phase. 00:35:21.000 --> 00:35:28.000 It's inherently a non-destructive process, it's just describing the transfer between two different types of media. 00:35:28.000 --> 00:35:33.000 Epa actually has two different criteria for establishing if a compound's volatile. 00:35:33.000 --> 00:35:40.000 And 14D meets the one based on vapor pressure, uh, since it's got a vapor pressure of 24, uh. 00:35:40.000 --> 00:35:50.000 Millimeters of mercury. Um, but it's… it's, uh… It's, uh, Henry's Law constant is really the one that's most important in here, because Henry's Law constant. 00:35:50.000 --> 00:36:02.000 Is what hap… what dictates what happens to a compound once it's already dissolved in water, and as we said, when peroxine likes to be dissolved in water, so the Henry's Law constant tends to drive things. 00:36:02.000 --> 00:36:14.000 And in this case, it's really, really low, as we saw in that previous table. So, in general, even though it might have a high vapor pressure, it's Henry's Law constant says that it's probably not going to be all that volatile. 00:36:14.000 --> 00:36:22.000 Uh, the exceptions then are environments where maybe it's not necessarily going to be a lot of water around, so maybe some dry, aerated environments. 00:36:22.000 --> 00:36:30.000 Maybe where you've got meat compound, or you're up in dry soils, um, those are cases where maybe volatilization might be a bigger deal. 00:36:30.000 --> 00:36:39.000 The next process is photodegradation. It's sort of a catch-all term, a destructive processes in this case, that occur in the presence of light. 00:36:39.000 --> 00:36:44.000 So that this might include contaminants like 1,4-dioxane once they're released to the atmosphere. 00:36:44.000 --> 00:36:55.000 So it's in the atmosphere, 1,4 dioxane can undergo photodegradation. It's not a direct reaction. One product is really a weak absorber of ultraviolet light. 00:36:55.000 --> 00:36:59.000 The compound really just doesn't have the chemical structure that sort of allows it to do that. 00:36:59.000 --> 00:37:05.000 Um, these are higher, you know, higher energy UV light, just not well absorbed. 00:37:05.000 --> 00:37:15.000 Instead, what happens when production is it undergoes indirect patolysis. And that occurs when you've got hydroxyl radicals, and that's that little OH with the dot by it. 00:37:15.000 --> 00:37:19.000 Uh, when those things are produced naturally in the presence of sunlight. 00:37:19.000 --> 00:37:24.000 Um, so this is a radical oxygen species. It then reacts with the 1-4-dioxane. 00:37:24.000 --> 00:37:31.000 It happens with a first-order kinetic relationship, so depends on the concentration of that radical itself. 00:37:31.000 --> 00:37:36.000 So the reaction is going to be faster if there's more of that radical, and slower if there's less. 00:37:36.000 --> 00:37:43.000 Based… sort of looking at literature reports, um, expected range for how much of that radical might be present in natural environments. 00:37:43.000 --> 00:37:53.000 You might expect one for a oxygen for the degradation rates on the order of a few hours to maybe a few days in natural settings. 00:37:53.000 --> 00:38:19.000 All right, next slide, uh, we're talking about advection, dispersion, and dilution. Uh, advection, um, that's really the movement of, of a… of a fluid, um, in response, or movement of compound in response to the bulk movement of the fluid on which it is present in. Typical example is really thinking about groundwater, then, where you've got these sort of pressure heads. It's moving, you know, with a hydraulic gradient. 00:38:19.000 --> 00:38:28.000 So something like that, when it's present in groundwater, can be really important in moving one forward oxygen relatively fast. As we've talked about before. 00:38:28.000 --> 00:38:39.000 Uh, one Pradoxin doesn't really like to sorb to soil, and so if it's moving within groundwater, it's not necessarily going to interact with those aquifer solids, and it could move relatively quickly. 00:38:39.000 --> 00:38:43.000 Fairly similar to the… to the rate of groundwater velocity itself. 00:38:43.000 --> 00:38:52.000 Um, if the one for the oxygen plume is moving due to infection, you do have these other processes, things like dispersion and dilution that can. 00:38:52.000 --> 00:39:08.000 Occur and can reduce the concentration of when Pradoxane. Dispersion in groundwater tends to be a relatively minor process, maybe more of a big deal once you've got a lot of plume expansion, or maybe even once it gets down gradient and is discharging into surface water. 00:39:08.000 --> 00:39:16.000 Um, discharge from surface water can be a concern for one… for dioxane due to its mobility. 00:39:16.000 --> 00:39:29.000 Um, when we're talking about when Protoxin, particularly advection and how fast it can move, one way to look at this is to sort of set up an example of how fast it might move relative to chlorinated solvents that it might be present with. 00:39:29.000 --> 00:39:41.000 So we're going to set up this hypothetical example with this question of how would one Freudioxane be expected to migrate in groundwater relative to other contaminants, chlorinated solvents, that may have been released along with it. 00:39:41.000 --> 00:39:47.000 So the key considerations, then, are thinking about the physical chemical characteristics of those co-occurring contaminants. 00:39:47.000 --> 00:39:56.000 Then the hydrogeologic characteristics of the aquifer into which it may have been released. Then the real key thing here is the timing of the release. 00:39:56.000 --> 00:40:03.000 And that's a big deal, because you may have these sites where one compound was used for a while, and then they switched to another solvent. 00:40:03.000 --> 00:40:14.000 So that switch between maybe TCE, or used earlier, then to TCA, which may have had one for dioxane. So that becomes a big deal as well. 00:40:14.000 --> 00:40:33.000 Um, so we're gonna look at this, uh, we're gonna look at plume sizes at a site where TCE was released in 1955, and then 11… One TCA was released at the same site later in 1970. In this case, we're going to assume a groundwater velocity, and then apply a simple 1D transport. 00:40:33.000 --> 00:40:39.000 Calculation, uh, where we conservatively assume that no degradation is happening to one protoxy. 00:40:39.000 --> 00:40:44.000 So this gives us an estimate, then, of how far each compound would be expected to travel by 2020. 00:40:44.000 --> 00:41:05.000 We can also look at, then, um. A range of FOC values in the aquifer to show how this influences the retardation factors for each compound, and that's reflected in those R values that are shown in the parentheses behind each compound. So we'll look at the parent compound as well as the other degradation products that are associated with that. 00:41:05.000 --> 00:41:07.000 And then we're going to project these out to, sort of. 00:41:07.000 --> 00:41:17.000 2020. Uh, so you'll see for that earlier release, you've got this maximum travel distance sort of out there near 1,300 feet. 00:41:17.000 --> 00:41:23.000 Particularly for 11DCE, and that's the hydrolysis byproduct, or in this case, sorry, it's the. 00:41:23.000 --> 00:41:31.000 The reductive dechlorination product of the TCE, that's out there pretty far, because that can be a relatively mobile compound. 00:41:31.000 --> 00:41:38.000 And the shaded bar there in that case, represents the range based on that range of FOCs that we've tried to. 00:41:38.000 --> 00:41:45.000 Current model. And if we look at the later release. Uh, this is 1970 at the same site. 00:41:45.000 --> 00:41:57.000 Um, one for docks and transport, it really isn't that dependent on FOC because, again, it's not served all that strongly, so it's… it's moved out there to sort of 1,000 feet. That's just reflecting the ground warm velocity during that. 00:41:57.000 --> 00:42:10.000 That period after it was released. But you'll see that that distance for one friend doxine, it's actually not that different than some of the chlorinated solvents, particularly those ones that may have been released as part of the earlier release. 00:42:10.000 --> 00:42:15.000 And in part, this reflects, you know, particularly in these low FOC environments. 00:42:15.000 --> 00:42:21.000 The fact that that, you know, some of these compounds really don't absorb that strongly either. 00:42:21.000 --> 00:42:32.000 As well as the fact that that 1955 release had 15 years head start, and so some of those compounds did get a chance to get out in front of that one for dioxane. 00:42:32.000 --> 00:42:38.000 It is this consideration of when you're evaluating these sites and thinking about how far things move, you do need to take into account the. 00:42:38.000 --> 00:42:53.000 Both the site settings and the release history. All right, so the last process that I'll talk about before turning over to Monica is matrix diffusion. And so matrix diffusion is a relatively new topic for something one for, like. 00:42:53.000 --> 00:43:01.000 One for dioxane, although it has been recognized for a while now as something that's relevant for things like chlorinated solvents. 00:43:01.000 --> 00:43:09.000 But what we're talking about here is just the ability of contaminant masks to diffuse into lower permeability zones that are present within an aquifer. 00:43:09.000 --> 00:43:14.000 Uh, so those sorts of soils, like clays or silts or rock that don't have a lot of inherent, uh. 00:43:14.000 --> 00:43:20.000 Inherent permeability. Um, and this is a non-destructive process by which. 00:43:20.000 --> 00:43:32.000 That mass is just diffusing into there, maybe persisting because there's no… there's not a lot of permeability, not a lot of reason for that stuff to get flushed out, so it sticks around a long time. 00:43:32.000 --> 00:43:38.000 It is subject to then diffusing back out, and that's why there's those double-sided arrows in there. 00:43:38.000 --> 00:43:47.000 But it's a pretty slow process, and again, that poses challenges for us, any of that mass that's gotten in there. How do you get it out? 00:43:47.000 --> 00:43:53.000 Um, graphics on the next slide sort of help show this maybe in a cartoon format. 00:43:53.000 --> 00:44:10.000 Um, how this influences where mass is over time. So, imagine, sort of, look at this left-hand side, you're in the early stages, initially after a release. The one for dioxane mass, it's mostly in that high permeability zone, so maybe that's a sand, and that's that red blob there. 00:44:10.000 --> 00:44:17.000 Again, this is just after release, so the concentration might be pretty high. In that case, um. 00:44:17.000 --> 00:44:25.000 You've got this concentration gradient, this driver for diffusion to work inwards from that high K zone into that lower K zone. 00:44:25.000 --> 00:44:31.000 And that's that process shown by that red arrows. Once again, once it's in there, advection's pretty low. 00:44:31.000 --> 00:44:38.000 So that mass is going to get flushed out very quickly. It's essentially getting stored up over time during those early stages. 00:44:38.000 --> 00:44:46.000 I was moving to the later stages, you know, maybe when we've gotten around to finally investigating this site, we've got sort of the reverse situation. 00:44:46.000 --> 00:44:58.000 So, in this case, you know, most of that mass that was in the original high K zone that's been depleted, uh, so we've got a reversal of that concentration gradient, so most of that driving force is from the low-K zone. 00:44:58.000 --> 00:45:08.000 Back into the high K zone. Concentrations might be pretty low in this case, because again, diffusion is slow, but this is a slow, persistent thing that. 00:45:08.000 --> 00:45:24.000 Process that can contribute to low concentrations within that high zone. High K zone over time. So at these sites where there's a good amount of heterogeneity, this might be a potential concern, something that might need to be built into the conceptual site model for. 00:45:24.000 --> 00:45:35.000 For that particular management of that site. All right, so that's it from me. I'll turn it over to Monica to go through the rest of this module. 00:45:35.000 --> 00:45:39.000 Thanks so much, Dave! So, next up is biodegradation. 00:45:39.000 --> 00:45:44.000 And this is a process where there has been a substantial shift in our understanding over the past decade. 00:45:44.000 --> 00:45:53.000 Because 1,4-dioxane was historically perceived as resistant to biodegradation. But we now know that biodegradation is possible under the right environmental conditions. 00:45:53.000 --> 00:45:57.000 And this is really important because biodegradation is a destructive process. 00:45:57.000 --> 00:46:02.000 So, 1,4-dioxide is not necessarily going to persist forever once it's released into the environment. 00:46:02.000 --> 00:46:14.000 If conditions are favorable for biodegradation. And importantly, as discussed further in the remediation training section, some of those favorable conditions can be engineered if they're not already present. 00:46:14.000 --> 00:46:24.000 So, as Dave mentioned earlier, 1,4-dioxane is biodegraded via oxidation. And this process is mediated by a variety of organisms that have been identified. 00:46:24.000 --> 00:46:31.000 I think my most recent count was 44 different organisms. Um, but all using oxygen in the first step. 00:46:31.000 --> 00:46:38.000 And it's very likely that there'll be further identification of relevant organisms and relevant genes that. 00:46:38.000 --> 00:46:44.000 Create the mono-oxygenase enzymes. That drive this process in the coming years. 00:46:44.000 --> 00:46:49.000 And the last point on this slide, you know, the availability of oxygen is key. 00:46:49.000 --> 00:46:57.000 So, we know that some compounds may be degraded via oxidation using either oxygen or alternative terminal electron acceptors. 00:46:57.000 --> 00:47:06.000 But each of those characterized pathways known to date. Berlin bordioxane is dependent on monoxtygenase enzymes, and those do require dissolved oxygen. 00:47:06.000 --> 00:47:21.000 So, importantly, this really means that the conditions that are most suitable for one bore dioxide biodegradation are different from the strongly reducing conditions that are suitable for biodegradation of the primary chlorinated solvents that 1,4-dioxane is associated with at many sites. 00:47:21.000 --> 00:47:25.000 And as such, an understanding of redox boundaries is really important. 00:47:25.000 --> 00:47:30.000 In predicting where the different biodegradation processes are likely to occur. 00:47:30.000 --> 00:47:36.000 In understanding 1,4 dioxide, fate, and transport in the context of mixed plumes with chlorinated solvents. 00:47:36.000 --> 00:47:45.000 And for characterizing natural attenuation, or designing other remediation strategies. As discussed further in the remediation training section. 00:47:45.000 --> 00:47:54.000 Uh, next slide, please. So, while each known 1,4-dioxide biodegradation pathway is mediated by monoxygenase enzymes. 00:47:54.000 --> 00:48:02.000 And requires oxygen, that first step. There are two different types of degradation possible, metabolic and co-metabolic. 00:48:02.000 --> 00:48:11.000 So, when the transformation of a constituent results in carbon and or energy yield to the microorganism, the process is termed metabolic biodegradation. 00:48:11.000 --> 00:48:21.000 Metabolic degradation is dependent on the 1,4-dioxide concentration, because those concentrations need to be high enough to meet the microorganism's demands for energy and growth. 00:48:21.000 --> 00:48:32.000 And what we know to date. Concentrations that are likely to support metabolic degradation are generally on the order of hundreds of micrograms per liter to milligrams per liter in groundwater. 00:48:32.000 --> 00:48:42.000 And as illustrated here, an organism called CB1190 is probably the most widely studied organism capable of 1-4 dioxane biodegradation. 00:48:42.000 --> 00:48:51.000 Although there are some others that are getting more attention. And microorganisms may also degrade 1,4-dioxane as a side effect of a targeted degradation. 00:48:51.000 --> 00:48:57.000 Of a different constituent. And that's the result, sometimes, of the low specificity of monoxygenase enzymes. 00:48:57.000 --> 00:49:02.000 For their primary substrates. And in this case, uh, it's termed co-metabolism. 00:49:02.000 --> 00:49:11.000 So, co-metabolic biodegradation of 1,4-dioxane has been documented using… with microbes using a variety of primary substrates. 00:49:11.000 --> 00:49:22.000 That include tetrahydrofuran, or THF. Propane, taruene, butane, um, and ethane have all been identified as some key primary substrates. 00:49:22.000 --> 00:49:27.000 And I want to call out, really, that ethane is particularly interesting as a cominibolic substrate. 00:49:27.000 --> 00:49:36.000 Because it's the product of complete reductive dechlorination of some of those chlorinated solvents that 1,4-dioxane is likely to have historically occurred with. 00:49:36.000 --> 00:49:41.000 And notably, in the cometabolic case, since 1,4-dioxide is not acting as a carbon or energy source. 00:49:41.000 --> 00:49:48.000 The rate and extent of degradation is largely controlled by the presence and concentrations of the primary substrates. 00:49:48.000 --> 00:49:54.000 Rather than the concentration of 1,4-dioxide. Next slide, please. 00:49:54.000 --> 00:50:02.000 So finally, on the topic of 1,4-dioxide biodegradation, it's notable that microbial inhibition is a potential concern. 00:50:02.000 --> 00:50:10.000 So, chlorinated solvents that are co-occurring in some metals, for example, copper, have been demonstrated to be inhibitory under some conditions. 00:50:10.000 --> 00:50:18.000 There are multiple inhibition methods, uh, hypothesized for these constituents, and this is described in greater detail in the guidance document. 00:50:18.000 --> 00:50:26.000 No, this is certainly still an area of active research, so at this time, our advice is to consider the potential for inhibition on the site-specific basis. 00:50:26.000 --> 00:50:32.000 And to keep up on scientific advances to our understanding of this process. 00:50:32.000 --> 00:50:40.000 Next slide, please. So, moving on from fate and transport processes, the next topic in this module is media. 00:50:40.000 --> 00:50:47.000 This graphic summarizes the primary media as well as the relative priority of each based on where one would expect to find 1,4-dioxane. 00:50:47.000 --> 00:50:50.000 And to a certain extent, what might be the risk drivers? 00:50:50.000 --> 00:50:56.000 And let me re-emphasize that these are relative priorities, and some sites are obviously going to differ. 00:50:56.000 --> 00:51:03.000 And the guidance document has a table that provides further detail on the rationale of the prioritization presented on this slide. 00:51:03.000 --> 00:51:11.000 So based on what we've talked about thus far, it shouldn't be a surprise that groundwater is a high priority, given 1,4-dioxide's properties. 00:51:11.000 --> 00:51:22.000 Surface water is also considered a high priority because of the potential for discharge from groundwater, and also because there are cases where direct discharge of 1,4-dioxane may occur from wastewater treatment plants. 00:51:22.000 --> 00:51:30.000 Or other sources. And this is a potential concern if that surface water is used as a source of drinking water. 00:51:30.000 --> 00:51:34.000 So you see here that soil and sediment are ranked as having a median priority. 00:51:34.000 --> 00:51:41.000 This is because the sorption of 1,4-dioxide is generally limited, and therefore it's not expected to persist in these media. 00:51:41.000 --> 00:51:47.000 However, since one for a dioxide may come into direct contact with these media during a release or after a discharge. 00:51:47.000 --> 00:51:54.000 There's some potential for one 4-doxin to be present, and it should be considered on a site-specific basis. 00:51:54.000 --> 00:52:00.000 So you see here, on the other hand, the indoor air and aquatic and terrestrial biota are ranked as a low priority. 00:52:00.000 --> 00:52:11.000 So, as mentioned before, it would require a fairly specific set of circumstances, including highly elevated concentrations and a complete vapor intrusion pathway to drive risk in this media. 00:52:11.000 --> 00:52:20.000 And risk to aquatic and terrestrial biota is considered to be low, based on the lack of evidence for bioaccumulation or other toxicity drivers. 00:52:20.000 --> 00:52:23.000 And this topic is discussed in detail in the training module on toxas. 00:52:23.000 --> 00:52:33.000 Toxology and Risk Assessment. So based on this prioritization of media, we've developed a framework to support decision-making from one 4-dioxane. 00:52:33.000 --> 00:52:38.000 During site assessment. So, next slide, please. 00:52:38.000 --> 00:52:47.000 And I first want to note that the flowchart presented here is an abbreviated version from that in the guidance document, and I encourage you to review that document for additional supporting details. 00:52:47.000 --> 00:52:58.000 Here, we want to start by emphasizing the highest priorities for site investigation, and that starts with a simple question, was 1-4 dioxane historically used or detected at the site? 00:52:58.000 --> 00:53:04.000 Uh, next slide. And if the answer to that question is no or unknown. 00:53:04.000 --> 00:53:09.000 The next relevant question is, were chlorinated solvents historically used or detected at the site? 00:53:09.000 --> 00:53:17.000 Because, as mentioned in the history of use module, one of the primary historical uses of 1,4 dioxane was as a stabilizer in chlorinated solvents. 00:53:17.000 --> 00:53:24.000 Therefore, where these constituents are present or suspected. Additional investigation of 1,4-dioxane may be warranted. 00:53:24.000 --> 00:53:36.000 Next slide, please. So, if the answer to either of these initial questions is yes, then site investigation should likely proceed to development of a CSM for 1,4-dioxane in groundwater. 00:53:36.000 --> 00:53:43.000 Considering first where the water is expected to travel, and then sampling at those appropriate locations. 00:53:43.000 --> 00:53:50.000 Concentrations of one for dioxide in groundwater, should they be compared to relevant standards or site-specific risk thresholds? 00:53:50.000 --> 00:53:59.000 If one for dioxane concentrations in groundwater are not greater than the relevant standards, then the next step is to implement additional sampling to refine the CSM. 00:53:59.000 --> 00:54:07.000 Our understanding of 1,4-dioxide fate and transport generally. And next slide, please. 00:54:07.000 --> 00:54:15.000 So, as mentioned in the discussion on media, groundwater and surface water are the primary concerns for 1-4 dioxane, but we want to take a few minutes to highlight other key considerations. 00:54:15.000 --> 00:54:21.000 Specifically, cases where 1,4-dioxane was or may have been released as a pure phase. 00:54:21.000 --> 00:54:31.000 Cases where there's surface water or permitted discharge? And cases associated with industrial wastewater treatment plants, septic systems, or landfill disposal. 00:54:31.000 --> 00:54:42.000 Next slide, please. So, as shown in these cases, other media may need additional investigation, including soil and soil vapor, if the pure phrase is present. 00:54:42.000 --> 00:54:47.000 Surface water or sediment, in the case of a surface water or permitted discharge. 00:54:47.000 --> 00:54:54.000 And any other potentially relevant media associated with industrial wastewater treatment plants, septic, or landfill disposal. 00:54:54.000 --> 00:55:01.000 Uh, next slide, please. 00:55:01.000 --> 00:55:12.000 So, our take-home messages here. So… First of all, hopefully after this module, you understand the key physical and chemical properties of 1,4-dioxane that really control where we find it in the environment. 00:55:12.000 --> 00:55:17.000 These include the low organic carbon partitioning coefficient and the Henry's constant. 00:55:17.000 --> 00:55:25.000 And also high solubility. Together, these characteristics of 1,4-dioxane make it very likely to occur in the water phase. 00:55:25.000 --> 00:55:31.000 Uh, with groundwater being, uh, usually the most important for characterization. 00:55:31.000 --> 00:55:36.000 Hopefully you can also identify the fate and transport processes that are relevant for 1,4 dioxane. 00:55:36.000 --> 00:55:47.000 Including infection with limited sorption in the subsurface, photodegradation in the atmosphere, and biodegradation in water where there's oxygen available. 00:55:47.000 --> 00:55:51.000 From this, you can develop a general conceptual site model for 1,4-dioxane. 00:55:51.000 --> 00:55:59.000 And remember that this must reflect your site-specific conditions, including any low permeability zones in the aquifer that may promote matrix diffusion. 00:55:59.000 --> 00:56:13.000 And finally, based on a collection of information about your site, you can establish an informed site assessment… strategy using existing characterization data for chlorinated solvents to help guide your positioning for 1,4-dioxane sampling. 00:56:13.000 --> 00:56:20.000 But also using your knowledge of the key chemical and physical properties of 1,4 dioxide to understand potential differences. 00:56:20.000 --> 00:56:26.000 And you can make decisions about sampling other media if dictated by site-specific characterizations. 00:56:26.000 --> 00:56:32.000 Including consideration of potential sources, release histories, and the hydrogeelectric setting. 00:56:32.000 --> 00:56:42.000 And that concludes the Fate and Transport module, and we'll open it up for the question and answer period. Thank you very much. 00:56:42.000 --> 00:56:55.000 All right, thank you, Monica. And as Monica just stated, we have reached our first Q&A portion of the training, and we do have a few open questions in the Q&A box. So I'll go ahead and ask those to our trainers. 00:56:55.000 --> 00:57:08.000 First one is 1,4-dioxane always found with TCA and TCE? If 1,4-dioxane is found without TCA and TCE, is this common? 00:57:08.000 --> 00:57:15.000 Um, this is Dave. I can take a first stab at that question. Um, we did a study a few years ago where we're looking at. 00:57:15.000 --> 00:57:24.000 You know, co-occurrence of, um. Of those… of one fraudoxin and chlorinated solvents, and essentially found that these are at contaminated sites that. 00:57:24.000 --> 00:57:42.000 95% of the sites were, um. One fronoxine was present, there was also chlorinated solvents present. Again, that's sort of looking at those contaminated sites. I will say that the exceptions to those cases that I've seen a good amount of is then at. 00:57:42.000 --> 00:57:55.000 At, like, uh, water production wells, you know, drinking water wells, and things like that that may be residential or neighborhood level, um, where you do see one-foot oxane in the absence of chlorinated solvents. And in general. 00:57:55.000 --> 00:58:00.000 If you remember back to where Janet was talking about personal care products and things like that. 00:58:00.000 --> 00:58:09.000 The potential of these other sources, um, septics and household releases and things like that. 00:58:09.000 --> 00:58:19.000 All right, thank you, Dave. And the next question for our trainers is 1,4-dioxane commonly detected at dry cleaning sites contaminated with. 00:58:19.000 --> 00:58:27.000 Pce or TCE? 00:58:27.000 --> 00:58:36.000 This is Dave again, I don't want to, uh… on the mic, but, um, we've looked at this, uh, as well. 00:58:36.000 --> 00:58:42.000 You know, it is… it tends to be present at a lot of those sites. 00:58:42.000 --> 00:58:47.000 Uh, in part because a lot of those sites are located in areas where there's other issues with the groundwater, so. 00:58:47.000 --> 00:58:55.000 They may not be co-occurring because the. The one for the oxyane had anything necessarily to do with the dry cleaning operations, but. 00:58:55.000 --> 00:59:10.000 We've also seen, then, the presence of 1,4-dioxane at. Dry cleaners, where there's also, uh, laundromats or things co-located on the same facilities, because again, going back to some of those uses of 1,4-deoxin that are related to. 00:59:10.000 --> 00:59:23.000 Um, laundry detergents and things like that, so they can't end up in the groundwater approximate, uh, or directly related to those, those sorts of dry cleaning operations. 00:59:23.000 --> 00:59:32.000 All right, thanks again, Dave. Um… Any of the trainers have anything else for that question? If not, I will be asking one more before we move on. 00:59:32.000 --> 00:59:42.000 In the interest of time. All right, and then the last question for our trainers. What do we know about chlorinated solvent? 00:59:42.000 --> 00:59:56.000 Nafls as a long-term source of 1,4 dioxane to GW. 00:59:56.000 --> 01:00:03.000 I guess GW's groundwater, if I had to guess. 01:00:03.000 --> 01:00:16.000 Well, um, I will take another stab at that one. We have done some modeling studies with that, basically having an apple that contains both chlorinated solvents and one for anoxane. 01:00:16.000 --> 01:00:29.000 Those predict, essentially, that when Fredoxine gets depleted relatively quickly out of a naple under idealized scenarios, just because of its solubility, obviously, relative to the other things that be in an apple. 01:00:29.000 --> 01:00:35.000 I think in reality, there could be some one-frodoxin still present in older NAPL. 01:00:35.000 --> 01:01:00.000 Just because of the fact that, you know, NAPL does tend to get into some areas where it's in poor space where there's not a lot of flushing, or maybe not even connected pore space, so… some of that napple may still have some one protaxine associated with it. But again, just because of the properties, you do… you do expect it to gel and deplete pretty quickly at an apple. 01:01:00.000 --> 01:01:05.000 All right, thanks, Dave. 01:01:05.000 --> 01:01:12.000 All right, I will go ahead and continue on with the training, but we will have another. 01:01:12.000 --> 01:01:22.000 Q&a session at the end of the training today, so if you have any more questions for our trainers, please continue to use that Q&A box as they are monitoring it during the training today. 01:01:22.000 --> 01:01:33.000 So, I will now be passing it off to Elizabeth Dentley to begin the sampling and analysis module of the training. 01:01:33.000 --> 01:01:37.000 Okay, thanks, Taylor. Can you hear me okay? Okay. 01:01:37.000 --> 01:01:45.000 Yes. 01:01:45.000 --> 01:01:57.000 I am just trying to get this… To go… 01:01:57.000 --> 01:02:04.000 Bites don't seem to be moving. There we go. 01:02:04.000 --> 01:02:16.000 Okay, so, um, today we're going to discuss some of the… kind of sampling precautions when sampling 1,4-dioxane, and there are only a few of those. 01:02:16.000 --> 01:02:22.000 Um, we're going to go over the requirements for bottle preservation and holding times. 01:02:22.000 --> 01:02:26.000 And how they may differ depending on the chosen analytical method. 01:02:26.000 --> 01:02:38.000 And finally, there are several different analytical approaches available for 1,4-dioxane, so we're going to summarize these and discuss what the benefits and limitations are of these methods, with particular attention paid. 01:02:38.000 --> 01:02:43.000 Um, to the groundwater matrix. 01:02:43.000 --> 01:02:57.000 So, when sampling 1,4-dioxane in soil, sediment, groundwater, surface water, and air, most of the time, conventional sampling approaches will be used. 01:02:57.000 --> 01:03:04.000 Um, so sampling methodologies that you would do for most other contaminants would also apply for 1,4-dioxane. But we're going to go over a few precautions for groundwater. 01:03:04.000 --> 01:03:12.000 Soil and equipment decontamination. So again, typical sampling methods can be used first when you're sampling groundwater. 01:03:12.000 --> 01:03:20.000 However, if passive diffusion sampling is used, you cannot use low-density polyethylene membranes. 01:03:20.000 --> 01:03:26.000 Which are in the standard passive diffusion bag. So 1,4-dioxane will not pass through this membrane. 01:03:26.000 --> 01:03:33.000 So you need to use other membrane materials or pore sizes that will facilitate diffusion of 1,4-dioxane into the samplers. 01:03:33.000 --> 01:03:43.000 And some examples of passive sampling techniques are provided here. Uh, the first two listed here are diffusion samplers, the rigid porous polyethylene sampler. 01:03:43.000 --> 01:03:55.000 And the dual membrane PDB sampler. There's also two grab samplers shown that could be used to collect samples at specific depth intervals. That's the snap sampler and the hydra sleeve. 01:03:55.000 --> 01:04:01.000 Also, there's one other potential issue with groundwater samples, and that could be for low-yield wells. 01:04:01.000 --> 01:04:12.000 And when this is the case, it may be difficult to fill two 1L bottles, and that could ultimately affect reporting limits, depending on the analytical method being used. 01:04:12.000 --> 01:04:20.000 But you should always check with your regulatory agency before using any specific approach to make sure that it is allowed. 01:04:20.000 --> 01:04:27.000 Um, as I mentioned, again, typical sampling methods can be used when you're sampling soil, but there's one small precaution. 01:04:27.000 --> 01:04:39.000 So, 1,4-dioxane can volatilize from dry soil samples, so if the soil samples are very dry, it's better for these samples to be collected as volatile organic compounds. 01:04:39.000 --> 01:04:50.000 Using the sampling, um, procedures described in SW846, Method 5035A. Um, in 8260 for analysis, and that would reduce the potential for volatilization. 01:04:50.000 --> 01:05:02.000 And we're going to talk in a minute about how this 1,4-dioxane can be analyzed. It's a volatile organic compound or a semi-volatile organic compound, but with very dry soils, it may be better to go the VOC route. 01:05:02.000 --> 01:05:09.000 And there's no specific soil and moisture levels that have really been identified as a cutoff for this consideration. 01:05:09.000 --> 01:05:18.000 So if you're in doubt, you are safe with the VOC sampling procedures for soil for 1,4-dioxane. 01:05:18.000 --> 01:05:32.000 So, one for… 01:05:32.000 --> 01:05:38.000 It's important to prevent residual detergent from remaining on the equipment. 01:05:38.000 --> 01:05:43.000 So be sure to use the necessary water and DI water rinses. 01:05:43.000 --> 01:05:54.000 Sorry about this, these slides are delaying. Um, there have been studies demonstrating, though, that it's not present in some common detergents used in the field, if they're used in accordance with manufacturer's instructions. 01:05:54.000 --> 01:06:03.000 So if you use disposable equipment or passive sampling equipment, you're going to eliminate that decontamination step, and it won't be an issue. 01:06:03.000 --> 01:06:13.000 All right, so 1,4-dioxane can be analyzed as a volatile organic compound or a semi-volatile organic compound. So using 8260 or 8270. 01:06:13.000 --> 01:06:20.000 And depending on the analytical method that you choose, or maybe that you're required to use. 01:06:20.000 --> 01:06:25.000 The choice of bottles and preservatives and subsequent holding times will be different. 01:06:25.000 --> 01:06:41.000 So the requirements for bottles, preservatives, and holding time for 1,4-dioxane in soil and water when it's analyzed as a VOC using 8260, is the same as it is for… any other VOC. So you use acid preservation for water. 01:06:41.000 --> 01:06:48.000 Low-level, high-level preservation for soils. Um, and a 14-day holding time for soil and water. 01:06:48.000 --> 01:06:59.000 For 1,4-dioxane in soil and water when it's analyzed as a semi-volatile, using 8270, the same thing. You're going to have a 7-day hold time for waters until extraction, 14-day hold time. 01:06:59.000 --> 01:07:06.000 For soils until extraction. And same bottles for soil and water as with other semi-bottle organic compounds. 01:07:06.000 --> 01:07:15.000 And for air, the same thing also. 30-day hold time, just like we have for other VOCs analyzed by TO15 or TO17. 01:07:15.000 --> 01:07:23.000 So, as I mentioned before, um. 1,4-dioxine, it can be analyzed, you know, as a VOC or an SVOC. 01:07:23.000 --> 01:07:34.000 But unlike sample collection, preservation, bottles, and holding times, we do need modifications to the typical 8260 or 8270 analytical methods. 01:07:34.000 --> 01:07:43.000 So, which method we choose is going to depend on the matrix. It's going to depend on the required sensitivity, or what reporting limits we need to achieve. 01:07:43.000 --> 01:07:50.000 It's also going to depend on what other contaminants may be in the sample, as well, of course, as the regulatory requirements. 01:07:50.000 --> 01:07:59.000 So choosing the correct analytical method requires knowledge on your part, and a need to really work with your lab so they understand what you need. 01:07:59.000 --> 01:08:04.000 And you understand what they're going to be doing, um, to meet your objectives. 01:08:04.000 --> 01:08:11.000 So, the message that requires some discussion, and the ones that we're highlighting today, are the 8260 and 8270 methods. 01:08:11.000 --> 01:08:17.000 Um, I do encourage you to review the TechReg document for more information on the other methods. 01:08:17.000 --> 01:08:20.000 So, the first two rows here are for the VOC analyses. 01:08:20.000 --> 01:08:28.000 Um, of water samples. And the very first row of this table is a typical VOC analysis with no modifications. 01:08:28.000 --> 01:08:40.000 And you can see the reporting limits from this technique, which is used for most of the other VOCs we normally analyze for, pretty high, at 200 to 500 micrograms per liter. 01:08:40.000 --> 01:08:52.000 The second row, though, shows what happens. When we modify 8260, and we add a heated purge heated purge and trap step, and selective ion monitoring, or SIM. 01:08:52.000 --> 01:09:06.000 So, since 1,4-dioxane is so soluble in water. The heated purge helps, um, improve the ability of getting that 1,4-dioxane out of the water during that purge step. 01:09:06.000 --> 01:09:12.000 And the SIM improves the sensitivity of the instrument, and it allows that GCMS instrument to selectively look. 01:09:12.000 --> 01:09:17.000 For the ions of 1,4-dioxine without looking for the other VOCs. 01:09:17.000 --> 01:09:26.000 Because normally, our GCMS systems are set up. To scan between 30 and 350 atomic mass units. 01:09:26.000 --> 01:09:33.000 For the entire analytical run, which allows the detection of VOCs, which have ions in the range of 35 to 350. 01:09:33.000 --> 01:09:39.000 But with SIM, we're telling the instrument to scan for specific ions instead of a wide range of ions. 01:09:39.000 --> 01:09:47.000 And that's why we get better sensitivity, and therefore lower reporting limits, now down to 2 to 5 micrograms per liter. 01:09:47.000 --> 01:09:57.000 The next two rows, um, are the semi-val analyses of water samples, and the first row here is a typical SVOC analysis with no modification. 01:09:57.000 --> 01:10:07.000 So the reporting limits from this technique are 5 to 10 micrograms per liter. They're much lower than the typical VOC analysis of 200 to 500 micrograms per liter. 01:10:07.000 --> 01:10:11.000 But they may still be too high to achieve regulatory criteria. 01:10:11.000 --> 01:10:18.000 Also, there can be some extraction efficiency issues with 1,4-dioxane by the 82.7 prep methods. 01:10:18.000 --> 01:10:25.000 The second, though, row of this 8270, uh, table here shows what happens when we modify 8270. 01:10:25.000 --> 01:10:34.000 And we add SIM, like we discussed for $82.60. And also, isotope dilution. And I'll show you in a minute why isotope dilution is really the gold standard. 01:10:34.000 --> 01:10:40.000 But this is the most accurate way to measure 1,4-dioxane at low levels. 01:10:40.000 --> 01:10:44.000 And it will probably be the recommended approach when you need to achieve low regulatory criteria. 01:10:44.000 --> 01:10:53.000 Um, in water samples. And then you can see soil samples with the same four analytical techniques we just saw for water samples. 01:10:53.000 --> 01:11:01.000 Typically, we don't need to see down to very low criteria for soil, so the modifications become less critical. 01:11:01.000 --> 01:11:09.000 So really, any of these soil methods are okay. The VOC one that's done, you know, with all other VOCs, the first of the rows here highlighted, it's probably okay. 01:11:09.000 --> 01:11:15.000 For most data quality objectives, and remember, that's the one that you're going to want for very dry soils. 01:11:15.000 --> 01:11:29.000 And we're going to discuss some of the comments here on this final, um… the final column here, we're going to discuss these on some of the next slides. 01:11:29.000 --> 01:11:38.000 Okay. 01:11:38.000 --> 01:11:49.000 Okay, so first, 1,4-dioxane DH, that's deuterated 1,4-dioxane. Has to be used as an internal standard in both the VOC and SVOC analyses. 01:11:49.000 --> 01:11:57.000 So it's always best to use the isotopic standard that closely matches the analay of interest when possible. 01:11:57.000 --> 01:12:17.000 And 1,4-dioxane, D8 fits that purpose. For VOCs, if it's not used as an internal standard, what we see is the resulting response factors on the instrument are extremely low, and many times we have had to reject those results per data validation guidelines, because the response factors are so low. 01:12:17.000 --> 01:12:25.000 Um, for VOCs and SVOCs, the 1,4-dioxane D8, again, it mimics the behavior of 1,4-dioxane. 01:12:25.000 --> 01:12:34.000 And it really just adds a really important level of accuracy to the method when we spike in a known amount of this compound, and then we measure its recovery. 01:12:34.000 --> 01:12:40.000 Um, as we showed on the previous table, that modify 8260 can be prone to interferences. 01:12:40.000 --> 01:12:49.000 So, if a sample has elevated levels of other VOCs, this can possibly interfere with the SIM analysis. 01:12:49.000 --> 01:12:53.000 So although the instrument is set up in the SIM mode. 01:12:53.000 --> 01:13:03.000 To selectively look for 1,4-dioxane. The other VOCs are still being transported to that instrument. They're still going to the TRAP, the GC column, and the mass spec. 01:13:03.000 --> 01:13:17.000 That can cause contamination of the system that the labs are trying to avoid. So, if the sample has elevated levels of other VOCs, and the lab is doing the SIM option, they will still likely have to dilute the sample. 01:13:17.000 --> 01:13:26.000 So that 2 to 5 microgram per liter reporting limits. Will probably increase accordingly, whatever they have to do, the dilution. 01:13:26.000 --> 01:13:36.000 So I've seen samples specifically with elevated levels of chlorinated VOCs, um, cause extremely high recoveries of the isotope standard 1,4-dioxane D8. 01:13:36.000 --> 01:13:44.000 And I'll show you an example of that shortly. So if you know a sample is going to have elevated levels of other compounds. 01:13:44.000 --> 01:13:53.000 The 8260 SIM may not be the best option. Isotope dilution, though. So the exact method of quantifying concentrations can differ between labs. 01:13:53.000 --> 01:14:00.000 And there's basically two general types of quantification, internal standard and isotope dilution. 01:14:00.000 --> 01:14:04.000 And isotope dilution, again, is really the most accurate quantitation method. 01:14:04.000 --> 01:14:10.000 So how it works is our samples are spiked with a known amount of 1,4-dioxane D8. 01:14:10.000 --> 01:14:19.000 Prior to the start of preparation. Um, so that 1,4-dioxane D8 is going through the entire preparation and analytical process with the sample. 01:14:19.000 --> 01:14:25.000 And the instrument is calibrated for both 1,4-dioxane D8 and 1,4-dioxane. 01:14:25.000 --> 01:14:34.000 And when the sample's analyzed, the concentration for 1,4-dioxane and the concentration of 1,4-dioxane D8 are calculated. 01:14:34.000 --> 01:14:39.000 But what you're going to see here, um, is that the actual concentration. 01:14:39.000 --> 01:14:47.000 Of the isotope. Sorry, there's a delay here. Um, is actually corrected. 01:14:47.000 --> 01:14:59.000 Um, it's actually correcting. If it's of… if the actual concentration of the isotope 1,4-dioxane D8 is above or below the true value, it's going to be reflected in the area count, and then 1,4-dioxane. 01:14:59.000 --> 01:15:06.000 Will be proportionally corrected by that amount. And that really allows, um, the analysis to account for any preparation. 01:15:07.000 --> 01:15:11.000 Or analytical errors, and really, most importantly, account for any matrix interferences. 01:15:11.000 --> 01:15:18.000 As the previous slide showed, you know, 1,4-dioxane sometimes can have poor extraction efficiency by 827D prep methods. 01:15:18.000 --> 01:15:34.000 Isotope dilution will compensate for the poor extraction efficiency issue. So again, it's really the gold standard for quantitation. Some regulatory agencies, like New York State, require the use of 8270 with isotope solution. 01:15:34.000 --> 01:15:43.000 Okay, as I mentioned before, I've seen some samples where elevated concentrations of chlorinated VOCs. 01:15:43.000 --> 01:16:00.000 Cause extremely high recoveries of 1,4-deoxin D8, that isotopic standard. So this sample has an unusually high recovery of 1,4-dioxane D8. You can see here on the left, it's like looking at about 87,000%, which seems highly suspicious. 01:16:00.000 --> 01:16:05.000 And this sample also has high concentrations of select chlorinated VOCs. 01:16:05.000 --> 01:16:14.000 So you can see here on the right, about 665 micrograms per liter of CIS12DCE and 8,290 micrograms per liter of TCE. 01:16:14.000 --> 01:16:19.000 And if you look on the right column of this table, you can see that these chlorinated VOCs. 01:16:19.000 --> 01:16:26.000 Have an ion in common with the isotope 1,4-dioxane D8, and that's ion 96. 01:16:26.000 --> 01:16:32.000 So there's a similar ion between 1,4-dioxane D8 and some chlorinated VOCs. 01:16:32.000 --> 01:16:43.000 And although the mass spec is just looking for the 1,4-dioxane DA ions, one of those ions is shared with the chlorinated VOCs, and it's therefore being detected. 01:16:43.000 --> 01:16:48.000 And interfering with the recovery of this isotopic standard, which salutes at around the same time. 01:16:48.000 --> 01:16:56.000 So a high recovery of this isotopic standard may not necessarily be indicative of a high bias for 1,4-dioxane. 01:16:56.000 --> 01:17:09.000 And may instead be due to interferences from chlorinated VOCs. So, as I mentioned earlier, the use of 8260 for 1,4-dioxane should be ruled out if you know you have elevated chlorinated VOCs. 01:17:09.000 --> 01:17:14.000 Note, this might be lab-dependent, so you want to check with your lab also. 01:17:14.000 --> 01:17:19.000 Um, and make sure I see if they can get chromatographic resolution between the chlorinated VOCs. 01:17:19.000 --> 01:17:28.000 Um, and the isotope 1,4-Dioxane D8, or just be safe and use that 8270 isotope dilution method. 01:17:28.000 --> 01:17:35.000 Okay, so I had shown you before that the 8260 SIM reporting limit was probably around 2 to 5 micrograms per liter. 01:17:35.000 --> 01:17:43.000 I would be leery of labs that say they can see down to 0.2 micrograms per liter by 8260 sim for 1,4-dioxane. 01:17:43.000 --> 01:17:49.000 Data start to become very questionable. When labs report down this low using 8260 SIM. 01:17:49.000 --> 01:17:59.000 So, in this example, you can see the extremely poor peak shape here on this chromatogram. It's even pushing the limit, if that's really a peak or just noise. 01:17:59.000 --> 01:18:04.000 In the area count, um, of the primary ion for 1,4-dioxane is 22. 01:18:04.000 --> 01:18:10.000 And that's a very low area count. So with an area count of 22, it will be virtually impossible. 01:18:10.000 --> 01:18:20.000 To see a good signal for the 1,4-dioxane conformation ion. Which should be about 60% of that primary ion, or 60% of that area count of 22. 01:18:20.000 --> 01:18:29.000 So this might be instrument-dependent, or might be lab-dependent, but when you're looking for 1,4-dioxane at very low levels, using 8260 SIM. 01:18:29.000 --> 01:18:36.000 I advise you to scrutinize the intensity of that primary quantitation ion, ask the lab for the raw data to review this. 01:18:36.000 --> 01:18:42.000 It's really important to evaluate this in relation to your project objectives. 01:18:42.000 --> 01:18:47.000 So, these are just, um, averages, but they are generally all the same order of magnitude. 01:18:47.000 --> 01:18:52.000 Um, you'll likely always pay a bit more for $82.70 with SIM isotope dilution. 01:18:52.000 --> 01:19:01.000 But that, again, is the gold standard. And, you know, you get what you pay for. So, they are usually… it's just usually a little bit higher in price. 01:19:01.000 --> 01:19:11.000 Okay, so, which analytical method should I use? So, it's going to depend on your project objectives and what criteria you're trying to achieve. 01:19:11.000 --> 01:19:16.000 It's going to depend on what other contaminants may be present in your sample, as we just talked about. 01:19:16.000 --> 01:19:22.000 You need to do a really good job of matching site conditions with the chosen analytical method. 01:19:22.000 --> 01:19:30.000 So, this kind of summarizes, you know, things we've already discussed, but if elevated concentrations of other VOCs are present, and you need low reporting limits. 01:19:30.000 --> 01:19:38.000 Use one of those 8270 methods. You know, even if the lab does 8260 SIM, they're still going to have to dilute that sample. 01:19:38.000 --> 01:19:50.000 Due to the other VOCs. And again, remember, if chlorinated VOCs are high, they may interfere with the accurate quantification of that isotope, 1,4-dioxane D8, in the 8260 analysis. 01:19:50.000 --> 01:19:56.000 Which will ultimately affect your 1,4-dioxane result. And then you want to look at how low do you need to go. 01:19:56.000 --> 01:20:05.000 Um, if you need to achieve, you know, 0.3 micrograms per liter, or even 1 microgram per liter, use 8270 with isotope dilution. 01:20:05.000 --> 01:20:11.000 The only downfall to 80-270 SIM is that it requires two 1L amber glass bottles. 01:20:11.000 --> 01:20:17.000 As opposed to $82.60, which only requires 3 40 mil vials. 01:20:17.000 --> 01:20:22.000 So it could be an issue with low-yield wealth, as I discussed earlier on in the presentation. 01:20:22.000 --> 01:20:36.000 And of course, you know, check with your regulatory agency on any specific requirements. 01:20:36.000 --> 01:20:50.000 One more slide, if I can get to it. Okay, so I'm not going to go through this flowchart today, but I did want to let you know that everything we discussed today is in a flowchart in the check reg. 01:20:50.000 --> 01:20:57.000 So ideally, you could use this to determine which analytical method will best suit your needs in the absence of any regulatory. 01:20:57.000 --> 01:21:05.000 Um, requirements. And now we're going to do a quick, um, knowledge check. 01:21:05.000 --> 01:21:18.000 Um, so I will read this. Uh, you were sampling groundwater for 1,4-dioxane, and you need to meet the regulatory screening criteria of 0.3 micrograms per liter. 01:21:18.000 --> 01:21:26.000 Prior rounds of sampling detected elevated concentrations of some chlorinated VOCs, for example, CIS12 dichloroethene. 01:21:26.000 --> 01:21:33.000 Which analytical method will you likely need to use in the absence of any regulatory requirement? 01:21:33.000 --> 01:21:41.000 So, A, SB468260. Would SIM, B, SW8468260, without SIM. 01:21:41.000 --> 01:21:56.000 Our SW8468270 with SIM, I… Tope dilution. 01:21:56.000 --> 01:21:59.000 Just gonna give it a couple more seconds for people to respond. 01:21:59.000 --> 01:22:06.000 Okay. 01:22:06.000 --> 01:22:10.000 All right, ending and sharing results. 01:22:10.000 --> 01:22:20.000 Okay, very good. So, most of you got the correct answer, which is 8270 with the SIM isotope dilution, due to the, um, presence of those chlorinated VOCs. 01:22:20.000 --> 01:22:38.000 Very good. So this concludes, um, the module on sampling and analysis, and I'm going to turn it back now to Janet Anderson for a presentation on toxicity and risk assessment. 01:22:38.000 --> 01:22:42.000 Thanks, Liz. Let's see if we can get the slides going. All right. 01:22:42.000 --> 01:22:54.000 So, uh, thanks for hanging in there this long. So now, um… In our story of evaluating 1,4-Daxane, you've gotten to the point where you have been able to characterize your site, you understand how 1,4-doxane. 01:22:54.000 --> 01:23:00.000 May be moving and transforming in the environment. You've got robust analytical methods, so now we're going to talk about. 01:23:00.000 --> 01:23:11.000 Um, how to interpret that data with regard to risk. Let's see if I can get these to advance. There we go. So I'm going to talk about risk drivers for both human health and eco. 01:23:11.000 --> 01:23:20.000 We're going to talk specifically about how the… what the controversy is around 1-4DOXIN and how it causes cancer, and how that may impact your risk assessment decisions. 01:23:20.000 --> 01:23:25.000 And then at the end, I'm gonna put in a plug for the Risk Communication Toolkit developed by ITRC. 01:23:25.000 --> 01:23:32.000 Um, because it can apply to 1,4-Doxane and may be helpful for risk communication. 01:23:32.000 --> 01:23:35.000 All right, so we're going to start with the human health risk assessment. 01:23:35.000 --> 01:23:42.000 In general, there are four steps that we usually think about, um, when we assess human health risk assessment. 01:23:42.000 --> 01:23:51.000 The toxicology component consists of the hazard identification, so that's figuring out what are the potential health effects that may be anticipated. 01:23:51.000 --> 01:24:02.000 If there is a human exposure to the contaminant. And the dose response assessment is important because it helps us understand at what levels do we think that those different health effects may occur. 01:24:02.000 --> 01:24:09.000 Combined with an exposure assessment, which is where we really think about either using default generic exposure assumptions. 01:24:09.000 --> 01:24:19.000 Or at a site-specific level, what the specific exposure routes and levels of concern might be. We combine all that with the toxicology component. 01:24:19.000 --> 01:24:27.000 To think about the risk characterization, which helps the risk assessor understand, then, what the risk is of a given health effect under your exposure scenarios. 01:24:27.000 --> 01:24:36.000 So we're going to use those steps, kind of, to guide our conversation today, and we're going to start with the hazard identification and dose response. 01:24:36.000 --> 01:24:49.000 We do have, um, a really nice database of… Uh, laboratory studies for 1-4noxane, where there's experimentally, um, designed controls, different doses, different exposure routes. 01:24:49.000 --> 01:24:58.000 Um, and well-designed and controlled laboratory settings. Uh, so most of our information for OneFridoxane does come from the rodent, um, lab setting. 01:24:58.000 --> 01:25:10.000 Um, in those, uh, studies, we see that at high doses, chronic exposure, um, non-cancer effects are in the liver and the kidney. 01:25:10.000 --> 01:25:18.000 Again, these are really high doses. If the rodents are exposed orally, if onefordoxane is in the air and there's an inhalation, again, at high doses, there's some, um. 01:25:18.000 --> 01:25:23.000 Irritation and respiratory effects of both the eye and the respiratory tract. 01:25:23.000 --> 01:25:27.000 But, as can be seen here and embolded, really the most important, um. 01:25:27.000 --> 01:25:38.000 Concern related to human exposure to 1-frodoxane, especially chronic, and at levels that one might anticipate having in your drinking water or at a contaminated site, is cancer risk. 01:25:38.000 --> 01:25:46.000 So the International Agency for Research on Cancer, or IARC. As classified 1,4-Doxane as possibly carcinogenic. 01:25:46.000 --> 01:25:53.000 And the U.S. Environmental Protection Agency has classified. One for vaccine isn't likely to be carcinogenic. 01:25:53.000 --> 01:25:59.000 And again, this data comes largely from rodent studies. I need the slides to advance here. 01:25:59.000 --> 01:26:07.000 There we go. Um, in the rodent studies, uh, where they've been, the rodents, both mice and rats, males and females. 01:26:07.000 --> 01:26:14.000 Have been exposed to a range of high doses of 1,4 vaccine, um, from different pathways of exposure. We see tumors. 01:26:14.000 --> 01:26:21.000 Um, in organs like the liver, the kidney, nasal passages, peritoneum, mammary gland, etc. 01:26:21.000 --> 01:26:26.000 So, generally, again, cancer is going to be the risk driver for human health. 01:26:26.000 --> 01:26:29.000 Um, and the good news is, all the experts really agree on that. 01:26:29.000 --> 01:26:35.000 The bad news is that there's some controversy over how we exactly interpret the cancer risk. 01:26:35.000 --> 01:26:50.000 And what that means from a risk assessment perspective. So really what that hinges on is what's called the cancer mode of action, and I'll present just two differing opinions of that. One is the U.S. Epa, and the second is Health Canada's and some others. 01:26:50.000 --> 01:26:57.000 That really show, um, why this, um, sort of controversy and difference of opinions exist. 01:26:57.000 --> 01:27:06.000 Okay, so starting with EPA, um, EPA has assessed the underlying cancer biology and cancer risk for Winfredoxine in several different key documents. 01:27:06.000 --> 01:27:12.000 Including the integrated risk information system, or IRIS, assessment that was issued in 2013. 01:27:12.000 --> 01:27:17.000 And then also in their toxic Substances Control Act, or TSCA assessments. 01:27:17.000 --> 01:27:28.000 Uh, that I mentioned before in the regulatory section. In those documents, EPA concludes that the mode of action, or how one frotoxane may cause an increased risk of cancer in humans, is unknown. 01:27:28.000 --> 01:27:37.000 And according to EPA's cancer guidelines. If we don't know, um, how a chemical like 1-protoxane may cause cancer. 01:27:37.000 --> 01:27:41.000 Uh, then we use what's the default. Dose-response model. 01:27:41.000 --> 01:27:52.000 And what… that is what's called a low-dose linear extrapolation. So EPA basically says the evidence is inadequate to really establish a mode of action, so they result. 01:27:52.000 --> 01:28:01.000 To using this, um, linear extrapolation. Which is pretty common for, um, carcinogens where we think that basically the assumption is that. 01:28:01.000 --> 01:28:17.000 Any increase in exposure increases your risk. In a linear or proportional fashion. And so that's why we get this cancer risk management range of 10 to the minus 6, or 1 in a million, to 10 to the minus 4, because then we can set our threshold. 01:28:17.000 --> 01:28:22.000 For excess or background theoretical exposure, or a theoretical excess cancer risk. 01:28:22.000 --> 01:28:35.000 Um, so again, EPA's default, um, and conservative and protective. Dose-response model is this LOTUS linear model, because they interpret the data as really inconclusive to establish. 01:28:35.000 --> 01:28:47.000 A mode of action. Um, this is in contrast, though, to Health Canada, um, also the World Health Organization, um, and several European agencies. 01:28:47.000 --> 01:28:51.000 Where they've looked at the data and said, using a weight-of-evidence approach. 01:28:51.000 --> 01:28:57.000 That the evidence supports what they determine to be a non-gunotoxic mode of action. 01:28:57.000 --> 01:29:03.000 Meaning, 1,4oxane does not inhibit the actual DNA or chromosomal genetic material. 01:29:03.000 --> 01:29:11.000 And instead, it's doing other mechanisms of action, such as, um, causing cellular… increased cellular growth and regeneration. 01:29:11.000 --> 01:29:19.000 Um, and that's how it's causing its cancer. So, Health Canada, for example, in their 2018 conclusion, said. 01:29:19.000 --> 01:29:29.000 That the mode of action analysis, the weight of evidence supports a non-genotoxic mode of action, inducing tumors through a regenerative proliferation-induced mode of action. 01:29:29.000 --> 01:29:37.000 And so what that means is that we use a different mathematical model, and that model is more common to what we see for non-carcinogens, which means. 01:29:37.000 --> 01:29:49.000 At a certain level of exposure, our bodies are able to handle that exposure, and there's no increase or unacceptable risk. And it's only once you exceed that threshold that then there is a potential increase for risk. 01:29:49.000 --> 01:29:57.000 So that's why regulatory agencies such as Health Canada, World Health Organization, and some of the European agencies have a solid threshold. 01:29:57.000 --> 01:30:04.000 Exposure limit for one Fredoxane, either in cancer or other regulatory settings. 01:30:04.000 --> 01:30:14.000 Okay, so why does this matter? No, we're here in the US, right? Well, it's important to understand the differences of opinion, um, because it results in different toxicity criteria. 01:30:14.000 --> 01:30:26.000 And depending on the regulatory and legal framework for your site, you may be in a situation where best professional judgment is needed, and a really robust justification is needed for your choice of toxicity criteria. 01:30:26.000 --> 01:30:32.000 So again, it's critical that for a given site or situation, you understand the legal and regulatory requirements. 01:30:32.000 --> 01:30:36.000 Of which toxicity information you should be using to assess risk. 01:30:36.000 --> 01:30:45.000 It's really important that you ensure that your best available science is used by your risk assessor and toxicologist, and you can justify your risk management and risk. 01:30:45.000 --> 01:30:52.000 Decisions and selection of toxicity criteria consistent with the legal requirements at your site. 01:30:52.000 --> 01:30:59.000 So, for example, under the EPA Superfund program and many state policies, risk assessors can choose for a hierarchy of. 01:30:59.000 --> 01:31:06.000 Toxicity information. Usually that U.S. Epa IRIS, so their Integrated Risk Information System, is considered the top tier. 01:31:06.000 --> 01:31:15.000 Gold standard, um, that, again, for one Fredoxane, was issued in 2013. So there's some information in the guidance issued by EPA. 01:31:15.000 --> 01:31:27.000 About making sure you're using the best available information. Um, so, within EPA's policy and guidance is a requirement to use the most current information and make sure that you're really justifying it, again, using that. 01:31:27.000 --> 01:31:36.000 Best available information. So, the choice of your cancer toxicity value and summary really can have a significant impact. 01:31:36.000 --> 01:31:45.000 On your drinking water or groundwater screening levels. At the regulatory, um, stage, we're seeing that as exemplified in the range of values. 01:31:45.000 --> 01:31:49.000 From 0.3 all the way up to 50 parts per billion. 01:31:49.000 --> 01:32:03.000 So, risk assessors really need to pay attention to the latest science and regulatory determinations. As I mentioned earlier, we do expect some new information to come out from California OHIA and their public health goal draft within, hopefully, a month or so. 01:32:03.000 --> 01:32:10.000 That'll be really helpful, and it'll be a new data point. There's been a host of publications and ongoing research in this area, from. 01:32:10.000 --> 01:32:19.000 Academia, for example, some good work coming out of Harvard. So, again, just continue to watch the science, and this is an active area of research. 01:32:19.000 --> 01:32:36.000 So when we think about, then, the combining the dose-response information and hazard information, whatever toxicity value you choose with exposure, um, this is where, at a site-specific setting, it's going to really matter if you think about what is your exposure setting, what are the relevant exposure pathways. 01:32:36.000 --> 01:32:42.000 Uh, what's the magnitude, frequency, and duration of that exposure? These are going to be really site-specific. 01:32:42.000 --> 01:32:48.000 But as Dave and Monica really highlighted well before us before, um, water is going to be the primary. 01:32:48.000 --> 01:33:04.000 Pathway of concern, so again, ingestion of potential drinking water, uh, 1-4 doxane, as Dave said, is unlikely to really volatilize out of the water. We have, um, low dermal absorption, so, um, it's really that direct ingestion, so one protoxyne's not dermally absorbed very well. 01:33:04.000 --> 01:33:16.000 Um, and given the fact that it can degrade under certain conditions, again, it's really its, um, presence in the water that's going to be the primary route. 01:33:16.000 --> 01:33:23.000 So, when you bring that all together, the site, again, describe the areas of uncertainty and variability in the risk characterization component. 01:33:23.000 --> 01:33:36.000 Think carefully about the toxicity evaluation, your exposure assumptions. Bring that all in together, and importantly, really make sure that you're clear, um, with your best professional judgment interpretation of cancer mode of action. 01:33:36.000 --> 01:33:43.000 Um, okay, so then moving on to ecological, um, from an ecological perspective. 01:33:43.000 --> 01:33:53.000 Um, the hazard identification's a little different. Again, we actually don't think that, uh, have no data to suggest that 1,4 vaccine is really very toxic to ecological receptors. 01:33:53.000 --> 01:33:58.000 Again, because of its potential presence in surface water, fish have been the most. 01:33:58.000 --> 01:34:09.000 Sensitive, um, species studied to date. Um, in mammals, we really don't even see effects until you're in the hundreds to thousands of milligrams per liter range. 01:34:09.000 --> 01:34:17.000 Um, and that would be, um… consistent with, sort of, what we understand about rapid metabolism and excretion. 01:34:17.000 --> 01:34:22.000 Um, one for duxane is generally not toxic to plants. It can be taken up from the roots. 01:34:22.000 --> 01:34:28.000 Um, but then, as mentioned earlier, it can vitalize from the foliage, so it's not really something that hangs around in the plants. 01:34:28.000 --> 01:34:34.000 What's really most important is when Protaxine does not bioconcentrate, so there's no bioconcentration, biomagnification. 01:34:34.000 --> 01:34:42.000 Bioaccumulation. None of… none of that stuff that we sometimes have to consider for other emerging contaminants that we all deal with. 01:34:42.000 --> 01:34:50.000 Um, that's not the case for one producine. Um, so it is metabolized, excreted, it doesn't bioaccumulate, there's no… 01:34:50.000 --> 01:34:58.000 Trophic libel, biomagnification, or secondary poisoning. We do have some ecological screening levels. 01:34:58.000 --> 01:35:06.000 Um, please feel free to go to the guidance document to get, sort of, the behind the details of how all of these were derived. 01:35:06.000 --> 01:35:13.000 But as you can see, they're all in the milligram per liter, or milligram per kilogram, if you're talking about sediment and soil. 01:35:13.000 --> 01:35:26.000 Level, so they're pretty high. Um, again, from an exposure assessment, it's the same thing. We're primarily going to be concerned about direct ingestion pathways, and most likely through the aquatic route. 01:35:26.000 --> 01:35:37.000 So, our aquatic species and perhaps consumption of water by wildlife would be the most, um, relevant pathways of concern for ecological risk. 01:35:37.000 --> 01:35:49.000 Generally, what I've seen in my experience is that, um, a screening-level risk assessment, so looking at your media and just doing a comparative of max concentration to any of those screening levels. 01:35:49.000 --> 01:36:01.000 Really is all that's required, and you can pretty quickly, um, maybe absent the… a direct spill or a highly contaminated area, but in most sites, a screening level risk assessment will check the box. 01:36:01.000 --> 01:36:12.000 And you don't have to consider ecological risk. All right, so then at the very end, there was communication toolbox that I promised to put in a plug for. 01:36:12.000 --> 01:36:16.000 The ITRC team that put this together several years ago now worked really hard. 01:36:16.000 --> 01:36:29.000 Um, to make sure that this toolbox and communication, um, guidance, although it was developed under the context for PFAS, really applies to any kind of emerging contaminant, where you might have a difference of opinion on risk. 01:36:29.000 --> 01:36:35.000 And how to communicate that effectively. And so it is applicable to one for a vaccine. The link is on the screen here for you. 01:36:35.000 --> 01:36:39.000 And I think, um, it's just a really great tool to help. 01:36:39.000 --> 01:36:46.000 Um, practitioners kind of understand how to better communicate when we do have differences of toxicity information. 01:36:46.000 --> 01:37:00.000 All right, so just my final slide in summary, then. Ecotox of 1-phrodoxane is low, it's not likely going to be a driver. Um, cancer risk for human health is the primary concern, especially for low-level, long-term exposures. 01:37:00.000 --> 01:37:13.000 The science is still evolving for exactly how one for dooxine causes cancer, so make sure whatever toxicity value you're using is consistent, not only with your legal and regulatory paradigm, but the best science, um, that's available at the time. 01:37:13.000 --> 01:37:18.000 And as always, uncertainties and limitations need to be fully communicated. 01:37:18.000 --> 01:37:26.000 I think with that, I turn it over to Fritz and Francisco to talk about, then, how you solve the problem. 01:37:26.000 --> 01:37:41.000 Ah, thank you so much, everybody. This is Fritz Krems with, uh, Trihydro Corporation, and thank you for sticking with us to the very end here, and Francisco and myself will get into treatment technologies. 01:37:41.000 --> 01:37:46.000 Uh, do I have… Do I have control here? 01:37:46.000 --> 01:37:57.000 Okay, here we are. So, we'll start by looking at our learning objectives, and these include understanding how, when, and why different technologies are appropriate. 01:37:57.000 --> 01:38:04.000 Reviewing various soil, groundwater, drinking water, and wastewater treatment technologies for 1,4-deoxin. 01:38:04.000 --> 01:38:14.000 Design considerations for well-established technologies, and identifying when certain technologies aren't appropriate for 1,4-dioxane treatment. 01:38:14.000 --> 01:38:21.000 We want to first introduce this figure, which you'll see throughout our presentation today. It's also a central part of our guidance document. 01:38:21.000 --> 01:38:29.000 You'll see that we have a 1,4-dioxine groundwater plume in orange, with several in-situ technologies listed down there. 01:38:29.000 --> 01:38:39.000 We also have some ex-situ treatment technologies listed alongside wastewater treatment and drinking water treatment. We'll touch on all of these today. 01:38:39.000 --> 01:38:47.000 Today, we'll be using a red, yellow, green stoplight motif to show how we've characterized these various technologies. 01:38:47.000 --> 01:38:58.000 Uh, red is a less effective technologies, which are those with negligible or limited capacity for one forward axion removal, either based on field demonstrations or theoretical considerations. 01:38:58.000 --> 01:39:06.000 Emerging options, in yellow, may be partially demonstrated or researched, typically those implemented at the bench or pilot scale. 01:39:06.000 --> 01:39:28.000 A fully demonstrated technologies in green are those that have been implemented or demonstrated under full-scale situations, which are typically well-documented. We'll focus primarily on fully demonstrated and emerging options, but we'll touch on some of the less effective technologies that could be potential pitfalls when 1,4-deoxin is present along with other chlorinated VOCs. 01:39:28.000 --> 01:39:35.000 You'll see the stoplight throughout the slide, so you can quickly identify what category a technology falls into. 01:39:35.000 --> 01:39:46.000 We've also broken down the technologies by where they may be best applied within the subsurface. The purple box shows the VEDO zone that includes various soil and soil vapor treatment technologies. 01:39:46.000 --> 01:39:52.000 In the groundwater plume, we have a source zone in pink with higher concentrations of 1,4-deoxane. 01:39:52.000 --> 01:40:00.000 Uh, then we show, uh, the groundwater plume, uh, with. Pink in higher concentrations, down gradient plume in green. 01:40:00.000 --> 01:40:07.000 Note that each of these technologies can have application in different areas of the subsurface. This graphic isn't meant to be limiting. 01:40:07.000 --> 01:40:16.000 As we talk through the treatment technology shown here, we'll briefly describe the technology, discuss how it applies to 1,4-dioxane, and identify special design considerations. 01:40:16.000 --> 01:40:32.000 We'll keep things at a high level for today, but the guidance document gets into more details. One last thing, the little post-it note that you see on the slides will help identify when we have a case study about a particular technology in the guidance document. 01:40:32.000 --> 01:40:44.000 We'll start with the VEDO zone and soil or soil vapor treatment technologies. As you heard in the Phaeton transport training, we've seen that there are a limited number of instances where soil or soil vapor treatment is needed for one Fort Axene. 01:40:44.000 --> 01:40:56.000 Typically, 1,4-axin will be transported into groundwater. However, in instances where one fortaxine was used directly or stored at a site, it's possible that it may remain in the VEDO zone. 01:40:56.000 --> 01:41:05.000 Also, it cites an arid environments might have residual 1,4-dioxane in soil, because there's not much precipitation to transport the 1,4-dioxane down to groundwater. 01:41:05.000 --> 01:41:12.000 Or because the groundwater may be very deep below ground surface. 01:41:12.000 --> 01:41:18.000 The VATOS zone has fully demonstrated emerging and less effective treatment technologies. 01:41:18.000 --> 01:41:25.000 The fully demonstrated technologies for VEDO zone treatment are standardized, regardless of whether it's 1,4-dioxine being removed or another compound. 01:41:25.000 --> 01:41:36.000 These include excavation, thermal desorption, solidification, and stabilization. Both oxenant soil blending and extreme SVE are approaches identified as emerging options. 01:41:36.000 --> 01:41:45.000 Extreme SVE differs from conventional SVE in that it typically includes heating of the subsurface and or higher pore volume exchange rates. 01:41:45.000 --> 01:41:56.000 There are a few less effective treatment technologies, including traditional SVE, bioventing, and biopiles. These aren't particularly effective due to the physical and chemical characteristics of 1,4-dioxin. 01:41:56.000 --> 01:42:02.000 As well as some of the limitations of most Indigenous microorganisms. 01:42:02.000 --> 01:42:10.000 Uh, now we switch gears into groundwater treatment. First, we'll start in the source zone and talk about treatment technologies that can be applied here. 01:42:10.000 --> 01:42:21.000 Just a reminder that these technologies could also be applied in the downgrading portion of the plume. They aren't meant to be limited to source zone treatment only. 01:42:21.000 --> 01:42:29.000 In situ thermal treatment can be used for 1,4-deoxane, and may be particularly helpful when it's present in a chlorinated solvent source area. 01:42:29.000 --> 01:42:36.000 The boiling point of 1-4-axane is higher than the chlorinated solvents, and it doesn't volatilize as well at ambient temperatures. 01:42:36.000 --> 01:42:43.000 However, heating the subsurface can help increase 1,4-dioxane volatility, and if heated enough, it will boil off. 01:42:43.000 --> 01:42:49.000 Different types of thermal treatment can be applied, including electrical resistive heating, thermal conductive heating. 01:42:49.000 --> 01:42:59.000 And steam-enhanced extraction. Each of these have their benefits and challenges. The biggest benefit of thermal treatment is that a large amount of mass can be removed over a short period of time. 01:42:59.000 --> 01:43:06.000 That's why we're highlighting it for source zone treatment. 01:43:06.000 --> 01:43:11.000 In such a chemical oxidation is another technology commonly considered for source area treatment. 01:43:11.000 --> 01:43:18.000 Different oxidants have varying strengths, as you can see from the list of standard oxidation potentials on the right-hand side. 01:43:18.000 --> 01:43:32.000 The larger table breaks down the common oxidants used to treat 1,4-dioxane, what the oxidant's physical state typically is, how long the oxidant lasts in the subsurface, and ability to be delivered to the subsurface via various methods. 01:43:32.000 --> 01:43:41.000 We've also tried to help identify which chemical species play a role in treatment of each chemical reagent using those colorful shapes that you see. 01:43:41.000 --> 01:43:51.000 Persulfate is a commonly used chemical accident for 1,4-dioxane treatment. It can be delivered as liquid sodium per sulfate solution, or as solid potassium persulfate. 01:43:51.000 --> 01:44:01.000 Persulfate requires an activation step to generate the most powerful. Reactive species, and the activator chosen will dictate what reactive species are generated. 01:44:01.000 --> 01:44:10.000 Common activators include alkaline solution, like sodium hydroxide, i.e. Base, various forms of iron, hydrogen peroxide, and heat. 01:44:10.000 --> 01:44:15.000 Depending on how it's being activated, persulfate can be delivered to the subsurface via direct push methods. 01:44:15.000 --> 01:44:25.000 Permanent injection wells, a slurry injection, or slow-release cylinders. Once there, persulfate can remain active in the subsurface on the order of weeks to months. 01:44:25.000 --> 01:44:35.000 If we hop down to the bottom of the table, we see that various forms of permanganate can be delivered to the subsurface in a similar manner, and can also remain reactive for months. 01:44:35.000 --> 01:44:45.000 Moving up a row, modified Fenton's reagent is a liquid injection based on hydrogen peroxide that has a faster reaction timeframe than persulfate or permanganate. 01:44:45.000 --> 01:45:00.000 And lastly, use of gas-based oxidants like ozone also have shorter reaction time frames, as well as different injection strategies, since gas distribution is a key component. 01:45:00.000 --> 01:45:12.000 One of the reasons why persulfate is used quite frequently for 1,4-dioxane treatment is because it can generate some very reactive species, like sulfate and hydroxyl radicals, both of which can react with 1,4-dioxane. 01:45:12.000 --> 01:45:21.000 Treatment of co-contaminants is an important consideration, with chlorinated ethanes. Being more difficult to treat than chlorinated ethanes. 01:45:21.000 --> 01:45:27.000 It's important to get the right oxidant dosing and activation method to get at those chlorinated ethanes. 01:45:27.000 --> 01:45:30.000 A lot of people start with bench testing for this reason. 01:45:30.000 --> 01:45:35.000 And just a reminder that while ISCO is commonly chosen as a source area treatment. 01:45:35.000 --> 01:45:42.000 It can also be applied further down gradient, perhaps in a permeable reactor barrier. 01:45:42.000 --> 01:45:51.000 A few things to consider with ISCO. It has been described as a contact sport. In order for it to work, the oxidant needs to come in contact with the contaminant. 01:45:51.000 --> 01:46:02.000 Depending on the subsurface conditions, you may want to choose an oxidant that will stick around for months, rather than weeks, and a delivery method that will get the oxidant where it needs to be in the subsurface. 01:46:02.000 --> 01:46:09.000 It's also important to understand the likelihood of the aquifer to backdiffuse contaminants into groundwater after the oxidant has worn off. 01:46:09.000 --> 01:46:14.000 The natural water quality is also an important consideration to understand for ISCO. 01:46:14.000 --> 01:46:20.000 Natural organic matter in the subsurface can scavenge the oxidant, meaning that higher dosing may be needed. 01:46:20.000 --> 01:46:28.000 Delivery of oxidant into the subsurface will temporarily change the redox conditions, which can lead to temporary metals mobilization. 01:46:28.000 --> 01:46:35.000 The type of accident used inherent subsurface conditions mean that various byproducts could form, some of which are regulated themselves. 01:46:35.000 --> 01:46:39.000 These are just more reasons to consider bench testing prior to field application. 01:46:39.000 --> 01:46:48.000 And before we get off this topic, I do want to point out that we have an ISCO case study in the guidance document. 01:46:48.000 --> 01:46:56.000 In situ metabolic bioremediation can also be a useful tool in the toolbox, particularly for source area treatment. 01:46:56.000 --> 01:47:05.000 Typically, when we think of bioremediation, we're thinking about metabolic bioremediation, i.e. Bacteria that make a living consuming target contaminants. 01:47:05.000 --> 01:47:13.000 If we think about petroleum hydrocarbons for a second, those microorganisms use the hydrocarbons and oxygen to generate energy and new biomass. 01:47:13.000 --> 01:47:26.000 It's the same for one forward axing. There are a handful of microbes that we know of to date that will utilize 1,4-dioxane and oxygen to generate energy in new biomass, while leaving only carbon dioxide behind. 01:47:26.000 --> 01:47:35.000 Based on our current understanding, they are aerobic bacteria and prefer to metabolize 1,4ioxane when relatively high concentrations of 1,4-dioxane are present. 01:47:35.000 --> 01:47:42.000 That's why this approach may be of interest for source area remediation. 01:47:42.000 --> 01:47:53.000 Because 1,4-axine metabolizers prefer higher starting concentrations, it's important to understand whether there's enough 1,4-dioxane in the subsurface to support this type of treatment strategy. 01:47:53.000 --> 01:47:59.000 It may be tougher to implement at downgrading portions of the plume where 1,4-deoxane concentrations are lower. 01:47:59.000 --> 01:48:10.000 Additionally, oxygen needs to be present. So if oxygen is not available naturally, then the treatment system will need to be engineered to deliver an adequate amount of oxygen into groundwater. 01:48:10.000 --> 01:48:24.000 Like I mentioned before, we currently only know of a few types of microorganisms that can degrade 1,4-dioxane through metabolic processes, so bioaugmentation may be necessary if those microbes aren't present in the subsurface already. 01:48:24.000 --> 01:48:38.000 The last word of caution with this approach is that high concentrations of some chlorinated solvents and some metals can inhibit the microbe's ability to degrade 1,4-dioxin. 01:48:38.000 --> 01:48:45.000 Now we'll move into discussing treatment technologies that are more commonly applied to the downgradient portion of the groundwater plan. 01:48:45.000 --> 01:48:57.000 These include both in situ and ex-situ treatment technologies. Just a reminder that these technologies can also be applied to other portions of the plume. 01:48:57.000 --> 01:49:09.000 With that, we transition into some in-situ treatment technologies, and start with phytoremediation, which is a fully demonstrated treatment technology that we happen to have a case study about in the guidance document. 01:49:09.000 --> 01:49:15.000 Well, there are several treatment mechanisms that can be involved with phytoremediation using trees. Phyto is. 01:49:15.000 --> 01:49:27.000 Phytoextraction is the dominant one at play for 1,4-dioxane. This is where 1,4-dioxane is pulled up through the roots of the trees and transpired into the atmosphere where it is destroyed by UV light. 01:49:27.000 --> 01:49:35.000 Phytoremediation is attractive because it's a relatively hands-off remedy, and it benefits from the high solubility of 1,4-dioxin in water. 01:49:35.000 --> 01:49:47.000 However, photoremediation can take longer than other in-situ treatment technologies, and the presence of deeper groundwater requires special design considerations. 01:49:47.000 --> 01:49:52.000 And this technology does require design and some of those considerations are listed here. 01:49:52.000 --> 01:49:57.000 First, it's important to use the right plants for the region in which the site is located. 01:49:57.000 --> 01:50:06.000 Phytoremediation is best employed when groundwater is less than 25 feet below ground surface, and the 1,4-dioxion impacts are within the top 5 feet of groundwater. 01:50:06.000 --> 01:50:15.000 However, use of engineered fighter remediation systems, like tree wells or solar-powered pumps, can be used to help reach deeper plumes. 01:50:15.000 --> 01:50:22.000 It's important to understand whether the transpiration rate of trees will be enough to counter the groundwater flux into the treatment area. 01:50:22.000 --> 01:50:26.000 This may start to dictate the number of trees and the potential spacing. 01:50:26.000 --> 01:50:37.000 And with that, I'll hand it over to Francisco for the second half of the remediation. 01:50:37.000 --> 01:50:50.000 Thank you very much, Fritz. All right, uh, so we have already talked about metabolic bioremediation in the context of source area treatment strategies. 01:50:50.000 --> 01:50:58.000 But now, we'll get into cometabolic bioremediation as a strategy that's typically employed downgrading of the plume. 01:50:58.000 --> 01:51:05.000 And cometabolic bioremediation, the microorganisms do not gain energy from using the 1-4 dioxane. 01:51:05.000 --> 01:51:08.000 In fact, it doesn't use the one for dioxin at all. 01:51:08.000 --> 01:51:15.000 It uses a primary substrate. Coupled with, uh, oxygen to generate energy and biomass. 01:51:15.000 --> 01:51:22.000 There's lots of primary substrates that can be used, including many of the alkane gases, like propane and ethane. 01:51:22.000 --> 01:51:29.000 Lucky for us, the enzymes that are produced as part of that process can also go onto the grade 1 for dioxide. 01:51:29.000 --> 01:51:36.000 Ultimately, to carbon dioxide. They can also degrade other constituents of concerns, like some chlorinated solvents. 01:51:36.000 --> 01:51:42.000 One nice thing about common metabolic bioremediation is that you don't have a concentration limitation. 01:51:42.000 --> 01:51:50.000 Like we've talked about for metabolic bioremediation. All you need is to have enough oxygen around, along with the permanent substrate. 01:51:50.000 --> 01:51:57.000 In the same place as one for dioxane. 01:51:57.000 --> 01:52:03.000 When engineering this type of treatment system, um. There are a few moving parts to consider. 01:52:03.000 --> 01:52:10.000 For example, enough oxygen and primary substrate need to be delivered to the subsurface, typically through sparging or gas-saturated water. 01:52:10.000 --> 01:52:19.000 There's a caption, too, where we don't want to give them too much of the primary substrate, because then the enzymes won't have a chance to go into the grade 1 for dioxin. 01:52:19.000 --> 01:52:24.000 So, it's a bit of a balance. Also, many of these primary substrates are flammable gases. 01:52:24.000 --> 01:52:29.000 Therefore, delivery systems need to be built with extra controls in place. 01:52:29.000 --> 01:52:32.000 The right microbes need to be present to do the work. 01:52:32.000 --> 01:52:40.000 And therefore, biommentation may be needed. They, uh, also likely need some macronutrients, like nitrogen and phosphorus. 01:52:40.000 --> 01:52:49.000 So those will need to be delivered into the subsurface. Like I mentioned before, cometabolic biodegradation can work for any starting concentration, one for dioxin. 01:52:49.000 --> 01:52:54.000 As has been shown to decrease concentrations to below 1 microgram per meter. 01:52:54.000 --> 01:53:04.000 It can also be used to create a chlorinated compounds, but there's a warning that high enough concentrations of some chlorinated compounds can actually inhibit biodegradation. 01:53:04.000 --> 01:53:09.000 We do have a fond case study that tracks this approach from bench skill testing all the way. 01:53:09.000 --> 01:53:18.000 To full-scale operation. 01:53:18.000 --> 01:53:28.000 So, when thinking about the automation processes relevant to one for dioxin, it's important to remind ourselves that it has a low heritage log constant and low KOC value. 01:53:28.000 --> 01:53:33.000 That means that volatilization and absorption to soil may not be the dominant attenuation mechanisms. 01:53:33.000 --> 01:53:40.000 Really, the relevant attenuation mechanisms for 1-4 dioxin include dilution, diffusion, and biodegradation. 01:53:40.000 --> 01:53:45.000 We've talked a lot about biodegradation in engineering systems, but now we're talking about natural systems. 01:53:45.000 --> 01:53:54.000 Luckily, we have both metabolic and cometabolic pathways available to us. In either case, the right microorganisms and oxygen need to be present. 01:53:54.000 --> 01:53:59.000 If we're evaluating the cometabolic pathway, then a permanent substrate also needs to be present. 01:53:59.000 --> 01:54:10.000 Uh, likewise, we need to make sure. That there are, uh, levels of chlorinated solvents or metals present that could inhibit the natural biodegradation. 01:54:10.000 --> 01:54:18.000 These are all the types of things that I would want to look for as part of a natural attenuation evaluation. 01:54:18.000 --> 01:54:25.000 Luckily, there is a growing arsenal of advanced analytical tools that we can use to evaluate natural automation mechanisms. 01:54:25.000 --> 01:54:31.000 These are similar to the tools that we use for evaluating other compounds, like chlorinated solvents. 01:54:31.000 --> 01:54:43.000 But have been tailored for one for dioxide. First up, uh, are the geochemical parameters. These can be used to confirm whether aerobic conditions are present, and if primary substrates. 01:54:43.000 --> 01:54:49.000 Are present that could foster comatabolic biodegradation. Next, we move on to microbial analysis. 01:54:49.000 --> 01:54:59.000 These include genetic targets designed to evaluate metabolic biodegradation of one protioxin, as well as targets designed to evaluate cometabolic biodegradation. 01:54:59.000 --> 01:55:08.000 Last is compound-specific isotope analysis, or CSIA. This is an analytical method that can demonstrate evidence of biodegradation. 01:55:08.000 --> 01:55:14.000 But it has limitations, particularly when lower concentrations of 1,4 dioxide are present. 01:55:14.000 --> 01:55:19.000 A word of warning, and as an industry, we're still developing these tools and learning how to best apply them. 01:55:19.000 --> 01:55:32.000 To evaluating natural attenuation of one for dioxin. Before we talk about some of the exito treatment technologies that are less effective against one for dioxin, I wanted to remind you. 01:55:32.000 --> 01:55:41.000 About some of the critical characteristics of one for dioxide. In particular, a reminder that 1 for dioxin has a low hemorrhage law constant. 01:55:41.000 --> 01:55:52.000 So it doesn't volatilize from water very much. Also, it has a low KUC value, which means it doesn't readily absorb the carbon. 01:55:52.000 --> 01:56:00.000 Similar to less effective ex-sito treatment technologies, we wanted to mention some of the less effective in-situ treatment technologies. 01:56:00.000 --> 01:56:06.000 Again, it's important to note that these technologies may still result in some treatment of amphotoxin. 01:56:06.000 --> 01:56:10.000 But they are not expected to meet targets over a reasonable timeframes. 01:56:10.000 --> 01:56:18.000 These technologies are commonly applied to chlorinated solvent plumes. So it's important to understand the limitations for 1-4 dioxin treatment. 01:56:18.000 --> 01:56:24.000 The low volatility of omphrotioxin makes air sparse, or SVE approaches less effective. 01:56:24.000 --> 01:56:33.000 Zero Valen iron may have some benefit in trading one for dioxin, but studies conducted to date indicate that the timeframes for this may be longer than desired. 01:56:33.000 --> 01:56:38.000 And we just spent some time talking about aerobic biodegradation of one for dioxin. It's important to note that. 01:56:38.000 --> 01:56:48.000 Anaerobic bioremediation strategies have not been shown. To have the same success. This is important, uh, because things like carbon software injections. 01:56:48.000 --> 01:56:55.000 Is very common for treatment of chlorine solvents. 01:56:55.000 --> 01:57:02.000 Now, similar to ISCO being a solid option for one per diox entrance in situ, advanced oxidation processes. 01:57:02.000 --> 01:57:13.000 Or AOPs are a commonly implemented approach for execute treatment. Again, similar to ISCO, different oxidants used in AOPs have varying amounts of destructive capability. 01:57:13.000 --> 01:57:20.000 You'll notice that most of the AOPs listed on this table utilize ultraviolet light in combination with various accidents and or catalysts. 01:57:20.000 --> 01:57:29.000 To generate reactive species. All of these AOPs can effectively destroy one product action and blur its ethians. However. 01:57:29.000 --> 01:57:34.000 Those that use ozone and hydrogen peroxide can also destroy some of the chlorine ethanes. 01:57:34.000 --> 01:57:40.000 That may be also present. Aops are typically used in conjunction with pump and treat systems. 01:57:40.000 --> 01:57:46.000 This can include groundwater extraction and treatment in the very classical sense, or in a more dynamic. 01:57:46.000 --> 01:57:55.000 Recirculation approach. Well, some of the considerations for AOPs are similar to ISCO, some are different. 01:57:55.000 --> 01:58:03.000 Aops are known for being, uh, energy intensive, and may require a large use of chemical oxidants. 01:58:03.000 --> 01:58:07.000 Similar to ISCO, matrix diffusion can play a role in concentration rebound. 01:58:07.000 --> 01:58:12.000 Particularly for more, uh, traditional. Compensate configurations. 01:58:12.000 --> 01:58:23.000 The characteristics of the infant water are also very important to understand. It may be necessary to conclude… to include other treatment processes before or after the IOP system to address things like. 01:58:23.000 --> 01:58:35.000 Natural recurring iron or generation of bromate. Aops can readily scale up or down, and can be retrofitted onto existing pump-petrate systems, if olford dioxin is found to be present after. 01:58:35.000 --> 01:58:41.000 Initial design. And, uh… 01:58:41.000 --> 01:58:47.000 Um, and we have a great case study in the guidance document about how impacted groundwater can lead. 01:58:47.000 --> 01:58:56.000 Crooked water providers, augmenting existing systems with an AOP to treat sulfur dioxide. 01:58:56.000 --> 01:59:01.000 Bioreactors are an emerging option being considered for execute treatment as well. 01:59:01.000 --> 01:59:14.000 Metabolic bioreactors built off of the same process as it was discussed for in-situ metabolic bioremediation. They can be useful when warfar dioxin concentrations are high, and require the presence of oxygen and the right microorganisms. 01:59:14.000 --> 01:59:23.000 While there have been lab and pilot-scale demonstrations. Our team hasn't, uh… wasn't aware of full-scale applications of this type of approach yet. 01:59:23.000 --> 01:59:28.000 However, cometabolic bioreactors have been used at both lab scale and full scale. 01:59:28.000 --> 01:59:34.000 The bioreactor treatment lens and leachet at the Lowry landfill is probably the longest-running combinable. 01:59:34.000 --> 01:59:45.000 Bioreactor, treating water dioxin in the presence of tetrahydrofurin. There are several things to consider when designing bioreactor systems to treat one for dioxin. 01:59:45.000 --> 01:59:54.000 The concentration of one for dioxin present, the effluent treatment requirements, and the potential presence of co-contaminants may guide the decision of whether to design a metabolic. 01:59:54.000 --> 02:00:02.000 For metabolic bioreactor. The necessary treatment floor rates and hydraulic retention time may dictate the type of bioreactor configuration chosen. 02:00:02.000 --> 02:00:07.000 It may be necessary to deliver oxygen, nutrients, or a primary substrate into the bioreactor. 02:00:07.000 --> 02:00:14.000 Lastly, sitting with the right microbi community and establishment of proliferation of that community is key. 02:00:14.000 --> 02:00:27.000 To maintaining the effectiveness of the reactor. We've already learned that one for dioxin has a low searching coefficient. This means that under many circumstances, most orbits are not particularly effective at removing one for dioxide. 02:00:27.000 --> 02:00:38.000 However, there is a subtle resin specifically designed to remove. One for dioxide from water. Ambersorb has been applied at full scale, and we have a case study about that in the guidance document. 02:00:38.000 --> 02:00:47.000 As with any sort of design, the size of vessels, number of vessels, the hydraulic rotation time, and the breakthrough monitoring all need to be specifically designed to site conditions. 02:00:47.000 --> 02:00:51.000 One of the benefits of EmberServe is that it can be regenerated using steam. 02:00:51.000 --> 02:00:56.000 However, then the one for dioxidants needs to be treated in that waste stream. 02:00:56.000 --> 02:01:05.000 So, as with other servant technologies, you only remove one for dioxide from water, you don't destroy it. 02:01:05.000 --> 02:01:14.000 With that in mind, we did want to touch on some of the less effective acuteotreatment technologies, mostly because these technologies are commonly employed for treatment of other compounds. 02:01:14.000 --> 02:01:18.000 Including the chlorinated solvents, one for dioxin may be co-located with. 02:01:18.000 --> 02:01:28.000 Note that while these technologies might be less effective at removing one for dioxin from water, they may still provide upwards of 50% removal when these technologies are applied. 02:01:28.000 --> 02:01:35.000 Eritin is, uh, one that is commonly used for removing fluorinated solvents from water, but won't remove much of Wulfur dioxin at the same time. 02:01:35.000 --> 02:01:42.000 Ion exchange or reverse osmosis are technologies that haven't shown a higher one for dioxide removal due to the size and charge of the molecule. 02:01:42.000 --> 02:01:50.000 Liquid phase granular activated carbon, or LGAC, is another. Technology company used to remove chlorinated solvents from water. 02:01:50.000 --> 02:01:56.000 But due to 1,4 dioxins, low absorption coefficients, use of LGAC. 02:01:56.000 --> 02:02:03.000 Needs to, um, be considered as well, but it needs to be monitored. 02:02:03.000 --> 02:02:13.000 Uh, really carefully. 02:02:13.000 --> 02:02:24.000 So, now, uh, we're gonna switch to, uh. To trigger water, uh, and wastewater treatment. 02:02:24.000 --> 02:02:35.000 So, uh, conventional drinking water and wastewater treatment, um. It provides a certain removals of one for dioxin, but similar to what we. 02:02:35.000 --> 02:02:43.000 Have been, uh, mentioning about the performance and… how well one for dioxin can be removed. There's some limitations. 02:02:43.000 --> 02:02:50.000 Uh, you do have some steps, like aerobic biological treatment, disinfection, and filtration, which. 02:02:50.000 --> 02:02:57.000 May provide some, uh, partial removal. Ovam for dioxin, however, uh, these are gonna be… 02:02:57.000 --> 02:03:02.000 Somewhat limited, especially with this infection, even though you use some oxidants. 02:03:02.000 --> 02:03:08.000 Uh, you're not gonna get, um… that great removal as compared to advanced fixation processes. 02:03:08.000 --> 02:03:13.000 So, you really wanna… Uh, keep an eye on, uh. 02:03:13.000 --> 02:03:18.000 How far those cons… those, uh, treatment technologies can get you. 02:03:18.000 --> 02:03:29.000 As, you know, as he was saying before. These technologies that were developed to remove other contaminants, you're gonna get some, uh, dioxin contaminants, but the same principles that we've discussed so far. 02:03:29.000 --> 02:03:36.000 Apply for commercial review water treatment, uh, as well, so… 02:03:36.000 --> 02:03:43.000 And like I mentioned, the inclusion of advanced turban options, especially advanced oxidation, it's really the safe bet. 02:03:43.000 --> 02:03:53.000 When it comes to these, uh, treatment systems. Um, even though biological destruction, uh, degradation works as well, the safest bet is going to be. 02:03:53.000 --> 02:04:01.000 The advanced succulation processes that we've discussed. 02:04:01.000 --> 02:04:06.000 So, uh, we can discuss residential drinking water treatment as well. As it was mentioned before. 02:04:06.000 --> 02:04:14.000 Um, uh, LGAC is a limited approach, uh, for conventional water treatment, however. 02:04:14.000 --> 02:04:23.000 In a residential shelter treatments, it may work. Mainly because of the scale and the flow rates that you're dealing with, and um… 02:04:23.000 --> 02:04:29.000 It's important to say that, uh, if designed properly, this LGAC can be effective for, uh. 02:04:29.000 --> 02:04:37.000 The removal of one for dioxin. However, the LGAC vessels. Have to be staged, you know, in the basement or a shed of the house. 02:04:37.000 --> 02:04:43.000 Um, but breakthrough monitoring and changes should be scheduled to maintain a high level of security. 02:04:43.000 --> 02:04:51.000 Um, you also have to note that things like small carbon filters for pictures and refrigerator of faucets do not provide the same level of protection. 02:04:51.000 --> 02:05:07.000 Likewise, commonly used particular filter, water softening devices, and UV disinfection systems will not adequately remove ofer dioxide from the water before use. 02:05:07.000 --> 02:05:16.000 And… oh, nice, that one slide. So, in summary, uh, there are many options for warm products in treatment for soil, soil vapor. 02:05:16.000 --> 02:05:25.000 Front water, drinking water and wastewater. Different options should be applied under different situations, and selection should be based on site-specific information. 02:05:25.000 --> 02:05:34.000 Don't forget that there are several technologies that are used for treatment of other common compounds, like chlorinated solvents, that aren't as effective at treating one for dioxide. 02:05:34.000 --> 02:05:40.000 We hope that this presentation was really helpful in providing an overview of 1-4 dioxin treatment technologies. 02:05:40.000 --> 02:05:47.000 Please remember that you can visit the web-based One for Dioxin guidance document for more details on all of these technologies. 02:05:47.000 --> 02:05:53.000 Thank you. 02:05:53.000 --> 02:05:59.000 All right, thank you, Francisco, and we've now reached our final Q&A portion of the training. 02:05:59.000 --> 02:06:10.000 Um, and the end of the training. So we just have a couple questions in the chat, and then I will send… say some final words, and um… that'll be the end of it. 02:06:10.000 --> 02:06:17.000 So, for Janet, what were the values presented for California in the map that you presented? 02:06:17.000 --> 02:06:29.000 Sure, I can answer that. Um, so California does have. Some regulatory water quality levels. They're not drinking water standards, so they're not yet the state's MCLs, but they have. 02:06:29.000 --> 02:06:39.000 Um, a notification level and what they call a public health protection level. Uh, their notification level is just one part per billion, and their public health protection level is. 02:06:39.000 --> 02:06:46.000 3, and then they also use EPA's Health Advisory level at 35 part per billion as their, um. 02:06:46.000 --> 02:06:58.000 Source removal or sort of response level. So those are the California numbers currently on the books, but as I mentioned, we're anticipating them to move forward with their, um, setting state drinking water standards, so an MCL. 02:06:58.000 --> 02:07:09.000 So we'll see a public health goal draft, hopefully, sometime this year, and then they'll move through the process of setting an MCO. 02:07:09.000 --> 02:07:17.000 All right, thank you, Janet. And one last question. What percentage or level of 1,4-dioxane in groundwater. 02:07:17.000 --> 02:07:21.000 Should regulators be concerned with? 02:07:21.000 --> 02:07:25.000 Um, I'll address that one as well. I think importantly, um. 02:07:25.000 --> 02:07:34.000 As everyone should know, every… site is under specific and different regulatory paradigms, so it depends on your state or federal or national. 02:07:34.000 --> 02:07:45.000 Um, sort of regulatory status. Um, and those numbers shown on the map for groundwater vary across the U.S. And across our neighbors to the north. 02:07:45.000 --> 02:07:56.000 Um, and range from 0.3% to 50 part per billion. Epa's health advisory is based on their interpretation of the science for cancer risk, and that's at 35. 02:07:56.000 --> 02:08:05.000 Part per billion. Um, but of course, our RSL is set at the 10 to the minus 6 level, so that's 0.35. 02:08:05.000 --> 02:08:10.000 Part per million, that RSL is sort of a trigger, then, for additional investigation, risk assessment. 02:08:10.000 --> 02:08:13.000 And all the other things that go under the CERCLA process. 02:08:13.000 --> 02:08:26.000 Um, so it's not a de facto cleanup level. Um, but those are the various numbers, so, um, specific to what a regulator, quote-unquote, should be concerned with. It really does depend on. 02:08:26.000 --> 02:08:38.000 Their specific program. Um, the scenario, and all of that is assuming that the groundwater is a drinking water source, that it's potable. 02:08:38.000 --> 02:08:43.000 All right, thanks again, Janet, and those are all the open questions we had in the Q&A box. 02:08:43.000 --> 02:08:58.000 Um, so thank you all for attending our training today, and a big thank you to our expert trainers for being here and for their contribution to the ITRC document. We would like to hear back from you, so please be sure to fill out the online feedback form that's linked on this last slide. 02:08:58.000 --> 02:09:05.000 Filling out the feedback form and certifying that you participated will allow you to receive a certificate of completion by email. 02:09:05.000 --> 02:09:10.000 I linked the clue-in page for feedback form earlier in the chat in this training today. 02:09:10.000 --> 02:09:20.000 If you need further clarification on the answers, or would like to ask more questions, feel free to email us at itrc at itrcweb.org. 02:09:20.000 --> 02:09:40.000 And we will follow up with our trainers to get your questions answered. Thanks again, everyone