WEBVTT 00:00:00.000 --> 00:00:00.000 And with that, it is my pleasure to welcome you officially to today's internet seminar. 00:00:00.000 --> 00:00:00.000 You should be joining us for our session in vitro bio accessibility essay or IBBA sampling guidance update. 00:00:00.000 --> 00:00:00.000 This is part one and we'll talk more about the additional sessions later on in our broadcast. Our session today has been sponsored by EPA's bioavailability technical review work group. 00:00:00.000 --> 00:00:00.000 In just a moment, I'll turn it over to your primary speaker who's also being joined by a number of panelists today but before I do that I'd like to walk through a series of reminders as your technical moderator. 00:00:00.000 --> 00:00:00.000 Joining you from EPA's Technology Innovation in Field Services Division. Again, my name is Gene Balance and I'll be here throughout the entire broadcast. 00:00:00.000 --> 00:00:00.000 And as a moderator, I wanted to remind everyone of just a few things. First and foremost, we have created a unique seminar homepage for today's session. 00:00:00.000 --> 00:00:00.000 The URL is shown in red on the slide and is available from today forward. This website is the same place you went to to register. 00:00:00.000 --> 00:00:00.000 It's the same place I sent you to and reminder emails, it's the same place you went to check in and it is the same place I will send you. 00:00:00.000 --> 00:00:00.000 After the webinar is over to download materials and share your feedback. You're welcome to bookmark this website because there's important information there including info on our speakers, links to download their presentation content as well. 00:00:00.000 --> 00:00:00.000 As browse do a series of related resources on our topic today. 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You'll have access to visual controls under the view and view options buttons in the upper center and upper right to adjust the size and scale of content. 00:00:00.000 --> 00:00:00.000 And then the live closed captioning or CC icon is at the bottom to turn on transcription services. 00:00:00.000 --> 00:00:07.878 And of course that all important Q&A button to send in your questions and comments in writing. So that very quick set of technical reminders, I think we are prepared to begin today's session. 00:00:01.687 --> 00:00:18.687 I can see your very first speaker. Clay Nelson already on camera. So Clay, I'm going to turn the view over to your video source and I'll have you turn on your presentation content. 00:00:17.834 --> 00:00:26.834 So as Clay is calling up the presentation materials on his end. I'll just remind everyone who's connecting. 00:00:24.765 --> 00:00:30.765 Go ahead and send a quick message into that Q&A. Let clay know how excited you are to be here. 00:00:29.387 --> 00:00:38.387 And how very interested you are in the topic today. And Clay is I'm looking at some of these messages coming in from your colleagues who are joining here. 00:00:33.009 --> 00:00:46.009 It looks like we have a very excited audience who are ready to take this session on in. And Clay, I do have confirmation. 00:00:47.953 --> 00:00:51.953 We have good visuals on your slides. So I'll turn the floor over to you to begin the presentation. 00:00:50.016 --> 00:01:04.016 Thanks, Gene. Appreciate it. Welcome everybody to today's introductory training session where we will provide a general overview of assessment of relative bioavailability of soil arsenic and lead. 00:01:04.401 --> 00:01:07.401 For use in human health risk assessment. 00:01:06.805 --> 00:01:15.805 Today's training will cover several topics including summarizing new guidance to support the assessment of soil arsenic and lead. 00:01:14.610 --> 00:01:21.610 Relative bioavailability. Hereafter, comely referred to by its acronym, RBA. 00:01:20.629 --> 00:01:30.629 When assessing risk to human health at soil arsenic or lead contaminated sites. We will provide rationale to support the use of RBA data. 00:01:29.625 --> 00:01:42.625 In human health risk assessments and guidance on how to measure and incorporate RBA data. We will discuss data quality objectives and sample planning when using RBA data. 00:01:43.744 --> 00:01:47.744 Finally, we provide resources for additional assistance. 00:01:48.381 --> 00:01:57.381 For more information about topics discussed in today's training session, You can email the current technical review work group, bioavailability committee co-chairs. 00:01:57.696 --> 00:02:08.696 Whose emails are provided here. Please note that BAC co-chairs may change with time. You can also email the BAC directly at BA Help at EPA. 00:02:10.165 --> 00:02:23.165 Gov. Or call the hotline at (866) 282-8622. We also encourage you to browse the BAC website, which can be accessed through the link shown here. 00:02:23.982 --> 00:02:31.982 Today's training is the first of 4 planned training sessions. Covering topics related to soil metal bioavailability. 00:02:33.125 --> 00:02:43.125 And his application to human health risk assessment of arsenic and lead contaminated soils. Where today we will be providing a general introductory overview. 00:02:43.281 --> 00:02:53.281 To start, what is bioavailability and why is it important? Stated succinctly, the total concentration of arsenic or lead in soil. 00:02:52.834 --> 00:03:02.834 May not provide an accurate measure of risk. Rather, it is the bioavailable fraction of our snicker-leden soil that poses risk to human health. 00:03:01.666 --> 00:03:10.666 Where bioavailability in today's context is generally defined as the fraction of total soil arsenic or lead. 00:03:11.785 --> 00:03:18.785 That upon ingestion. Is absorbed across the gut wall. And available for distribution in the body. 00:03:18.405 --> 00:03:28.405 Even cowboys in the Wild West understood that lead and arsenic come in different forms and that these different forms varied with respect to risk to human health. 00:03:27.685 --> 00:03:33.685 And while I do live in Texas, a cowboy accent's not something that I wish to mimic today. 00:03:34.480 --> 00:03:41.480 So I will instead pause for a few seconds to let you read the cartoon. Using whatever accent you wish. 00:03:51.719 --> 00:04:02.719 This image provides another example to help us understand soil metal bioavailability. The candy in the upper left hand portion of the graphic shows a peppermint. 00:04:02.279 --> 00:04:11.279 With equal proportions of red and white. Whereas the candy below it is only 25% red and 75% white. 00:04:10.606 --> 00:04:21.606 Imagine the colors in these candies represent the bio available in red. And nonbi available in white. Fractions of arsenic and soil. 00:04:21.366 --> 00:04:28.366 Note how the 2 hypothetical containment contaminated soils to picked it here by the brown rectangles. 00:04:27.678 --> 00:04:35.678 Have different numbers of candies representing different total soil arsenic concentrations of 80 parts per 1 million. 00:04:34.495 --> 00:04:46.495 And 160 parts per 1 million respectively. Recall that the total concentration of arsenic or lead in soil may not provide an accurate measure of risk. 00:04:45.995 --> 00:04:59.995 It is the bioavailable fraction rather that more accurately determines risk. With this in mind, if you ignore the non-bi available portions shown in white, and sum up only the bioavailable fractions in red. 00:05:00.267 --> 00:05:08.267 Both soils have an equal concentration of 40 parts per 1 million bioavailable arsenic per kilogram of soil. 00:05:07.892 --> 00:05:15.892 In the left soil, you would say that soil arsenic bioavailability was 50% of the total concentration. 00:05:16.513 --> 00:05:24.513 In the soil on the right, you would say that soil arsenic bio availability. Was only 25% of the total concentration. 00:05:25.512 --> 00:05:34.512 Let's move to a bit more technical discussion. Biovailability can be quantified in 2 ways. 00:05:33.946 --> 00:05:42.946 Absolutely, or relative by availability. We're absolute by availability is defined as the fraction of an ingested dose. 00:05:42.025 --> 00:05:54.025 That is absorbed into the human body. Relative bioavailability, on the other hand, is defined as the ratio of the absolute bioavailability of a contaminant. 00:05:52.676 --> 00:06:00.676 In this case of lead or arsenic in soil. To the absolute bioavailability of that same contaminant. 00:06:00.417 --> 00:06:10.417 In the standard used to develop the toxicity value for that contaminant. This is the definition applicable to the remainder of today's presentation. 00:06:10.384 --> 00:06:17.384 Where we discuss RBA as being equal. To the absolute bioavailability of arsenic or leaden soil. 00:06:18.699 --> 00:06:22.699 Divided by its absolute bioavailability in drinking water. 00:06:23.791 --> 00:06:37.791 This image represents how RBA data is used to adjust the total soil metal concentration. Both arsenic and lead have a default soil RBA value of 60%. 00:06:36.801 --> 00:06:46.801 This is a generalized assumption based on pooling, historical observations made at many contaminated sites throughout the US. 00:06:46.299 --> 00:06:54.299 Using default RBA values enables us to quickly adjust total soil arsenic or lead concentration measurements. 00:06:53.995 --> 00:07:04.995 By a fraction of 0 point 6. Or 60%. To provide a default estimate of the bioavailable concentration of lead or arsenic and soil. 00:07:05.948 --> 00:07:09.948 This can be done without the need to collect any additional data. 00:07:09.532 --> 00:07:22.532 Alternatively, site specific RBA values, which can vary from the default assumption of 60%, can be estimated using simple, validated methods. 00:07:22.220 --> 00:07:34.220 Use of site-specific RBA estimates may result in either higher or lower RBA adjusted soil metal concentrations, then use of default values. 00:07:33.466 --> 00:07:46.466 For arsenic, we expect in most cases More specifically, 95% of the time. Use of site-specific RBA estimates will yield lower RBA values. 00:07:46.159 --> 00:07:58.159 Than use of default assumptions. For lead, we expect that about 50% of the time. Site specific RBA estimates will be lower than default assumptions. 00:07:59.526 --> 00:08:07.526 These differences are due to the different approaches that were used to determine default RBA assumptions for arsenic and lead in soil. 00:08:07.026 --> 00:08:14.026 Importantly, use of site-specific RBA data will always result in lower. 00:08:12.716 --> 00:08:22.716 Or in rare instances, equivalent. Bioavailable soil concentrations. When compared to the total soil concentration. 00:08:23.973 --> 00:08:27.973 And they will enable more accurate estimates of exposure risk. 00:08:30.176 --> 00:08:41.176 So how is risk adjusted for bioavailability? Bioavailability values, whether based on default values, or on site specific assessments. 00:08:40.820 --> 00:08:49.820 Can be incorporated into lead risk models. Including the integrated exposure uptake biokinetic model. Or i. 00:08:48.345 --> 00:08:56.345 EUBK for short. And the adult lead methodology. Or ALM. 00:08:55.723 --> 00:09:03.723 For arsenic, they can adjust toxicity values, including the reference dose, or cancer slope factor. 00:09:03.223 --> 00:09:11.223 RBA adjusted soil arsenic or lead concentrations can also be compared directly to soil screening levels. 00:09:13.165 --> 00:09:20.165 And has already been noted, site-specific RBA data can be used to replace default RBA assumptions. 00:09:22.276 --> 00:09:37.276 To further highlight the value of assessing bioavailability, Here's a specific example of how site-specific RBA data may be used in a site assessment to more accurately and cost effectively meet cleanup goals. 00:09:36.889 --> 00:09:45.889 These numbers represent real-world data from an actual soil arsenic contaminated site located in the US. 00:09:45.272 --> 00:09:58.272 Initially, before site specific bioavailability data was generated, It was determined that 117 acres of soil needed to be remediated at the site. 00:09:58.460 --> 00:10:04.460 EPA's Office of Research and Development conducted a site-specific bioavailability assessment. 00:10:04.304 --> 00:10:12.304 And found that only 30% of the soil arsenic was bioavailable. This enabled a reduction in cleanup levels. 00:10:12.104 --> 00:10:23.104 From 117 to 88 acres of soil that required remediation. Saving approximately 9 million dollars in cleanup costs. 00:10:24.616 --> 00:10:33.616 This example highlights a general rule of thumb. The lower the site specific RBA value. The more cost effective it is to meet site cleanup goals. 00:10:35.136 --> 00:10:46.136 So how is RBA directly measured? Several animal models have been used in the past to generate direct measures of arsenic or lead RBA. 00:10:46.389 --> 00:10:56.389 He's include rats, mice, monkeys, and swine. These animal bioassays rely on measurements of letter arsenic and blood, tissue, or urine. 00:10:56.206 --> 00:11:02.206 To measure the fraction of an ingested dose. That was absorbed across the gut wall by the animal. 00:11:03.324 --> 00:11:08.324 Enabling a direct in vivo measurement of bioavailability. 00:11:07.767 --> 00:11:20.767 Of the animal models that have been used, juvenile swine were historically the most commonly used. However, more recently, EPA developed a high throughput, more cost-effective mouse model. 00:11:19.725 --> 00:11:30.725 For measuring soil, arsenic, and lead RBA. The mouse model has been shown to produce similar measurements of RBA to that of the Swine assay. 00:11:30.347 --> 00:11:39.347 A more detailed discussion of the use of animal models to directly measure RBA. Will be presented in Training Session 4. 00:11:40.692 --> 00:11:43.692 Currently scheduled for April first of this year. 00:11:46.382 --> 00:11:54.382 For RBA data to be routinely and cost effectively incorporated into site assessments of containment, contaminated soil. 00:11:53.900 --> 00:12:07.900 Alternative to use of animal models is essential. Fortunately, EPA has validated an inexpensive fast and accurate analytical method that estimates RBA. 00:12:06.484 --> 00:12:16.484 By measuring the amount of lead or arsenic and soil. That dissolves from the soil matrix when exposed to gastrointestinal like conditions. 00:12:15.937 --> 00:12:26.937 Now known as EPA Method 1340. Method 1340 measures the in vitro bioaccessible fraction of arsenic or lead in soil. 00:12:26.090 --> 00:12:37.090 Or IVBA for short. Where bio accessibility refers to the fraction of total arsenic or lead that is soluble in a gastric like extraction medium. 00:12:37.093 --> 00:12:45.093 This extraction medium is made using simple chemicals in a laboratory. Is designed to mimic key parameters of the human stomach. 00:12:46.532 --> 00:12:56.532 Notably, running the extraction and in a in a acidic environment. In a water bath or air inubator heated to human body temperature. 00:12:56.781 --> 00:13:08.781 These IVBA assays are low cost and high throughput. And have been shown to be reliable predictors of RBA because they have a strong correlation with RBA measurements. 00:13:08.180 --> 00:13:19.180 As shown in the figure here on the right. This figure was taken from a study of 84 arsenic contaminated soils that varied in soil type. 00:13:20.182 --> 00:13:35.182 Contaminant source, and arsenic concentration. Note that IVBA measurements were able to account for roughly 87% of the observed variability in measured RBA across the 84 soils assessed. 00:13:35.014 --> 00:13:42.014 Multiple regional EPA and commercial labs are already experienced in running EPA Method 1340. 00:13:40.514 --> 00:13:49.514 And new labs can acquire the equipment and reagents necessary to run this method. Easily and inexpensively. 00:13:48.900 --> 00:13:58.900 Use of bioavailability data fits with other soil assessment best practices. Including planning and development of data quality objectives. 00:13:58.214 --> 00:14:12.214 Implementing, implementing efficient sampling protocols. Like incremental composite sampling. And using soil s to a specific particle size to better represent human exposure. 00:14:13.719 --> 00:14:25.719 And again, use of IVBA assays enables RBA estimates to be easily and cost-effectively incorporated decide assessment of arsenic or lead contaminated soils. 00:14:27.762 --> 00:14:38.762 Understanding the advantages of including assessment of RBA as part of your overall site assessment. Is critical to its widespread adoption and increased use. 00:14:38.025 --> 00:14:49.025 Perhaps the most important benefit is increased confidence in the accuracy of the risk assessment. In many cases, enabling substantially lower cleanup costs. 00:14:47.813 --> 00:15:08.813 Reducing the likelihood of making a cleanup decision error regarding the need for or extent of remediation. Given these benefits, current Office of Land and Emergency Response Guidance Recommends the RBA be assessed at all soil arsenic and lead contaminated sites. 00:15:08.329 --> 00:15:18.329 A new EPA led policy is expected to require assessment of LED RBA to support human health risk assessments at lead contaminated sites. 00:15:19.573 --> 00:15:31.573 Importantly, new tools and methods, many of which have been developed or validated by EPA scientists, enables more efficient and cost-effective means for assessing RBA at sites. 00:15:33.972 --> 00:15:42.972 So this concludes the first half of today's presentation. We're not going to pause for our first of 2 Q&A sessions and I'll hand controls back to Gene. 00:15:40.733 --> 00:15:50.733 Alright, thank you so very much. So this is a gentle reminder to the audience. You'll be submitting your questions and comments into the Q&A window. 00:15:50.334 --> 00:15:55.334 If you haven't done that yet now is the Q&A window. If you haven't done that yet, now is the time. 00:15:54.039 --> 00:16:00.039 We still have plenty of time to accept some additional questions. We still have plenty of time to accept some additional questions, but Clay, we still have plenty of time to accept some additional questions, but Clay, we do have some that came in already. 00:15:58.789 --> 00:16:10.789 And then we'll keep going depending on how many more come in here. So a quick clarification. 00:15:59.655 --> 00:16:03.655 So I think I'm gonna start with a handful that we've gotten into the queue already. 00:16:08.484 --> 00:16:21.484 When you're talking about the site specific RBA, this work is only applying to lead in arsenic or RBA, this work is only applying to lead in arsenic or there are other metals that this would apply to. 00:16:25.168 --> 00:16:31.168 So is there a one of the EPA panelists that would like to answer that question? 00:16:31.753 --> 00:16:35.753 Sure, Clay. This is Karen Bradam. I can try to answer that question for you. 00:16:34.488 --> 00:16:44.488 Right now we only have an in vitro in vivo correlation that we've determined for arsenic and lead at this time because that's the most there's the most commonly occurring. 00:16:43.204 --> 00:16:56.204 Contaminants found at national priority listing sites. So the methods that we are discussing here are currently only approved for Arsenic and LAN. 00:16:55.115 --> 00:17:06.115 Okay, thank you. Another question. Can we always use this site specific RBA or do they need to justify its use first? 00:17:12.545 --> 00:17:15.545 Again, Karen, I'll differ to you. 00:17:20.020 --> 00:17:29.020 You can use a site specific RBA. You don't need to justify it to use, as Clay's previous slide. 00:17:26.701 --> 00:17:33.701 I don't know if we can go back play, but you mentioned in one of your previous slides it is now recommended in the guidance document. 00:17:32.697 --> 00:17:45.697 To collect RBA for arsenic and lead sites. And as you mentioned here, the new EPA life policy is likely to recommend collecting this information as part of the new policy to support. 00:17:46.201 --> 00:17:48.201 Human health risk assessments. 00:17:46.717 --> 00:18:01.717 And I'll just add that the second half of the presentation will discuss a little bit more about the importance of proper planning and data quality objectives when including our BA data inside assessments. 00:18:00.974 --> 00:18:09.974 So Karen or Sydney, correct me if I'm wrong. But I would assume that so long as you're following that guidance, you can always use site specific. 00:18:10.380 --> 00:18:14.380 RBA estimates. 00:18:13.988 --> 00:18:22.988 Yeah, I will pop in just with the caveat that this ultimately turned into a manager decision if they don't wanna be using it. 00:18:19.728 --> 00:18:36.728 So as a risk assessor or as a project manager, you should be collecting RBA and then present that as used in the risk assessment, but ultimately that becomes a management call if they don't want to use site specific. 00:18:37.552 --> 00:18:47.552 Okay. Alright, thank you. And you all have just addressed another question. Why not always use the sites specific RBA then if it's usually lower. 00:18:46.559 --> 00:18:59.559 So thank you for tackling that one too. We do have another question here. Can method 1340 be used to measure RBA of drinking water or is that only applicable for soils? 00:18:59.763 --> 00:19:02.763 It is only applicable for soils. 00:19:00.913 --> 00:19:11.913 Okay. And then Clay, can you go back to slide number 8? And the attendee was asking if you could just further clarify. 00:19:07.719 --> 00:19:23.719 What this illustration is trying to depict. Perhaps if you could use a specific example, I think they're they're seeing both site specific RBAs above and below that default RPA. 00:19:24.913 --> 00:19:27.913 So if you could maybe go through this illustration one more time, that'd be helpful. 00:19:25.591 --> 00:19:38.591 Sure, so just for a simple example, if you were assessing lead at a site and your total soil lead concentration was 100 parts per 1 million. 00:19:38.229 --> 00:19:48.229 You could adjust that total concentration for bioavailability. Using either the default RBA assumption of 60%, which is this middle arrow. 00:19:48.418 --> 00:19:56.418 In which case your bioavailable soil lead concentration would be 60% of 100 or or 60. 00:19:53.997 --> 00:20:06.997 Alternatively, you can do a site specific assessment of led by availability. In that case, with lead. 00:20:06.372 --> 00:20:20.372 There is about a 50 50 probability based on historical data that your site-specific measured RBA value will either be lower than, or or higher than the default assumption of 60%. 00:20:19.468 --> 00:20:25.468 And so if you apply the site-specific measurement, let's just say it's 30%. 00:20:25.124 --> 00:20:38.124 BA. Then your bioavailable soil lead concentration would be lower than both the total soil concentration and the default RBA assumption that. 00:20:37.344 --> 00:20:49.344 Alternatively could have been used. Alternatively, if your site specific measurement of lead RBA was higher than 60%, anywhere from 61% to 100%. 00:20:48.875 --> 00:21:01.875 Then use of site specific RBA would result in a higher RBA adjusted soil lead concentration than use of the default assumed value for RBA of 60%. 00:21:01.447 --> 00:21:08.447 And then I noted again that. If we were to instead talk about arsenic instead of lead. 00:21:08.066 --> 00:21:21.066 We would expect instead of a 50 50 probability of having a RBA adjusted soil concentration either greater than or below use of default values. 00:21:17.557 --> 00:21:29.557 For our snake we'd expect 95% of the time. That use of site specific RBA data would result in a lower RBA adjusted soil concentration. 00:21:30.583 --> 00:21:45.583 And again, that that difference is based on the methods and approaches that were used to define default RBA assumptions which differed between lead and arsenic and I cannot go into the reasons for that difference. 00:21:46.986 --> 00:22:06.986 So thank you. Quickly going back to that 60% bioavailability. One of the participants asked that since you mentioned the default 60% bioavailability is based on historical monitoring throughout the US. 00:21:47.079 --> 00:21:49.079 I'm just aware that that is the case. 00:21:47.090 --> 00:21:53.090 Okay. The attendee, thank you very much. That's exactly the explanation they were looking for. 00:22:07.520 --> 00:22:15.520 Do you have any comparison to other countries or do you think that that default, 60% could be generally applied worldwide? 00:22:14.502 --> 00:22:22.502 And I'll hand this over to Karen, but I realized I assumed it was in the United States, but that could actually be incorrect. 00:22:21.509 --> 00:22:30.509 So Karen or Sidney, do you I know Karen you were involved with some of that development of the default assumptions. 00:22:23.522 --> 00:22:25.522 Okay. 00:22:30.673 --> 00:22:33.673 Was did that just include data? In the US. 00:22:33.416 --> 00:22:41.416 Yeah, good question. No, actually that's 60% actually included some soils from contaminated sites in Australia. 00:22:41.604 --> 00:22:49.604 Those were our only other country locations that we included in that 60% evaluation. 00:22:48.739 --> 00:22:58.739 Okay. Alright. How about this next one? Does this method apply only to exterior scenarios. 00:22:58.519 --> 00:23:03.519 For example, would interior dust with elevated lead levels be applicable? 00:23:08.238 --> 00:23:10.238 Karen, do you wanna take a step at that one? 00:23:13.624 --> 00:23:21.624 Sure, right now we're only, using and have, validated this method for soils at this particular time, not interior dust. 00:23:19.438 --> 00:23:38.438 Okay. Okay. Alright, we're gonna go back to that default led bioavailability and one of the attendees is questioning why wouldn't the default led bioavailability be higher if 50% of the sites might have higher bioavailability, what is the reasoning behind that decision? 00:23:39.457 --> 00:23:50.457 That is a great question and. Again, I do not know the answer to that question as I previously stated, but, if one of the other panelists would like to comment. 00:23:52.530 --> 00:23:58.530 I can, this is Gary, Diamond. The D. 00:23:59.404 --> 00:24:06.404 Is the default, to the. Seize me. 00:24:09.090 --> 00:24:17.090 Yeah, the default value is input to the IDVK model. Which uses, central estimates. 00:24:17.047 --> 00:24:27.047 Alright, thank you, Gary. Alright, just a few more questions here and I do want to remind the audience you can continue to send your questions into the Q&A. 00:24:22.118 --> 00:24:32.118 I did notice a few hands that went up. Typically it's a lot faster for us to take questions. 00:24:29.612 --> 00:24:37.612 If they come into the QA. So if you've been trying to type in the chat and it's not opening for you or it's not working. 00:24:35.609 --> 00:24:46.609 That's the way it's supposed to work for today the chats disabled you can see things I send you but you can't write in the chat but you can type questions and comments into that QA. 00:24:46.110 --> 00:24:54.110 So let me turn back to that Q&A and very quickly, Clay, can you remind everyone what is the default? 00:24:50.537 --> 00:24:57.537 Bioavailability for arsenic and soil? 00:24:57.532 --> 00:25:07.532 60%. Alright, and then another question. Are there site conditions that could change the site specific? 00:24:57.735 --> 00:25:00.735 60%, which is true for both arsenic and lead. 00:25:00.621 --> 00:25:11.621 RBA in the future that could change the site specific RBA in the future that we should be thinking about? 00:25:11.215 --> 00:25:20.215 Sure. I'll, the short answer is yes. There are a lot of factors that influence site-specific bioavailability. 00:25:20.566 --> 00:25:33.566 That includes the local soil geochemistry, which is not a static thing. Soil chemistry can change over time and that change could influence change in bioavailability or bio-accessibility. 00:25:32.616 --> 00:25:40.616 Also the, source of the lead or arsenic contamination can have an influence on that. 00:25:41.662 --> 00:25:51.662 And there are other factors that well as well. I won't go into every single one. But the short answer is yes, this is a value that can change over time. 00:25:52.534 --> 00:26:00.534 Okay. If performing an IVBA is not possible, is it feasible to refine the RBA using a mineral form. 00:26:04.166 --> 00:26:07.166 That's probably a good question for Karen or Brad. 00:26:09.679 --> 00:26:21.679 Well, we've certainly looked at different mineral forms and found that they have a arsenic or lead, different accessibility and by abilities. 00:26:19.825 --> 00:26:23.825 So that could be possible if that's the only information that you have. 00:26:24.998 --> 00:26:37.998 Okay. Okay. And next question, is regarding state regulations. How would an RBA inform a state promulgated standard as a cleanup standard? 00:26:37.004 --> 00:26:45.004 So that is a good question. That is a good question that's difficult to answer today. 00:26:40.313 --> 00:26:57.313 The answer is it depends upon that particular state method. We will be getting into that a little bit more today and I believe we'll be tackling that in more depth. 00:26:56.530 --> 00:27:07.530 At a later date, but just to generally try to answer that question today. As we will talk about here in the second half of today's presentation. 00:27:07.067 --> 00:27:21.067 You have a choice to either apply RBA data to adjust the cleanup or action level. And in which case how you would do that will be dependent upon how you develop that cleanup or action level. 00:27:13.152 --> 00:27:30.152 You know, Gary referenced the IE UBK. Lead model and that is one of several models that are used to develop action or cleanup levels. 00:27:28.911 --> 00:27:40.911 Alternatively, you can use bioavailability data to adjust the total soil. Metal concentration, compared that to a cleanup or action level. 00:27:39.496 --> 00:27:57.496 That doesn't isn't based on Considering bioavailability. And we will discuss that quite a bit in a future training session, I believe training training session 3 will go into a lot more detail about those different. 00:27:58.608 --> 00:28:03.608 But it's a very important, very good question. So I don't know if any of the other panelists want to expand upon that. 00:28:06.573 --> 00:28:31.573 So thank you, Clay. Just very quickly confirming. Resources. So I think what the one participant is asking if There is a place where all of these variations or particular compounds and the methods that might apply to them, where can they find these? 00:28:07.054 --> 00:28:13.054 Not seeing any other mics coming open. Now we did get a thank you from the participant on that answer. 00:28:33.332 --> 00:28:38.332 And I think you shared that website near the beginning, but perhaps you could. Return to that link. 00:28:36.828 --> 00:28:39.828 Sure. That is. 00:28:44.404 --> 00:28:46.404 I guess. Well, here we go. 00:28:44.655 --> 00:28:46.655 There we go. Yeah. 00:28:46.284 --> 00:28:52.284 So the, this is the. Technical review work group, bi availability committee's website. 00:28:48.087 --> 00:28:50.087 Okay. 00:28:53.680 --> 00:28:57.680 Okay. Okay. 00:28:54.066 --> 00:29:09.066 Here and I assume Gene that we can link this in the chat as possibly as well as obviously. Everyone will get a recording of this so if they don't have time to jot this down today They, it will be available. 00:28:59.838 --> 00:29:01.838 Yep. 00:29:07.082 --> 00:29:17.082 Yes, alright, so, have taken that website and put it back into the meeting chat for everyone. It was also listed on the seminar homepage and I'll cover that at the end of the session today. 00:29:16.165 --> 00:29:26.165 But I am seeing questions again. Are there RBAs for lead and arsenic minerals and sources for different chemical forms? 00:29:26.489 --> 00:29:33.489 Could we use that data instead of the default? Again, where are they gonna find it? And I'm gonna assume we're pointing them back to that website. 00:29:32.024 --> 00:29:42.024 I'm going to assume that I don't know if that information is available in the website. 00:29:37.277 --> 00:29:47.277 I think If you wanted to look at that, the more appropriate place would be in the peer reviewed literature. 00:29:47.373 --> 00:30:05.373 Karen, would you agree with that? And then I don't know if EPA has developed specific guidance yet on the process that they would recommend using if you were to to adjust the default assumption based solely on having mineralogy. 00:29:48.281 --> 00:29:50.281 Okay. 00:30:06.979 --> 00:30:10.979 Our speciation data but not have measurements of ipba. 00:30:09.792 --> 00:30:26.792 The first part is there is a good bit of information about any understanding we had about mineral forums in the guidance documents that you provided clay in your in your presentation. 00:30:10.128 --> 00:30:16.128 I can answer the first part of that question, but I might defer to Sydney or Gary for the second part. 00:30:27.747 --> 00:30:33.747 So if we had any understanding of arsenic and lead metrology, we tried to include that in those guidance documents. 00:30:34.521 --> 00:30:47.521 Hey, I wanted to add. The mineral form that you may have as a source may not adequately represent what's in the soils. 00:30:42.076 --> 00:30:54.076 And the neurology of the source may change over time as a result of being exposed in the environment. 00:30:58.228 --> 00:31:07.228 So that would be one reason why it may not be a 00:31:05.552 --> 00:31:12.552 Alright, thank you. And Brad, just a quick note. I don't think the mic is coming in the best. 00:31:11.251 --> 00:31:16.251 I'll work with you to see if we can swap out to a different microphone for you in the background, but I did catch that. 00:31:13.386 --> 00:31:24.386 So thank you. Alright, Clay, if it's okay, I'm just gonna take one or 2 more questions and then we'll carry on with the presentation. 00:31:25.626 --> 00:31:27.626 Sure. 00:31:25.682 --> 00:31:31.682 Can you confirm does the bio of available fraction equal the soluble fraction? 00:31:32.155 --> 00:31:49.155 No. So The. Soluble fraction will depend upon. What the extraction medium that was used if you're following EPA method 1340 that's a very specific extraction medium. 00:31:49.141 --> 00:31:58.141 I mean, you'll get a measurement of in vitro bio accessibility, which again is a measurement of solubility in a specific extraction medium. 00:31:57.401 --> 00:32:04.401 But then you will need to convert that to a measurement of RBA. And that's where you get into use of these. 00:32:06.220 --> 00:32:14.220 Validated linear regression models. Where if you get a measurement of 60% IVBA, can you see my cursor? 00:32:13.619 --> 00:32:23.619 If you let's just say you got a measure of 60% IVBA. You would convert that to a measure of relative bioavailability. 00:32:14.984 --> 00:32:16.984 Yes, we can. 00:32:22.692 --> 00:32:37.692 That would approximately be, let's just call that somewhere between 45 to 50% relative bioavailability which is ultimately the number that you will use as your adjustment in your risk assessment. 00:32:38.190 --> 00:32:42.190 So they aren't equivalent, they are just correlated. 00:32:41.128 --> 00:32:52.128 Okay. Okay. Alright, and then, last question I'm gonna take now, although there are some other questions in the queue, we can come back to them later. 00:32:51.244 --> 00:32:57.244 So again, if you're in the middle of typing a question, gated in, you can keep going and we will be pausing again. 00:32:58.080 --> 00:33:06.080 But this last question. Can you just in general say, in which cases? Is the IVBA recommended. 00:33:06.011 --> 00:33:16.011 I think the general recommendation is it's always recommended. And there may be reasons why you don't. 00:33:15.094 --> 00:33:23.094 Directly measure ipba be a collection and analysis of samples collected from the contaminated, contaminated site. 00:33:24.432 --> 00:33:26.432 Whether that's. 00:33:26.073 --> 00:33:38.073 You know, cost or other factors. May perhaps Sydney or Karen might have a better example of specific situations where it may not be. 00:33:37.764 --> 00:33:44.764 As highly recommended for lack of a better word, but I think in general it's always recommended. So. 00:33:45.586 --> 00:33:47.586 It 00:33:48.210 --> 00:33:58.210 Okay. Alright, I do not see anybody else coming off of mute. So Clay, I think just in the interest of time, let's carry on with the presentation. 00:33:57.135 --> 00:34:05.135 I do see some other questions coming in and just I will thank the audience. We will pause again. So keep those questions and comments coming in. 00:34:05.771 --> 00:34:15.771 Alright, thanks, Jean. So let's switch gears just a little bit now and discuss essential planning procedures when RBA data are to be used. 00:34:07.831 --> 00:34:09.831 And Clay, I'll turn the floor back to you. 00:34:14.888 --> 00:34:23.888 As part of the site assessment. Systematic planning is standard for collection of all data, including RBA data. 00:34:22.481 --> 00:34:31.481 Data quality objectives for measuring total arsenic or lead in soil. Should include discussion of how RBA data will be used. 00:34:31.118 --> 00:34:38.118 Including whether default RBA assumptions will be used. Or if site-specific RBA will be estimated. 00:34:40.182 --> 00:34:44.182 Be a measurement of IVBA in accordance with EPA Method 1340. 00:34:45.317 --> 00:34:54.317 In these next few slides, we're going to dive deeper into the primary EPA guidance document for sample collection. 00:34:53.194 --> 00:35:03.194 When IVBA data is to be collected and analyzed. This document is entitled Guidance for Sample Collection for in vitro bio accessibility assay. 00:35:04.809 --> 00:35:10.809 For arsenic and lead in soil and applications of relative bioavailability data in human health risk assessment. 00:35:11.188 --> 00:35:24.188 The purpose of this guidance is to update previous 2015 guidance to more thoroughly address application of arsenic and lead RBA data to risk assessments. 00:35:24.004 --> 00:35:36.004 To better assist risk assessors and risk managers in collecting and using RBA data, to promote consistent application of RBA data across regions. 00:35:38.379 --> 00:35:48.379 To improve accuracy of soil arsenic and lead risk assessments. And finally, to increase the cost effectiveness of risk assessment and associated risk management. 00:35:48.621 --> 00:36:00.621 The 2021 guidance discusses the importance of systematic planning and development of data quality objectives. To ensure data collection will support decision needs. 00:36:00.152 --> 00:36:15.152 With an emphasis on study designs and sampling plans that use appropriate statistics and proper data application. Such systematic planning can be used for both future soil sampling efforts. 00:36:16.839 --> 00:36:22.839 And for assessment of archived soils when performing a retrospective RBA assessment. 00:36:26.234 --> 00:36:39.234 This slide describes the overall organization of the 2021 guidance document. The guidance is split into 10 sections that include overall purpose, organization and terminology. 00:36:38.741 --> 00:36:49.741 Rationale for collecting RBA data. A section on laboratory methods. Application of RBA data to human health risk assessments. 00:36:48.477 --> 00:36:57.477 Systematic planning for RBA data collection. And discussion of sample collection, equipment, and handling. 00:36:57.093 --> 00:37:05.093 Quality control, and important health and safety topics. Note the color coding of this slide. 00:37:05.901 --> 00:37:18.901 Sections in black denote information that was included in the original, 2,015 guidance. Whereas sections in blue denote revised information and those in red denote new information. 00:37:20.213 --> 00:37:31.213 The next few slides go into more detail about new sections of the guidance. Section 4 discusses laboratory methods for measuring RBA. 00:37:30.546 --> 00:37:46.546 Including references to where to find more information on animal models. Used to directly measure RBA. A description of EPA method, 1340, the validated essay used to measure in vitro bio accessibility. 00:37:47.769 --> 00:37:59.769 Arsenic and leaden soil. And a discussion of the regression equations for arsenic and lead used to convert IVBA measurements derived via Method 1340 to estimates of RBA. 00:38:03.412 --> 00:38:13.412 Section 5 of the guidance discusses how to apply RBA data to human health risk assessment. Including RBA adjustments to bioavailability parameters. 00:38:13.100 --> 00:38:21.100 And lead risk models. Soil exposure point concentrations. Soil contaminant daily oral intakes. 00:38:21.223 --> 00:38:30.223 Or soil risk based screening or action levels. Note that RBA adjustments can be made to any one of these parameters. 00:38:29.939 --> 00:38:36.939 However, in most, if not all instances, Adjustments should only be applied to one parameter. 00:38:37.442 --> 00:38:41.442 Not multiple times to multiple parameters. 00:38:43.567 --> 00:38:55.567 Section 6 details planning for collection of RBA data. Including discussions of data quality objectives. Retrospective RBA assessments of archived soil samples. 00:38:54.969 --> 00:39:06.969 Evaluation of RBA data accuracy. Selection of appropriate statistics. Estimation of a site wide RBA value using data for multiple decision units. 00:39:07.665 --> 00:39:23.665 Use of a conceptual site model to inform sampling. Use of soil concentration data to select samples for IVBA measurement and information on mineralogy, including speciation, to support selection of RBA samples and methods. 00:39:26.734 --> 00:39:37.734 Appendix A of this guidance document presents critical information to help estimate the number of samples needed for RBA assessment to meet data quality objectives. 00:39:37.292 --> 00:39:50.292 Analysis presented in this appendix assume that sample and data collection needs are for hypothesis testing. To determine whether or not the estimated mean RBA adjusted soil concentration. 00:39:51.544 --> 00:39:54.544 Or contaminant exceeds a specified action level. 00:39:53.733 --> 00:40:06.733 And for information presented in this appendix may also be applicable to evaluation of data quality objectives when our BA data is used to adjust risk-based action or cleanup levels. 00:40:05.854 --> 00:40:14.854 Derived using the IE UBK model. The adult lead methodology or other parameters listed here. 00:40:15.650 --> 00:40:26.650 The appendix includes lookup tables for sample numbers needed to achieve decision confidence objectives. For both discrete and incremental composite sampling approaches. 00:40:26.901 --> 00:40:39.901 Information presented in Appendix A will be supported by a web-based tool. That enables the user to quickly and easily estimate whether a given sampling plan meets decision confidence goals. 00:40:39.381 --> 00:40:50.381 Without requiring the user to have a detailed understanding or mastery of technical statistics. The tool will be presented in the upcoming Training Session 3. 00:40:51.921 --> 00:40:54.921 Currently scheduled for March 18 of this year. 00:40:54.937 --> 00:41:01.937 Finally, the 2,021 EPA guidance document includes a series of attachments listed here. 00:41:02.306 --> 00:41:09.306 Including frequently asked questions. Descriptions of calculations and presentation of case studies. 00:41:11.005 --> 00:41:17.005 I'm going to pause just to allow you to quickly look through. These attached examples. 00:41:24.971 --> 00:41:32.971 For additional guidance, both including and in addition to information discussed today, Please refer to the following reports. 00:41:36.970 --> 00:41:39.970 And additional reports are listed here. 00:41:44.196 --> 00:41:55.196 And as a reminder, for more information on topics presented in today's training session, Please contact BAC Cochairs or email or call the TRW BAC hotline. 00:41:55.297 --> 00:41:59.297 And again, we encourage you to browse the BA. BAC website at the link shown here. 00:41:59.801 --> 00:42:09.801 Building on today's initial overview training, 3 additional trainings are planned. These trainings will go into more detail about many of the topics presented today. 00:42:09.043 --> 00:42:18.043 Tensative dates and topics for these trainings are listed here. And you can contact the BAG C co-chairs to learn more. 00:42:20.001 --> 00:42:28.001 And this concludes the presentation portion of today's training session. I will now hand it back over to Gene for the second round of QA. 00:42:26.584 --> 00:42:34.584 All right, thank you so much. So Clay, we do have another healthy queue of questions that built up. 00:42:31.771 --> 00:42:39.771 I will continue to invite our participants. We have plenty of time for additional Q&A with our panelists and presenter. 00:42:35.639 --> 00:42:54.639 So please continue to type your messages into the Q&A. If you have no additional questions, you can also send a message like that that you have no questions into the Q&A just to help us engage if we're meeting everybody's needs. 00:42:52.787 --> 00:43:00.787 I'll also invite my panelists to come on camera if they can. So make it a little bit faster and getting some of those responses out. 00:43:00.654 --> 00:43:11.654 Cause some of these questions may involve some back and forth and actually I'm looking here at the question and Gary, if it's okay with you, I think I'm gonna send one your way first. 00:43:10.369 --> 00:43:16.369 So we'll give Clay a brief minute here. So let me bring you up here to the spotlight. 00:43:15.409 --> 00:43:21.409 And Gary, I'm gonna read this question out loud. Is it a little bit longer than some of the other ones? 00:43:21.749 --> 00:43:31.749 But this first question, states that it was mentioned that site-specific value RBAs can be used at arsenic and lead contaminated sites. 00:43:31.323 --> 00:43:45.323 The participant goes on to say that they're not sure if this question will be covered later, but the IV IV validation and the regression equations were developed for a specific range of soil concentrations in soil types. 00:43:44.824 --> 00:43:57.824 So they ask, can you comment on the lower concentration range used in the IVV validation? And if the RVA would be over or under predicted at that lower concentration range. 00:43:58.622 --> 00:44:08.622 And then there's a third part. Does EPA accept site specific RBA outside of the lower soil concentration range that was used in the IVIV validation. 00:44:08.845 --> 00:44:17.845 Yeah, so, I'm going to, there's different. Aspects to this question. 00:44:16.711 --> 00:44:28.711 One is, the limits of the soil concentration needed for the IVVA. Defer that to Karen, but. 00:44:28.421 --> 00:44:38.421 Regarding, soil concentrations and their effect on RBA. For arsenic, we, looked at that question. 00:44:36.548 --> 00:44:47.548 In the, validation data set, which consisted of some 80 plus samples collected from all over. 00:44:47.095 --> 00:44:55.095 Various types of sites. mining, smelting, pesticides, etc. 00:44:54.425 --> 00:45:04.425 And there was no relationship between concentration and RDA. That's for a broad sample of. 00:45:04.393 --> 00:45:16.393 Of a collection of samples, from various sites within a site, however. They could very well be a relationship between concentration and RBA because concentrations. 00:45:15.676 --> 00:45:29.676 Might vary geographically. And which may mean that, at different concentrations, there might be different sources of latter arsenic in the soil or different. 00:45:30.622 --> 00:45:34.622 Soil characteristics that might affect RVA. 00:45:34.487 --> 00:45:44.487 As to whether or not EPA would accept. Rba measurements outside the range. 00:45:42.718 --> 00:45:54.718 I'm gonna leave that for someone at EPA to answer. And again, maybe Karen can speak to, the concentration limits for the actual. 00:45:57.164 --> 00:46:03.164 Thank you. 00:46:00.181 --> 00:46:14.181 Sure, thank you, Gary. So we have tested a different variety of limits. The real limitation for testing those lower concentrations for arsenic and lead comes into a analytical challenge when we're trying to test. 00:46:13.739 --> 00:46:25.739 Whether it's the IVBA, accessibility, if there's really low concentrations or also in the mouse assay where we're testing the tissues to look at those really lower concentrations. 00:46:24.867 --> 00:46:30.867 We have tested some as low as, you know, background concentrations in a number of cases. 00:46:30.180 --> 00:46:38.180 As for the last question, I'll just refer to Sydney maybe, about site specific outside the lower range. 00:46:39.979 --> 00:46:53.979 I'm not sure that I have anything to add to that. We have had cases where IT is all the way down by 10% and it just, you know, it's an inverse relationship. 00:46:40.227 --> 00:46:42.227 Do you have any additional input there? 00:46:54.418 --> 00:47:06.418 So as your IDBA goes up or down, you know. The higher IVA, the lower your clean up was gonna go so again this kind of goes back to 00:47:07.700 --> 00:47:17.700 You can present it a certain way as a risk assessor and show them what the data is showing but the ultimate decision of what your cleanup goal will be is going to be a management decision. 00:47:16.758 --> 00:47:23.758 And I'll just add to that. And again, Karen, correct me if I say anything that. 00:47:23.071 --> 00:47:33.071 Is wrong or you disagree with but EPA method 1340 does list macimum soil concentrations for arsenic and I believe for lead as well. 00:47:34.732 --> 00:47:55.732 That can be used in the assay. Believe the main reason for that doesn't have anything to do with its correlation to RBA data, but based on the soil solution ratio used, if there's If the soil is too concentrated, you may get saturation issues that aren't reflective of the true solubility of letter arsenic in the soil. 00:47:55.395 --> 00:48:02.395 That's right, Clay. There are upper limits. I'm sorry. I was actually referring to the lower limits when someone asked that question. 00:48:04.823 --> 00:48:10.823 There are uproar limits and those are detailed in method 1340 and it is due to saturation. 00:48:08.152 --> 00:48:19.152 Alright, you are getting many thanks from the attendees on this very detailed response. So, relay that they appreciated it and found this very helpful. 00:48:18.328 --> 00:48:25.328 Alright, I'm gonna turn to our next question. There are a handful of people who are asking about media. 00:48:25.005 --> 00:48:34.005 So we have one attendee who notes that they are brand new to this field and they're just learning about lead contamination in the environment. 00:48:35.260 --> 00:48:41.260 And they wonder should the RBA be applied to a wetlands contaminated site with arsenic or lead? 00:48:46.770 --> 00:48:50.770 Karen or Gary, I'll defer to you on that question. 00:48:51.223 --> 00:48:58.223 We have not tested wetlands and we have also not tested air or water. This is specifically a soil method that was developed. 00:48:59.420 --> 00:49:01.420 Okay. 00:49:00.359 --> 00:49:08.359 Correct, I'm wrong, but if they're talking about soils in wetland conditions, we have I believe some of the soils that were used. 00:49:07.653 --> 00:49:16.653 Or at least assessed included soils that may be saturated, you know, may be under hydric conditions like that of a wetland. 00:49:15.537 --> 00:49:28.537 And I think. So I think believe that's been looked at, but I don't know if there's specific guidance on soils that are in you know in a wetland or hydric type of condition. 00:49:29.755 --> 00:49:35.755 The, IVB, the, 1340 has been used, to assess. 00:49:34.788 --> 00:49:50.788 A beach sediments, not saturated with water, but sediments that might be periodically saturated, but at the time they were sampled were dry. 00:49:51.776 --> 00:49:58.776 So I know of at least one site where that was done and the information was used to 00:50:01.065 --> 00:50:07.065 To estimate the RVA, adjusted concentrations and used in the human health risk assessment. 00:50:08.682 --> 00:50:10.682 Okay. 00:50:08.810 --> 00:50:10.810 To my knowledge. 00:50:12.509 --> 00:50:23.509 In the validation of the. That's the 1340 for lead. And arsenic there were no Sediment samples. 00:50:25.774 --> 00:50:31.774 I agree, Gary. I was referring to the validation. We did not have any wetlands included in the validation portion. 00:50:31.548 --> 00:50:34.548 And I agree with that. That's absolutely. 00:50:32.561 --> 00:50:38.561 Okay. And then again, just circling back to confirm. There's some people are still asking about media. 00:50:38.792 --> 00:50:45.792 Can you ever use the RBA when the media is water or air. 00:50:45.748 --> 00:50:57.748 Well, I'll start and if any of the panelists want to expand upon that. EPA Method 1340 is specific to soil and that's what's been tested and validated. 00:50:57.390 --> 00:51:11.390 In terms of correlating with RBA data. Could it be used in water? I think hypotheticalically it could, but EPA hasn't done that. 00:51:11.327 --> 00:51:20.327 If you recall from a previous slide we talk about relative bioavailability as being defined as the absolute bioavailability of that contaminant. 00:51:19.916 --> 00:51:36.916 In the relevant source to that. As was used to develop the Toxicity standard. So in the case of arsenic I believe the toxicity standards were based on arsenic in water. 00:51:34.466 --> 00:51:44.466 So I don't know that A relative by availability. Assessment would, would be of as much interest in that example. 00:51:45.848 --> 00:51:47.848 As would be in the case of soil. 00:51:49.097 --> 00:52:06.097 Okay. Alright. Let's take a look at some other questions about the RBA and a few individuals have asked about the presence of other compounds that could influence the ERBA. 00:52:04.561 --> 00:52:11.561 So one attendee wanted to know if the presence of antimony would influence the arsenic RBA or cleanup value. 00:52:13.100 --> 00:52:20.100 I'll let any of the panelists expand upon this, but I believe the answer is it could. 00:52:19.282 --> 00:52:28.282 Depending upon the element, obviously, Speciation is important. And Redox chemistry is important in determining. 00:52:27.655 --> 00:52:38.655 A bioavailability. So, That being said, it's a very, very complex system, so I don't know. 00:52:37.907 --> 00:52:45.907 How much you could tease out something like Antimony does X or Y to arsenic bioavailability just to give an example. 00:52:46.550 --> 00:52:54.550 I think the answer is going to be it depends on an immeasurable other number of factors that are also at play in many cases. 00:52:54.656 --> 00:53:02.656 Okay. And so then in general, the presence of other metals or organics and soil can affect the RBA. 00:53:02.290 --> 00:53:12.290 Certainly there are correlations that have been measured and observed and published in the literature. You know, a high presence of iron or aluminum. 00:53:09.155 --> 00:53:11.155 Okay. 00:53:14.449 --> 00:53:24.449 May have a general trend that you'd expect to see. In terms of arsenic or led bioavailability, but I don't think you can say it's always going to be the case in every soil. 00:53:23.376 --> 00:53:28.376 Okay, does the guidance acknowledge that possibility? 00:53:30.064 --> 00:53:35.064 That's a question for EPIs. Karen. 00:53:33.997 --> 00:53:46.997 Oh, the guidance strongly recommends measuring it. Rather than trying to guess what. Many, many factors in the site, including other contaminants, might do it. 00:53:45.550 --> 00:54:09.550 To affect the there are some instances, some conditions, where we know. That the IVBA assay doesn't correlate very well with RVA because of certain substances in the soil, the only one that's discussed in the guidance is Soils that have been treated with high levels of phosphate. 00:54:10.786 --> 00:54:12.786 Okay. 00:54:13.445 --> 00:54:22.445 As an amending agent to lower RPA. But Karen, perhaps you can have other. Amplify on that. 00:54:19.432 --> 00:54:26.432 I agree with your, assessment, Gary. I think testing is most, most important to see what's actually there. 00:54:26.313 --> 00:54:35.313 There is some guidance, about testing in the, 2,021 guidance document that Clay has highlighted in his slides. 00:54:38.259 --> 00:54:40.259 So I would refer to that for additional details. 00:54:39.374 --> 00:54:51.374 Okay. Alright. Lay, let's go to slide 22 and one of the attendees is asking if you can elaborate on the notes on that slide that only one adjustment should be made. 00:54:50.531 --> 00:54:53.531 And not more. 00:54:53.057 --> 00:55:01.057 I will do so. Sure. And then, but before I do so, I will say this is. 00:55:00.401 --> 00:55:13.401 A topic that we get into quite a bit in training session 3. But Generally speaking, It would be inappropriate to apply RBA data. 00:55:05.937 --> 00:55:07.937 Okay. 00:55:12.497 --> 00:55:36.497 To adjust both the Action level and the total soil concentration. So for example with lead. If you were to have a site specific RBA measurement, you could choose to either apply that to adjust the cleanup level, for example, applying it to the IE UBK model. 00:55:36.253 --> 00:55:45.253 Or you could use it to adjust the total soil concentration but you should not Use it twice to adjust both parameters. 00:55:46.627 --> 00:55:48.627 That would be inaccurate. 00:55:48.690 --> 00:55:57.690 Okay. Alright, so let's go back to a question on work, with the TRW. 00:55:55.684 --> 00:56:06.684 Is there any current work by the TRW to develop in vitro methods to measure bioavailability of other inorganics or dioxin in soil. 00:56:08.011 --> 00:56:15.011 Or perhaps to develop default soil. They say ABA, but I think they mean RBA values for these constituents. 00:56:19.559 --> 00:56:22.559 Karen or Derry or Sydney? 00:56:21.438 --> 00:56:28.438 Sure, I'll take that one. So currently there are new plans, for the TR W. 00:56:25.840 --> 00:56:44.840 If there's interest in that, I would encourage our regional offices to bring that information forward or that interest forward to the viability committee. 00:56:27.965 --> 00:56:34.965 Bobbyability Committee to develop, Rba's or to look at other inorganic ability committee to develop RBAs or to look at other inorganics or dioxin. 00:56:46.034 --> 00:57:02.034 We do have a help line. It's actually, I think here on, a clay slide, a help line as well as, an EPA email that you could email that suggestion into. 00:56:58.671 --> 00:57:11.671 Alright, excellent. And I'm gonna interject here by far the most common question I have sitting in the queue, which is an indication of how popular this topic is, is when can we register for the upcoming sessions. 00:57:00.036 --> 00:57:02.036 And we can definitely take a look at 00:57:10.923 --> 00:57:17.923 So I just want to stop before I get any more of these questions. Number one, registration for these sessions is not open yet, but it will be. 00:57:14.186 --> 00:57:27.186 We'll be posting it on Cluin very soon and we will email all of the registrants in today's session when these additional sessions are available. 00:57:24.233 --> 00:57:36.233 And I do want to clarify these sessions are not being sponsored by ITRC. So if you reach out to the ITRC team, they will not know what they which ones you're talking about they will send you back to me. 00:57:35.467 --> 00:57:40.467 So these are coming, from EPA. But we will get registration open soon. 00:57:40.299 --> 00:57:46.299 I promise I will email each one of you when the sessions are available for registration, which will be very soon. 00:57:45.048 --> 00:57:53.048 So just with that brief interlude, we're gonna go back to the technical questions. I just wanted to prevent anybody from sending that question in again. 00:57:53.746 --> 00:58:02.746 Let's get back to some of the media. For method 1340, Clay, how was the quote soil defined? 00:58:02.730 --> 00:58:05.730 I'll leave that one to Gary or Karen. 00:58:06.793 --> 00:58:16.793 Well, we defined it as the less than 1 50 micron sip size fractions. Generally the sub size fraction that would adhere to children's hands. 00:58:17.793 --> 00:58:23.793 And be ingested through hand to mouth activity. Gary, do you have any additions to? 00:58:29.876 --> 00:58:36.876 So, historically, the, in Vivo, the swine model was developed. 00:58:38.258 --> 00:58:45.258 And tested to, measure RVA soil and quote unquote soil like materials. 00:58:45.506 --> 00:58:54.506 And I think that caveat was. For 2 reasons. Some of the soils tested were. 00:58:53.148 --> 00:58:59.148 Soils that had been. If you will, spiked or amended with various. 00:58:58.489 --> 00:59:08.489 Substances like, and perhaps to open the doorway to, We don't, we haven't tested say indoor does, but. 00:59:09.063 --> 00:59:17.063 Maybe the expectation is it probably will. Do as well. For those types of, materials. 00:59:16.971 --> 00:59:25.971 But I don't think there's anything in the VIC guidance that's specifically defines what is the soil and what is not a soil other than. 00:59:26.418 --> 00:59:33.418 It is. The material that's going to be used in the soil pathway risk. Assessment. 00:59:34.869 --> 00:59:36.869 That is 00:59:38.451 --> 00:59:47.451 Identified in the DQO for the sampling and. And for the, inputs to, to the risk assessment. 00:59:46.880 --> 00:59:56.880 That's probably not a very helpful answer, but I don't think there's just any, there's anything that says this is a soil and this is not a soil. 00:59:56.265 --> 01:00:04.265 Materials that. Have been used in the validation. 00:59:57.921 --> 00:59:59.921 Okay. 01:00:01.158 --> 01:00:13.158 We're surface samples. And they're ultimately dried before their, their assay. 01:00:14.843 --> 01:00:21.843 But, but I, I don't know what they're constraints would be. On the definition of. 01:00:24.029 --> 01:00:37.029 Very excellent. Let's take a look at this question. It came in earlier. Is there a certain R 2 value that is set as the benchmark for estimating soil availability, bioavailability. 01:00:36.746 --> 01:00:49.746 I will start by saying, R squared was. An important factor in validating the IVBA assay method. 01:00:50.940 --> 01:00:56.940 But in terms of application of IVBA data to estimate RBA. 01:00:56.634 --> 01:01:04.634 Is not something we're an R squared value would be considered once the method has been validated. If that makes sense. 01:01:03.744 --> 01:01:15.744 There would be no way to measure that I can think of to measure an R squared value of How well does my measured IBBA. 01:01:16.690 --> 01:01:24.690 Value relate to. An RBA data point. Without also directly measuring RBA. 01:01:26.313 --> 01:01:34.313 And in the validation, the, So, DPA was looking for a method that would achieve in our squared of at least point 8. 01:01:34.822 --> 01:01:36.822 There you go. 01:01:36.074 --> 01:01:45.074 Okay, let's see, can you derive a site specific RBA from XRF sample results or would that be discouraged? 01:01:47.107 --> 01:02:00.107 The only way to derive an IVBA is via Method 1340. It does require measurements of totals, Gary or anyone else correct me if I'm wrong. 01:01:55.230 --> 01:02:07.230 I believe those toil total values could be based on XRF data. They could be date based on ICP data as well. 01:02:06.642 --> 01:02:13.642 I don't think that there's a rule or requirement that it's one or the other, but I could be wrong on that. 01:02:15.244 --> 01:02:22.244 Permit EPA Method 1340 recommends the use of ICP OES or ICP mass spec for total measurements. 01:02:22.362 --> 01:02:32.362 I will add here that, Robert Ford is working on a paper. He did a study to see the relationship between XRF and bio accessibility. 01:02:22.980 --> 01:02:24.980 Okay. 01:02:27.060 --> 01:02:40.060 So, that has not been published yet, but it is going through like a data review and everything like that. 01:02:38.211 --> 01:02:41.211 So that is something that we can maybe keep an eye out for to share. 01:02:41.416 --> 01:02:49.416 Okay. Alright, how stable is the RBA typically over time in soil or is it highly site-specific? 01:02:50.866 --> 01:02:59.866 It is site-specific. The extent to which side-specific, don't know or can't say. 01:03:01.909 --> 01:03:14.909 I believe the EPA and others have looked at stability of. Of RBA and IVBA measurements, particularly in standard reference material soils that are used as part of the QC procedures. 01:03:13.805 --> 01:03:25.805 And but that's going to depend upon another, a number of factors. And this was something that Brad discussed earlier, but just to give one example. 01:03:24.818 --> 01:03:40.818 With arsenic if If the if you find that A lot of the arsenic is in arsenic 3 or arsenite and it's a highly oxidative environment you're going to expect oxidation to arsenic 5. 01:03:40.062 --> 01:03:51.062 And, I believe an increase in bioavailability or bio accessibility over time. That's probably one example of of many. 01:03:51.560 --> 01:03:59.560 Types of relationships that may or may not be happening. And the particular soil of interest that would determine the answer to that question. 01:04:00.281 --> 01:04:12.281 Okay. Alright, can we look and discuss if RBA affects regional background concentrations of arsenic that the site is cleaned up to. 01:04:16.154 --> 01:04:18.154 Sydney, do you wanna take that one? 01:04:20.526 --> 01:04:30.526 We haven't really applied RBA to regional background concentrations. I think that's kind of maybe the double counting of seeing you could. 01:04:30.184 --> 01:04:38.184 Develop the site specific but then you'd also need to have site specific background that has run IVBA data on it itself. 01:04:38.639 --> 01:04:44.639 I don't think that you can just naturally apply what you've done at the site to the background. 01:04:45.263 --> 01:04:57.263 Okay. Alright, 2 more questions. The audience is cheering you all on. They appreciate you hanging in for some very difficult questions and they really appreciate the ample time for Q&A. 01:04:56.293 --> 01:05:06.293 So I just wanted to pass the the notes of gratitude on here. Can you talk more about the connection between bio accessibility and bio availability? 01:05:06.973 --> 01:05:11.973 How is bio accessibility factored into relative bioavailability? 01:05:13.964 --> 01:05:18.964 So I'm going to go back to the. Correlation so 01:05:19.606 --> 01:05:30.606 The connection is that there is a correlation between Bio accessibility, which is a term used to imply that it's an in vitro measurement. 01:05:28.427 --> 01:05:45.427 It's not something It's been measured. And their EPA has a validated method for both lead and arsenic that would be used to convert a measure of bio accessibility or IVBA. 01:05:45.294 --> 01:05:58.294 To a measure of RBA. The RBA measurements are based off of animal use of an animal model to gather an in vivo measurement of bioavailability. 01:05:59.554 --> 01:06:01.554 So. 01:06:02.046 --> 01:06:09.046 But I guess as best as I can answer is that this figure that you're looking at right now that explains the correlation. 01:06:09.551 --> 01:06:14.551 Between IVB and RBA is the best way that I can answer that question. 01:06:13.025 --> 01:06:25.025 So conceptually, the way I think of it is that I think or lead in soil can be in a variety of different physical and chemical states. 01:06:24.107 --> 01:06:33.107 And. Before it can be absorbed, it has to dissolve, has to be in solution. 01:06:32.879 --> 01:06:37.879 This is generality, but it's a sort of conceptual model I have in my head. 01:06:37.124 --> 01:06:47.124 That's by that's bio accessibility. So in vivo when it dissolves in the stomach or elsewhere in the GI tract. 01:06:46.657 --> 01:06:54.657 Where it can subsequently be transported into. But. 01:06:53.809 --> 01:07:04.809 That is the vial accessibility process that's being mimicked in the test tube. By dropping the soil into an acid environment. 01:07:04.057 --> 01:07:12.057 Once it's dissolved, it can be come a substrate for a variety of different. 01:07:12.247 --> 01:07:19.247 Physiological. Mechanisms that move the land or snake out of the GI tract fluid environment into the blood. 01:07:17.938 --> 01:07:26.938 And that's the bioavailability part. And that's why this plot that, Clay showed is. 01:07:26.197 --> 01:07:35.197 Is not a plot of IVA versus. Bioavailability. It's a plot of IPA versus relative by availability. 01:07:35.567 --> 01:07:43.567 The absolute bioavailability. Is not necessarily a hundred percent. But the route, but we. 01:07:42.654 --> 01:07:50.654 Because there's lots of other physiological factors that may limit the actual bioavailability of the metal. 01:07:49.684 --> 01:08:05.684 But There is a strong correlation between bio accessibility measured in vitro. And the bioavailability of the metal relative to its fully dissolved form. 01:08:06.951 --> 01:08:14.951 That might, which occurred which might occur in drinking one. I hope that helps. 01:08:16.282 --> 01:08:33.282 Thanks. And we did have a comment that came in. I'll just share this one of the attendees noted that there's a formula to calculate RBA from IVBA, which is available in an EPA document, Oswer, 92 85 dot 7 dash 77. 01:08:31.095 --> 01:08:41.095 I don't know if that. Sounds like a familiar document to any of the panelists, but if that is a, I'll have you guys look at that resource and if it's a relevant resource we can add that to the resources for today. 01:08:41.773 --> 01:08:42.773 Session. 01:08:44.248 --> 01:08:52.248 I think that yeah and Just to add since we're looking at it. To give you an example of what that looks like. 01:08:45.374 --> 01:08:49.374 Okay. Okay. 01:08:51.947 --> 01:09:05.947 The equation here. I believe is the ultimately ultimately with a validated. EPA method 1340 equation is to convert Arsenic IBBA to RBA. 01:09:06.698 --> 01:09:14.698 So this would be specific to arsenic. There's a similar but different equation for converting lead IVBA to RBA. 01:09:12.584 --> 01:09:20.584 Okay. Alright, and the last question that I see in the queue before we start closing things out. 01:09:20.106 --> 01:09:33.106 We had had several questions about site specific conditions. That could impact. The numbers here and one of the participants went back to that and asked if you could touch on exactly how. 01:09:28.026 --> 01:09:39.026 Soil properties can affect. Metals bioavailability relative to 1340. 01:09:38.197 --> 01:09:50.197 I will start and if Brad or if anyone else wants to add to it, There's been a lot of research out there in the period read literature that looks at the relationship between soil properties. 01:09:50.330 --> 01:09:58.330 I've and in vitro bio accessibility or relative bioavailability. I don't think we have time. 01:09:57.891 --> 01:10:11.891 To go into all of those. Again, just to give you a few examples. If arsenic or lead in the containment soil is in a mineral phase. 01:10:12.710 --> 01:10:15.710 And, and if a lot of that. 01:10:17.831 --> 01:10:36.831 Of the arsenic or that is is is tied up inside that mineral. You're generally going to see lower bioavailability or bio accessibility, then you would if it's Adsorbed, primarily an absorbed form of arsenic or lead in the contaminant. 01:10:37.047 --> 01:10:44.047 And so again, that's where mineralogy and speciation comes into play. Presence of organic matter. 01:10:44.327 --> 01:10:49.327 Play content. Correlations with other 01:10:50.778 --> 01:10:59.778 Elements present in the soil like iron. Have all been shown to have relationships. Whether those are direct. 01:11:02.100 --> 01:11:08.100 Causal relationships or indirect correlative relationships with bioavailability or by accessibility. 01:11:12.402 --> 01:11:15.402 Alright, any other panelists wish to chime in? 01:11:18.775 --> 01:11:39.775 I hope you can hear me okay. One of the things we've also seen. Maybe not specifically with arsenic and from the IVP, but you can get to all conditions you can get across the form around the, conditions you can get across the form around the mineral particles. 01:11:36.626 --> 01:11:48.626 So that you limit the solubility of, could you imagine a particle arsenic or a part of roll of lead that falls into the soil. 01:11:48.835 --> 01:11:57.835 To financial conditions if you formed a ride around the outside of the particle that may limit the disolution that comes as well. 01:11:52.891 --> 01:12:10.891 So it's another reason why we stress that this is a site specific. Factor, and depending on sources of. 01:12:10.924 --> 01:12:20.924 Alright, thank you, Brad. Okay. Not seeing any other questions in the queue, Clay. 01:12:16.370 --> 01:12:28.370 Oh, saying of it, the last one just came in, right? This should be the last question we will take before we go through our final reminders today. 01:12:28.355 --> 01:12:40.355 This participant asks if the IVBA results are negative. What default low number do you put into the linear correlation equation just mentioned to calculate the RBA. 01:12:42.461 --> 01:12:48.461 That is entered into IEUBK. Putting in a 0 seems inaccurate, but you don't want that number to be too high either. 01:12:49.746 --> 01:13:02.746 Well. Gary, feel free to stop me, but Generally speaking, IVBA values can only range between 0 to 100%. 01:13:03.248 --> 01:13:04.248 It's 01:13:05.689 --> 01:13:25.689 Possible that you could see and this is more the case with lead a value greater than 100% but you shouldn't ever see negative values because the lowest value possible in any of the analytical measurements used would be 0. 01:13:25.886 --> 01:13:33.886 In the case, since I mentioned it, in the case of LED, where you might see an IVBA value greater than 100%. 01:13:32.523 --> 01:13:49.523 That just implies that it's a bit of a unique soil. Where more of the lead dissolves when extracted using the EPA, 1340 extraction medium, then was extracted when you ran your totals. 01:13:49.144 --> 01:14:00.144 Assay, whether that was microwave digestion or hot block digestion followed by analysis with whatever analytical instrumentation you used. 01:13:57.918 --> 01:14:10.918 So it's possible. That whether that's a real behavior or just due to variability and uncertainty in your analytical methods that were used. 01:14:11.420 --> 01:14:15.420 When measuring either IVBA or totals. 01:14:20.609 --> 01:14:26.609 Okay, I think we're gonna call that a wrap if anybody else is going to chime in. 01:14:25.302 --> 01:14:33.302 This is your last champ. Alright, so at this time I truly see no more questions in the Q&A. 01:14:27.690 --> 01:14:42.690 So we're gonna go ahead and wrap things up. Clay if you wouldn't mind taking us back to those last 2 slides just reminding the audience of those points of contact. 01:14:37.843 --> 01:14:48.843 In the email hotline and the website, I put those in the chat earlier. They're also posted on the seminar homepage. 01:14:47.110 --> 01:14:57.110 I'm gonna put these back up on the screen in just a minute. But if you've downloaded a copy of Clay slides, you have this information. 01:14:53.799 --> 01:15:02.799 And then Clay, if I could ask you to move forward to that next. Slide again we will have several other webinars open on the topic. 01:14:57.922 --> 01:15:11.922 I once we get registration open for each of these we will be sharing a separate email. To all of the registrants with the links to each of these sessions to register. 01:15:06.861 --> 01:15:15.861 So I promise we'll get those posted very, very soon and you can tell all of your friends about it. 01:15:16.705 --> 01:15:23.705 So before I take the screen back and do some final close-out reminders, Clay, any final thoughts you'd like to leave the audience with. 01:15:22.633 --> 01:15:34.633 None for me other than I just encourage you to. Follow up and continue with the other 3 training sessions because we'll be able to Do a much deeper dive into some of these topics. 01:15:30.372 --> 01:15:40.372 You know today's Session was primarily mentioned to be an overview and there's a lot to take in here. 01:15:41.510 --> 01:15:46.510 So. Just encourage everyone to continue. I hope to see you in future training sessions. 01:15:45.141 --> 01:15:56.141 Excellent. Thank you so much. So I'm gonna take over the presentation view and put up a screen here on my end and walk through just a few final reminders today. 01:15:55.345 --> 01:16:03.345 I do want to echo Clay's thanks to the participants who joined us. We had over 230 live attendees from all over the world. 01:16:01.723 --> 01:16:10.723 And I want to thank Clay without a doubt for your time and expertise in fielding those questions as well as your panelists who joined us. 01:16:09.769 --> 01:16:16.769 Gary and Sydney and Brad and Karen and Julie thank you so much for sharing your time and information today. 01:16:16.071 --> 01:16:27.071 The first reminder I have is I encourage everybody to visit us at the Cleanup Information Network or Clue in.org where we continue to collect and share information related to hazardous way site characterization and cleanup. 01:16:26.162 --> 01:16:32.162 When you visit Clue and please be sure to sign up for our free monthly newsletter tech direct. 01:16:30.349 --> 01:16:37.349 I send that out on the first of each month and I'll highlight new resources and online training such as today's webinar. 01:16:36.342 --> 01:16:41.342 So when we get those other sessions open, we will be highlighting those in future tech direct editions. 01:16:39.592 --> 01:16:47.592 As a completely free listserv. 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