 Hello, everyone. Welcome to this webinar briefing of the National Academy's report, Health Considerations for Use of Unencapsulated Steel Slag. My name is Ray Wassell, and I was the National Academy's responsible staff officer during the study that resulted in this report. Can I have the first slide, please? Today's briefing will have two parts. Dr. Aaron Barczowski, who served as chair of the authoring committee, will provide an overview of the report. After that, Dr. Barczowski will be joined by other committee members and answering questions submitted by those who are live streaming the session. Next slide, please. The committee's report was released back in November and can be downloaded for free from the National Academy's press website. Next slide. Just a few words about the organization that the committee operated under. The National Academy's is an overall term for the National Academy of Sciences, Academy of Engineering, Academy of Medicine. These three organizations work together to provide advice to the nation. All three are private nonprofit organizations. And since they are not part of the government, they do not provide any legal requirements or federal policies. Next slide. The committee members of the agency such as EPA requests a study to help address a complex problem. A National Academy's committee is formed of people having relevant expertise and experience to carry out a written task. The committee members agree to serve as unpaid volunteers and work within the Academy's study process. They set up so that committee members gather information in sessions that are open to the public. However, they do their analysis and write their report in private meetings without the involvement of government officials or other stakeholders. After the committee's report is successfully goes through a rigorous review process. It is only then that it's submitted to the sponsoring agency and released to the public. Next slide. Here's a list of members of the committee members who wrote the report to be discussed today. I like each of them were attending today's webinar to briefly introduce themselves. We'll start with the chair. Hello, I'm Aaron barchowski. I am a professor in environmental and occupational health at the University of Pittsburgh, and I have expertise in mechanisms of metals toxicology. I'm Michael Aschner. I'm in the Department of Molecular Pharmacology at Albert Einstein College of Medicine. And where I'm a professor and my interest is in the neuro toxicity of metals. Thank you. Hi, I'm Dan Bain, an associate professor in the Department of Geology and Environmental Science the University of Pittsburgh research interests in the environmental behavior of trace metals. I don't know if Alan Kram has joined us at this time. Okay. Phil Goodrum, can you introduce yourself. Phil is on the phone. Hi, my name is Phil Goodrum. I am a principal toxicologist with GSI environmental, and my area of expertise is metals toxicology and environmental risk assessment. I'm John Kissel. I'm professor emeritus of environmental occupational health scientists, sciences at the University of Washington in Seattle, and I am a human exposure scientist. Debney Meyer. I am Debney Meyer I'm a professor at the University of Maryland am I in a civil and environmental engineering and I work on equity and justice issues and the built environment. Peggy O day. Hello, I'm Peggy O day I'm a professor in the Department of life and environmental sciences at the University of California Merced, and I study environmental geochemistry primarily of heavy metals. Hi, my name is Ruth O'Donnell from 2013 to 2020 I work for the Wisconsin Department of Natural Resources in the Bureau of waste management. And I was part of the beneficial use of industrial byproducts team. Hi, I'm Dave Walker. I'm professor emeritus of earth and environmental sciences at Columbia University. I specialized in mineralogy. My research career was already devoted to understanding the phase equilibrium and thermochemistry of crystallizing silicate and oxide liquids. Hello Bob right. I'm a pediatrician medical toxicologist and epidemiologist at the icon school of medicine at Mount Sinai and majority of my research has been in metal toxicity and children. Thank you. Are there any other committee members who did not get a chance to introduce themselves. Okay. Hi, I'm on Rebecca, Rebecca Fry met the university. Hi, University of North Carolina Chapel Hill in environmental sciences and engineering. Thanks so much. Very good. Round it out. Okay. Next slide please. And this slide gives the names of the folks on our staff who supported the work of the committee. I just wanted to introduce them to introduce themselves. I just wanted to show their names. Now, before I ask Dr barchowski to provide an overview of the report. I want to mention that a video recording is being made of this webinar and an internet link to access the recording will be available on the event page for this webinar by as early as tomorrow. And then if anyone live streaming this session would like to submit a question to the committee. Please use the q amp a feature located at the bottom of your zoom screen. And then after Dr barchowski is finished with the presentation, then we'll get to the questions. Thank you. And now I'll turn it over to Dr barchowski. Okay, Nick. Next slide please. Hello and just to start off, let's all get on the same page and get a good understanding for what we're discussing. And what is slag, and especially electric art furnace slag. So, like our electric art furnaces produce slag. And the steel basically can be produced from iron ore or steel scrap using several processes. The electric arc furnace are used to produce about 75% of the steel made in the United States. The rest remain are blast furnaces. In this process, an electric current is used to melt scrap steel or other iron containing materials. And as a result of this process, a layer of molten slag is formed that floats on top of the liquid metal and can contain toxic metals at various concentrations. The position intended function and the quantity formed really depend on which type of steel is being produced and the various chemicals added in the process. After the slag layer is removed from the furnace, it's cooled and solidifies into a very hard rock like material. And this can be crushed into different sizes for various applications, often instead of using quarried rock fragments. Next slide please. As seen in this slide, there are the shows to slag. There are really two main uses of the slag or two types of the slag uses. The first would be encapsulated or bound uses. And here we're using these aggregates of the in concrete or encapsulated in asphalt for road beds. And encapsulated unbound form is used in applications such as loose ground cover for landscaping, driveway beds, parking lots and railroad beds. Next slide please. We do have some concerns. And those concerns come from the fact that the electric furnace slag can contain toxic metals at elevated levels. The US EPA said it is unclear whether unaccapsulated EAF slag use near residents in schools causes a risk. They do have some concerns. And one of their remedies was to recommend various steps residents can take to minimize contact with the slag dust and small particles in the slag. In addition, EPA has undertaken research to address key concerns and uncertainties. And as a part of its overall research efforts, EPA asked the National Academies to independently assess potential human health risks from the use of unencapsulated electric arc furnace slag in residential areas. Next slide. Using the available information analysis, the committee was asked to assess human health risks associated with using the unencapsulated electric arc furnace slag. And we were asked to include a number of considerations, those being where and how the how much electric arc furnace slag is used in the United States. Effects of weathering on the chemical and physical properties of applied slag over time. Ways in which humans can be exposed to toxic chemicals in slag and how those exposures compare with exposures associated with incidences of cancer and other adverse effects in other kinds of environmental studies. We're also concerned with factors that may lead to the highest health risks from slag exposures. And this would include looking at life stage of those exposed, for example, children, elderly, etc. socioeconomic living conditions that may lead to increase susceptibility to adverse effects. Research recommendations were also asked for addressing important information gaps. So where don't we have enough information. Next slide please. The committee heard presentations and received written materials from EPA, the National Slag Association, an industry group, and its consultants and other researchers, including studies of slag composition leaching of toxic metals from the slag and risks expected to under possible exposure scenarios. In considering the potential adverse health effects associated with exposures to the kinds of toxic metals contained in slag, the committee mainly considered manganese and hexavalent chromium as lead metals of concern. This focus was basically requested by the EPA, and they are potentially the highest risks that might be found. Manganese has posed high potential for concern in various slag assessments. It's a neurotoxic and hexavalent chromium is a site constituent for which exposure is associated with a theoretical excess cancer risk and has also been found in as a slag constituent. Because general data limitations, the committee did not attempt to develop an overall characterization of the health risk. We were not really charged with coming up with a full risk assessment from the unencapsulated slag use. We did provide insights and identified key data needs for a better understanding of this risk at the national level. Next slide, please. So the importance is the national level and the committee identified 117 different EAF steel plants in 33 states. So a wide distribution associated with these are 91 slag processing facilities that are serviced very locally. The amount of slag produced annually is about 10 to 15% of the amount of steel produced at these EAF plants. And that was roughly about 6.3 million tons of slag that were sold in 2022. The slag is really heavy and generally it's only distributed locally. So it's generally transported to projects in close proximity to those processing plants and primarily by truck. And quantitative information on how and where unencapsulated slag is used is actually limited. The majority of steel furnace slag use appears to be road bases and surfaces and this would include railroad track of certain beds. And however, you know, the annual amount of slag used for residential applications at the national level is really not tracked and is somewhat unknown. Next slide, please. So composition. The slag composition varies a great deal, according to the grade of steel produce the source of scrap that's used in speed for the for the steel, and also the operational practices. So this can vary quite a bit across those different facilities. The slag is rich in compounds containing iron, manganese, calcium, silicon and aluminum. And a majority of what's produced is stainless steel and the stainless steel EAF slags contain high levels of chromium. Other chemicals can be present at low concentrations and these can be metals such as nickel, cadmium, lead, zinc, vanadium, titanium, molybdenum, tin, arsenic, antimony and barium. Slag concentrations of manganese, chromium, vanadium, and in a few cases arsenic can be greater than the levels EPA sets for considerations of those metals in soils for site remediation planning. Also a potential concern are several poly aromatic hydrocarbons that have been detected in production at relatively low concentrations compared to EPA soil screening levels. But the PAHs are in general a class of chemicals referred to as persistent organic pollutants that are toxic chemicals, which take a long time to break down the environment. But again, assessment of the risk from these in slag has not really been adequately approached. Next slide please. A major concern is the size of particles that could be affecting human exposures. And exposure to the small particles are of most concern with assessment risk being limited in using the unencapsulated slag. The small particles can be more chemically reactive because they have a larger surface area and they also can be more deeply inhaled into a person's airways. Generally, what we're concerned with are particles that are maybe 100 or 1000 times smaller than a grain of sand. Much of the physical testing of slag has been done on its resistance to break down in various encapsulated mixes such as asphalt rather than its unencapsulated uses. Approaches for testing the strength of the unencapsulated slag fragments very widely and they focused on how much of the slag remains intact rather than on the amount of small particles worn off. Because of those data limitations, the committee could not draw general conclusions about the amounts and properties of smaller particles generated over time from the wearing down of the unencapsulated slag. Next slide please. In addition to the particles, there's concern about leaching of the toxic metals from the slag and that has been examined mostly using standardized testing in a laboratory not out in the environment. Short-term testing generally is focused, has found that minimal leaching of toxic chemicals or metals from the AF occurs and concentrations of the leached metals are not detectable or below regulatory limits. In general studies to date have not examined the long term state of slag chemicals released under variable environmental conditions. The most commonly reported result from weathering and leaching of slags is that in highly alkaline or basic leached water flowing from surface into surface water from the groundwater so again a very high level of base. A few studies have shown that alkaline water occurring in near old slag piles is neutralized rapidly and migration off site is limited. However, generation migration and neutralization of alkaline water from slag weathering has not been extensively studied in the unencapsulated applications such as in landscaping. Next slide please. So this slide has a nice scheme and it's an example of a generic model for how humans would be exposed to slag constituents in a residential setting. Assessment of human exposure to chemicals involves consideration of concentration of chemicals in food, air, water, soil or on surfaces that come in contact with individuals. Example would be dust coming into homes. Exposure pathways are the pathways the chemicals take from the source to the exposed person so source being EAF slag and then exposure route being that last column. Exposure routes refer to how metals or chemicals enter the body. This slide shows a generic model that may apply to sites where EAF slag is used in an unencapsulated manner in a residential setting such as for driveway cover or yard landscaping. It is important to note that the actual model at each site will depend on numerous factors and those include the amount and type of slag used human activity patterns around the slag use and local soil and climate conditions. Next slide please. Exposure considerations such as those climate conditions potentially important exposure pathways and routes include incidental ingestion of slag particles mixed in outdoor soil and indoor dust, inhalation and dermal contact. Also, exposure pathways for consideration include ingestion of home produced foods grown on properties with electric arc furnace slag being applied and ingestion and dermal contact with surface waters and groundwater receiving metals leached from slag. When mixed with outdoor soil and indoor dust, EAF slag may alter the overall human uptake and absorption of slag chemicals of concern. Therefore, use of site specific data would be preferable to using estimates from literature and laboratory experiments when making exposure calculations. Next slide. As I mentioned, we mainly focused on toxicity of chromium and manganese as potential metals of concern in the slag. There are many other metals but this focus was because we just wanted to look at the major leaders of concern. And there may be additional looks at some of the toxicities in the future. But with chromium, the major concern is cancer and the, and it's really only the hexavalent form of chromium that poses the hazard. That may be a bit complicated to understand, but hexavalent chromium is basically chromic acid, whereas a chromium III or trivalent chromium is actually thought of as a nutrient supplement and not a hazard. A few studies have really addressed the extent of formation of hexavalent chromium in slag directly, but the available data suggests that the amount under ambient weathering conditions is relatively low. The absorption of chromium is greatly limited by our body's protective ability to reduce the hexavalent chromium to trivalent chromium in the fluids that line the gastrointestinal tract and the lung airways. And it's not clear whether there's sufficient accessible hexavalent chromium that's coming from the slag or slag dust to overwhelm this reductive capacity. Based on limited data, it may be that pregnant women, young children, elderly individuals and individuals with particularly genetic susceptibilities might be more likely to be vulnerable to this effect of hexavalent chromium from the slag. The hexavalent chromium exposure might exacerbate health conditions in individuals with pre-existing pathologies or disease burdens in the GI tract, liver, lungs, and blood. But unfortunately, there is really a lack of epidemiological studies of environmental exposures to hexavalent chromium compared to occupational exposures. And so because of this, the data is insufficient to exclude the risk of non-cancer disease endpoints in susceptible populations. Manganese, as I mentioned, also poses a major toxicity. The primary toxicity with manganese is that it's a neurological toxicant with some evidence for other health effects such as liver toxicity. Again, pregnant women, early childhood individuals, especially considering the manganese effects on developmental neurological and cognition endpoints, and elderly individuals would likely be more vulnerable to manganese exposure from the slag. Those with chronic neurological diseases such as autism, Alzheimer's disease, and pre-existing liver disease can also be at increased risk in their vulnerability to manganese exposures. The exposures during pregnancy and early childhood have been associated with lower neurodevelopmental test scores, test and motor function, and depressive symptoms, amongst other effects. However, in general, the majority of studies are in adults and also mostly occupational exposures making direct comparisons with children's studies complicated, and there really is a large need for more environmental exposure studies. Next slide, please. Continuing the theme of increased susceptibility, especially in overburdened communities, the committee assessed whether people are exposed to numerous different chemical pollutants and other stressors from a wide array of sources over their life spans. Disadvantaged communities have a higher burden of cumulative exposures to multiple stressors, including chemical stressors such as the environmental pollutants that might come from slag, and nonchemical factors such as diet, healthcare, access, policies leading to residential segregation and socio-economics. Exposure to chemical stressors such as chromium and manganese can result from various sources in addition to slag in disadvantaged communities and other stressors such as lead and nonchemical stressors can exacerbate health effects associated with chromium and manganese. The committee examined two areas, one in Allegheny County, PA, and Pueblo, Colorado as cases, case examples to illustrate disadvantaged communities in reasonable proximity to slag processing facilities, and it might have access to the unencapitated slag use. Femalative exposures that are disproportionately borne by disadvantaged and overburdened individuals and communities can exacerbate health risks of EAF slag chemicals, including the risk of negative cognitive effects. Next slide, please. So the, with previous risk assessments of EAF slag use, the committee considered five past risk assessments. There's actually a large long history of this, but one main one was with the Wisconsin Department of Health Sciences that focused on slag from a very specific EAF steel plant. For others were funded by the steel slag coalition or the National Slag Association, again industry groups, considered a slag from multiple facilities. The concepts and approaches applied in assessments tended to represent rather narrowly defined conditions, which are likely not reasonable for extrapolating to the national level. For example, exposure scenarios in which slag covers only the driveway of a residence rather than a large portion of a property such as an industrial plant where you have a large parking lot, just surface hearing. Ranking chemicals. Next slide, please. So, again, a future consideration, there's a need to rank chemicals in the slag and to illustrate a method for identifying slag chemicals that weren't further considered consideration as potential risk contributors. The committee applied a hazard ranking approach in which data on slag composition were compared with EPA's regional screening levels for residential exposures to soil. Next slide, please. We also did a hazard ranking of the slag metals. And this graph shows that the highest ranking is for manganese, iron, hexavalent chromium, vanadium, and valium and antimony are also among the higher ranked chemicals. Next slide, please. So in identifying risks, the committee identified factors considering to have the potential to contribute to the highest risk from the use of unencapsulated EAS slag. The relative importance of these factors is expected to differ in a case-by-case basis. And again, this is primarily because all those different EAF facilities are taking in different sources of scrap, etc., so there'll be different composition. The relative importance of these factors is expected to differ in different locations. The factors also comprise key data needs. A greater understanding of these factors will ensure that the calculated slag-related risks are not overestimated or underestimated. Next slide, please. So this gets to be very complicated and elaborate, but we did identify key risk factors and data needs. So a number of bullets, but to go through them, the amount of slag used for residential application. The focus on this report is on residential applications of EAS slag. However, currently available information does not allow for characterization of the amount of EAS slag used nationally for that kind of application. In the case of slag particle size distribution, the small size particles that can be transported in air and stick to clothing and be tracked into the home and deposit into various outdoor and indoor surfaces are important. The concentration of some chemicals of potential concern can increase as particle size decreases, and the particle size distributions for fresh and weathered slag are very poorly characterized. Particle exposures, including indoor residential. Children can ingest slag particles while playing on the ground outdoors or on the floor indoors from dust. Adults may also ingest slag particles that adhere to food or their hands. Inhalation exposures may occur depending on the particle size, their distribution of slag, and the extent of areas where the slag is applied. Specific residential uses that may result in exposures, particularly to susceptible groups, is, and more broadly, it is a really key data gap. Nearness of humans to applied slag and the frequency of human contact. Exposure factors and exposure routes, such as those related to an extent of slag coverage for residential property, can substantially affect the result of at risk. Calculation and the exposure time factors associated with health outcomes of interest are another important consideration. For example, cancer outcomes are typically associated with longer periods of exposure than for non cancer outcomes. Chemical and physical weathering. Again, a key factor that needs to be looked at many environmental factors, such as climate conditions and factors directly related to slag influence the rate at which chemicals of potential concern are mobilized from unencapsulated slag. How concentrations of slag constituents change over time is an important uncertainty. The pH of the water or the alkaline water conditions from weathered slag, weathering and leaching of EAS slag can result in high alkaline water degrading the quality of surface water and groundwater. More information is needed about those effects and the long term fate of potentially hazardous slag metals released into the environment under different climate conditions. Exposure to manganese, exposure to high concentrations exhibits neurological toxicity with some evidence of other health effects such as liver toxicity. However, comprehensive re-evaluation of toxicological and epidemiological literature for manganese is needed, especially with environmental exposures. Exposure to exobalant chromium, estimates of cancer risk from chromium in slag are highly sensitive to estimates regarding the chemical form of the chromium present in the slag and to changes in that may occur over time. View studies have directly assessed the extent of formation of exobalant chromium in applied slag and how much of the amounts of people are exposed to gets absorbed into a person's body. Exposure to other high hazard chemicals, a number of chemicals other than manganese and exobalant chromium can occur within EAS slag at concentrations of interest, especially antimony, arsenic, iron, dallium and vanadium. Also, it needs to be determined whether analysis for persistent organic pollutants should be included in future testing of EAS slag risk. Susceptible life stages, we need to be cognizant of different life stages where there is increased susceptibility such as pregnancy, early life exposures and exposures during development such in childhood and adolescence in an old age where our defenses are diminished. Elevated manganese exposure during pregnancy and early childhood have been associated with lower neurodevelopmental test scores, but again, the epidemiology is really not there for understanding risks from the slag. Cumulative exposures in overburden communities is a major concern and inequitable cumulative exposures to people in communities can exacerbate health risk associated with exposures to slag components. And this is also of major concern since there are many other co exposures in these communities that may increase susceptibility. Next slide please. So in concluding remarks, the committee considered screening level analysis of residential use scenarios of slag that indicated an exceedance of established risk thresholds and assessment of other scenarios reported risk below those thresholds. Due to uncertainties in the current evidence stream, the committee was unable to make an overall characterization of health risk related to the unencuped slated use of EAS slag in the US. And until more environmental studies have been conducted and characterized a wider range of weathered EAS slag material and environmental conditions. The committee cautions against making generalizations from conclusions from the public risk published risk assessments. A greater understanding of the risk factors and data needs identified by the committee will help ensure that calculated slag related risks are not overestimated or underestimated. And with that, I believe I'll be glad to answer any questions or the committee can answer any questions. And please put your questions into chat. Oh, there is one question that came in. And maybe Phil could answer it. Do you want to read it? I'm not seeing it. Perhaps you could Ray in the chat. Okay, but the question is, can you please provide more information on the meeting of a hazard quotient exceeding one on slide 22. Sure, I can I can answer that. So, generally, what a hazard quotient means is that it's an estimate of an exposure relative to some reference dose or reference concentration. And finally, that's a ratio and a hazard quotient greater than one just means that the exposure might exceed that specific to that slide just to explain a little bit more what the committee did to run a screening level assessment. And so there's a series of PAs regional screening level approach. And so there's a series of equations that takes into account the various pathways that Dr Pichowski laid out so soil ingestion dermal exposure in elation. And we looked at concentrations that are reported in some of the risk assessments. So those are summary statistics sort of average concentrations that have been measured at various areas. And that gives us some idea of sort of the relative magnitude of concentrations of some of these models. So again, what what we did was to use those estimates that kind of represent an average, and we applied standard equations that EPA uses to estimate exposure, and then we related that to the established toxicity values for these compounds. And by applying the same process to each compound. It allows us to have some relative ranking. And so that's the basis for the grouping is sort of applying the same screening approach. Chemical specific toxicity values and estimates of average concentrations measured in soil that has been amended in some way with the unencapsulated slide. So I think the final thing I'll say is an exit. This is a screening level assessment and so an exceedance of a screening level in and of itself. It doesn't mean that there's necessarily a risk and again our effort here wasn't a risk assessment per se it was a relative ranking is a hazard sort of ranking approach. And what what we were really trying to do is take the composition information and come up with some way of sort of rank ordering the importance of the compounds and what we see is for example manganese and hexavalium in the entire there in that group that could potentially exceed a hazard portion of one. Maybe I'll stop there Ray unless there's a follow up. Sounds good. So in the questions from Renee guy. And this to you Ray. Will you be sending out the presentation or I guess how does the public have access to this public to this presentation. The presentation will be part of the video recording that will be available after a day or so after today. And there'll be a link provided on the event webpage. Thank you. And from Tara Hubner. This one, I think we'll go back to Dr Goodrum but the committee recommends that the site specific exposure factor values as opposed to literature or guidance document based values be used when assessing risk from residential applications of slag. What approaches are available to develop site specific incidental ingestion rates of slag find particles. Now first say that I think that what we meant by site specific is trying to evaluate what exposures might be expected from the different plants overall but Phil you want to answer the second part of that for incidental ingestion rates. Sure. By and large when site specific risk assessments are done the, you know, the question is about the soil and dust ingestion rates specifically. And we do have estimates of those for young children as well as adults. And actually, that particular exposure factor, which is in an exposure assessment is based on a recommended guidance value and those guidance values are derived from the literature and most recently some publications that look at or rely upon really extensive data sets where we have measurements in environmental media and then we have internal measurements of blood lead. So there's been a recent use of lead exposure modeling to help inform the soil and dust ingestion rate. But again, especially at site risk assessment site specific risk assessments. We don't have a study conducted specifically of contact rates and soil and dust ingestion rates and instead we rely on recommended guidance values from the US EPA. Thank you and Thomas Simmons asked, can we speak about the particle size distribution? For instance, did you see in your research that EAF readily breaks down and that there's significant small particles? I don't believe that there's been adequate research in this area but I'll defer to Dr. O'Day if she's still on regarding the exposures. Yeah. Actually, if Dr. Bain is on, I think he's the one that actually looked at the particle size distribution. So if he's on, he's probably better positioned to answer. Sure. Sure. Thank you, Peggy. Thank you, Erin. We can't speak more because that is one of the glaring gaps in the information. We just, there's, and some, you know, there's limited data, the data that is there, there's quite a bit of variability and breakdown rates. And, you know, then the focus is on breakdown in terms of aggregate. So the really fine particles, there's extremely small amounts of data to evaluate that. So we really can't say much more than what we said in the report. From A. Gibson, what is the risk to environment if the slag is laying in a river? And I'm afraid that that's kind of outside of our purview is that wouldn't be a residential use. And I'm not sure whether there's that much information on that. And it suggests that if it was under water that's flowing and it's good in aerobic water that you'd have a limited amount of chromium exposure, but I don't think that there's any real data there. Follow up from Thomas Simmons. And further did you see any difference in metals concentrations at different particle sizes? I just echo what Dr. Bain said, and I don't think that there is adequate information out there on that. Phil might have a comment on that as well. Okay. Well, no. No, I think that's right. We don't have a lot of data on the enrichment factor, unfortunately. There's a lot of data gaps. Again, there are a lot of data gaps. Thomas Simmons. I just lost it. I just saw one from Thomas Simmons again, but. Thank you. We just answered that one. Okay. I think he had a follow up, but. Yeah, we did. We did so. Did you review and include in your assessment the leaf method, leach testing. And also particle size analysis on both fresh and weathered slag that the EPA and Vanderbilt University performed. Yes, we, we, the leaf was presented to us. And we definitely considered it. I guess this one for Dr. O'Day. Yeah, that's right. But I think one of the difficulties here was that we got a preliminary or presentation of the preliminary results. And the committee was never provided with the final results from the Vanderbilt group. Because they had not issued their report. So we saw some preliminary data, but we did not include that data in our report because we didn't have the final version of the data. The preliminary data was consistent with other leaf testing showing that at alkaline conditions that you don't generally mobilize metals, but we didn't have the full set of data so we couldn't evaluate everything. And Dr. Day, I think that's where my comments about alkaline water, et cetera, came from. Right. Correct. Yeah. Yeah. I don't see any open questions. Ray, it looks like there's no more questions in the queue. Correct. We're close to the end of our hour. Should we wrap it up or. Yeah, I think, I think we're, we're at the end. Since there are no more questions. I think we can send our thanks to, to the interest people showed in hearing about the report. And we hope the video recording will be available soon. We'll make sure it gets up expeditiously so folks have access to it. And remember the full report is available for free. Downloading for free from our Academy's website. And with that, I'd like to thank the committee members, Academy staff, and all the folks who listened in on the live stream.