U.S. ENVIRONMENTAL PROTECTION AGENCY (EPA)
               SCIENTIFIC ADVISORY COMMITTEE ON CHEMICALS (SACC)

                                 OPEN MEETING

Draft TSCA Screening Level Approach for Assessing Ambient Air and Water Exposures to Fenceline Communities Version 1.0

                                 SACC WEBSITE:
                     https://www.epa.gov/tsca-peer-review
                                DOCKET NUMBER:
                         EPA - HQ - OPPT - 2021-0415

                    Virtual Location via Zoom.gov platform

                               March 15-17, 2022

                                  ATTENDEES
DESIGNATED FEDERAL OFFICIAL

DR. ALAA KAMEL, PHD
OFFICE OF PROGRAM SUPPORT
OFFICE OF CHEMICAL SAFETY AND POLLUTION PREVENTION
TSCA SACC CHAIR

DR. DANIEL SCHLENK, PHD
DEPARTMENT OF ENVIRONMENTAL SCIENCES
UNIVERSITY OF CALIFORNIA, RIVERSIDE
TSCA SACC MEMBERS

UDAYAN APTE, PHD
DEPARTMENT OF PHARMACOLOGY, TOXICOLOGY, AND THERAPEUTICS
UNIVERSITY OF KANSAS MEDICAL CENTER
MARISSA BAKER, PHD
DEPARTMENT OF ENVIRONMENTAL & OCCUPATIONAL HEALTH SCIENCES
UNIVERSITY OF WASHINGTON SCHOOL OF PUBLICH HEALTH
SHERI BLYSTONE, PHD
SNF HOLDING COMPANY
CHRISTINE CHAISSON, PHD
THE LIFELINE GROUP
GEORGE P. COBB, PHD
BAYLOR UNIVERSITY
DEPARTMENT OF ENVIORNMENTAL SCIENCE
HOLLY DAVIES, PHD
WASHINGTON STATE DEPARTMENT OF HEALTH
WILLIAM DOUCETTE, PHD
(RETIRED) UTAH WATER RESEARCH LABORATORY
DEPT. OF CIVIL & ENVIRONMENTAL ENGINEERING
WENDY HEIGER-BERNAYS, PHD
DEPARTMENT OF ENVIRONMENTAL HEALTH
SCHOOL OF PUBLIC HEALTH
BOSTON UNIVERSITY
MARK JOHNSON, PHD
US ARMY PUBLIC HEALTH CENTER
JOHN KISSEL, PHD
(RETIRED) ENV. & OCCUPATIONAL HEALTH SCIENCES
SCHOOL OF PUBLIC HEALTH
CARMEN MESSERLIAN, PHD
DEPARTMENT OF ENVIRONMENTAL HEALTH
DEPARTMENT OF EPIDEMIOLOGY
HARVARD T.H. CHAN SCHOOL OF PUBLIC HEALTH
JENNIFER PRZYBYLA, PHD
AGENCY FOR TOXIC SUBSTANCES AND DISEASE REGISTRY
CENTERS FOR DISEASE CONTROL AND PREVENTION
DAVID REIF, PHD
NORTH CAROLINA STATE UNIVERSITY
CRAIG ROWLANDS, PHD
UNDERWRITERS LABORATORIES, LLC
SHEELA SATHYANARAYANA, MD
SEATTLE CHILDREN'S RESEARCH INSTITUTE
UNIVERSITY OF WASHINGTON
CHARLES V. VORHEES, PHD
COLLEGE OF MEDICINE AND DIVISION OF NEUROLOGY
CINCINNATI CHILDREN'S RESARCH FOUNDATION
UNIVERSITY OF CINCINNATI
TSCA SACC AD HOC PEER REVIEWERS

RYAN CALDER, SCD, PE
VIRGINIA POLYTECHNIC INSTITUTE AND STATE UNIVERSITY
JOHN FERRY
DEPARTMENT OF CHEMISTRY AND BIOCHEMISTRY
UNIVERSITY OF SOUTH CAROLINA

MATTHEW O. GRIBBLE, PHD, DABT
SCHOOL OF PUBLIC HEALTH
UNIVERSITY OF ALABAMA AT BURMINGHAM
LUCAS HENNEMAN, MS, PHD
DEPT. OF CIVIL, ENVIRONMENTAL, & INFRASTRUCTURE ENGINEERING
GEORGE MASON UNIVERSITY
LI LI, PHD
SCHOOL OF PUBLIC HEALTH
UNIVERSITY OF NEVADA, RENO
RICK REISS, SCD
EXPONENT, INC
MONICA E. UNSELD, PHD, MPH
UNTIL JUSTICE DATA PARTNERS, INC.
PRESENTERS AND EPA STAFF

MARK HARTMAN
EPA/OCSPP/OPPT

MICHAL FREEDHOFF, PHD
EPA/OCSPP
KEVIN VUILLEUMIER, PHD
EPA/OCSPP/OPPT/ECRA
KEITH JACOB, PHD
EPA/OCSPP/OPPT/ECRA
FRANKLYN HALL, PHD
EPA/OCSPP/OPPT/ECRA
JASON TODD, PHD
EPA/OCSPP/OPPT/ECRA
REHAN CHOUDHARY, PHD
EPA/OCSPP/OPPT/ECRA
PUBLIC COMMENTERS

DAN BAKER
CONSULTANT
ENVIRONMENTAL REACTION ENGINEERING EXPERTS CONSULTING
UNI BLAKE
AMERICAN PETROLEUM INSTITUTE
EBONI COCHRAN
REACT
PAUL DELEO
AMERICAN CHEMISTRY COUNCIL
ELKE JENSEN
THE DOWN CHEMICAL COMPANY
RASHMI JOGLEKAR
EARTHJUSTICE
AMY KYLE
UNIVERSITY OF BERKELEY, SCHOOL OF PUBLIC HEALTH (RETIRED)
SONYA LUNDER
SIERRA CLUB
LINDSAY MCCORMICK
ENVIRONMENTAL DEFENSE FUND
MAYA NYE
COMING CLEAN
KATHELINE PIERRE
FOUNDATION OF MEDICINE 501C3 PRIVATE FOUNDATION
MOLLY RAUCH
MOMS CLEAN AIR FORCE
SWATI RAYASAM
UCSF PROGRAM ON REPRODUCTIVE HEALTH AND THE ENVIRONMENT
KARI RHINEHART
IF IT WAS YOUR CHILD
JENNIFER SASS
NATURAL RESOURCES DEFENSE COUNCIL
KAREN SLANEY
MOMS CLEAN AIR FORCE

TABLE OF CONTENTS

OPENING OF MEETING	6
INTRODUCTION AND IDENTIFICATION OF PANEL MEMBERS	12
INTRODUCTION AND WELCOME	22
WELCOME AND INTRODUCTORY COMMENTS	25
OPPT TECHNICAL PRESENTATION  -  OVERVIEW OF DRAFT TSCA FENCELINE METHODOLOGY	37
SACC QUESTIONS ON OPPT TECHNICAL PRESENTATION	93
PUBLIC COMMENTS	147
CHARGE QUESTION 1	248
OPENING OF MEETING - DAY 2	307
PANEL MEMBERS: FOLLOW-UP ON PREVIOUS DAY	311
CHARGE QUESTION 2	318
CHARGE QUESTION 3	357
CHARGE QUESTION 4a	421
CHARGE QUESTION 4b	467
OPENING OF MEETING - DAY 3	524
PANEL MEMBERS: FOLLOW-UP ON PREVIOUS DAY PRESENTATIONS	528
CHARGE QUESTION 4C	535
CHARGE QUESTION 4D	585

OPENING OF MEETING

                  DR. ALAA KAMEL:  Well, good morning, everyone.  My name is Alaa Kamel, and I'll be serving as the Designated Federal Official to the U.S. EPA Science Advisory Committee on Chemicals.  For this meeting, and in my role, I will be opening this public meeting.  I want to thank Dr. Daniel Schlenk for agreeing to serve as chair of the Committee for this meeting.  I also want to thank both members of the Committee, ad hoc reviewers, and the public for attending this important meeting.
                  We appreciate the time and efforts of the Committee members in preparing for this meeting, taking into account the busy schedules.  In addition, I also want to thank EPA's Office of Pollution Prevention and Toxics, OPPT, and my colleagues at the peer review and ethics branch in EPA for their hard work in preparing for this important review of EPA's draft TSCA Screening Level Approach for Assessing Ambient Air and Water Exposures to Fenceline Communities Version 1.0.
                  As an added note, Dr. Todd Peterson, my colleague and Designated Federal Official, and Steve Knott, our executive secretary -- they are online this week, and they will serve as backups to my role as Designated Federal Official.  Now, the SACC is a Federal Advisory Committee that provides independent scientific peer review and advice to the EPA on chemical-related issues regarding impact of proposed regulatory actions on human health and the environment.  The SACC provides advice and recommendations to EPA; decision-making and implementation authority remains with the Agency.  The SACC for this meeting is comprised of 17 members who are expert in toxicology, environmental risk assessments, exposure assessments, and related sciences.
                  The expertise of these members is augmented by ad hoc reviewers who are temporary participants in SACC activities providing additional scientific expertise including models to estimate chemical fate and transport in ambient air and water pathways and public health protection for at-risk communities in order to assist in reviews conducted by the SACC Committee.
                  As the DFO of this meeting, I serve as a liaison between the SACC and the Agency.  I am also responsible for ensuring provisions of the Federal Advisory Committee Act, FACA -- that they are all met.  Federal Advisory Committee Act of 1972 established a system that governs the creation, operation, and termination of executive branch advisory committees.  SACC meetings are subject to all FACA requirements.  These include open meetings, timely public notice of meetings, and document availability to the public.
                  All documents are available to the public in the docket at www.regulations.gov.  As the Designated Federal Official for this meeting, a critical responsibility is to work with appropriate agency officials to ensure that all appropriate ethics regulations are satisfied.  In that capacity, Committee members receive training and provisions of federal conflict of interest laws.  In addition, each participant has filed a standard government financial disclosure report.  Our deputy ethics official for the Office of Program Support in EPA and in consultation with the Office of General Counsel have reviewed these reports to ensure all ethic requirements are met.
                  The SACC will review challenging scientific issues over the next three days.  We have a full agenda, so meeting times are approximate.  Thus, we may not keep to exact times as noted due to the discussions and public comments.  We strive to ensure adequate time for Agency presentations, public comments, and Committee deliberations.  For presenters, SACC members, and public commenters, please identify yourself and speak into the microphones provided or actually your computer microphone since this meeting is being webcasted, transcribed, and recorded.
                  I'd like to note that there is a live video webcast of this meeting via YouTube.  To access this website, or this webcast, please go to the meeting website at www.epa.gov/tsca-peer-review.  Copies of all EPA presentation materials, written public comments, and other documents related to this meeting are available in the public docket at regulations.gov.
                  Copies of presentation materials submitted this week by public commenters will be available in the public docket within the next week.  The docket number and website are noted on the meeting agenda.  For this meeting, there are so far over 180 registered attendees; 24 of them will be giving oral comments.  Registration is open until the last day of the meeting on March 17.  Members of the Committee and ad hoc reviewers are encouraged to fully consider all written and oral public comments submitted for this meeting.
                  At this time, the agenda is full.  However, as we move through the proceedings, if time allows, we may be able to accommodate additional brief oral comments of five minutes or less.  For members of the press, EPA media relations staff are available to answer your questions about this meeting.  Please address all questions to Cathy Milbourn, and her email is<EMAIL_ADDRESS>
                  At the conclusion of the meeting, the SACC will prepare a report as a response to questions posed by the Agency, background materials, presentations, and public comments.  This final report also serves as meeting minutes.  We anticipate the final report and meeting minutes to be completed in 60 days after the meeting.
                  Again, I wish to thank the Committee and ad hoc peer reviewers for your participation.  I'm looking forward to both a challenging and interesting discussion over the next three days.  And now, I turn the meeting over to our chair, Dr. Daniel Schlenk.  Thank you.
                  DR. DANIEL SCHLENK:  Thanks, Alaa.  Good morning, everybody.  Thanks for joining us this morning for our Draft TSCA Screening Level Approach for Assessing Ambient Air and Water Exposures to Fenceline Communities Version 1.0.  I'd like to thank EPA and Alaa for putting this all together -- the EPA staff.  I'd like to thank the presenters that will be presenting here in a few minutes, as well as the public commenters which will be presenting after them, and for their participation.  And we look forward to a very useful meeting that would be able to provide some information for the Agency in this regard.

INTRODUCTION AND IDENTIFICATION OF PANEL MEMBERS

                  DR. DANIEL SCHLENK:  At this point in time, I'd like to introduce the panel and the Committee.  Forgive me for keep using "panel." I keep using that word from the FIFRA panel that I chaired a few years ago, but it's a Committee.  So, at this point in time, we'd like to introduce members of the Committee.  So, I'm going to go through the list alphabetically and, if you would just state your name, your organization, and a brief statement of your expertise, and then we'll move forward with that.
                  So, at this point, Dr. -- well, maybe I should begin myself.  My name is Daniel Schlenk.  I am an environmental toxicologist.  I'm at the University of California, Riverside, and I'll be chairing this committee for the next three days.  Our next member would be Dr. Apte.
                  DR. UDAYAN APTE:  Hi, my name is Udayan Apte.  I'm a professor of toxicology at the University of Kansas Medical Center.  My expertise is in liver toxicology, environmental chemical effect on the liver.  I'm a board-certified toxicologist.
                  DR. DANIEL SCHLENK:  Thank you.  Dr. Baker.
                  DR. MARISSA BAKER:  I'm Marissa Baker.  I'm an assistant professor at the University of Washington in environmental and occupational health sciences.  I'm an industrial hygienist and exposure science person.
                  DR. DANIEL SCHLENK:  Thanks.  Dr. Blystone.
                  DR. SHERI BLYSTONE:  Hello.  Sheri Blystone.  I'm a chemist by training.  I've worked in the chemical industry for a long time now.  I'm doing safety and compliance currently with SNF Holding Company.
                  DR. DANIEL SCHLENK:  Thank you.  Dr. Calder.
                  DR. RYAN CALDER:  Hi, I'm Ryan Calder.  I'm assistant professor of environmental health and policy at Virginia Tech.  I am a professional engineer, and my background is in water quality modeling and coupling models of environmental systems to models for human exposure assessment.  I'm interested in minimizing human exposures to chemical contaminants in the environment.
                  DR. DANIEL SCHLENK:  Great.  Thanks.  Dr. Chaisson.
                  DR. CHRISTINE CHAISSON:  Hello.  I'm with the LifeLine Group and I'm a toxicologist, but most of my career has been with exposure assessment, risk assessment methods, and models, with particular emphasis on unique communities ranging from urban centers to tribal and rural lands.  Really pleased to be part of the Committee.
                  DR. DANIEL SCHLENK:  Yeah.  Thanks.  Dr. Cobb.
                  DR. GEORGE COBB:  Hi, I'm George Cobb.  I'm an environmental analytical chemist studying fate and transport and exposure assessments as well.  I'm here at Baylor University in Waco, Texas.
                  DR. DANIEL SCHLENK:  Thanks, George.  Dr. Davies.
                  DR. HOLLY DAVIES:  Hi, I'm Holly Davies.  I'm a toxicologist at the Washington State Department of Health.
                  DR. DANEIL SCHLENK:  Great.  Dr. Doucette.  I think you're on mute, Bill.
                  DR. WILLIAM DOUCETTE:  Right.  I thought I hit it.  One more time.  I'm Bill Doucette, environmental chemist and recently retired Professor at Utah State University and previous member of the SACC Committee.
                  DR. DANIEL SCHLENK:  Thanks.  Dr. Ferry.
                  DR. JOHN FERRY:  My name's John Ferry.  I'm a chemistry professor at the University of South Carolina.  I'm an environmental chemist, and I do research in the reactive attenuation of organic materials.
                  DR. DANIEL SCHLENK:  Thank you.  Dr. Gribble.
                  DR. MATTHEW GRIBBLE:  Hello, my name is Matthew Gribble.  I'm an associate professor of epidemiology at the University of Alabama at Birmingham School of Public Health.  I'm an environmental epidemiologist and also a diplomat of the American Board of Toxicology.
                  DR. DANIEL SCHLENK:  Great.  Thanks.  Dr. Heiger-Bernays.
                  DR. WENDY HEIGER-BERNAYS:  Wendy Heiger-Bernays, professor of Environmental Health at the Boston University School of Public Health.  My expertise is in risk assessment methods with a focus on vulnerable and susceptible populations.
                  DR. DANIEL SCHLENK:  Thank you.  Dr. Henneman.
                  DR. LUCAS HENNEMAN:  Morning.  Lucas Henneman.  I'm an environmental engineer, assistant professor at George Mason University.  My background's in air quality modeling and health assessments.
                  DR. DANIEL SCHLENK:  Thank you.  Dr. Johnson.
                  DR. MARK JOHNSON:  Hello, everybody.  My name is Mark Johnson.  I'm director of toxicology for the Army's Public Health Center.  My background's environmental toxicology and human health in its applications to risk assessment.  I'm a fellow of the Academy of Toxicological Sciences.
                  DR. DANIEL SCHLENK:  Thanks.  Dr. Kissel.
                  DR. JOHN KISSEL:  Hi, I'm John Kissel and I'm Professor Emeritus of Environmental and Occupational Health Sciences at the University of Washington in Seattle.  I'm an engineer by training and a human exposure scientist by practice.
                  DR. DANIEL SCHLENK:  Thank you.  Dr. Li.
                  DR. LI LI:  I'm Li Li.  I'm assistant professor of environmental health at the University of Nevada, Reno.  I'm leading a research group that develops computational models, fate and exposure models to assess how chemical substances reside, travel, and change in the modern media environment and how they get into the human beings.
                  DR. DANIEL SCHLENK:  Thank you.  Dr. Messerlian.  Sorry.
                  DR. CARMEN MESSERLIAN:  That's okay.  My name is Carmen Messerlian.  I'm a professor of environmental reproductive epidemiology at the Harvard Chan School of Public Health, and I'm the director of the scientific early life environmental health and development program at Harvard Chan.  And I study how environmental chemicals and the environment defined more broadly impacts fertility, pregnancy, and child health.
                  DR. DANIEL SCHLENK:  Thank you.  Dr. Przybyla.
                  DR. JENNIFER PRZYBYLA:  Good morning.  I'm Jennifer Przybyla, an environmental epidemiologist at the Agency for Toxic Substance and Disease Registry.  My expertise are environmental epidemiology, human health risk assessment.
                  DR. DANIEL SCHLENK:  Thanks.  Dr. Reif?
                  DR. RICK REISS:  Hi, this is Rick Reiss.  I'm a group vice president in principle scientist at Exponent, and my expertise is in exposure and risk assessment and dispersion modeling.
                  DR. DANIEL SCHLENK:  Okay.  Thanks.  Dr. Reif, please?  I think you jumped the gun a bit there.  No worries.
                  DR. DAVID REIF:  A couple letters off.  Yeah.  I'm David Reif.  I'm a professor at North Carolina State University.  I sit in the bioinformatics center, and I'm in the department of biological sciences.  My lab studies environmental health sciences, data integration, data science applications, and computational toxicology.  And my background is in statistics and human genetics.
                  DR. DANIEL SCHLENK:  Thanks.  Dr. Rowlands.  I think you're on mute, Craig.  Do we have Dr. Rowlands?  No, I guess not.  I guess we'll skip him.  Dr. Sathyanarayana.   Sathyanarayana.
                  DR. SHEILA SATHYANARAYANA:  Hi, I Sheila Sathyanarayana, and I'm a pediatrician and epidemiologist at Seattle Children's Research Institute in the University of Washington.  I'm a professor that focuses on environmental exposures in early life and human health outcomes and have focused on translation to policy.
                  DR. DANIEL SCHLENK:  Thanks.  Dr. Unseld.
                  DR. MONICA UNSELD:  Hi, Monica Unseld.  Executive director and founder of Until Justice Data Partners here in Louisville, Kentucky.  My background is in endocrine disruption and environmental signaling.  I also have a master's in public health.  For almost 15 years, I've worked with fenceline communities to see how we can better get modeling and algorithms and data to fit the reality of daily life in these communities.
                  DR. DANIEL SCHLENK:  Thank you.  And Dr. Vorhees.
                  DR. CHIP VORHEES:  Hi, Chip Vorhees.  I'm a professor of neuroscience at the University of Cincinnati and Cincinnati Children's Hospital in the division of pediatric neurology.  My research is on animal models of ADHD and developmental neurotoxicity, particularly of pesticides.

INTRODUCTION AND WELCOME

                  DR. DANIEL SCHLENK:  Thank you, everyone.  Thanks for going through that.  At this point in time, we will have some introductory material that will be presented by various members of the Agency.  Our first presenter will be Mark Hartman who's the deputy director for management at EPA OCSPP.  Office of Pollution and Prevention and Toxics.  Mr. Hartman.
                  MR. MARK HARTMAN:  Thank you, and good morning, everyone.  I am Mark Hartman, I'm the Deputy Office Director for Office of Pollution and Prevention and Toxics.  It's a pleasure to be with you today as we're very glad to welcome back those of you who have previously served on the Committee as well as welcoming our new members to the SACC experience.  It's hard to believe that the last time the SACC met was back in June of 2020.  We're thankful for the important role the SACC plays -- has played and continues to play in our risk evaluation process under TSCA.
                  Thank you for your time, your consideration for what we are presenting here today, and the thoughtfulness of your input.  We're proud of the EPA team that has worked so diligently on this effort and look forward to your feedback on this very important work.  It is also my pleasure today to introduce to you the Office of Chemical Safety and Pollution Preventions System Administrator Michal Freedhoff.  Dr. Freedhoff has more than 20 years of government experience, most recently as the minority director of oversight for the Senate Environment and Public Works Committee.
                  She began her career of congressional service in 1996, in then-Congressman Ed Markey's office as a congressional science and engineering fellow after receiving a Ph.D. in physical chemistry at the University of Rochester.  Dr. Freedhoff has also served on the staffs of the House of Science Committee, House Select Committee on Energy Independence and Global Warming, the House Energy and Commerce Committee, and the House Natural Resources Committee.
                  With environmental expertise spanning a range of policy areas for legislative work includes the 2019 legislation to address PFAS contamination, the Fuel Economy Provisions, and the 2007 Energy Independence and Security Act, and allowing the creation of an online database potential consumer product safety defects.  However, much of her time was spent on the 2016 reauthorization of the Toxic Substances Control Act.
                  She played an integral role in drafting this legislation and now brings that expertise to EPA to lead TSCA implementation under the Biden/Harris Administration.  In the year-plus that I've had the pleasure of working with Dr. Freedhoff, I have witnessed her strong commitment to scientific integrity using the best available science to drive decision making and her support for EPA's career staff.   Welcome, Dr. Freedhoff.
                  DR. DANIEL SCHLENK:  Thank you.  Dr. Freedhoff.
                  DR. MICHAL FREEDHOFF:  Thanks so much.  Thanks very much, Mark.  Can you all hear me okay?
                  MR. MARK HARTMAN:  Yes.
                  DR. DANIEL SCHLENK:  Yes.

WELCOME AND INTRODUCTORY COMMENTS

                  DR. MICHAL FREEDHOFF:  Great.  Thanks.  Well, good morning.  I'm Michal Freedhoff, the assistant administrator of the EPA's Office of Chemical Safety and Pollution Prevention.  And thank you so much for your participation in this peer review of EPA's Approach for Assessing Exposures to Fenceline Communities.  Your support and commitment as both SACC members and as ad hoc expert reviewers is critical in helping EPA to continue to meet its mission.
                  Part of that mission is ensuring that science and scientific integrity remain the backbone of our regulatory work.  And that's why the peer review that SACC provides is so critical.  And we also greatly appreciate the SACCs continuing assistance with completing reports as expeditiously as possible so that we can incorporate your feedback into the chemical safety protections we expect and hope to provide to communities all across America.
                  As you all know, under the last administration science on certain exposure pathways -- like exposure through ambient air, water, and disposal -- were excluded from most risk evaluations.  And what that effectively meant is for purposes of TSCA it didn't count if you drink it, and it didn't count if you breathed it.  But that's not what TSCA says.  TSCA tells EPA to conduct risk evaluations to determine whether a chemical substance presents no reasonable risk to health and the environment under the conditions of use, including an unreasonable risk to relevant potentially exposed or susceptible sub-populations.
                  You've actually all told the Agency that over and over again.  For example, in the peer review report for 1,4-Dioxane, you noted that the lack of an exposure assessment for the general population may leave substantial portions of the population at risk, which is particularly concerning for drinking water exposure.  And also, during that peer review meeting, the Committee observed that if each office at EPA says someone else is assessing the risk, the U.S. public will never get a comprehensive risk assessment.
                  As a second example, in both the carbon tetrachloride and the perchloroethylene (phonetic) reports, the Committee said that excluding multiple routes of exposure from the risk evaluation could not be justified by saying that some other part of the Agency regulates them.  And similarly, in your review of 1-BP, you state, and I quote, "The lack of consideration for general population exposures excludes the vast extent of the U.S. population who are exposed to 1-BP, perhaps on a daily basis.  The lack of consideration of the general population of exposure is concerning given the strong evidence of widespread exposure to a chemical that may be 1-BP based on biomonitoring data."
                  That report goes onto say the exclusion of the general population, quote, "does not instill confidence that objectivity is being maintained in Agency assessments as part of TSCA," end quote.  We agree with you, and that's why we reversed that policy.  So as a very first step to understanding risks to the general public via these exposure pathways, we've developed this version 1.0 of a methodology designed to assess any potential risk in the air and water exposures that were excluded from the risk evaluations to fenceline communities or those communities within close proximity to chemical facilities.
                  It's important to be clear about what this screening methodology is and what it is not.  We're charged under TSCA with providing chemical safety protections once we find unreasonable risk in a risk evaluation.  A great deal of science and analysis was done in those risk evaluations despite some notable policy deficiencies associated with them, and unreasonable risks were found across almost all uses of all of the chemicals.
                  We feel a strong sense of urgency and a strong sense of responsibility to note quickly to address those risks.  But we also don't want to leave communities out.  We want to be sure that the rules we write are as protective as they need to be and are also scientifically and legally defensible.  So, the version 1.0 methodology is just that.  It's an initial attempt to develop a meaningful screening-level approach which will assist the Agency in making go or no-go decisions on whether health and environmental protection is best served by either proceeding quickly to rulemaking for a chemical or by formally supplementing the risk evaluation.
                  If the results of this screening methodology show there are no likely added fenceline community risk for a substance, or if the rule were contemplating for that substance based upon the existing risk evaluation would also address those risks, we'll continue our rule-making process quickly.  As a very extreme example, if the previously finalized risk evaluation supports a complete ban or phase-out of a chemical, clearly no further revision of the risk evaluation should be needed.
                  However, if the refined screening methodology tells us that the rules supported by the last administration's risk evaluation is not going to be sufficiently protective of fenceline communities, we will perform additional analysis and supplement the risk evaluation.  We've already made the decision that we'll need to do that for 1-dioxane, in part because we agree with the Committee, as well as with the many stakeholders whose express concern is the lack of consideration of all exposure routes to 1,4-Dioxane including as a byproduct in a number of both occupational, as well as consumer uses.
                  But the implications of formally supplementing the risk evaluations are significant because the 9 to 15 months it would take us to do that for each chemical would also push our rule-making for that chemical into 2025 or even later.  These rules are where the rubber meets the road to realizing the great promise of TSCA, and we're all eager to get there.  So, I want to take just a few more minutes to be really clear about what version 1.0 is and is not.
                  It is a proposed screening level methodology using reasonably available data, information, and models to quantify environmental releases, evaluate exposures, and characterize risks associated with such releases and exposures.  It is clearly not the more comprehensive analytic approach that the Agency intends version 2.0 to be that we'll develop and use in future risk evaluations.  Version 1.0 doesn't include a method to address broader potential environmental justice concerns, nor does it attempt to quantify aggregate exposures.
                  We recognize that these and other considerations are important, and we look to expand our capacity to evaluate these concepts in the next 20 risk evaluations and beyond.  But in light of this, my ask of you is two-fold.  One, under what circumstances can this draft screening level approach be used to help us make our go/no-go rule-making decisions?  And two, for the next iteration of this approach, what could we add, build upon, and further develop to make this more comprehensive so that it can be used as one of our scientific building blocks during risk evaluation for the next 20 chemicals?
                  Peer review's a cornerstone of EPA's work, and your work ensures that EPA uses sound science for decision making by honoring innovation and fostering meaningful stakeholder good feedback.  Each of these, and you, are essential for EPA to promote chemical safety in this country.  Thank you, once again, for your efforts, especially during these challenging times.
                  We greatly appreciate your dedication, your sacrifice, and your critically important role in helping EPA to implement this new methodology to understand chemical exposures to communities, particularly fenceline communities, who've been disproportionately exposed to pollution for generations.  Thank you.
                  DR. DANIEL SCHLENK:  Thank you, Dr. Freedhoff.  We are ahead of schedule.  A couple of questions of clarification.  Dr. Kissel, I see your hand is up.
                  DR. JOHN KISSEL:  So, in the previous incarnation of SACC during the Trump administration, we were explicitly told that spills are not conditions of use and therefore are not considered as toxic releases.  Given the importance of the groundwater pathway in the superfund world generally, my question is has that definition of conditions of use been revisited, and can we expect -- obviously, it's not in this -- in the 1.0 version of the document we're dealing with today.  But can we anticipate that the groundwater will be considered in version 2.0?
                  DR. MICHAL FREEDHOFF:  I don't think we've made specific decisions about 2.0 yet.  I think we're hoping to use some of your feedback to inform that.  But I would agree that reasonably foreseeable disposal conditions of use are within scope of TSCA risk evaluations and need to be considered.  I think that's about all I can say with regard to when a disposal action is reasonably foreseeable and when it is not because that's something that we're currently discussing pretty actively within the Agency.
                  DR. DANIEL SCHLENK:  Okay.  Thanks.  Dr. Sathyanarayana.
                  DR. SHEELA SATHYANARAYANA:  Hi, thanks.  Great to hear the background on this.  In the previous iteration, we had a lot of discussion about the regulation allowing for the ability to go back and ask industry for data to fill holes for risk assessment.  And it seems like the regulation allows for that.  But in version 1.0, I still don't see that, and I'm just wondering what the Agency's thoughts are on this piece because there are many chemicals where we don't have data to truly inform risk assessment.
                  DR. MICHAL FREEDHOFF:  I mean, this is a bit separate from this particular methodology, but I would agree entirely that the Agency's authority to obtain data from industry was not as expansively utilized as it could've been in the first few years of TSCA implementation.  And we're looking at a number of different ways to expand upon that.  One is the order authority under TSCA that I'm sure you're very familiar with, under Section 4.
                  But the other thing that we've recently begun to explore is a way to kind of standardize information collection activities under a rule-making that would inform the Agency that conditions of use or health and safety studies that are in the possession of industry and a range of other baseline information.  And so, what we've been working on -- and we did have hold a public meeting on that several months ago -- is a way to say that if you're being considered as a high-priority chemical, then as part of CDR reporting you need to provide this additional data set.
                  If you're undergoing a risk evaluation, then that data set might expand to include other information, and when EPA is done with the risk evaluation, then those additional data requirements would disappear.  Since I'm sure you know what was sort of happening in the first few years of the program in the constant budget crunch because no additional funding had ever been requested for implementing the new law -- is that the Agency scientists would get far along into a risk evaluation and then realize that the data gaps existed late in the process, which made it very difficult to use some of those data gathering authorities to inform the risk evaluations and also make the deadlines.
                  So, we're looking at going forward as a way -- at ways to sustainably ensure that we're getting the baseline data early in the process, that we're writing the TSCA test orders early in the process and that all that information would then be available as we move through the risk evaluation process.
                  DR. DANIEL SCHLENK:  Great.  Thank you, Dr. Freedhoff.

OPPT TECHNICAL PRESENTATION  -  OVERVIEW OF DRAFT TSCA FENCELINE METHODOLOGY

                  DR. DANIEL SCHLENK:  Without any further questions, let's go ahead and move forward with our technical presentation, which is the Overview of Fenceline Community Exposure Screening Level -- the approach.  This'll be presented by Kevin Vuilleumier and Rehan Choudhary.  Hopefully, I got your name right there, Kevin.
                  DR. KEVIN VUILLEUMIER:  Thank you, Dr. Schlenk.  You got pretty close.  I've even got that French aspect to it, right?  At the end.  Yeah.  But, yeah, it's Kevin Vuilleumier, so thank you.  So, what we're going to do is we're going to share my screen.  Okay.  Okay.  Can everyone see the screen okay?
                  DR. DANIEL SCHLENK:  Yeah.  Yes.
                  DR. KEVIN VUILLEUMIER:  Okay.  Great.  Thank you.  So, I want to start by saying good morning to the Scientific Advisory Committee on Chemicals, public commenters, and stakeholders.  My name is Kevin Vuilleumier, and I am the assessment lead for the fenceline team.  Our management leads are Rehan Choudhary and Yvette  Selby-Mohamadu.  I'm fortunate to be part of a very dedicated, knowledgeable, and talented team whose work is reflected in this presentation, as well as a draft fenceline report currently undergoing review.
                  Today I'll be presenting an overview of the fenceline work on behalf of the team.  Before we dive into the presentation, I want to remind everyone the draft fenceline methodology report was released to the public on Friday, January 21st, and is nearing the end of its 60-day public comment and review period which ends March 22nd, 2022.  With that, let's get started.
                  Over the next hour, I'll walk you through the Draft Toxic Substances Control Act, or TSCA, fenceline methodology, including some background information.  I'll begin with a brief overview.  Next, I will describe the proposed fenceline methodology in three sections: the air pathway, water pathway, and hazard and risk characterization methodology.  I will close out the presentation by briefly discussing the three case studies and associated findings included in the draft report, as well as anticipated next steps for the fenceline work.
                  Before continuing, I do want to be clear that the three case studies included in the draft report and this presentation are intended to be illustrative examples of applying the proposed fenceline methodology and the efficacy of such application.  While the case studies consist of three real chemicals to which EPA published risk evaluations in 2020 and 2021, the results and associated findings as presented do not represent final Agency action and will not be used for purposes of risk management actions or rule-making at this time.
                  I want to start by establishing a level playing field and common understanding of the background leading to the fenceline effort, as well as the intended purpose of the fenceline methodology.  The Office of Pollution, Prevention, and Toxics, or OPPT, published the first ten risk evaluations under the amended TSCA in 2020/2021 timeframe.  At the time of publication, a policy decision was in place which resulted in certain pathways not being assessed because they fell under the jurisdiction of other EPA administered laws, such as the Clean Water Act or the Clean Air Act.
                  That policy decision was reversed in June 2021, leading to a targeted effort to assess certain pathways previously excluded from the published risk evaluations.  The targeted effort is the fenceline effort and includes development of the fenceline methodology.
                  With that background in mind, the purpose of the fenceline methodology includes conducting screening-level evaluations to ensure potential exposures and associated risks were not overlooked for fenceline communities for seven of the first ten chemicals for which OPPT has published risk evaluations; also, to focus on certain ambient air and water pathways previously not assessed in the published risk evaluations; and third, to inform risk management actions and rulemaking for those seven published risk evaluations.
                  Turning briefly to the table on the right on this slide, you'll see the two pathways included within the fenceline methodology and the seven chemicals for which we intend to conduct a screening-level analysis for fenceline communities.  You'll notice two of the chemicals have a red X under the water pathway which indicates a screening-level analysis is not planned for that chemical for the water pathway.
                  Why is this the case?  For 1,4-Dioxane, EPA is conducting a supplemental and risk evaluation which will address the water pathway, and therefore screening level analysis is not warranted.  For 1-BP, the water pathway is not a concern based on review of P-chem and fate properties, as well as extremely low releases -- about one pound per year for all facilities -- and this is further discussed in the 1-BP published risk evaluation.
                  In the previous slide, I reference a term fenceline community several times.  So, what is a fenceline community?  For the purposes of the fenceline methodology, fenceline community consists of members of the general population that are in proximity to air emitting facilities or receiving waterbody and who therefore may be disproportionately exposed to a chemical undergoing risk evaluation under TSCA Section 6.
                  For the ambient air pathway, proximity goes out to 10,000 meters from an air emitting source.  For the ambient water pathway, proximity does not refer to a specific distance measured from a receiving waterbody but rather to those members of the general population that may interact with the receiving waterbody and, thus, may be exposed.
                  Slide five outlines what is not included as part of the fenceline work presented here or in the draft report.  The key message we want to express here is a proposed fenceline methodology is intended to be a starting point, or springboard, from which we can build and expand beyond the limits we set for this initial work.  I also want to draw your attention to the footnote associated with the final two bullets on this slide.
                  As stated, although aggregate\cumulative exposures, as well as identification of potential environmental justice concerns, are not addressed in this current work, EPA is seeking SACC input on potential applications of the proposed methodology and built-in flexibilities to evaluate aggregate\cumulative exposures and potential environmental justice concerns as part of the charge for SACC review of this work.
                  Now, let's move to the discussion of the specific methodologies developed for the fenceline effort beginning with the air pathway.  Here I'll give you an overview of the air pathway starting with the graphic on the right.  We start by looking at the air emissions from a releasing facility, or the source, which may be either, or both, stack and/or fugitive in nature.  Next, we use the release data to model ambient air concentrations at select distances from the releasing facility via the pathways.
                  For purposes of the air pathway fenceline work, we focus on only the inhalation route as the route of exposure and identify exposures and associated risks to fenceline communities with receptors for that route of exposure.  The general approach for estimating air releases from a source is to use 2019 Toxics Release Inventory, or TRI data.  If there are data gaps in the 2019 TRI reporting, we try to identify TRI surrogate data for the use and scenario under consideration.  If data gaps remain, we rely on our existing suite of models and release estimation methods used to support the first ten published risk evaluations.
                  Ambient air exposure concentrations are estimated at select distances extending out to 10,000 meters using AERMOD.  AERMOD refers to the American Meteorological Society/Environmental Protection Agency Regulatory Model.  One additional item I'd like to mention, when we do not have release data from TRI, we estimate releases as described above and use those estimated releases as inputs to model a series of exposure scenarios considering various factors as shown in the estimated release boxes on this slide.
                  Two case study chemicals were selected for the air pathway methodology: 1-bromopropane, or 1-BP, and methylene chloride, or MC.  In order to support the evaluation of receptors proximal to facilities that may release chemicals undergoing risk evaluation, we extracted air release data from the 2019 TRI for the air pathway.
                  EPA followed the five-step approach on this slide for estimating air releases, only deviating from this approach when evaluating occupational exposure scenarios for which no 2019 TRI data existed.  Step one begins with extraction of the chemical-specific release data from the TRI basic plus files which contain the relevant information for the release analysis including data elements such as releases, chemical activity and uses, and other facility-specific information.
                  Steps two and three, with those steps we associate each facility release with an occupational exposure scenario, or OES, and the corresponding release days both obtained from the published risk evaluations.  Steps four and five involve estimating releases from an alternative approach for OES that have no 2019 TRI data and summarizing all release results for use in the exposure modeling.
                  The next several slides will focus on steps two, three, and four.  I'd like to take a moment to describe OESs and how they relate to the conditions of use, or COUs, in the published risk evaluations.  COUs, as defined in the risk evaluations, are the circumstances under which a chemical is expected to be manufactured, processed, distributed, used, or disposed.  For the purposes of identifying and using similar assessment approaches based on expected exposure and/or releases, COUs may be grouped or mapped into broad categories referred to as OES.
                  In some cases, this mapping may be fairly simple where one COU maps directly to one OES.  However, in many cases, there isn't a one-to-one mapping.  In such cases, multiple COUs may sit under one OES, or alternatively, one COU may be mapped to multiple OES due to distinctly different exposure scenarios that would not result in similar releases and exposures.
                  Slide ten discusses mapping TRI use information to an OES, which involves evaluation of the documented uses and sub-uses as reported to TRI using the TRI form R.  Uses and sub-uses are reported on per chemical, per facility basis.  Alternatively, facilities meeting certain requirements may be able to report basic site information using TRI form A.  TRI form A, however, does not require the reporting of use and sub-use information.
                  So, EPA uses a North American Industry Classification System, or NAICS, code along with information from company websites to determine the use and sub-use information for form A reporting facilities.  The use information is compared to the list of industrial function categories as reported for the chemical data reporting rule, or CDR.
                  The industrial reporting category describes a specific function that a chemical provides when used in the formulation of a product or used with an industrial process.  A similar mapping was performed between COUs and OESs when developing the published risk evaluations.  The final mapping step uses the CDR industrial function codes as a bridge to bring together the TRI to CDR mapping and the COU to OES mapping to establish the link between the reported TRI facility use information and the OESs from the published risk evaluations.
                  The third step in the release estimation process is estimating the days of release.  Since the TRI release information is reported on an annual basis, estimating the days of release are necessary to combine with reported annual TRI releases.  This combination produces a daily release estimate used for exposure model.  The daily release estimates used in the fenceline work are from the published risk evaluations, and they're provided here for context.
                  The rationale for the estimated days of release are also provided to show estimates may vary across OES based on underlying assumptions and supplemental release information sources.  For an OES where a model from the published risk evaluation was used for the release days estimate, there may be a distribution of release days provided, as shown in the last row of this table for the aerosol spray degreaser and cleaner OES rather than a single value.
                  This slide outlines a hierarchy decision tree developed to estimate releases for OES without 2019 TRI data.  When there is no 2019 TRI data, level one starts the hierarchy by considering prior TRI reporting year data, in this case 2016 through 2018 data.  The second level in the hierarchy relies on air release estimation modeling already completed in the published risk evaluations or new modeling using our existing suite of models to estimate releases.
                  The third level in the hierarchy considers existing literature sources used in the published risk evaluation.  The fourth level in the hierarchy considers use of surrogate data.  This uses 2019 TRI data from another TRI reporting facility which would have been mapped to a somewhat similar but decidedly different OES.  That other TRI facility acts as a surrogate facility and is a source of the release data modeled.  The final level in the hierarchy covers remaining options.  If this level's relied upon for the fenceline work, it is discussed in the chemical-specific case studies.
                  Closing out the air release portion of the air pathway, this slide shows several assumptions and uncertainties which could have potential quantitative impacts on the release estimates.  The TRI database only contains information on facilities that are subject to TRI reporting and meet the reporting requirements.  As a result, not all sites releasing a TRI chemical will report to the TRI.
                  Those facilities will neither be captured in the TRI database nor be included in the fenceline release summary.  The facility use information as reported to TRI is limited, and therefore may not contain adequate information needed to confidently map facilities to a corresponding OES.  This could impact the estimated days of release and associated daily releases to the ambient air.
                  Finally, a primary requirement for form A is that the combined facility releases are below 500 pounds per year.  However, actual releases are not required to be reported.  For these facilities, EPA assumes an upper bound of 500 pounds per year for releases, which factors into how exposure modeling is performed for form A reporters.
                  Moving into the exposure proportion of the air pathway methodology, this slide provides a visual roadmap of the three methodologies used to evaluate exposure via the air pathway for the fenceline work.  I will speak to each of these methodologies in more detail in the coming slides.  But in general, this slide visually displays some of the differences between the approaches as they relate to releases, exposure scenarios, and models used.
                  Slide 15 provides a brief comparison and explanation of how each methodology is applied for purposes of the fenceline work.  The pre-screening methodology, as applied in the fenceline work, is independent of facility and condition of use.  Findings from the pre-screening methodology are intended to inform whether a full screening analysis is warranted based on whether pre-screening does or does not identify potential risks to select receptors at three predefined distances within the IIOAC model.
                  In contrast, the full-screening methodology is both facility and COU-specific.  Additionally, while we limit our use of the full-screening methodology in the current work to screening-level analyses for fenceline communities, the capabilities of the full-screening methodology are not as limited.  Additional, more detailed analyses can be performed with the full-screening methodology, although such analyses require, among other things, more detailed facility-specific data which may or may not be reasonably available information.
                  The co-resident methodologies is separate from the pre-screening and full-screening methodology in that it is designed for unique case specific conditions of use and receptor configurations.  Additionally, the proposed co-resident methodology looks at indoor air transport phenomena rather than ambient air directly.
                  Beginning with the pre-screening methodology, this flow chart shows the approach and exposure scenario components applied to the fenceline effort.  As shown in the roadmap, the prescreening methodology uses EPA's IIOAC model.  Starting at the left of this slide, the pre-screening methodology uses two air release values from the TRI data set for model inputs: the maximum release value, which is the highest individual facilities reported total release value for the chemical undergoing risk evaluation among all facilities reporting that chemical to TRI and the average, or mean release value, which is the arithmetic average of all facility reported total release values for the chemical undergoing risk evaluation across all facilities reporting that chemical to TRI.
                  Moving left to right, we built out a series of 16 exposure scenarios for each release value considering the release type, topography, meteorological data, and the release scenario.  Each of these inputs and the basis for selection are described in more detail within the draft report currently undergoing review.
                  For purposes of risk calculations and identifying potential risks, the pre-screening methodology selects the highest exposure concentrations from all exposure scenarios modeled based on the pre-screening work performed for the fenceline effort so far.  The scenario resulting in the highest exposure concentrations follows the exposure scenario highlighted orange in this diagram.
                  This slide lists some of the assumptions and uncertainties associated with the pre-screening methodology.  The key point to remember is the pre-screening methodology is designed to maintain a conservative approach for estimating exposures as it is intended to inform the need for a full-screening analysis.  As a result, we do not want to miss potential risk and screen out the need for a full screening analysis prematurely.  To retain the conservative nature of the pre-screening methodology, EPA recognizes the default values for stacked parameters and plume characteristics represent the low, slow-moving, non-buoyant plume, which tends to lead to more conservative exposure estimates at the model distances.
                  This slide closes out the pre-screening methodology by sharing some strengths and limitations of the proposed methodology.  For strengths, the IIOAC model is an Excel-based tool which readily defines necessary inputs as relatively easy to learn.  The model allows quick evaluation, which can be conducted in-house without the need for specialized expertise, saving both time and level of effort.
                  The primary limitation is the construct of the model itself.  The model is built on pre-run scenarios created and run through AERMOD, which inherently limits the inputs, defaults, and meteorological data to those used for the pre-run scenarios.
                  Moving to the full-screening methodology, this slide introduces details about the approaches used for the fenceline work using AERMOD.  The first bullet describes the overall purpose and goal of the full-screening methodology which is to estimate ambient air concentrations and associated exposures at varying distances and receptor locations from a facility releasing the chemical undergoing risk evaluation.
                  The full-screening method evaluates exposures at eight finite distances: 5, 10, 30, 60, 100, 2,500, 5,000, and 10,000 meters, and one area distance, 100 to 1,000, meters from a releasing facility.  For each finite distance, receptors are placed in a polar grid at equal distances around the associated distance ring: every 22.5 degrees.  This results in a total of 16 receptors around each distance ring.  Visually both the distances and receptor locations can be seen in the diagram in the top right of this slide.
                  Finite distances are represented by different colored rings.  The area distance is represented by the shaded donut ring.  Receptor locations are represented by the boxes placed around the ring.  For the one area distance evaluated, receptors are placed in a cartesian grid between approximately 200 meters and 900 meters from the releasing facility at 100 meters spacing.
                  This results in a total of 456 receptors with a daily and annual average exposure concentration estimates for the area distance represent the arithmetic average, the mean exposure concentration, across all 456 receptors within the area distance for each day, and across an entire year.  The remaining bullets on this slide provide some other parameters considered as part of the full screening methodology approach and associated inputs for the model.
                  Slide 20 summarizes the outputs obtained from full-screening methodology based on the distances and receptor locations evaluated.  The left box shows a total number of modeled exposure concentrations obtained for the two types of release estimates provided.  When 2019 TRI data is available, we estimate exposure concentrations using one year of meteorological data resulting in a total of 5,856 separate daily averaged and 16 annual averaged exposure concentrations around each distance ring evaluated.
                  When alternate release estimates are provided, we estimate exposure concentrations using five years of meteorological data.  Since the default meteorological stations are pulled from IIOAC, which uses five years of met data, this results in 29,216 separate daily average and 16 annual average exposure concentrations around each distance ring evaluated.
                  Moving to the right box, post-processing script is used to extract various statistics and percentile concentrations from the base concentration distributions obtained from AERMOD.  A key component to this effort includes extraction of three percentile concentrations: the 10th, 50th, and 95th percentiles, which are used for purposes of risk calculations and identifying associated potential risks.  In essence, this provides a low-end, central tendency, and high-end concentration-based risk estimate for purposes of risk characterization for each facility at each distance evaluated.
                  Here I highlight some of the assumptions and uncertainties associated with the full screening methodology.  The key point to remember here is the full screening methodology as presented in the draft report, is used for screening-level analyses.  While we limit user-defined inputs to several key parameters of particular interest for screening level purposes, the capabilities of full screening methodology allow inclusion of many additional user-defined inputs which can be considered and included in a more detailed analysis or an expanded analysis beyond screening level.
                  Closing out the full-screening methodology, this slide outlines a few strengths and a limitation associated with the full-screening methodology.  The primary strengths of the full-screening methodology revolves around the capabilities of the model used and the potential options for additional more detailed analysis in the future when and if data is available.  However, AERMOD is a complex model which requires specialized expertise to build scenarios within the model, to run the model, and to extract desired data for evaluation.
                  Moving to the final air pathway methodology, this slide provides an overview of the co-resident methodology and approach presented in the draft report.  The application of the co-resident methodology within the draft report is limited to only one case study and only the dry-cleaning condition of use.
                  The co-resident methodology utilizes IECCU, which is a deterministic model used to simulate effects of sources in unconditioned zones, a releasing facility, on the indoor environmental concentrations in condition zones in the residences or apartments.  Since the effects on condition zones depends on the building configurations, for example, how the zones are or are not interconnected, the draft report includes analyses for two building configurations: architecturally connected or architecturally separated.
                  The figure on the right provides a general building schematic showing the primary inputs for the IECCU model.  This example shown here represents a building configuration where the two zones are architecturally connected via a staircase.  So, we're on the left side here.
                  The second bullet provides the mass balance equations used for the simulations.  These provide a concentration per unit time in the condition zones, which are then adjusted to the appropriate averages needed for purposes of evaluating exposure concentrations, risk calculations, and associated risks when compared to the benchmarks.
                  This slide provides a few assumptions and uncertainties associated with the co-resident methodology, which they are discussed in more detail within the draft report.  Slide 25 closes out the co-resident methodology as well as the air pathway discussion by identifying some strengths and limitations of the co-resident methodology.
                  General strengths revolve around IECCU being an indoor air pollutant transport model with multiple modules and capabilities to consider sources and syncs with the indoor environment, as well as a variety of potential exposure scenarios.  Limitations are primarily focused on the complexity of the model which requires specialized expertise to run.
                  Additionally, since there are no default values included within the model, model inputs and limitations of such inputs often are dependent on the accuracy and strengths of the literature values or the capabilities of other models to provide accurate and representative estimates of values, which are then used as inputs to the IECCU model.
                  Now, I will move to the water pathway methodology.  Here I'll give you an overview of the water pathway, starting again with the graphic on the right.  We start by looking at the water releases from a releasing facility, the source, which may be either or both direct and/or indirect in nature.  Next, we use the release data to model ambient water concentrations resulting from the facility releases, via the pathways.  For purposes of the water pathway fenceline work, we focus on the dermal and oral ingestion route of exposure and, again, identify the exposures and associated risk to fenceline communities' receptors for each route of exposure.
                  The general approach for estimating water releases for the fenceline work relies upon water release information from the published risk evaluations.  The release information include develop releases scenarios representing known direct and indirect chemical releasers.  These direct and indirect releases represent known industrial facilities and wastewater treatment plant releases.
                  The releases are modeled in the Exposure and Fate Assessment Screening Tool -- specifically E-FAST 2014 -- to predict environmental exposure concentrations in the published risk evaluations.  During this process, ambient water concentrations are modeled, and drinking water concentrations and doses are auto-calculated.
                  EPA uses the modeled surface water concentration to evaluate both incidental dermal and oral ingestion to fenceline communities.  EPA extracts the auto-calculated drinking water data for use in evaluating ingestion from drinking water, again, to fenceline communities.  The modeled surface water and auto-calculated drinking water data is adjusted, as applicable, to incorporate various 2019 exposure factors handbook input information and age group considerations including intake rate, ingestion rate, body weight, skin surface area, and/or exposure time to evaluate exposures.
                  One additional item I'd like to mention, EPA did search for available monitoring information for the water pathway work within the fenceline effort.  This is discussed in more detail within the draft report.  Two case study chemicals were selected for the water pathway methodology.  Those are N-Methylpyrrolidone, NMP, and methylene chloride.
                  E-FAST 2014 is a tool which estimates chemical concentrations in various media, including ambient water resulting from discharges to both free-flowing and still water bodies.  The tool uses upper percentile and/or mean exposure parametric values that result in possible conservative exposure estimates.  Advantages of this tool are that it requires minimal input parameters and has undergone extensive peer review by experts outside of EPA.
                  This slide shows the inputs and associated calculation within E-FAST 2014 to determine surface water concentrations.  Among the inputs used for this calculation are a number of release dates, the chemical release to wastewater, chemical removal from wastewater treatment, and surface water flow information.
                  Release days represent the number of days per year that a chemical is discharged and is used to calculate a daily chemical release to wastewater amount based on known annual releases and loading information from either or both TRI and discharge monitoring reports, or DMR, when available.  Since direct discharging facilities are not required to report the number of days associated with chemical releases, release scenarios developed in the published risk evaluations are used to provide an upper and lower bound of release days used to calculate the associated surface water concentrations.
                  Surface water flow information is included within E-FAST 2014 database.  However, flow information is dependent on whether the release comes from a known or unspecified location.  For those locations where there is a known national pollutant discharge elimination system, or NPDES permit, for the discharging facility, the E-FAST database is searched by the NPDES permit number, name, or known discharging waterbody reach code to obtain relevant flow information.
                  Where a site-specific NPDES code is unavailable, a surrogate NPDES code for a nearby facility that discharges to the same waterbody may be used.  If there is no known NPDES code, or the exact location of a chemical loading is unknown, the standard industrial classification code -- SIC option -- within E-FAST is used.  This option uses a 10th and 50th percentile receiving 7Q10 stream flows for dischargers in a given industry sector.  The most representative SIC for an evaluated release is used.
                  Slide 30 outlines the approaches and various inputs used for estimating drinking water and recreational oral/dermal exposures for the fenceline effort.  Starting with drinking water exposures in the left box, drinking water exposures are at the water body of release with water treatment set at zero percent.  For acute exposure, modeled stream concentrations are based on 30Q5 flow information and 95th percentile consumer data from the 2019 exposure factors handbook for drinking water intake rates.
                  For chronic exposure, modeled stream concentrations are based on the harmonic mean flow information and mean per capita data from 2019 exposure factors handbook, which is used for the drinking water intake rates.  Moving to recreational oral/dermal exposures -- or it's also referred to as incidental oral/dermal exposure -- in the right box, approaches for recreational oral and dermal exposure follow those originally undertaken in the published risk evaluations for 1,4-Dioxane and NMP.  Chemical-specific skin permeability coefficients are used for the dermal evaluation.  Estimated surface water concentrations use a previous E-FAST facility release scenarios and modeled 30Q5 and harmonic mean concentrations for acute and chronic dose estimations, respectively.
                  For all water pathways, exposure concentrations are estimated across various age groups ranging from infants to adults, although results presented in the body of the draft report are for the more sensitive chemical-specific populations.  All age group calculations are included in the supplemental materials to the draft report.
                  This slide closes out the water pathway methodology by identifying some assumptions and uncertainties associated with the water pathway methodology.  The key point to remember here is the proposed screening level methodology for the water pathway is designed to maintain a conservative approach for estimating exposures.
                  A couple key assumptions which help maintain this conservative approach include, estimating the surface water concentrations at the point of release without consideration of post-release environmental fate or degradation, assumptions associated with recreational oral/dermal exposures occurring at the point of release without the consideration of transport, illusion, or treatment.
                  One final note, the applied streamflow distribution is a key driver of estimated results within E-FAST 2014.  However, the age of the streamflow distribution dataset within the E-FAST 2014 tool, and the selection of representative flow data, brings in some uncertainties which can impact the representativeness of the overall modeled result for more current release data.
                  I'll now present an overview of the human health hazard and risk characterization methodology.  This slide summarizes previously identified hazard endpoints from the published risk evaluations used for each of the three case study chemicals included in the draft fenceline report.  For the fenceline analysis, EPA started with the same human health endpoints -- endpoints of departure -- as were derived in the published risk evaluations for each chemical and only adjusted the human equivalent concentrations or human equivalent doses to a continuous exposure basis so they could be applied to evaluate continuous fenceline exposures.
                  As you can see, 1-BP and methylene chloride both have acute, chronic non-cancer, and cancer hazards; while NMP has acute and chronic non-cancer but no cancer hazard identified.  This analysis uses the most sensitive endpoints from each published risk evaluation that was the basis of risk determination.  In several cases, they were based on effects during sensitive life stages.
                  To calculate risks, EPA used the same approach described in the published risk evaluations.  Non-cancer risk was calculated using a margin of exposure of approach where the hazard value was divided by the predicted human concentration.  EPA interpreted the MOE risk estimates in reference to benchmark MOEs.
                  Benchmark MOEs are the total uncertainty factor for each non-cancer POD.  The MOE estimate is interpreted as a health risk if the MOE estimate is less than the benchmark MOE.  Cancer risk is calculated by multiplying the predicted human exposures body inhalation unit risk for inhalation exposures or by the cancer slope factor for oral and dermal exposures.  The cancer risk estimate is interpreted as a health risk if the cancer risk estimate is greater than the benchmark of one times ten to the minus six for fenceline communities.
                  For the water pathways, cancer risk is estimated both for individual life stages and integrated across lifetimes.  EPA also applies age-dependent adjustment factors, or ADAFs, to carcinogens acting to a mutagenic mode of action -- IE methylene chloride -- to account for increased risk from early life exposures via the water pathways.
                  Slide 35 depicts an overview of the land-use evaluation considerations and associated decision tree.  As part of the risk characterization for the air pathway, the fenceline methodology includes a land-use evaluation around facilities where risk is indicated.  This evaluation is used to determine whether an actual inhalation exposure and an associated potential health risk is expected to fenceline communities within the radius around the facility where risk is indicated.  For all the facilities with TRI-reported releases, location information in the form of latitude and longitude -- we used ARC-GIS to map facility locations and create buffer rings around each facility for each distance evaluated.
                  We then use ARC-GIS and Google Map to visually examine the land use within the farthest distance from the facility where there is an indication of acute, chronic non-cancer, and/or cancer risks for low, central, and high tendencies.  For residential, industrial, commercial-end businesses, or other public spaces are present within that distance, EPA considers those receptors within the fenceline communities and therefore reasonably expects a potential exposure and associated potential risk to fenceline communities.  When the farthest distance that at which risk is indicated falls within the boundaries of facility property, or includes only uninhabited areas, EPA does not reasonably expect an exposure or an associated risk to fenceline communities.
                  This slide presents some strengths and limitations associated with the land-use evaluation methodology.  A few key takeaways from this slide, it's a simplified method which can be performed using a Google Maps search engine and provides a quick visual image of the area around a given facility.  EPA only applied the land-use analysis methodology to the air pathway in this current fenceline work.  Although, it has potential for use with other pathways, such as the water pathway, as well as additional or more detailed analyses.  Most of the limitations with the land use analysis methodology involve the reliance on certain information and maps data outside of EPA's purview.
                  This slide closes out the risk characterization methodology by identifying some assumptions and uncertainties related to the hazard and risk characterization for the fenceline to work.  There are several assumptions and uncertainties to keep in mind for the risk characterization overall, including specific strengths and limitations of the analysis.  First, this analysis assumes that an individual living near a facility will be exposed to a chemical at a similar concentration for all hours of the day.  That means it is most relevant for individuals in the fenceline community who spend all day at home or very nearby.
                  The chronic lifetime cancer risk estimates are most relevant for people who remain in the fenceline community for years and do not relocate.  Second, the precision of the risk estimates is limited by a couple of factors.  Because modeling for the air pathway focused primarily on finite distances from the facility --  for example, we evaluate risk at 60 meters and 100 meters but not in between -- there is some uncertainty about what the risk may be in between those distances when risk is indicated at 60 meters but not at 100 meters.
                  In addition, for facilities with physical locations, we were able to evaluate land-use patterns.  However, from modeled theoretical facilities with no physical location, we are not able to evaluate land use.  Finally, considered duration of sensitive life stations and subpopulations is consistent with what is described in the published risk evaluations.  Since hazard values are based on PODs derived in the published risk evaluations, they incorporate the same considerations for potentially exposed in subpopulations.
                  In depth discussion of the assumptions and uncertainties associated with the chemical-specific PODs can be found in the published risk evaluations for each chemical.  For oral and dermal exposures via the water pathway, risks are calculated based on life stage specific exposure scenarios.  For inhalation exposures via the air pathway, risks are calculated based on air concentrations and therefore do not incorporate any life stage differences in dosimetry.  This is consistent with Agency guidance and assumes that the ten times interspecies uncertainty factor accounts for any life stage specific differences in dosimetry.
                  Next, I will briefly discuss the case studies we included in the draft report, followed by a short summary of anticipated next steps for the fenceline work.  Here's a quick recap of the case studies I'm going to discuss.  We include three case study chemicals in the draft fenceline report: two for the air pathway, 1-BP and methylene chloride; and two for the water pathway, methylene chloride and NMP.
                  The purpose of these case studies is to provide illustrative examples of the application and efficacy of the proposed methodologies described in the draft report with the goal of identifying if there are potential risks previously not captured due to the exclusion of certain pathways from the published risk evaluations.  While the case studies do represent three chemicals for which EPA has published risk evaluations, the results presented in the draft report and in this presentation, again, do not represent final Agency actions.
                  Slide 40 begins the 1-BP case study, which was only evaluated for the air pathway in the draft report.  This case study will include a bit more detail than the other two because I'll talk through slides with results for the first time and provide an example facility which walks through the entire methodology, including land-use analysis.
                  Here is a tabulated snapshot of the results obtained for the release assessment and exposure assessment through application of the proposed methodologies for the air pathway.  While the ranges of release data and exposure concentrations are shown here, a full set of releases are included in the draft report and accompanying supplemental files.
                  The left two columns present each OES evaluated along with the number of facilities within each OES evaluated.  Where you see a dash under the TRI facilities column header, it means there is no TRI-reported data available for that OES.  As such, the releases are estimated using the alternative release estimation hierarchy described earlier.  The next two columns show the range of estimated annual air releases obtained for the release assessment for both fugitive and stack releases.
                  The last four columns show a very small subset of the daily averaged and annual averaged modeled exposure concentrations obtained through application of the full screening methodology using AERMOD.  For context, these minimum and maximum concentrations represent only the minimum/maximum 95th percentile exposure concentrations across all facilities within a given OES across all distances modeled for a given OES.
                  For purposes of risk calculations, we present and use the minimum, mean, and maximum 95th percentile exposure concentrations across all facilities within a given OES.  Those values and associated risk calculations are presented by OES and distance within the draft report.
                  This table summarizes the results of the risk calculations for cancer risk based on the maximum 95th percentile exposure concentrations by OES and distance.  Overall, 14 occupational exposure scenarios were evaluated for 1-BP inhalation risk.  Thirteen of the 14 OES indicate excess cancer risk as far out as the area distance of 100 to 1,000 meters from a facility releasing 1-BP to the ambient air.  Three OES indicated risk from acute exposures.  Two OES indicate non-cancer risk from chronic exposures.
                  One quick note related to 1-BP, it was just recently designated as a hazardous air pollutant, or a HAP, under the Clean Air Act.  Breaking down the results of the fenceline methodology a bit more for 1-BP, this slide provides an example facility to which fenceline methodology has been applied for the air pathway.  All this information is provided within the draft report and accompanying supplemental files to the draft report.
                  To begin, there are three main components to the fenceline methodology: the release assessment, exposure assessment, and risk characterization.  The first two boxes are tied to the release assessment component showing the facility-specific mapping of OES and COU as well as the total releases and release type.  The third box is tied to the exposure assessment component presenting the range of modeled exposure concentrations across all nine distances modeled, as well as the three percentiles used for purposes of risk calculations: 10th, 50th, and 95th percentiles.
                  The fourth box is tied to the risk characterization component presenting the estimated MOE or cancer risk for acute, chronic, non-cancer, and cancer respectively, as well as the exposure concentration percentiles and associated distances indicating risk.  Following the indication of potential risk at one or more evaluated distances from the example facility based on a comparison of the estimated MOE or cancer risk to the respective benchmarks, this slide shows application of the land-use evaluation methodology to the example facility.
                  In this particular example, risk was indicated from 5 to 1,000 meters to a releasing facility.  A quick look at the map shows the area surrounding the facility, in particular within the distance of 100 to 1,000 meters radius.  Within that distance is included functional zoning containing mixed residential, commercial, industrial, institutional, and recreational areas.  As examples, we see residential areas to the north and south and a school -- which in this case the community college -- to the west among other land uses.
                  Based on this visual review of land use around the example facility, receptors within the fenceline communities do live and work within the radius of indicated risk.  With that, we determine there is an expected potential exposure to, and therefore associated potential risks to, fenceline communities.
                  Slide 45 closes out the 1-BP case study by summarizing the key results from applying the fenceline methodology, including land use evaluations.  EPA identified risks from fenceline air concentrations for 52 of the 62 TRI reporting release facilities covering 13 of 14 OES.  Based on land-use considerations, actual fenceline community exposures are expected for 39 of the 49 GIS located facilities for which risk was indicated.
                  These risk conclusions are based on the 95th percentile modeled exposure concentrations representing a conservative screening-level analysis.  EPA expects these estimates sufficiently capture any risk to fenceline communities.  For most facilities, risk is also indicated at lower percentiles as well, mitigating some of the uncertainty.  Although not included in this presentation, risk is also identified for co-residences of dry-cleaning facilities under all modeled scenarios.  And you can see that in the draft report.
                  Now, I'll move to the methylene chloride case study which includes both the air and water pathways.  As with 1-BP, this slide provides a snapshot of the results obtained from methylene chloride from the release assessment and exposure assessment through application of the post-screening level methodologies for the air pathway.  This table summarizes the results of the risk calculations for cancer risks, again based on the maximum 95th percentile exposure concentrations by OES and distance from methylene chloride for the air pathway.  Overall, 17 exposure scenarios were evaluated for methylene chloride inhalation risk.
                  Eight of the 17 OES indicate excess cancer risk at distances as far out as 100 meters from the facility releasing methylene chloride to the ambient air.  Two OES indicate risk from acute exposures.  Three OES indicate non-cancer risk from chronic exposures.  This slide provides a snapshot of the number of releases modeled and results from the exposure assessment through application of the proposed methodologies for the water pathways for methylene chloride.
                  This table shows the number of releases obtained from the release assessment for two release scenarios, 20-day and maximum days, using both 2016 TRI and DMR data.  The last three columns summarize the ranges of modeled exposures for each released scenario for all three routes evaluated.  The ADR, ADD, and LADD for drinking water are provided with respective risk calculations.  The ranges provided here are combined across respective age classes.
                  The full set of estimated exposure concentrations in doses, and associated risk calculations, are provided in the draft report and accompanying supplemental files to the draft report.  For purposes of risk calculations, we present results by OES and age class within the draft report.
                  Slide 50 closes out the methylene chloride case study by summarizing the key results from applying the fenceline methodology, including land-use evaluation for the air pathway.  The EPA identified risk at fenceline air concentrations for 14 of the 195 real facilities assessed, covering 8 of 17 OES for the air pathway.  Based on land use considerations, actual fenceline community exposures are expected for 2 of the 14 GIS located facilities for which risk was identified.
                  Again, these risk conclusions are based on the 95th percentile modeled exposure concentrations and, again, representing a conservative screening level analysis for the air pathway.  For the air pathway, the EPA expects these estimates to efficiently capture any risk to the fenceline communities.  For half of the facilities, risk is also indicated at lower percentiles as well, again, mitigating some uncertainty.  EPA also identifies risk via drinking water for one recycling and disposal facility based on acute non-cancer risk to infants and lifetime cancer risk.  Risks are not identified via recreational contact with water, however.
                  For the final case study, I'll briefly discuss NMP.  This slide provides a snapshot of the number of releases modeled and results of the exposure assessment through application of the proposed methodologies for the water pathways from NMP.  While this slide provides a snapshot of the results, again, the full set of releases, estimated exposure concentrations, doses, and associated risk calculations are provided in the draft report and accompanying supplemental files to the draft report.  This table shows the number of releases obtained for the release assessment for two release scenarios, 12-day and maximum days, using only TRI data from both 2015 and 2018 TRI reporting years.
                  One thing to point out for NMP, in addition to adults, infants, and youth age classes, NMP includes the age class of pregnant females due to the reproductive and developmental hazards identified for NMP.  The last three columns summarize the ranges of modeled exposures for each release scenario for all three routes evaluated.
                  Closing out the NMP case study, EPA did not identify any risks from NMP for fenceline communities via either drinking water or recreational contact with water.  Exposures were greater than 10-fold below levels which would result in risk for any exposure scenario.  Based on these findings, EPA feels this represents a health-protective assessment and EPA has increased confidence in the conclusions of no risk via these water pathways.
                  Slide 54 briefly touches on next steps for the fenceline work.  The first step, revising and finalizing the fenceline methodology -- following public and peer review, EPA will review comments, recommendations, and improvements received.  EPA will modify the post-screening level methodology, as appropriate, and finalize the screening methodology as a framework to conduct screening level analyses.
                  One revision already planned for the air pathway is to revise the current cancer risk calculations in the draft report to consider a 33-year residential exposure duration from the exposure factors handbook, adjusted to lifetime for cancer risk per EPA's cancer guidelines.  This will be in the current methodology in line with the methodology applied for the water pathway and EPA's cancer guidelines.  The current methodology assumes a full lifetime of exposure, or 78 years, via the air pathway for calculating cancer risk.
                  For the fenceline considerations for seven of the first ten risk evaluations, the final screening-level analysis methodology framework will be used to conduct screening-level analyses for seven of the first ten chemicals for which EPA published risk evaluations between 2020 and 2021 to help determine if there are potential exposures and associated potential risks to fenceline communities from the air and water pathways that were previously not assessed.  For future TSCA or risk evaluations, the final screening-level methodology framework can also be used for future chemicals undergoing risk evaluation under TSCA Section 6.
                  And this concludes our presentation of the fenceline methodology and associated case studies.  I'd like to than the SACC panel, public, and stakeholders for taking the time to listen, review, and provide comment on the draft report and the fenceline screening methodology.  I just want to say thank you.  This lists the fenceline team members as well as the management leads I mentioned at the beginning of the slide.  Thank you.
                  DR. DANIEL SCHLENK:  All right.  Thank you, Kevin.  Appreciate that presentation.  Before taking questions or clarification, I think let's go ahead and take a quick 15-minute break.  I just want to remind the Committee, if you do have questions of clarification, please raise your hand, and I'll get to them in order as we go.  But at this point, let's go ahead and take a 15-minute break, and then we'll come back for questions.  Thanks.  So, return at 45 past the hour.

                                    [BREAK]

SACC QUESTIONS ON OPPT TECHNICAL PRESENTATION

                  DR. DANIEL SCHLENK:  Okay.  Kevin, I guess you are present.  Looks like I see your name there.  Yeah.  Good.  Thanks.
                  DR. KEVIN VUILLEUMIER:  Yup, I'm here.
                  DR. DANIEL SCHLENK:  We've got a few questions of clarification.  Before we get started, we do have another Committee member joining us.  At this point, Craig, if you wouldn't mind just introducing yourself and your area of expertise if that's okay?  Dr. Rowlands, you on now?  Dr. Rowlands?  Okay.  I see you listed on the participant list.  Maybe you haven't gotten back to your screen yet.  Okay.  Let's go ahead and move forward then with questions.
                  Let me just remind the panel a couple things.  First of all, the slides are available from the presentation.  Alaa will send you the link directly to that if you don't have it directly.  But if you would like to peruse the slides, particularly this evening, prior to your deliberations for tomorrow those will be available.  Also, let me just point out -- particularly for our ad hoc reviewers -- that, again, this is a period of questions of clarification, not necessarily for comments.
                  The comments, obviously, will be provided during the question period which will follow this.  So please use this time for questions to the EPA -- for specific questions of clarification of their presentation and of materials that you've been presented at this point and hold your comments until the time when those are available for the questions.  Okay.  I have --
                  DR. KEVIN VUILLEUMIER:  Dr. Schlenk.
                  DR. DANIEL SCHLENK:  Yes?
                  DR. KEVIN VUILLEUMIER:  This is Kevin, sorry.  I just wanted to point out we're going to work with -- Rehan Choudhary is going to kind of field this portion of the comments and clarifications, as well as the questions and comments that come in later on.  So, we'll have Rehan pulled up as well.  We'll both be on, but he's going to receive it and manage it so the whole panel has one point of contact.  Does that make sense?
                  DR. DANIEL SCHLENK:  Are you talking about right now?
                  DR. REHAN CHOUDHARY:  Yes.
                  DR. KEVIN VUILLEUMIER:  Yeah, right now and moving forward.  Yes.
                  DR. DANIEL SCHLENK:  Okay.  Yeah.  The only thing I would say is just make sure you state your name prior to the response for the written record.  Also, too, for panel members as well, please -- I'll call on your name, but please state your name before you make your question or any comment so that we get that on the record upfront.  Okay.  Okay.  Dr. Chaisson, if you want to go first.
                  DR. CHRISTINE CHAISSON:  Oh, thank you.  Thank you for the presentation.  It was really helpful.  I had been trying to follow the use of data or values throughout the different mathematics in your algorithms -- or presumably in your algorithms.  But I sort of got lost in that effort, so maybe you could help me with this.  Where in the -- when you're using quote "available data" or default values or assumptions or any value applied to an algorithm, would the model of that values that are averages or other middled values from a distribution and apply those to what you would call the maximum calculations?
                  So, for example, if you're using an exposure handbook value, is that a middled value, or is that somehow unique?  Or is that the full distribution?  So that's where I lost the thread, and maybe you can help me understand that part.  Thank you.
                  DR. REHAN CHOUDHARY:  Dr. Chaisson, this is Rehan Choudhary from the EPA.  My apologies, parts of your questions were blocking out, and I could not hear them in entirety.  Could you please repeat what you're focusing on?
                  DR. CHRISTINE CHAISSON:  Right.  I'm focusing on the values within distributions for any metric used in the algorithms in the screening models.  So, my question was I understand when you're using specifically as you pointed out maximum values for the concentrations that are expected or amortized across time.  But in doing the calculations to exposure you're also using values or assumptions from other sources -- for example, the exposure handbook.
                  Are those values middled values somehow, or are they also representing the spectrum -- the distribution of values within that metric?
                  DR. REHAN CHOUDHARY:  Okay.  So this is again Rehan Choudhary from the EPA.  So, we've got two pathways here, one the air pathway and one the water pathway.  I will first pivot to Kevin Vuilleumier for the air pathway so he can comment on that, and then I'll pivot to Jason Todd to see how he can respond to your comment for the water pathway.  Kevin, go ahead.
                  DR. KEVIN VUILLEUMIER:  Okay.  Thank you, Rehan.  This is Kevin Vuilleumier with the EPA.  Yeah, the input values I believe are where you're trying to get to for the models.  In particular, IIOAC has default stack heights -- the fact velocities out the stack.  We also assume some meteorological data.  The data sources vary from where they come from.  In the case of the exposure factors handbook, sometimes it's an average.  Sometimes they give you a range.  And then within the model and the documentation behind the modeling they generally explain what values they use as default and where they come from.
                  So, there may be some instances where an exposure factor is a mean that's used in a model parameter.  There may be other times when it tends to pull out a higher-end, or you may be able to have both of them.  Okay?  So it's the way we'd go about doing that is where the data comes from.  You'd have to look at the manuals and kind of see what the default value is, and then you can look up that reference and find out is it a range, is it a maximum value or something like that, okay.  So, the inputs vary.
                  The outputs that we use to do the calculations, as you had said, were a bit clearer where we used 95th percentile.  We used a mean.  So that's where the data comes from.  Does that help?
                  DR. CHRISTINE CHAISSON:  Did you -- well, you're zeroing in on where I lost the trail, essentially, because I didn't understand if you had chosen to -- where you had the choice to use a range or an upper.  If you look particularly at the beginning, say the pre-screening methods, are you employing the upper end for each of these values when you do have, in fact, the choice of doing that, or are you systematically using the average number?
                  What are your methodologies and criteria for choosing any of these other values that are going to be part of the algorithm?
                  DR. DANIEL SCHLENK:  That was Dr. Chaisson.
                  DR. KEVIN VUILLEUMIER:  And this is Kevin Vuilleumier.  In the case of the model for pre-screening IIOAC, the default values are established within the model itself.  So they don't change with some of the parameters.  For a stack release, we have different types of stack releases.  We'd only focus on the stack release though instead of like incinerator.  But that stack release is set at ten meters high.  It has a set velocity.  And we outline those defaults in the draft report itself.  Okay?
                  Where it comes from, I'd suggest -- because they vary, I'd recommend we would need to go into the manual itself to see where each value came from.  Generally speaking, I think some of the stack parameters and all were taken across like a national average.  Okay.  But we go to the source -- we go to the manual to find out where it's coming from.
                  DR. CHRISTINE CHAISSON:  Thank you.
                  DR. DANIEL SCHLENK:  Okay.
                  DR. REHAN CHOUDHARY:  Thank you, Kevin.  This is, again, Rehan Choudhary from the EPA.  And I'll pivot to Jason Todd to see if he has any inputs and clarifications to your question for the water pathway with respect to default inputs or parameters so that it can help you identify what those are.  Jason, go ahead.
                  DR. JASON TODD:  Hi, this is Jason Todd from EPA.  My answer would be very similar to Kevin's on the air side.  On the water side, it's dependent on the input that you'd be asking about.  But generally speaking -- and those are detailed both in the -- at least, on the water side we relied mostly on the use of the E-FAST tool, which Kevin outlined in his presentation.
                  And the inputs -- the default inputs for those are found both within the report and in the manual for that tool.  I'd also refer you to the supplementary Excel files for both the case studies that outline the inputs that were used for the evaluation of the calculated or estimated exposures there.  And so, it would be somewhat dependent on this specific input you're asking about.  But in some cases, we used more conservative values, and others we used more mean values.
                  And so, if you have specific inputs in mind that you're asking about, we can look into that.  But I generally refer you to both the supplemental files and the tool handbook.
                  DR. REHAN CHOUDHARY:  Okay.  Thank you, Jason.  This is, again, Rehan from the EPA.  I think we can move on to the next question, Dr. Schlenk.
                  DR. DANIEL SCHLENK:  Okay.  Dr. Chaisson, has your question been answered there?
                  DR. CHRISTINE CHAISSON:  Yes.  Thank you very much.
                  DR. DANIEL SCHLENK:  Okay.  Dr. Doucette?
                  DR. WILLIAM DOUCETTE:  Yes.  I think I got two what I think are clarification questions.  The first one is on the TRI data.  Looking at some of your spreadsheets, if you look at the details, there are multiple ways that industries are allowed to estimate the TRI data.  For example, they can do it by mass balance calculations.  There's engineering best judgment, monitoring data.  And I'm trying to get a handle on how you compare those different TRI results since they're made using different estimation techniques and what the variability associated with that.
                  In other words, I'm worried about garbage in/garbage out.  And I'm wondering if you could just kind of explain to me how you assess that variability.
                  DR. REHAN CHOUDHARY:  Okay.  Thank you for that question.  This is, again, Rehan Choudhary from the EPA.  You are correct that there are basis codes in TRI that help you understand what a company or reporter is saying what the basis for their numbers are.  And I think we commented on the uncertainty related to the basis that is used.  So, I'm going to pivot to Franklyn Hall who is our expert on the release side, so he can comment on your question.  Franklyn, go ahead, please.
                  DR. DANIEL SCHLENK:  We're not hearing you.  You might be on mute.
                  DR. FRANKLYN HALL:  Sorry about that.  Good morning.  This is Franklyn Hall.  So, Dr. Doucette, as Rehan had just indicated, the TRI does require that submitters provide a basis of estimate, and as you've indicated it can be done in a number of different ways.  At this time, we've just provided an explanation of those bases of estimates for context, but we have not done any analysis on the variability or the impacts of that variability on the actual estimates as they've been provided on facility-level or even as they've been aggregated at the OES level.
                  However, that is something that we are considering looking at moving forward.  As indicated early on, this is just a screening-level approach, so this is just one of the ways that we're going to try to better characterize the release estimate information by using those bases of estimates and providing some kind of context to provide readers with an idea as to uncertainty with some of those estimates that are provided by facilities.
                  DR. WILLIAM DOUCETTE:  Thank you.
                  DR. REHAN CHOUDHARY:  Thank you, Franklyn.  This is, again, Rehan from the EPA.  And just to add to that, Dr. Doucette, we do recognize there are various bases, and internally we started to talk about maybe should there be some sort of hierarchy that we implement based on what basis a reporter is saying.  Is it a measurement?  Is it a mass balance estimate?  But I think we would also be looking forward to any feedback that the SACC Committee has on setting up a hierarchy or dealing with different basis or different ways.
                  DR. WILLIAM DOUCETTE:  Okay, thank you.  And my second clarification question was dealing with a case study for methylene chloride.  You looked at water exposures for methylene chloride which I was a little surprised given the volatility or Henry's law constant for methylene chloride.  And you talked about recreational exposures in water.
                  Did you consider or at least discuss the possibility of exposures in the same way through bathing and showers?  It would seem like that would be more of a likely water exposure for something like methylene chloride than recreational use.
                  DR. REHAN CHOUDHARY:  Okay.  Thank you, Mr. Doucette.  This is, again, Rehan Choudhary, from the EPA.  I'm going to pivot to Jason Todd to see if he can clarify that question.
                  DR. DANIEL SCHLENK:  Not hearing you, Jason.
                  DR. JASON TODD:  Yeah, sorry.  There was a lag in my video starting.  Again, this is Jason Todd.  Yeah, good question.  Thank you for that.  We did not assess the exposures due to bathing.  That is something we are considering moving forward as kind of a 2.0 level analysis.  We welcome any thoughts or considerations from the panel on ways to evaluate that or moving forward.
                  But we did not look at that particular pathway for this fenceline analysis.  I'll hand it back to Rehan to see if he has any additional comments there.
                  DR. REHAN CHOUDHARY:  Thank you, Jason.  Nothing additional.  I hope that's helpful, Mr. Doucette.
                  DR. WILLIAM DOUCETTE:  Yes, it is.  Thank you very much.  And I also greatly appreciate the presentation, which I thought was very well done and helped clarify the document itself.
                  DR. REHAN CHOUDHARY:  Thank you very much.
                  DR. DANIEL SCHLENK:  Thanks, Bill.  Mark Johnson.
                  DR. MARK JOHNSON:  Thanks, Dan.  Yeah, admittedly, I'm not a modeler of this type, but the devil's always in the details; right?  So, I've got a question that relates to the air pathway and then water pathway.  I'll start with the air first.  Does the model estimate wet deposition and dry deposition?  I mean, maybe not for these compounds but does it do that?
                  DR. REHAN CHOUDHARY:  I think from a modeling capability perspective, AERMOD -- yes, it can take that into account.  Are you asking whether that was actually incorporated into our estimation method?
                  DR. DANIEL SCHLENK:  That was Dr. Choudhary.
                  DR. MARK JOHNSON:  Yeah, I was asking if the model does account for wet and dry deposition to estimate environmental load, the soil?
                  DR. REHAN CHOUDHARY:  Okay.  Again, this is Rehan Choudhary.  Kevin, could you please field that?
                  DR. KEVIN VUILLEUMIER:  Yes.  Thank you, Rehan.  And good question, Mr. Johnson.  The modeling -- as Rehan said, AERMOD can consider deposition of multiple types.  We did not do that for the fenceline effort, but it is something we can consider moving forward, especially with some of the future chemicals which may not all be so volatile.  Right?  So you can have a bit more deposition to worry about.  But AERMOD is capable of doing that.
                  IIOAC also has a capability to a degree.  We're still putting together the logic behind what we get from that for prescreening purposes, but for the full screening methodology, AERMOD can consider both.  It can consider deposition, wet and dry deposition, given the right data that you need to be able to calculate that and use them as inputs.
                  DR. MARK JOHNSON:  Okay.  So that kind of answers my second question which has to do with well water.  So, I guess we're not looking at pathways or transport to well water.  We're just looking at releases to municipal water supplies, ultimately for drinking water, correct?
                  DR. REHAN CHOUDHARY:  This is Rehan Choudhary, again.  I'll let Jason Todd chime in with more details, but on the surface, no, we're looking at releases to surface water.  So, Jason, please elaborate as needed.
                  DR. JASON TODD:  Yeah, this is Jason.  Rehan is right.  In that respect, we did not look at potential releases to groundwater.
                  DR. MARK JOHNSON:  Okay.  Awesome.  Thank you.
                  DR. DANIEL SCHLENK:  Thanks, Mark.  Dr. Reiss.
                  DR. RICK REISS:  Yes.  I wanted some clarity on how you're accounting for the property line of facilities.  Is that done in the land use analysis?  Meaning, where you're excluding consideration of concentration estimates that occur on the property line or within the property line -- meaning, not at the fenceline?
                  DR. REHAN CHOUDHARY:  This is Rehan Choudhary from the EPA, again.  I believe the way the land-use analysis is working we have a lat/long coordinate from TRI, and then we're able to map that and visually inspect what's happening in this vicinity.  Based on the exposure and risk calculations, we can get a sense of how far we are estimating that risk.  So, when we have different boundary or buffers around the lat/long coordinates, we're taking a look at, well, what are the uses around that boundary so to speak.  And visually, we can tell sometimes that we're still on the facility itself, or we are in an area that is officially in recreational areas and things like that.
                  So, it's a visual inspection that helps us distinguish where we think we are as an intial screen.  I'm going to pivot to Kevin to see if he has anything to add to that.  Kevin Vuilleumier, please go ahead.
                  DR. KEVIN VUILLEUMIER:  Thank you, Rehan.  This is Kevin Vuilleumier, and yeah, I think Rehan pretty much captured it.  It is an initial visual inspection out to the distances where we've found risk.  And on some of the very small properties, it can be difficult to see if it's right on that boundary, right?  Is it two meters away, or is it more than that?  But on a much larger facilities, like on a chemical manufacturing process -- that might be acres -- you can see a clearer delineation of where the property boundaries actually end.
                  But generally speaking, it's just a visual inspection based on the various distance rings and buffers that we put around it, and then we see within those rings where we find risk.  Do we expect fenceline communities to live there or work there and move from there.
                  DR. RICK REISS:  Thank you.
                  DR. DANIEL SCHLENK:  Okay.  Dr. Heiger-Bernays.
                  DR. WENDY HEIGER-BERNAYS:  I think Dr. Kissel was before me, but it's up to you.
                  DR. DANIEL SCHLENK:  He disappeared when I hit your name.  Now he's back but go ahead.
                  DR. WENDY HEIGER-BERNAYS:  Okay.  I'll go, and then Dr. Kissel.  So, thank you.  Wendy Heiger-Bernays.  I have a few questions.  Most of them have been clarified, and the presentation was fantastic.  Thank you for doing such a thorough job.
                  I have a question that relates to just the previous question, which is regarding the observations, the geo-spatial and where the facility is located.  So, these assume current use considerations and nothing about land use in the future?  And so, that's one question.  I'll start with that.
                  DR. REHAN CHOUDHARY:  This is Rehan Choudhary from the EPA.  You are correct.  This is trying to take a look at current use.  It does not incorporate local municipalities and their zoning plans or projections.
                  DR. WENDY HEIGER-BERNAYS:  Okay.  And along those lines, when you take a look at the location, if -- and I don't know -- you have seen -- you might have determined where there are multiple facilities within a particular geospatial area, and if there were multiple facilities, how would you address that in the screening assessment for that fenceline community?
                  DR. REHAN CHOUDHARY:  So, right now, yes, when the team or assessors are zooming in visually to see what is in the vicinity of where we see risk, they may make note that there are other facilities in the same buffer.  But right now, the methodology itself focuses on the effects of single sources or single releasors.  It does not get into aggregate exposures or cumulative exposures.  And I think we are specifically requesting feedback from the SACC Committee on how we might expand the capacities of the current approach and take that into account.
                  So even though visually an assessor may see there's another facility that falls within a buffer of an existing facility, it will be left at that.  It will not be taken further with respect to aggregate approaches or cumulative approaches with version 1.0 of the methodology.
                  DR. WENDY HEIGER-BERNAYS:  Okay.  Thank you very much.  Another question with regard to the water pathway, has the screening assessment incorporated combined sewer overflow events?  There are, according to EPAs estimates, about 860 communities that experience that.  And I'm wondering whether the contribution from the CSOs is included in the discharge and ultimately the risk estimates for the communities around those facilities.
                  DR. REHAN CHOUDHARY:  I'll take an initial stab at that.  This is, again, Rehan Choudhary from the EPA.  If those releases are somehow captured in TRI reporting, then we would be incorporated because they would be reported as direct or indirect discharges to surface waters.  But at this point, I think I'll pivot to Jason Todd to see if he has more -- can elaborate more.  Go ahead, Jason.
                  DR. JASON TODD:  Yeah, thanks, Rehan.  This is Jason Todd from the EPA, again.  As of right now, we do not include other releases such as that, that would potentially influence chemical concentrations in the water column or in the nearby vicinity.  But, I think, again, I would point you to that this was a screening-level analysis, and if there were information like that that would potentially influence our ultimate estimate, like, that would be part of a 2.0 level of evaluation.  Currently, we do not take those sorts of releases into consideration in this evaluation.
                  DR. WENDY HEIGER-BERNAYS:  Okay.  Thank you.  And one other, I think, quick question.  This relates to the actual risk calculations.  And I'm looking specifically on some of the case studies, for example, slide 49 with the methylene chloride aquatic exposure summary.  And there's looking at 20 days, for example.  And the question I have is what is the averaging time over which that is assessed?
                  DR. REHAN CHOUDHARY:  Okay.  Again, this Rehan Choudhary.  Jason, do you know that off the top of your head, or should I pivot to the human health assessors?
                  DR. JASON TODD:  Yeah, I might defer to my human health assessors on this one.  But for the 20 days of release, that is the averaging time of the whole release.  So, we have an annual release that's provided, and we divide by those days of release to get a daily release.  But for the risk characterization, I'll defer to my human health colleagues on that one.
                  DR. REHAN CHOUDHARY:  Okay.  This is, again, Rehan Choudhary.  I'll pivot to Keith Jacobs to see if he can elaborate on that.
                  DR. KEITH JACOBS:  This is Keith Jacobs.  I missed the specifics of the particular question there.
                  DR. WENDY HEIGER-BERNAYS:  Yeah, thank you.  I'm interested in understanding the averaging time for the less than -- I'll say less than daily exposures.  Right.  So, if you've got 20 days, what's the averaging time that you're using in the risk estimates?
                  DR. KEITH JACOBS:  I assume you are referring to for chronic.  For acute scenarios --
                  DR. WENDY HEIGER-BERNAYS:  Yeah, I'm talking about chronic.
                  DR. KEITH JACOBS:  I will confirm that.  I believe that the averaging time should be the days of release relative to 365 days a year.  Basically, the numerator is release days, and the denominator is days in a year.  I can ask Susanna if she has any clarification.  Susanna Wegner, do you want to clarify anything?  But we can check that also in our files.
                  DR. WENDY HEIGER-BERNAYS:  Sure.  If you could get back to me, that would be great.
                  DR. KEITH JACOBS:  Okay.  Yeah, and Susanna just messaged me that we need to check.  So --
                  DR. WENDY HEIGER-BERNAYS:  Okay, thank you so much.
                  DR. KEITH JACOBS:  -- we can get back to you and clarify.  But I'm pretty sure that it's basically release days over days of the year.  And then for cancer, it's a bit different because we also -- as mentioned, typically we account for --
                  DR. WENDY HEIGER-BERNAYS:  Lifetime.
                  DR. KEITH JACOBS:  Lifetime, yeah.  The exposures vectors handbook has a standard value for basically residency time relative to lifetime.  And there were some differences between air and water, but we're going to make those consistent.
                  DR. WENDY HEIGER-BERNAYS:  Okay.  Thank you very much.
                  DR. REHAN CHOUDHARY:  All right.  Thank you, Keith.
                  DR. DANIEL SCHLENK:  Dr. Kissel.
                  DR. JOHN KISSEL:  Hi, John Kissel.  On page 53 of the version 1.0, there's a permeability coefficient for NMP listed of 4.78 times 10 to the minus 4 centimeters per hour, and it's attributed to Poet.  It's a rat number or it's extrapolated from Poet.  Poet offers a rat number which doesn't have that many significant figures.  It's only 4.7 times 10 to the minus 3.  So, my question is, did you just take a rat number and divide by ten to get a human number, and if so, why are there three significant figures instead of two?
                  And if you didn't do that, what did you do, and why are you using something extrapolated from a rat number instead of a human algorithm which you're using for methylene chloride?
                  DR. REHAN CHOUDHARY:  Okay.  This is Rehan Choudhary from the EPA, again.  So, if I understood correctly, Dr. Kissel, you are referencing page 53 of the fenceline report?
                  DR. JOHN KISSEL:  Right.
                  DR. REHAN CHOUDHARY:  And you are looking at table 2-7 and asking about the permeability coefficient.
                  DR. JOHN KISSEL:  Yes.
                  DR. REHAN CHOUDHARY:  All right.  And specifically, your question is about we have three significant figures there and how was this parameter incorporated into the risk calculations?
                  DR. JOHN KISSEL:  No, no.  Where did it come from?  So that NMP number, it says in the right-hand column, "Recalibrated from data in Poet."  Poet offers a rat number which is 4.7 times 10 to the minus 3.  So, this might be the rat number divided by ten, which would certainly not be conservative.  But that doesn't make sense because you added an additional significant figure.  So, the origin of that 4.7 times 8 -- times 10 to the minus 4 is mysterious, and that's what I'm asking.
                  DR. REHAN CHOUDHARY:  Okay.
                  DR. JOHN KISSEL:  What is the origin of that number?
                  DR. REHAN CHOUDHARY:  Okay.  Let me first pivot to Jason Todd if he has further clarification on that.  And Jason, if not, we can pivot to our human health assessors.
                  DR. JASON TODD:  This is Jason Todd, again.  I don't have clarification on that.  That is something that I would have to look at a little bit more to figure out the derivation of that number.
                  DR. REHAN CHOUDHARY:  Okay, Jason.  Let me pivot to Keith or Susanna.  Any input with respect to the number Dr. Kissel is asking about and the Poet and all reference?  I believe the PPK model or so?
                  DR. KEITH JACOBS:  This is Keith Jacobs, EPA.  I think we would -- I would defer to Jason Todd's answer.  We would have to look into how we incorporate it and how we derived that value from the study.  We'd have to look back at all of our Excel files and the derivations of that.
                  DR. REHAN CHOUDHARY:  Okay, thank you, Keith.  So, Dr. Kissel, I think we'll have to follow up on that question.  But it's been noted.  Thank you.
                  DR. JOHN KISSEL:  Okay.  Thanks.
                  DR. DANIEL SCHLENK:  Just to follow up, will that information be available this afternoon, or is this something that will require something for tomorrow morning's beginning?  This is to the EPA.
                  DR. REHAN CHOUDHARY:  Well, I think we -- our staff people are trying to look into it as we speak.  So, if they get an answer to us during today, we will relay that back to you.  But if not today, then we would aim to have that available to you tomorrow.
                  DR. DANIEL SCHLENK:  Okay.  Thanks.  Okay, Dr. Calder.
                  DR. RYAN CALDER:  Hi, Ryan Calder speaking.  A lot of the risk calculations turn on parameter values like emission days per year and so on.  And you, in many cases, have maybe one citation for a parameter value like release days per year that are driving all of the exposure assessments.  And the underlying citations don't really seem to have much to do with the specific facilities you're assessing risk from, and they don't even come from the United States in many cases.  And I'm wondering if there's a plan to assess how uncertainty around those values influences screening risk results because, in some cases, they may just be guesses.
                  DR. REHAN CHOUDHARY:  Dr. Calder, let me see if I understood the correction correctly.  This is, again, Rehan Choudhary from the EPA.  I believe if I refer to the SACC presentation we just gave, slide 11 is kind of talking to the estimating days of release by the various conditions of use or occupational exposure scenarios, and I think what you're saying --
                  DR. RYAN CALDER:  Yes --
                  DR. REHAN CHOUDHARY:  And you're saying in the report you usually see one reference, or if you dive into it, these are sources that may be international in nature.  I believe the protocol we used here is, we took what we had published in our risk evaluations -- the finalized risk evaluations -- and we carried that forward with respect to assumptions on days of release by various scenarios.  Manufacturing, processing, or other scenarios.
                  I'm going to pivot to Franklyn Hall to see if he can elaborate on that, but that is my understanding that that is a carry-over from what we did in the risk evaluation.  So even back then the SACC Committee had a chance to review that and comment on that, and we would be looking to the Committee as well to see if you could identify additional sources or methodologies where we could get/have more reflective numbers of those various scenarios or industries.  But let me pivot to Franklyn Hall to see if he wants to add to what I've said.
                  DR. FRANKLYN HALL:  Hi, Dr. Calder.  Yes, so as Rehan said, these release days, or estimated days of release, are provided or presented on an OES basis, and they are from the published risk evaluations.  And primarily the releases that are provided from TRI are provided on an annual basis.  So, we use these estimated days of release from sources such as generic scenarios and emission scenario documents, which again are from the published risk evaluations, to try to develop a daily release.
                  We are certainly open to getting further feedback on that approach.  Hoping that's answered your question.  If not, please certainly follow up if I have not answered your question adequately.
                  DR. RYAN CALDER:  Okay.  Thank you.
                  DR. DANIEL SCHLENK:  Okay.  Dr. Apte.
                  DR. UDAYAN APTE:  Yeah, hi.  This Udayan Apte.  My question is about the fenceline definition of 10,000 meters for air and then the water.  I was looking at the report, and it basically says that this was decided because beyond 10,000 meters other EPA jurisdiction takes over.  It also says in the introduction that this is associated with professional opinion that beyond 10,000 meters there is less concentration.
                  I'm just wondering what kind of data were used to come to that conclusion based on -- what was it based on, basically?
                  DR. REHAN CHOUDHARY:  Thank you for the question.  This is Rehan Choudhary from the EPA, again.  I will provide an initial response to that and then pivot to Kevin Vuilleumier to see if he wants to elaborate.  You are correct.  In the report, or the presentation itself, we lay out what we consider to be fenceline communities.  And I believe you're asking on the air pathway side what kind of helped us to come to initially 10,000 meters.
                  DR. UDAYAN APTE:  Yes, sir.
                  DR. REHAN CHOUDHARY:  I think we mentioned in the report that based on past modeling experiences, having done past assessments, the professional judgment was that people usually see the risks dying out around, I believe, 1,000 meters.  But because we had consulted other offices at EPA, they suggested going farther out to characterize, well, even if it's dying out, going further out would help you to better understand how quickly or slowly it dies out.
                  So, we took that professional judgment of about of 1,000 meters, and we took it out of an order of magnitude.  So that was the genesis behind that.  Kevin, do you want to add to that?
                  DR. KEVIN VUILLEUMIER:  Thank you, Rehan.  This is Kevin Vuilleumier from EPA.  Rehan pretty much captured it.  One thing I'll add to it is we chose 10,000 meters.  We didn't indicate that anything farther than that would be addressed by other statutes or other programs.  We just selected that as a limitation for our boundary of fenceline community.  However, with regards to the fenceline methodology itself, it's not limited to only 10,000 meters.  We can go out much farther and see what the impacts are farther out.
                  One thing that you may be driving toward is you can sometimes see risks much farther out that you don't see closer in.  That's dependent on the stack parameters.  If you have a much higher stack, it's going to carry much farther, right?  So, in that aspect, since we have limited our stack heights to the defaults of ten meters of low plume, that's why we also kept it within the bounds of 10,000 meters.  But we can go out farther, especially if, like, risk is indicated out toward that distance and recognize that it can be affected with much larger stacks.
                  DR. UDAYAN APTE:  I have one related question to this, again, and then this is really about double exposure in a way.  So, there is possibility of a lot of those workers occupational exposure, that are having occupational exposure in the facility, may live within the fenceline community.  And so, they essentially are double exposed.  I was wondering has that been considered?
                  DR. DANIEL SCHLENK:  That was Dr. Apte, again.
                  DR. REHAN CHOUDHARY:  Okay.  This is Rehan Choudhary, again, from the EPA.  So, you are correct in that those kinds of exposures can happen where someone may be exposed while they are working at a facility and then they live close by -- they're part of fenceline community.  The version 1.0 does not take that into account.  Right now, it's delineating what the exposure would be if you're within this fenceline distance.  We have not attempted to aggregate those exposures from those various conditions.
                  DR. UDAYAN APTE:  Thank you.  That is very -- that solves my problem.  Thank you.
                  DR. DANIEL SCHLENK:  Okay.  Dr. Li.