TERA Staff


TERA's professional staff bring diverse backgrounds to the development of risk assessment values and methods. To find contact information for an individual TERA staff member, click on the name below. General questions or comments can be sent to tera@tera.org.

Click a name for biography and contact information.
Michael L. Dourson, PhD, DABT, FATS, FSRA, President

Phone: (513) 542-RISK (7475), extension 105
FAX: 513.964.9472
EMAIL: Dr. Dourson


Dr. Dr. Michael Dourson is a board-certified toxicologist serving as TERA's President and Director of Science. Most recently, he was Senior Advisor in the Office of the Administrator at the US EPA. Prior to this position, Dr. Dourson was a Professor in the Risk Science Center at the University of Cincinnati, College of Medicine and worked at TERA and US EPA. He was awarded the Arnold J. Lehman award from the Society of Toxicology, the International Achievement Award by the International Society of Regulatory Toxicology and Pharmacology, and 4 bronze medals from the U.S. Environmental Protection Agency. He has been elected as a Fellow of the Academy of Toxicological Sciences and as a Fellow for the Society for Risk Analysis. He has co-published more than 150 papers on risk assessment methods or chemical-specific analyses, and co-authored hundreds of government risk assessment documents, many of them risk assessment guidance texts. He has made over 150 invited presentations to a variety of organizations, and has chaired over 150 sessions at scientific meetings and independent peer reviews. He has been elected to multiple officer positions in the American Board of Toxicology (including its President), the Society of Toxicology (including the President of 3 specialty sections), the Society for Risk Analysis (including its Secretary), and President of the Toxicology Education Foundation, a nonprofit organization with a vision to help the public understand the essentials of toxicology. In addition to numerous appointments on government panels, such as EPA's Science Advisory Board, he is a current member on the editorial board of Regulatory Toxicology and Pharmacology.. 

Bernard K. Gadagbui, M.S., Ph.D., DABT, ERT, Senior Toxicologist

PHONE: (513) 542-7475, extension 104
FAX: 513.964.9472
EMAIL: Dr. Gadagbui


Dr. Gadagbui has over 14 years of professional experience in environmental health, risk assessment, and toxicology. Dr. Gadagbui specializes in evaluation of adequacy of EPA uncertainty factors for database deficiency in protecting against effects on reproduction, hazard ranking and screening methods for chemicals in support of product hazard assessments, consumer safety assessments, and the threshold of toxicological concern approach. Prior to joining TERA in 2004, Dr. Gadagbui held toxicologist positions at the University of Florida and the Bureau of Pesticides of the Florida Department of Agriculture and Consumer Services (FDACS). Dr. Gadagbui has received numerous awards.  In 2010, he led a project that received honorable mention for the Alice Hamilton Award for top risk assessment work at NIOSH. He also led a team of TERA scientists that won the 2010 Risk Reduction Achievement Award from the Alliance for Chemical Safety, a regional professional organization with a mission to promote public understanding and involvement in chemical risk management.


A board-certified toxicologist, Dr. Gadagbui has been active in professional societies where he has held, or currently holds, leadership positions. These include: Toxicologist of African Origin (TAO) Specialty Interest Group of the Society of Toxicology (SOT) (President, 2008-2009), Ohio Valley SOT (OVSOT) (Councilor), African Society of Toxicological Sciences (ASTS) (Vice President), and Ohio Chapter of the Society for Risk Analysis (OSRA) (Secretary).  



Bethany D. Hansen, M.A., Communications Specialist

Phone: (513) 542-RISK (7475), extension 104
FAX: 513.964.9472
EMAIL: Ms. Hansen


Mrs. Hansen recently joined TERA as the Communications Specialist, and is leading TERA’s social media, public outreach, and public toxicology education. Mrs. Hansen earned her M.A. in Communications from Northern Kentucky University.  She has 6 years of experience in Communications through her former role as Executive Assistant at Cincinnati State Technical and Community College. 

Chijioke Onyema, M.Sc., MPH, Junior Toxicologist

Chijioke Onyema is a Medical Microbiologist and Master of Public Health (MPH) graduate who hails from Lagos, Nigeria. His interest in human health was spurred by personal experience, having had a fair share of illnesses in his childhood (jaundice, pneumonia, and malaria, to mention a few). An internship at the Nigerian Institute of Medical Research (NIMR), an award for the second-best graduating student in his undergraduate class, and a master’s degree in Medical Microbiology from the University of Lagos, Nigeria only served to further fuel his quest for knowledge.


Having joined the Toxicology Excellence for Risk Assessment (TERA) in 2016 while pursuing his MPH degree at the University of Cincinnati, Chijioke is presently particularly interested in toxicological evaluations and risk/exposure assessments and has co-authored a few exposure assessment reports. He currently works as a Junior Toxicologist with TERA and is a member of the renowned Society of Toxicology (SOT).

Christen Williams, MTSC, MCSE, CISSP, CCENT, IT & New Technology Manager

PHONE: (513) 542-7475, extension 101
FAX: 513.964.9472
EMAIL: Ms. Williams


Ms. Christen Williams is TERA’s IT Services and New Technology Manager. Ms. Williams has worked with TERA since 2010 and has 29 years of experience in graphic design, computer support, networking and design, server support, cloud computing, and cyber and network security. She is certified as Moxa Technical Support Certification, Microsoft Certified Systems Engineer, Certified Information Systems Security Professional, and Cisco Certified Entry Networking Technician.


Valerie Ayers, Executive Office Administrator

Phone: 513-542-7475, extension 104
FAX: 513.964.9472
EMAIL:  Ms. Ayers


Ms. Ayers joined TERA in 2006. She brings with her a wealth of administrative experience.





TERA Visiting Scientists and Fellows Programs

TERA has developed both the Visiting Scientist and TERA Fellow Programs to encourage collaboration with others and to improve risk assessment practices.  Our program includes:

bullet Visiting Scientists are those engaged with TERA for a fixed period of time or on a defined project.  Project work may or may not be onsite at TERA’s Cincinnati office.  While visiting scientists are often senior, positions can also be considered for scientists who are beyond internship level, but for whom a period at TERA would be of mutual benefit. 


bullet TERA Fellows are senior scientists associated with TERA on a longer-term basis with ongoing scientific interactions. 


TERA Fellows and Visiting Scientists are not employees of TERA, but rather scientists who share TERA's mission and values and seek to improve the practice of risk assessment. TERA collaborates with Visiting Scientists and/or TERA Fellows on projects of mutual interest.    


In the past, scientists have worked with TERA and coauthored manuscripts or reports on a variety of topics, including methods for evaluating persistent and bioaccumulative chemicals, exposure assessment methods, dose-response modeling, mixtures assessment, and investigating the magnitude of adult-to-child toxicokinetic differences in inhalation dosimetry of gases. 


Individuals interested in either program should contact Dr. Michael Dourson at 513-542-7475 x105 or dourson@tera.org


TERA Fellows & Visiting Scientists

A. Wallace Hayes, Ph.D., D.A.B.T., FATS, FTBiol, FACFF, FACN, ERT, CNS, TERA Fellow

Dr. Wally Hayes holds degrees from Auburn University (Ph.D. and MS) and Emory University (AB). He was an NSF predoctoral fellow at Auburn University, an NIH individual postdoctoral fellow at the Vanderbilt University School of Medicine, a NATO Senior Scientist at the Central Veterinary Laboratory in Weybridge, England, and held an NIH Research Career Development Award. Dr. Hayes is currently an Adjunct Professor, Center for Environmental Occupational Risk Analysis and Management, College of Public Health, University of South Florida and Institute for Integrative Toxicology, Michigan State University. He has been a member of numerous NIH, US EPA, US FDA, US DOD, and NAS scientific panels. Dr. Hayes has authored more than 330 peer-reviewed publications, is the editor of Hayes’ Principles and Methods of ToxicologyHuman and Experimental Toxicology,  Cutaneous and Ocular ToxicologyToxicology Research and Application, and the co-editor of the  Target Organ Toxicity Series of books. Dr. Hayes is the Editor-in-Chief emeritus, Food and Chemical Toxicology, and the co-author of Loomis’ Essential of Toxicology. Dr. Hayes is a past Secretary-General of IUTOX (two terms), past board member of the American Board of Toxicology, a past president of the American College of Toxicology, the Toxicology Education Foundation, and the Academy of Toxicological Sciences, and a past member of the council of the Society of Toxicology. He is currently the President of the Toxicology Forum.  Dr. Hayes is a diplomate of the American Board of Toxicology, the Academy of Toxicological Sciences, the American Board of Forensic Medicine, and the American Board of Forensic Examiners. He is a Fellow of the Academy of Toxicological Sciences, the Royal Society of Biology (UK), the American College of Forensic Examiners, and the American College of Nutrition. Dr. Hayes is a registered toxicologist in the European Union (ERT) and a certified nutrition specialist (food safety). He was honored by the Society of Toxicology in 2006 with the Society’s Merit Award, by the Mid-Atlantic Society of Toxicology with its Ambassador Award in 2012, by the American College of Toxicology in 2012 with its Distinguished Scientist Award, and by the International Dose-Response Society in 2013 with its Outstanding Leadership Award. Dr. Hayes was named a Distinguished Fellow by the American College of Toxicology in 2013 and a fellow of the American Association for the Advancement of Science in 2014.


Charles Anthony Pittinger, Ph.D., TERA Fellow



Dr. Pittinger is an environmental scientist with broad experience in ecotoxicology, environmental fate, and ecological risk assessments of organic chemicals, metals and mining products. He provides leadership and success to multi-national corporations in meeting global product stewardship needs of their chemical products. He has worked broadly in public (e.g., SETAC, the EPA’s Science Advisory Board) and private venues to provide technical insight and advancement in health and environmental fate and effects, regulatory compliance (e.g., GHS, REACH, HPV), technical external relations, and product sustainability (e.g., life-cycle analysis).


Dr. Pittinger has 27 years of experience in chemical safety and regulatory compliance, including 17 years with The Procter & Gamble Company and 10 years in environmental consulting with multiple industry sectors such as industrial and specialty chemicals, metals and mining, consumer goods, and pharmaceuticals. Recently, he has also led projects for trade associations including the American Cleaning Institute, the International Council on Mining and Metals, and the Water Environment Research Foundation (WERF). He brings technical, regulatory, and external relations experience to enable the freedom to market safe and sustainable products in highly dynamic global markets. 


As a Fellow, Dr. Pittinger and TERA have successfully leveraged their respective strengths in human health toxicology and industrial hygiene, and in ecotoxicology and environmental fate, to offer our project sponsors the full range of product stewardship services described below. They assemble and manage multi-disciplinary staff at senior and junior levels to support project teams efficiently and cost-effectively, with excellent communications with clients. Some examples include:


For WERF, a TERA team compiled and analyzed complex chemical fate, health and environmental effects data for trace organic substances in biosolids and sludge-amended soils.


For mining firms and local, provincial and national regulatory agencies, Dr. Pittinger chaired a peer review coordinated by TERA, of long-term soil amendment programs to restore lands near Sudbury Ontario impacted by historical mine smelting operations.


For a private paint manufacturer, TERA developed and applied hazard prioritization scoring to product ingredients to evaluate substances of special concern and opportunities for product improvement in green chemistry.


Dr. Pittinger and TERA have actively developed regulatory submissions including REACH dossiers and Chemical Safety Reports, CLP notifications, and High Production Volume Chemical Summaries and Test Plans.


For a number of private firms preparing GHS-compliant Material Safety Data Sheets (GHS = Globally Harmonized System for Classification and Labeling of Chemicals), Dr. Pittinger has developed environmental hazard classifications and sound, weight-of-evidence justifications for organic and inorganic substances and mixtures.


Dr. Pittinger has conducted chemical and product life-cycle sustainability evaluations, including verification of green certification criteria and product use consumption of water and energy.


read moreErrol Zeiger MS, Ph.D., J.D., Fellow ATS, TERA Fellow


Dr. Zeiger received his BS in biology the from City College of New York in 1960, MS (1973) and PhD. in Microbiology from George Washington University, Washington DC, and a JD (1991) from North Carolina Central University, Durham NC.


His expertise is in the areas of genetic toxicology and its relation to rodent carcinogenesis. He began his research in in the Genetic Toxicity Branch of the US FDA genetic toxicology before moving to the National Institute of Environmental Health Sciences (NIEHS) where he was responsible for designing, implementing, and managing the National Toxicology Program’s genetic toxicity program in addition to his research program.  He served as Project Officer or co-Project Officer on more than 40 U.S. Government research and development contracts and inter-agency agreements for the development and use of genetic toxicity tests, their validation, and report preparation, among others.  Among his responsibilities in these efforts was the design of the Statements of Work and oversight of the studies.  From 1999-2000 he served as an on-site consultant to the OECD in Paris for the development of toxicology test guidelines and guidance documents, and supervising in vivo validation studies for endocrine disrupting chemicals.


Dr. Zeiger has been working as an independent consultant since his retirement from the NIEHS. His consulting clients have included chemical and pharmaceutical companies, US and other Government and multinational organizations, consulting organizations, testing laboratories, and law firms. As part of these activities, he has produced a number of detailed reviews of chemicals and chemical classes of interest and has made presentations on behalf of clients to the FDA, EPA, and non-U.S. regulatory authorities.


Dr. Zeiger has authored or co-authored more than 230 peer-reviewed, and other, publications, primarily addressing the uses and interpretation of genetic toxicology tests and endpoints and their relationship to carcinogenicity.  He co-edited the Handbook of Carcinogenic Potency and Genotoxicity Databases, and Jet Fuel Toxicology. He is a member of the Environmental Mutagenesis and Genomics Society (EMGS; since 1969), SOT, and Fellow of the Academy of Toxicological Sciences. He was the Editor-in-Chief of Environmental and Molecular Mutagenesis, and is currently on the Editorial Boards of EMM and Genes and Environment, was a former member of the Mutation Research Editorial Board, and is a reviewer for approximately 10 journals. He has won a number of awards, including the EMS Recognition Award, the EM(G)S Service Award (twice), DHHS Superior Performance Award, NIH Merit Award, and the GEMS Lifetime Achievement Award.


read moreJeffrey R. Lewis, PH.D., TERA Fellow
LEWIS, R. Jeffrey is currently an independent consultant in epidemiology and human health risk assessment. He was a Distinguished Scientific Associate in the Epidemiology, Health Surveillance and Quality Assurance Section of ExxonMobil Biomedical Sciences, Inc (EMBSI) from 1990 to 2021. In this role, he supported ExxonMobil scientific programs related to naphthalene, 1,3-butadiene, human health risk assessment, regulatory affairs and regulatory impact analysis. He also served as Chair of EMBSI's Senior Technical Council. Dr Lewis has more than 30 years of experience and numerous scientific publications in occupational epidemiology and human health risk assessment. He has served on a number of industry trade association scientific committees (e.g., American Chemistry Council), external science advisory boards (e.g., the Alliance for Risk Assessment Expert Science Panel, U.S. Environmental Protection Agency Science Advisory Board for 1,3-butadiene) and was a member of the American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Value (TLV) Committee. Dr. Lewis also served as Treasurer for both the Society for Risk Analysis and the Society for Benefit-Cost Analysis. Dr. Lewis received his Bachelor of Science degree in biology from the University of Kansas and M.S. and Ph.D. degrees in Epidemiology from the University of Texas School of Public Health. In addition, he earned a Master of Business Administration degree from Rutgers University.
John P. Christopher, Ph.D., DABT, TERA Fellow




John P. Christopher, Ph.D., DABT., was named a TERA Fellow in 2009. Dr. Christopher received his education at Georgetown University (B.S., 1967), Stanford University (M.A., 1972), and Oregon State University (Ph.D., 1979). After working in contract laboratories for five years as a director of safety studies in animals, he came to California government in 1985. He served as a risk assessor for pesticide registration, evaluation of toxicity of chemicals, and regulatory risk assessment for hazardous waste sites for four years, then worked in the private sector as an environmental consultant from 1989-1992. He returned to the California Department of Toxic Substances Control (DTSC) in 1992, from which he is retiring in March, 2010. Dr. Christopher’s principal duties at DTSC included regulatory review of risk assessments for hazardous waste sites, especially military bases. He has been the internal expert at DTSC on biostatistics and analysis of ambient levels of metals. Dr. Christopher has served on some 30 panels since 1997 as a peer reviewer for TERA , U.S. EPA , U. S. Department of Defense, and Health Canada . Subjects for review included toxicity criteria for industrial and environmental chemicals, bioavailability of metals, children’s risk assessment, and evaluation of non-lethal weapons. In 2008, he led a successful team competing for a $900,000 grant from U.S. EPA on bioavailability of arsenic in soil from former mining lands. Dr. Christopher is a member of the Society of Toxicology. He is also a founding member and past President of both the Risk Assessment Specialty Section and Northern California Chapter of the Society of Toxicology. He has received numerous service awards from DTSC, the Risk Assessment Specialty Section and the Northern California Chapter of SOT. In 2007, he received a Lifetime Achievement Award for waste cleanup from the International Symposium on Contaminated Soil, Groundwater and Air.

Mark S. Johnson, Ph.D., DABT, Fellow ATS, TERA Fellow

Director, Toxicology, US Defense Centers for Public Health - Aberdeen, Aberdeen Proving Ground, MD, USA (retired)


Dr. Johnson has worked extensively in the evaluation of the toxicity of military unique compounds and development and evaluation of a phased approach to the gathering toxicity data for new compounds under development.  He has authored over 130 peer-reviewed publications, book chapters, and technical reports and serves on several NATO and EPA panels. He has been a member of Society of Environmental Toxicology and Chemistry (SETAC) since 1997 and is the current vice president for SETAC North America. He previously served on the Science Advisory Committee on Chemicals for the USEPA and is also past co-chair for the Toxic Exposures Research Working Group and the Toxic Exposure Work Group initiated by the PACT Act. He is a member of the World Science and Education Committees for SETAC and SETAC North America. Dr. Johnson is also a charter member of the International Board of Environmental Risk Assessment (IBERA). He has been a member of the Society of Toxicology since 2009. He currently is a member of the editorial board of Integrated Environmental Assessment and Management.


Dr. Johnson is a fellow and a member of the Board of Directors of the Academy of Toxicological Sciences, Past chair of the Tri-Service Toxicology Consortium (TSTC), past Steering Committee Chair of the Joint Army-Navy-NASA-Air Force (JANNAF) Subcommittee on Safety and Environmental Protection, the past president of the American Board of Toxicology (ABT).

Michael A. Babich, Ph.D., TERA Fellow
Dr. Michael Babich served as the Director of the Division of Toxicology & Risk Assessment at the U.S. Consumer Product Safety Commission (CPSC) from 2013 until his retirement in 2023. He served as a staff scientist at CPSC since 1987, where he was the principal author of numerous CPSC exposure and risk assessments involving chronic hazards associated with consumer products, including flame retardant chemicals in upholstered furniture and diisononyl phthalate in children's products. He managed numerous regulatory and research projects, including the CPSC chronic hazard risk assessment guidelines, and the Chronic Hazard Advisory Panel (CHAP) on phthalates, and coordinated the agency's Chemical Hazards Program for 9 years. This work contributed to the development of seven federal regulations, four national voluntary standards, and the CPSC risk assessment guidelines. Currently, Dr. Babich is active as a peer reviewer for scientific journals and as guest editor of a special issue on flame retardants. Prior to joining CPSC, Dr. Babich was engaged in basic research in the field of carcinogenesis, mutagenesis, and DNA repair. Dr. Babich received postdoctoral training at the University of Rochester Medical Center and the National Cancer Institute (NCI), National Institutes of Health (NIH).
Pamela R. D. Williams, Sc.D., TERA Fellow




Dr. Pamela Williams is a Principal at E Risk Sciences, LLP, an independent scientific consulting firm that provides sound analyses and tools to support risk-based decision-making related to human health and the environment.  She is also a Clinical Assistant Professor in the Department of Environmental and Occupational Health at the Colorado School of Public Health as well as a Fellow with TERA.  She previously served as a Senior Science and Policy Advisor in the Office of Research and Development (ORD) at the United States Environmental Protection Agency (EPA) and as a Health Scientist consultant in the public and private sectors.  Dr. Williams’ experience includes investigating and characterizing human exposures and health risks to a variety of carcinogenic and non-carcinogenic chemicals in the environment in community and occupational settings.  She specializes in the areas of industrial hygiene, exposure science, risk assessment, and risk management.  She has authored or co-authored over 160 articles, book chapters, technical reports, and presentation abstracts on these topics, which includes 37 peer-reviewed publications.  She has also served as a technical peer-reviewer for a number of scientific journals, peer review panels, and government agencies.  Dr. Williams’ routinely lecture in undergraduate, graduate-level, and/or continuing education courses related to industrial hygiene, exposure science, and risk assessment methods and tools including at the University of Colorado School of Public Health and School of Pharmacy, Harvard University School of Public Health, Clarkson University Institute for a Sustainable Environment, and American Industrial Hygiene Association (AIHA).

Dr. Williams is past President of the Society for Risk Analysis (SRA) and past Chair of AIHA’s Risk Committee.  She has received several awards for her contributions to the fields of risk analysis, exposure science, and industrial hygiene.  These include the Chauncey Starr Distinguished Award granted by the SRA for excellent contributions to the field of Risk Analysis, the Joan M. Daisey Outstanding Young Scientist Award granted by the International Society of Exposure Science (ISES) for outstanding contribution to the science of human exposure analysis, and both a Leadership Award and Outstanding Individual Contributor Award granted by AIHA in recognition of leadership and outstanding contributions to AIHA.  Dr. Williams has a B.A. in Sociology and Applied Social Research from San Diego State University, M.S. in Health and Social Behavior from Harvard University, and ScD in Environmental Health and Health Policy and Management from Harvard University.  She is also a certified industrial hygienist (CIH).  

Patricia McGinnis, PhD, DABT., TERA Fellow

PHONE: (513) 542-7475, extension 102
FAX: 513.964.9472
EMAIL:Dr. McGinnis

Dr. Patricia McGinnis, PhD., DABT is an experienced toxicologist and human health risk assessor.  She currently serves as a TERA Fellow.  Since joining TERA in 2014, Dr. McGinnis has contributed to projects for government, legal research, and commercial entities.  Formerly an executive at SRC, Inc., a large not-for-profit organization, Dr. McGinnis led the Chemical, Biological, and Environmental Center, one of four business units within the company.  Her business skills include strategic and operational thinking, organizational vision and planning, management of profit/loss centers, organizational policies and procedures, and staff development programs. Among Dr. McGinnis’ unique leadership skills is her ability to build and manage teams and to develop sound and sustainable scientific business partnerships to achieve technical excellence and innovations for sponsors. 

Dr. McGinnis is a board-certified toxicologist.  She has served on the NAS AEGL Subcommittee, on the Expert Consultation Panel for EPA’s National Homeland Security Research Center (NHSRC), and as an  external peer reviewer for regulatory risk assessment methods and documents, including EPA’s IRIS, Drinking Water toxicological reviews, and U.S. Department of Agriculture (USDA) human health assessments. She has authored more than 200 government reports, publications, and presentations.


Raymond York, Ph.D., DABT, ATS, ERT., TERA Fellow




Dr. York is a board-certified toxicologist with almost 30 years of experience in the field of toxicology, specializing in reproductive and developmental toxicology. He has served as a study director on over 700 GLP safety evaluation studies, and published over 100 manuscripts, review articles, book chapters and abstracts, and has been an invited speaker at international conferences. Dr. York earned his Ph.D. in Toxicology at the University of Cincinnati Medical Center, Kettering Laboratory and completed a two-year postdoctoral fellowship at the Children's Hospital Research Foundation in Cincinnati, in the area of developmental toxicology.


Dr. York has directed or participated in studies to evaluate safety exposure to chemicals from consumer products and pharmaceuticals to pesticides and water contaminates to assess compliance with USEPA (TSCA, FIFRA), FDA, ICH, and OECD requirements. He has designed numerous acute, subchronic and chronic toxicology, teratology, and carcinogenicity studies in mice, rats, rabbits, dogs and primates. Dr. York has planned, analyzed, interpreted and summarized toxicity data for the endocrine disruptor screening program (EDSP), multi-generational, development neurotox- and immunotoxicity studies, and is familiar with sperm morphology, vaginal cytology, fetal visceral and skeletal evaluation techniques.


Dr. York has been a member of the Teratology Society since 1984 and has been a member and served as the President for both Midwest Teratology Association (MTA; 1989) and the Middle Atlantic Reproduction and Teratology Association (MARTA; 2004). He has also been a member of the Society of Toxicology since 1985, and the American College of Toxicology since 1998. As a member of the Reproductive and Developmental Toxicology Specialty Section of SOT, he served on its Nominating Committee in 2006 and currently the President for SOT's Mid-Atlantic Regional section (MASOT). Dr. York has served as a reviewer for Toxicology and Applied Pharmacology and International Journal of Toxicology and as a member of the Editorial Board of Fundamental and Applied Toxicology. He was the reproductive toxicologist reviewer for the USEPA Biodiesel Program and on the peer consultation panel for assessment of the potential risk of health effects from exposure to tertiary-butyl acetate (TBAC). 


Richard Hertzberg, Ph.D., TERA Fellow




Richard Hertzberg, Ph.D. is a biomathematician who is internationally recognized for innovations and expertise in quantitative methods for environmental health risk assessment of chemical mixtures. Dr. Hertzberg has a B.S. in mathematics from Harvey Mudd College and a Ph.D. in biomathematics from the University of Washington. He retired from the U.S. Environmental Protection Agency in 2006 after working for 25 years as a Mathematical Statistician with EPA’s Office of Research and Development, National Center for Environmental Assessment. He is presently a visiting Associate Professor at Emory University, and on the graduate committee for one student at Emory and one student at Carnegie-Mellon University.


Dr. Hertzberg is the primary author of both the EPA’s 1986 Mixtures Guidelines, the first such guidelines by any federal agency, and the EPA's 2000 Supplementary Guidance for the Health Risk Assessment of Chemical Mixtures, and chaired both workgroups that developed those reports. He led the creation of MixTox, the EPA's database on binary toxicologic interactions, and co-developed with Patrick Durkin the EPA's interaction-based Hazard Index, which allows quantitative incorporation of toxic interaction information into a mixture risk assessment. He has co-developed and presented a mechanistically based model for a combination of two herbicides, showing significant interaction only at near lethal exposure levels, and has evaluated the numerical properties of the interaction-based Hazard Index using data on trihalomethanes. For the past ten years, he has co-taught a workshop on risk assessment of chemical mixtures at both the Society for Risk Analysis and the Cincinnati Toxicology and Risk Assessment annual meetings. Dr. Hertzberg initiated the use of ordinal regression to describe toxic severity, an approach that spawned the EPA's CatReg software and its use for acute exposures to air toxics. He has worked on EPA’s Office of Pesticide Programs' Cumulative Risk Work Group, EPA's Risk Assessment Forum cumulative risk technical panel, and external advisory groups on mixture risk for ATSDR, NIOSH and the Dutch Health Council. While at EPA he received two silver and two bronze medals and several awards for his advances and leadership in chemical mixtures risk assessment. He is a member of the Society for Risk Analysis, and the American Statistical Association, and is a recipient of the distinguished achievement medal from the ASA section on Statistics and the Environment.


Robert Roy, Ph.D., DABT, Fellow ATS, TERA Fellow

Dr. Robert (Rob) Roy received his BA in Chemistry and Biology from Augsburg  College, and his MS and PhD degrees in Environmental and Occupational Health (Program in Toxicology) from the University of Minnesota School of Public Health. Following postdoctoral work at the University, he joined the Minnesota Department of Health as a toxicologist in the section of human health risk assessment. In 1997, Dr.Roy joined the 3M Company where, over his 26-year career, he supported the toxicology and regulatory toxicology activities of numerous business units including Consumer Health Care, Advanced Materials, Medical Specialties, 3M Pharmaceuticals, and Specialty Chemicals. He also chaired many internal committees, such as the 3M Corporate Occupational Exposure Limit (OEL) Committee, and the Corporate Proposition 65 Committee. Rob retired from 3M as a Corporate Staff Toxicologist in July 2023 and is currently the Managing Principal of Northland Toxicology Consultants, LLC where he provides toxicology and regulatory toxicology support to the industrial chemical, consumer product, pharmaceutical and medical device sectors. Rob has significant experience in the derivation of health-based OELs, PDEs, ADIs, NSRLs/MADLs, and DNELs/DMELs; health hazard assessment of base chemicals, intermediates and products; human health risk assessment; pre-clinical biocompatibility testing of medical devices (ISO 10993, etc.) ; CRO study monitoring; regulatory toxicology (Prop65; OSHA HazCom; CPSC; REACH; GHS); and toxicology training and education (development and presentation of professional CE classes, webinars, etc.).

During his toxicology career, he has been actively involved as a member of many national and global toxicology organizations including the Occupational Alliance for Risk Science (OARS) Workplace Environmental Exposure Levels (WEEL™) Committee; American Chemistry Council (ACC) workgroups; European Centre for Ecotoxicology and Toxicology of Chemicals (ECETOC) Task Forces; and as an appointed member of the US NIOSH Board of Scientific Counselors (NIOSH Federal Advisory Committee). Dr.Roy is an adjunct professor (Toxicology Program), and a member of the graduate faculty, in the School of Public Health (Division of Environmental Health Sciences) at University of Minnesota where he presents graduate-level toxicology lectures, serves on toxicology and industrial hygiene advisory committees, mentors graduate students, and serves on MPH, MS and PhD thesis committees. He is currently a member of the editorial boards for four peer-reviewed toxicology journals, has been a Diplomate of the American Board of Toxicology (ABT) since 1994, served as a member of the ABT Board of Directors from 2013 to 2017, was elected as a Fellow of the Academy of Toxicological Sciences (ATS) in 2019, and currently is a member of the ATS Board of Directors.  Rob has been a TERA Fellow since April 2024.


Sher Bacha, Ph.D., Visiting Scientist
Dr. Sher Bacha completed PhD from National Key Laboratory of safety, China University of Mining and Technology, Xuzhou, P.R. China in 2021, research focuses on sustainably, safety and environment and served as Assistant Professor at Baluchistan, University of IT, Engineering and Management Sciences, Pakistan. He has research and field experience in the field of health, safety, geo hazards and environment. Performed research on dust monitoring and exposure analysis including coal dust which cusses black lung disease (Pneumoconiosis). He has been involved in many projects of safety, sustainability and environment and served many reputed organizations both nationally and internationally. He has been involved in teaching, research and industry for more than 15 years and supervised many students and projects. He has worked for the establishment of engineering laboratories with Japan International Cooperation Agency (JICA). Dr. Bacha is author and co-author of 17 journal and conference papers. He has participated and presented papers in national and international conferences mainly focused on, safety, environment and sustainability. He has visited many countries as professional delegate. He is also working as reviewer for research journals. He is currently working as Process Assistant for Amazon at CVG9 North American Sortation Centers and actively involved in sortation process of all departments at CVG9 focusing on health and safety. His area of interest is occupational health, safety and environment.
Steven Lasee, PH.D, Visiting Scientist

Dr. Steven Lasee is a toxicologist and chemist with expertise in risk assessment, chemical fate and transport, exposure, and the Per- and Polyfluoroalkyl Substances (PFAS) chemical group.  He received a BS in biology from the University of Wisconsin Stevens Point, a MS and Ph.D from Texas Tech University in Environmental Toxicology, and completed a toxicology research fellowship with the EPA Office of Research and Development. 

Dr. Lasee was the first person to publish on the discovery of micro plastics in an aquifer.  He has developed risk assessment tools for PFAS exposure that have been used by the private and public sectors.  TERA and Dr. Lasee worked together to publish 3 chapters (short-chain PFAS, fluoropolymers, and organic peroxides) in the 7th edition of the Patty’s Toxicology encyclopedia. 

Dr. Lasee has advised and worked with state and federal agencies on projects surrounding PFAS and PFAS contamination and has given several presentations on PFAS exposure to the EPA and at national Society of Environmental Toxicology and Chemistry conferences.  Dr. Lasee’s focus is on understanding human and environmental exposure to toxicants.  He currently runs “Lasee Research and Consulting” and primarily consults on PFAS.

Steven Lewis, Ph.D., D.A.B.T., TERA Fellow




President & Principal Scientist, Integrative Policy & Science, Inc.
Adjunct Professor, Robert Wood Johnson Medical School
Fellow, Toxicology Excellence for Risk Assessment (TERA)
Distinguished Scientific Associate, ExxonMobil Biomedical Sciences, Inc. (retired)
Senior Fellow, University of Texas at Dallas


Dr. Lewis holds a B.A. in Chemistry from Indiana University at Indianapolis (1970) and a Ph.D. in Toxicology (minor in Biomedical Sciences) from Indiana University School of Medicine (1975).


During the period of his graduate-school training and research, Dr. Lewis served as Analyst and Manager of the Indiana State Tumor Registry (the state-wide statistical cancer research unit). After joining Exxon (now, ExxonMobil), he held various technical, consulting and management positions, including Head of the Petroleum & Synthetic Fuels Group. For more than 28 years, Dr. Lewis served as a corporate advisor on scientific and science-policy issues in occupational and environmental health. Dr. Lewis’ research and safety assessment activities have focused on assessing potential health risks from exposure to petroleum and chemical carcinogens, toxicants to the nervous system, and chemical hazards to reproductive health. On special assignment, Dr. Lewis served as the senior on-site health scientist (in Alaska) following the oil spill event of 1989. His assignments included managing the human scientific program to assess potential human health impacts of the oil spill and clean-up. Dr. Lewis is a four-time winner of ExxonMobil’s most prestigious awards for excellence in the health and environmental sciences: Exceptional Achievement Award in 1993 and consecutive ExxonMobil Ambassador Awards in 2001, 2002 and 2003.


Following retirement from ExxonMobil Biomedical Sciences, Inc. (December 2003), Dr. Lewis founded an independent consulting service, Integrative Policy & Science, Inc. (IPSi). The mission of IPSi is to provide public and private sector clients with advice in the specific areas of Dr. Lewis’ expertise, including general toxicology, qualitative and quantitative assessment of risk from occupational and/or environmental hazards, science policy (i.e., the interplay of the biomedical and environmental sciences with environmental health policy-making), and legislative/regulatory affairs. Dr. Lewis has extensive experience in facilitating public engagement in environmental issues and decision-making, as well as in the area of risk communication.



In the role of Adjunct Professor, Department of Environmental and Occupational Medicine, Robert Wood Johnson Medical School (University of Medicine and Dentistry of New Jersey), Dr Lewis collaborates in undergraduate and post-graduate teaching. Dr. Lewis is also a regular lecturer in the Science and Engineering Departments of Raritan Valley Community College (of New Jersey).


Dr. Lewis is a Diplomate of the American Board of Toxicology (certified in 1980, recertified in 1985, 1990, 1995, 2000, 2005). He has served on the editorial boards of 4 scientific journals and is currently Associate Editor of Dose-Response (formerly, Nonlinearity in Biology, Toxicology and Medicine). Dr. Lewis is very active in a variety of professional societies, including the Society for Risk Analysis (past-member of the governing Council and nominee for the office of President), the International Society for Regulatory Toxicology and Pharmacology (elected to governing Council in 2002; re-elected in 2006), and the Society of Toxicology.


Dr. Lewis has served as a Consultant to the U.S. EPA Science Advisory Board, and as a Member of the Risk Communication Subcommittee of the EPA Board of Scientific Counselors (of the Office of Research and Development). He frequently provides comments on scientific and regulatory issues before U.S., state and international agencies and has repeatedly served as a selected peer reviewer for toxicological profiles, summaries and risk assessments. He is a Past-Chair of the American Petroleum Institute’s Toxicology Committee, and a former member of the Board of Directors of the Toxicology Forum, past Chair of the American Industrial Health Council’s Science Policy Committee, and a former member of the Science Program Committee of the Chemical Industry Institute of Toxicology. Dr. Lewis served as a member and Chairman of the Board of Trustees of TERA/ITER (a not-for-profit organization specializing in the assessment of health and environmental risks). He is continuing his association with TERA in the role of collaborative Fellow. Dr. Lewis recently completed his term as a member of the U.S. National Research Council’s panel on "Public Participation in Environmental Decision-Making."


Dr. Lewis retains the title of Senior Fellow (Cecil and Ida Green Center for the Study of Science & Society, University of Texas at Dallas), where he was a Visiting Scholar in 1995. Dr. Lewis has published and presented the results of his work widely. He has delivered numerous invited seminars and other presentations.


William Hayes, MPA., TERA Fellow


Mr. William Hayes has had a long career spanning many facets of education, management, business, environment, and industrial hygiene.  Specifically, his experience includes:

ž Management of financial operations,
ž Supervisor, team leader, and facilitator,
ž Extensive study and application of the principles of project management, and
ž Active in the community and in professional organizations.


He is a Fellow for Toxicology Excellence for Risk Assessment (TERA), an environmental science NGO located in Cincinnati, Ohio.  He is also an adjunct professor of public and environmental affairs, a certified industrial hygienist (ret), a registered environmental health specialist, and a registered professional sanitarian.  His academic credentials include a B.S. in Public Health (major, environmental health) from the Indiana University School of Medicine, and a Master of Public Affairs (major, management) from Indiana University.