John D. Schell, Ph.D.

Dr. Schell has more than 20 years of environmental assessment experience, focusing on human health and ecological impacts of PCBs, dioxins, volatile organic, chlorinated pesticides, and metals. He is a former member of the faculty at the University of Florida, and has held adjunct teaching positions at the University of South Florida and the University of Florida. He has experience performing human health and ecological risk assessments under state and federal programs such as Superfund, RCRA, and state Risk-Based Corrective Action (RBCA) programs. His experience includes assessing the toxicity of PCBs, dioxins, VOCs, pesticides, aromatic hydrocarbons, and metals, investigating their mode of action, and their impact on human health and the environment. His activities include work on some of the largest river sites in the U.S., and he has worked on projects in 27 states across the country.

Prior to joining Exponent, Dr. Schell was a staff toxicologist at the St. Johns River Water Management District where he worked with scientists from the Florida Department of Health in developing fish advisory, and has served as a consultant to the District for their Lake Apopka and Everglades restoration programs. Dr. Schell has served on advisory bodies on chemical risk assessment issues in Florida and Michigan, has presented to international regulatory and scientific bodies and numerous public hearings, and has provided Congressional briefings in Washington D.C. Dr. Schell is a former member of the USEPA Pesticide Program Dialogue Committee, and he has been qualified as an expert in toxicology in both federal and state courts.

Ebert ES, Wilson N, Wacksman M, Loper JR, Schell JD, Fowler A. Utilization survey of a rural creek fishery in central Alabama. Risk Analysis 2011; 32(3):416–432.

Schell JD, Pardus MJ. Preliminary risk-based concentrations for tungsten in soil and drinking water. Journal of Land Contamination 2009; 17(1):179–188.

Wernke MJ, Schell JD. Solvents and malignancy. In: Clinics in Occupational and Environmental Medicine. Bennett-Bailey E (ed), Elsevier, Inc. Philadelphia, PA, 2004.

Schell JD, Budinsky RA, Wernke MJ. PCBs and neurodevelopmental effects in Michigan Children: An evaluation of exposure and dose characterization. Regulatory Toxicology and Pharmacology 2001; 33:300–312.

Budinsky RA, DeMott RP, Wernke MJ, Schell JD. An evaluation of modeled benzene exposure and dose-estimates published in the Chinese-National Cancer Institute collaborative epidemiological studies. Regulatory Toxicology and Pharmacology 1999; 30:244–258.

DeMott RP, Jones HD, Schell JD. Environmental risk assessment of a Lake Apopka muck farm wetlands restoration. St. Johns River Water Management District Special Publication SJ98-SP7, 1998.

James MO, Altman AH, Li J, Schell JD. Biotransformation, hepatopancreas DNA binding and pharmacokinetics of benzo(a)pyrene after oral and parenteral administration to the American lobster, Homarus americanus. Chemico-biological Interactions 1995; 82:456.

Keller AE, Schell JD. Lower St. Johns River Basin Reconnaissance: Sediment Characteristics and Quality. Volume 5. St. Johns River Water Management District Technical Publication SJ93-6, 1993.

James RC, Busch H, Tamburro CH, Harbison RD, Schell JD, Roberts SM. Polychlorinated biphenyl exposure and human disease. Journal of Occupational Medicine 1993; 35(2):136–148.

Schell JD, Campbell DM, Lowe E. Bioaccumulation of 2,3,7,8-tetrachlorodibenzo-p-dioxin in feral fish collected from a bleach-kraft paper mill receiving stream. Environmental Toxicology and Chemistry 1993; 12:2077–2082.

James MO, Schell JD, Barron MG, Li J. Rapid, dose dependent elimination of phenol across the gills, and slow elimination of a novel conjugate of phenol in urine of phenol-dosed lobster, Homerus americanus. Drug Metabolism and Disposition 1991; 19:127–131.

James MO, Schell JD, Boyle SM, Altman AH, Cromer EA. Southern flounder hepatic and intestinal metabolism and DNA binding of benzo(a)pyrene (BaP) metabolites following dietary administration of low doses of BaP, BaP-7,8-dihydrodiol or a BaP metabolite mixture. Chemico-biological Interactions 1991; 79:305–321.

Schell JD, James MO. Glucose and sulfate conjugation of phenolic compounds by the spiny lobster (Panulirus argus). Biochemistry and Toxicology 1989; 4(2):133–138.

James MO, Schell JD, Magee V. Bioavailability, biotransformation and elimination of benzo(a)pyrene and benzo(a)pyrene-7,8-dihydrodiol in the lobster, Homarus americanus. Bulletin of the Mount Desert Island Biological Laboratory 1988; 28:21–23.

James MO, Barron MG, Schell JD. Conjugation and excretion of phenolic compounds by the lobster, Homarus americanus. Bulletin of the Mount Desert Island Biological Laboratory 1987; 27:9–11.

Schell JD. Interactions of halogenated hydrocarbon mixtures in the embryo of the Japanese medaka (Oryzias latipes). Ph.D. Thesis, Rutgers University, 1987.

Schell JD, Cooper KR. Microsomal mixed function oxidase activity in the Japanese medaka (Oryzias latipes). Environmental Toxicology and Chemistry 1987; 6:717–721.

Scientific Presentations

Carlson EA, Schell JD, Bodreddigari S, Sutter TR, Sutter CH. Species differences in PCB toxicodynamics and toxicokintetics relevant to the Aroclor 1254 reference dose. Dioxin 2012, Cairns, Australia, August 2012.

Schell JD. Health risks from fracturing fluids: Are they real? Invited Speaker, Engineering and Technology Developments in Hydraulic Fracturing. Denver, CO, July, 2012.

Schell JD, Carlson EA, Silkworth JB, Bodreddigari S, Sutter TR, Sutter CH. The Aroclor 1254 reference dose as a case study for the development of data-derived extrapolation factors to replace the interspecies uncertainty factor. Society of Toxicology, March 2012.

Ebert ES, Wilson N, Wacksman M, Fowler A, Schell J, Loper J. Results of a one-year fish consumption survey in Alabama. Society of Toxicology, March, 2011.

Schell JD. Nanotoxicology: Is there a there, there? Annual International Conference on Soils, Sediments, Water and Energy, University of Massachusetts at Amherst, 2010.

Keenan RE, Gwinn PO, Schell JD, Carlson EA, Silkworth JB. Application of nonlinear dose-response methods based on mode of action for polychlorinated biphenyls (PCBs). Society of Toxicology, Baltimore MD, 2009.

Schell JD. Tungsten risk-based screening values: A preliminary assessment and benchmarking. Association for Environmental Health Sciences, San Diego, CA, March 2009.

Keenan RE, Gwinn PO, Schell JD, Carlson EA, Silkworth JB. Cancer risk estimates for PCBs are reduced using nonlinear dose-response methods based on mode of action. Dioxin 2008, Birmingham England, 2008.

Schell JD. Preliminary assessment of tungsten risk-based screening values and toxicity benchmarking. Force Health Protection Conference, Louisville, KY, August 9, 2007.

Schell JD, Giolando ST, Pardus MJ. Tungsten carbide/cobalt hardmetal powder: Are they carcinogenic? Air & Waste Management Association Annual Meeting, New Orleans, LA, June 23, 2006.

DeMott RP, Jones HD, Schell JD. Prospective ecological risk assessment for risk/benefit and risk management of proposed wetlands restoration. Society of Environmental Toxicology and Chemistry Annual Meeting, November 1998.

James RC, Schell JD, Roberts SM, Price B, Freeman RW. Using human data to develop better cancer slope factors: PCBs as an example. Abstract for Society of Toxicology, March 1995.

Schell JD, Borgert CJ, James RC, Freeman RW, Williams CA. The contribution of soil half-life to risk assessment conservatism. Abstract for Society of Toxicology, March 1995.

Schell JD, Williams CA, Jones HD. Impact of site-specific data on PCB-related risk estimates using Monte Carlo analysis. Abstract for Society of Risk Analysis, December 1994.

Schell JD, Jones HD, Williams CA. Effect of spatial considerations on PCB cancer risk using sediment accumulation models. Abstract for Society of Environmental Toxicology and Chemistry, November 1994.

Glooschenko V, Brim M, Augspurger T, Schell J. Monitoring needs in the U.S. Southeast: Impact of dioxin and other industrial wastes on wildlife. Abstract for Society of Environmental Toxicology and Chemistry, November 1994.

Schell JD, Campbell DM, Brody R. Bioaccumulation of environmental contaminants in feral fish populations of the St. Johns River, Florida. Society of Environmental Toxicology and Chemistry, November 1991.

Schell JD, Cromer EA, James MO. Benzo(a)pyrene (BaP) DNA-adducts in southern flounder (Paralichthys lethostigma) fed contaminated shellfish. The Toxicologist 1989; 9:165.

James MO, Schell JD. Bioavailability and biotransformation of benzo(a)pyrene (BaP) and BaP-7,8-dihydrodiol (BaP-7,8-D) in the lobster, Homarus americanus. The Toxicologist 1989; 9:164.

James MO, Li J, Schell JD. Disposition of a sulfadimethoxine/ormetoprim combination in the lobster, Homarus americanus. The FASEB Journal 1989; 3(3):3844.

Schell JD, James MO. In vitro glucose and sulfate conjugation of 4-methyl umbelliferone (4-MeU) by the spiny lobster (Panulirus argus). The Toxicologist 1988; 8:220.

Schell JD, Cooper KR. Role of metabolism in the toxicity of carbon tetrachloride in the Japanese medaka (Oryzias latipes) embryo. The Toxicologist 1987; 7.

Schell JD, Cooper KR. Induction of the xenobiotic metabolizing system of the Japanese medaka (Oryzias latipes). Society of Environmental Toxicology and Chemistry, Washington D.C., November 1986.

Schell JD, Cooper KR. Chemical interactions of halogenated hydrocarbon mixtures on lethal and sublethal parameters in the Japanese medaka (Oryzias latipes). The Toxicologist 1986; 6(1):107.

Cooper KR, Schell JD, Kahn P, Gallo M. The effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on the development and survival of the Japanese medaka (Oryzias latipes). The Toxicologist 1986; 6(1):108.

Schell JD, Cooper KR. Chemical interactions-halogenated hydrocarbon toxicity in the embryo of the Japanese medaka (Oryzias latipes). Society of Environmental Toxicology and Chemistry, St. Louis, MO, November 1985.

Cooper KR, Schell JD, Umbreit T, Gallo M. Bioavailability of sediment bound dioxin as detected by the Japanese medaka (Oryzias latipes) embryo bioassay. Society of Environmental Toxicology and Chemistry, St. Louis, MO, November 1985.

Schell JD, Cooper KR. The effects of carbon tetrachloride (CCl4), chloroform (CHCl3), trichloroethylene (TCE), and tetrachloroethylene (PCE) on the developing embryo of Oryzias latipes. SETAC Hudson/Delaware Chapter; New Brunswick, NJ, April 1985.

Schell JD, Cooper KR. Alterations in 59Fe distribution in rainbow trout following toluene and benzene exposure. The Toxicologist 1985; 5(1):90.

• Principal and Technical Director – ENTRIX, Inc., 2007–2011
• Principal and Vice President – Blasland, Bouck & Lee, Inc./Arcadis Inc., 2000–2007
• Assistant Professor – College of Public Health, University of South Florida, 1998–2002
• Vice President and Director, Risk Assessment Group – TERRA, Inc./ATRA Occupational & Environmental Services, Inc., 1995–2000
• Toxicologist –– TERRA, Inc., 1992–1995
• Staff Toxicologist –– St. Johns River Water Management District, Environmental Scientist, 1989–1992
• Associate Scientist –– University of Florida, Center for Environmental and Human Toxicology, 1991–1997
• Postdoctoral Research Associate –– University of Florida, The Whitney Laboratory, 1987–1989
• Graduate Assistant –– Rutgers University, Department of Toxicology, 1985–1987
• Teaching Assistant –– Rutgers University, Department of Pharmacology, 1984–1985
• Research Specialist –– Hospital of the University of Pennsylvania, Nephrology Department, 1977–1982

Developed Innovated Hazard Ranking System for Fracturing Fluids for Major Chemical Producer
Participate in team that developed an assessment protocol for evaluating the components of fracturing fluids based on their human and ecological toxicities and physical/chemical properties. The scoring system is consistent with the recent European Union’s (EU) new directive on Global Harmonization of Labeling. The system is being used by the client to optimize the environmental safety and performance of their fracturing fluid systems.

Developed Risk-Based Drinking Water Screening Concentrations for Tungsten
At the request of Global Tungsten & Powders, Corp, used the Benchmark Dose modeling approach with data from studies conducted by the Department of Defense to derive preliminary risk-based screening concentrations in order to evaluate groundwater at one of their US facilities. These results were presented to the local water commission as part of an outreach program.

Investigation into Environmental Conditions Associated with an Apparent “Cancer Cluster” in Children
On behalf of a client, participated in the evaluation of environmental data and associated materials developed by the Centers For Disease Control (CDC) as part of an investigation into a so-called “cancer cluster” of acute lymphocytic leukemia in children living in a Nevada town. Participated in developing comments on the CDC reports and developing technical information material for the community.

Presentation to the Senate Commission of the Deutsche Forschungsgemeinschaft
On behalf of the international Tungsten Industry Association, participated in an oral presentation to the Senate Commission of the Deutsche (DFG [German Research Foundation]) in an effort to prevent the Foundation from categorizing Hardmetal (cobalt with tungsten carbide) as a category 1, or known human carcinogen.

Health Assessment and Corrective Measure Evaluation for PCBs in a Southeastern Watershed
Evaluated historical data, community blood surveys, and watershed characteristic data to determine the need for and the level of remedial activity related to PCB-associated sediments in a large river system in the Southeastern U.S.

Developed Alternative Lead Cleanup Levels for Railroad Refueling Sites
Provided to the State of Mississippi alternative soil lead cleanup levels using modified biokinetic approaches and site-specific exposure scenarios. The alternative approach and cleanup levels were reviewed and approved by the USEPA’s Technical Advisory Workgroup for Lead.

Assess Exposure and Potential Developmental Effects from Lead Exposure, Pennsylvania
Technical support for defense expert witness in case of alleged injury to children from lead exposure in homes originating from the manufacturing facility. The body of scientific literature on the causal relationship between low level maternal body burdens of lead and neurodevelopmental effects in children exposed in utero were summarized to refute the alleged association.

Developed Alternative Risk-Based Drinking Water Criteria for 1,4-Dioxane
Using EPA’s recently adopted methodology for deriving the dose-response relationship for cancer (I.e., the benchmark dose methology), used the available experimental animal data set to derived an alternative cancer slope factor for 1,4-dioxane. Assuming default exposure assumption for drinking water, developed an alternative risk-based value protective of this exposure pathway.

Adopted the Risk-Based Corrective Action (RBCA) Model for Use in the Health and Environmental Assessment Portion of a RCRA Permit Application
Demonstrated to the State regulatory agency and USEPA that the methodology outlined in the RBCA guidance was consistent with the ”action level” approach prescribed in the RCRA guidance. Employed this agency-approved methodology in the HEA section of the Part B permit application.

Critiqued Methodology and Scientific Assumptions Used to Derive Dioxin TMDL
The USEPA had proposed establishing a TMDL for dioxin and dioxin-like compounds for a waterbody in Ohio and West Virginia. The TMDL was based on certain assumptions concerning the fate of dioxin in an aquatic system, bioaccumulation into aquatic organisms and exposure and toxicity to humans of these compounds. These assumptions and models were evaluated and alternative methodologies proposed for EPA’s reevaluation.

Litigation Support: City of Chicago
Expert witness in litigation against an owner of an abandoned paint manufacturing plant. Established target cleanup levels for the facility situated in an urban area adjacent to a low income housing project.

Established Alternative PCB Cleanup Levels for an Active Jet Engine Manufacturing Facility
Using Monte Carlo analysis and consideration of site-specific conditions to define the exposure distributions, developed alternative target cleanup concentrations for PCBs in soil and groundwater.

Developed Risk-Based Lead Clean-Up Levels, Saginaw Malleable Iron Plant, Michigan
As part of a RCRA Remedial Investigation in the state of Michigan, developed alternative lead cleanup levels based on site-specific modifications of USEPA’s “Adult Lead Model” to account for unique exposure conditions to plan workers.

Former Tungsten Processing Facility, Pennsylvania
As part of a Brownfield Initiative, a former tungsten processing facility was proposed for conversion to an interactive “industrial museum.” Elevated levels of lead were on the property and the company requested alternatives to the residential cleanup level of 400 ppm be developed. Modifications to the USEPA’s IEUBK model resulted in proposed lead concentrations that required no further action.

Determination of Potential Routes of Exposure and Associated Risks to PCBs
Developed the site conceptual model and delineated potential exposure routes to quantitatively evaluate associated cancer and non-cancer risks from PCB historically released to a waterway from a major production facility.

Derived Risk-Based Remedial Goals for PCBs at a Chemical Production Facility
Following procedures outlined in the Risk-Based Corrective Action for Non-Petroleum Sites, developed site-specific, risk-based levels of PCBs in soil protective of on-site worker population.

Evaluation of Contribution of PCBs to Total Cancer Risks Associated with Ocean Sediments
Critiqued memorandum from USEPA which estimated PCBs bioaccumulated into fish were quantitatively more important than other bioaccumulated chlorinated compounds. Developed fate and transport estimates in sediments to use in estimating bioaccumulation of PCBs into resident fish populations.

Qualitative Assessment of PCB Risks Associated with Releases from Gas Pipeline Pumping Stations
Proposed to the regulatory agencies that default assumptions required in standard quantitative risk assessments were irrelevant to these sites. Proposed evaluating each location on a site by site bases and developed qualitative estimates of risk for each site. Procedure has been accepted by federal and state regulatory community.

Developed Assessment of Risks from Future Use of an Abandoned Wood Treatment Facility on Mobile Bay
Provided estimates of cancer and non-cancer risks from chemicals found in soil, sediment and groundwater resulting from historical wood treatment activities. Use of alternative approaches, include the development of new toxicity values, lead to changes in the proposed remedial strategy by the State of Alabama.

Litigation Support: McDonald vs. Coronodo, Florida
Expert witness for client alleged to have caused neurodevelopmental affects in a young child because they used lead paint in the housing unit leased to the plaintiffs. Developed causation analysis and an incident-specific IEUBK model to demonstrate the paint in the home could not cause the alleged injury.

Qualitative Assessment of the Human Health Implications of PCBs Found in a Small Intermittent Stream in New York
Evaluated the likely impact on the health of local residents of low levels of PCBs found in an intermittent stream which drains into Lake Erie. Proposed an alternative remedial strategies based on the demonstration of minor risks associated with the chemical constituents.

Health Assessment of the Relative Quantitative Contribution of DDT and PCBs to Fish Consumers in California
Estimated the magnitude of PCBs and DDT in the total risk estimates to hypothetical populations of fish consumers. This assessment include unique characteristics and behavior patterns of a particularly sensitive target population.

Potential of an Abandoned Lead Site to Impact the Lead Body Burden in Children from the Local Community
Quantitatively estimated the change in the total body burden of lead in children living near an abandoned lead paint facility located in an urban environment.

Human Health Risk Assessment in the Michigan Upper Peninsula
Evaluation of the reproductive and immunological hazards and cancer risks from consumption of fish from a PCB contaminated harbor. Developed alternative exposure scenarios which more accurately reflected community characteristics. These alternative were adopted by U.S.EPA in developing the final remedy for the site.

Develop Appropriate Fish Tolerance Levels for Hexachlorobenzene and Hexachlorobutadiene
Developed risk based tolerance level for HCB and HCBD in fish tissue which represented safe exposure levels for recreational and commercial fishers.

Assessment of Acute Toxicity of 2,4-D
Estimated probable doses to occupationally exposed individuals and evaluated the potential for acute toxic effects based on a review of the scientific literature.

Health Assessment of 2,3,7,8-Tetrachlorodibenzo-p-dioxin in a Bleach Kraft Paper Mill
Determined the hypothetical risk of non-Hodgkin’s lymphoma to individuals employed at a bleach kraft paper mill occupationally exposed to 2,3,7,8-TCDD.

Assessment of the Reproductive and Developmental Toxicity of PCBs
Estimated the risks of neurological effects to children born of women who consume Great Lakes fish as a significant portion of their diet.

Toxicological Support for the Manganese Interest Group
On behalf of a consortium of auto and steel manufactures, developed the technical support document for the nomination of manganese for inclusion into EPA’s IRIA 2007 agenda.

Conducted Epidemiological Feasibility Study
For the International Tungsten Industry Association’s (ITIA) Hardmetal Work Group, managed an investigation into the feasibility of conducting an epidemiological investigation of an international cohort of hardmetal workers. Conducted Congressional briefings regarding the ongoing research activity.

• Society of Environmental Toxicology and Chemistry
• Society of Risk Analysis
• Society of Toxicology