Nathan Karch
Nathan J. Karch, Ph.D., DABT
Principal Scientist
Health Sciences
  • Washington, DC

Dr. Karch has more than 30 years of experience in evaluating scientific and technical questions relating to complex environmental and public health problems. The context has principally involved multidisciplinary, evidence-based questions of medical causation in litigation, with claims of personal injury, toxic tort or product liability. This work has focused on evaluations of the extent and effects of human exposures arising from manufacture, storage, distribution, or use of products containing chemicals or from environmental or accidental releases. Other evaluations have covered many aspects of product stewardship, such as exposure and risk assessment of multimedia pollution, hazardous waste site evaluations, risk ranking, comments on proposed regulatory policy, product development and registration, hazard communication compliance, and materials handling.

As a consultant, Dr. Karch has worked primarily for industrial clients, but also for government and public interest organizations. 

For more than 17 years, Dr. Karch was president of Karch & Associates, Inc., a firm specializing in toxicology, epidemiology, and risk assessment. Dr. Karch directed the health and environmental staff of the Council on Environmental Quality in the Executive Office of the President of the United States, served on the staff of the National Research Council—the staff arm of the National Academies of Sciences and of Engineering, and served on the staff of the American Chemical Society that worked with Board and Council committees to provide advice on chemical matters under a charter from Congress. Dr. Karch was involved early in establishing risk assessment methods used by regulatory agencies for estimating cancer risks and in evaluating reproductive and neurological hazards. 

After receiving his Ph.D. from Yale University, Dr. Karch took additional classes in toxicology, epidemiology, and biostatistics at the Foundation for Advanced Education in the Sciences, the non-accredited graduate school of the National Institutes of Health, in Bethesda, MD. 

CREDENTIALS & PROFESSIONAL HONORS

  • Ph.D., Physical Organic Chemistry, Yale University, 1973
  • M.Phil., Chemistry, Yale University, 1969
  • B.S., Chemistry, Illinois Institute of Technology (IIT), 1966
  • Member, Joint Board-Council Committee on Environmental Improvement (1988–1993) of the American Chemical Society

    Member, National Academy of Sciences Committees: Served on Toxicology Information Program Committee (1992–1994), which provided advice to the National Library of Medicine; served on the Subcommittee on Jet Fuels, Committee on Toxicology (1993–1996), which set occupational exposure limits for exposure to jet fuels on naval vessels 

LICENSES & CERTIFICATIONS

Diplomate, American Board of Toxicology

Publications

Guzelian P, Quattrochi L, Karch N, Aylward L, Kaley R. Does dioxin exert effects in humans at or near current background body levels?: An evidence-based conclusion. Human and Experimental Toxicology 2006; 25:99–105.

Karch NJ. Conference Report: Dioxin 2004. Environ Sci Pollut Res 2004; 11:415.

Karch NJ, Watkins DK, Young AL, Ginevan ME. Environmental fate of TCDD and Agent Orange and bioavailability to troops in Vietnam. Organohal Comp 2004; 66:3640–3645.

Iannuzzi TJ, Armstrong TN, Ludwig DF, Karch NJ, Firstenberg CE. Persistent organic pollutants in sediments and aquatic organisms from intertidal habitats in an urban river. Organohal Comp 2001; 51:188–190.

Kirman CR, Aylward LL, Karch NJ, Paustenbach DJ, Finley B, Hays SM. Is dioxin a threshold carcinogen? A quantitative analysis of the epidemiological data using internal dose and Monte Carlo methods. Organohal Comp 2000; 48:219–222.

Kirman CR, Hays L, Aylward LL, Karch NJ, Paustenbach DJ. Is TCDD a threshold carcinogen? A quantitative analysis of the epidemiological data. Society for Risk Analysis Annual Meeting and Exposition, Phoenix, AZ, 1998. 

Arfsten DP, Aylward LL, Karch NJ. Chromium. Chapter 4. In: Immunotoxicology of Environmental and Occupational Metals, Zelikoff JT, Thomas PT (eds). Taylor and Francis, London, 1998. 

Aylward LL, Karch NJ, Hays SM, Paustenbach DJ. Response to comment on relative susceptibility of animals and humans to the cancer hazard posed by 2,3,7,8-tetrachlorodibenzo-p-dioxin using internal measures of dose. Environ Sci Technol 1998; 32(4):551–552. 

Thomas PT, Aylward LL, Karch NJ. Immunotoxicity of dioxin: Is the TEF concept premature? In: Chlorine and Chlorine Compounds in the Paper Industry. Sleeping Bear Press, Michigan, 1998. 

Aylward LL, Hays SM, Czernec J, Brien B, Paustenbach DJ, Karch NJ. Relative doses of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) using alternative dosimetrics: Comparison of the NIOSH and Ranch Hand populations. Organohal Comp 1997; 34:6–9. 

Hays SM, Aylward L, Karch NJ, Paustenbach DJ. The relative susceptibility of animals and humans to the carcinogenic hazard posed by exposure to 2,3,7,8-TCDD: An analysis of standard and alternative dosimetric measures. Chemosphere 1997; 34(5–7):1507–1522. 

Hays SM, Aylward LL, Mocarelli P, Needham LL, Brambilla P, Gerthoux P, Patterson DG, Czernec J, Paustenbach DJ, Karch NJ. Comparative dose-response of the NIOSH and Seveso populations to the carcinogenic hazard of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) using alternative dosimetrics. Organohal Comp 1997; 34:305–310. 

Aylward LL, Hayes SM, Karch NJ, Paustenbach DJ. Relative susceptibility of animals and humans to the cancer hazard posed by 2,3,7,8-tetrachlorodibenzo-p-dioxin using internal measures of dose. Environ Sci Technol 1996; 30(12):3534–3543. 

Henderson RF, Carter DE, Feigley CE, Karch NJ, Medinsky MA, Mullick FG, Snyder R, Witschi HR. Permissible exposure levels for selected military fuel vapors. National Academy Press, Washington, DC, 1996. 

Minear RA, Ford AM, Needham LL, Karch NJ (eds). Applications of molecular biology in environmental chemistry. CRC Press, Boca Raton, FL, 1995. 

Paustenbach D, Karch N, Golden R, Kerger B, Leung HW. The relative susceptibility of animals and humans to carcinogenic hazard posed by exposure to 2,3,7,8-TCDD: An analysis of standard and alternative dosimetric measures. Organohal Comp 1995; 26:31–34. 

Rodan BD, Karch NJ, Cordasco EM, van der Kuyp F. Pulmonary function testing in epidemiological studies of particulate air pollution: Interpretative issues. Inhal Toxicol 1995; 7(9):1259–1291. 

Golden RJ, Schupak LH, Karch NJ. Differences between animals and humans in the gastrointestinal absorption of barium. Int J Environ Studies 1989; 34:217–225. 

Karch NJ, Golden RJ, Lowenbach WA, Yost LJ, Weiss AL. Identification and ranking of chemical hazards for the railroad industry. J Am Coll Toxicol 1987; 6(2):171–184. 

Nisbet ICT, Karch NJ. Chemical hazards to human reproduction. Noyes Data Corporation, New Jersey. 1983. ISBN 0-8155-0931-6; originally published in limited quantity by the Council on Environmental Quality, U.S. Government Printing Office (1981). 

Karch NJ. Polychlorinated biphenyls in the environment. pp. 220–224. In: The National Research Council in 1978. National Academy of Sciences, Washington, DC, 1978. 

Karch NJ. Explicit criteria and principles for identifying carcinogens: A focus of controversy at the Environmental Protection Agency. pp. 119–206. Vol. IIa: Case Studies. National Academy of Sciences, Washington, DC, 1977. 

Karch NJ, Koh ET, Whitsel BL, McBride JM. An X-ray and EPR structural investigation of oxygen discrimination during the collapse of radical pairs in crystalline acetyl benzoyl peroxide. J Am Chem Soc 1975; 97:6729. 

Karch NJ, McBride JM. Lattice control of free radicals from the photolysis of acetyl benzoyl peroxide. J Am Chem Soc 1972; 94:5092. 

Karch NJ. Two cases of solvent effects on photolytic decomposition. Dissertation, Yale University, 1973. 

Professional Affiliations

American Chemical Society

Society for Risk Analysis

Society of Toxicology

Society for Epidemiologic Research

International Society for Environmental Epidemiology

American College of Occupational and Environmental Medicine (associate member) 

Project Experience

Provided scientific support litigation as a confidential consultant to attorneys in cases involving exposures to dioxin (2,3,7,8-TCDD), PCBs, pentachlorophenol, tetrachloroethylene, trichloroethylene, asbestos, hexavalent chromium, lead, cadmium, benzene, toluene, xylene, various pesticide chemicals (such as DDT and atrazine), silicones, and a range of complex chemical mixtures. This work generally included most or all of the following: evaluations of the scientific and medical information available to determine whether to defend or settle cases, identifying scientific and medical issues in litigation; identifying and preparing expert and fact witnesses; analyzing opposing experts for deposition and trial; assisting in the preparation of demonstrative evidence; assisting in preparation of motions for summary judgment, Daubert and related challenges, and various other motions in limine; assisting in preparation of appeal briefs; risk communication information for investors and various regulatory bodies; and assisting in public communications about the litigation.

Directed litigation support projects in more than 400 cases involving multiple plaintiffs or substantial assets at risk, including toxic tort, personal injury, and product liability lawsuits, many of which involved class action. Analyses included evaluating exposure and dose, including assessing chemical manufacturing processes, fate and transport of chemicals, and modeling in air, water, and soil; assessing applicable regulatory standards and state-of-the-art issues; assessing toxicity and mechanism of action based on human, animal, and cellular studies; reviewing alternative causes of medical conditions, criteria for sound application of causation criteria, and principles of toxicology and epidemiology. Served as expert witness in a few cases.

Assisted private clients in matters involving citations for violations under various federal statutes, including the Toxic Substances Control Act and the Occupational Safety and Health Act, and in matters involving state regulations of toxic substances, including one matter where a state standard was set before remediation of ground water could be completed.

Directed a complex rail project that involved developing a unique model for ranking the potential for acute lethality and long-term adverse health effects of chemicals in more than 750 hazardous materials carried by rail nationwide. The project focused on inhalation hazards to surrounding communities following large spills of volatile chemicals in hazardous materials. Also, the project involved presentations of the approach and relevant conclusions to U.S. Environmental Protection Agency, the U.S. Department of Transportation, and the U.S. Congress to promote consistency of approach to defining hazardous materials and in labeling them.

Directed as staff the work of a panel on scientific and engineering data of the Committee on Environmental Decision Making, National Academy of Sciences/National Research Council (NAS/NRC), which evaluated all of the U.S. EPA’s research and regulatory programs, the sources of information on which the programs relied, and the scientific criteria used. For another committee, provided staff support to a committee reviewing the carcinogenicity of Heptachlor and Chlordane, during which pathologists reviewed slides from animal bioassays through a four-headed scope to reach consensus.

Executive Director of a 22-agency task force on toxic substances, which consisted of regulatory and research agencies of the federal government. Prepared a draft report to the President on research and regulation of toxic substances and served on an interagency committee that determined which substances would be tested by government and the priority for the tests.

Knowledge

CREDENTIALS & PROFESSIONAL HONORS

  • Ph.D., Physical Organic Chemistry, Yale University, 1973
  • M.Phil., Chemistry, Yale University, 1969
  • B.S., Chemistry, Illinois Institute of Technology (IIT), 1966
  • Member, Joint Board-Council Committee on Environmental Improvement (1988–1993) of the American Chemical Society

    Member, National Academy of Sciences Committees: Served on Toxicology Information Program Committee (1992–1994), which provided advice to the National Library of Medicine; served on the Subcommittee on Jet Fuels, Committee on Toxicology (1993–1996), which set occupational exposure limits for exposure to jet fuels on naval vessels 

LICENSES & CERTIFICATIONS

Diplomate, American Board of Toxicology