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Date:  July 27, 2006
Contacts:  Bill Kearney, Director of Media Relations
Michelle Strikowsky, Media Relations Assistant
Office of News and Public Information
202-334-2138; e-mail <news@nas.edu>

FOR IMMEDIATE RELEASE

EVIDENCE GROWING ON HEALTH RISKS FROM TCE;
CURRENT DATA ARE SUFFICIENT FOR EPA TO FINALIZE RISK ASSESSMENT

WASHINGTON -- A new report from the National Academies' National Research Council recommends research to improve understanding of how the environmental contaminant trichloroethylene causes cancer and other adverse health effects, but adds that enough information exists for the U.S. Environmental Protection Agency to complete a credible human health risk assessment now.

In 2001 EPA issued a draft risk assessment on trichloroethylene, a solvent widely used as a degreasing agent that is contaminating air, soil, and water at several military installations and hundreds of waste sites around the country.  The release of the draft risk assessment was followed by much debate about the quality of evidence on trichloroethylene and how that evidence should be assessed.  This prompted an interagency group to request that a Research Council committee review issues related to assessing the health risks from exposure to trichloroethylene, commonly referred to as TCE.  The committee was not asked to conduct a risk assessment of its own.

The evidence on cancer and other health risks from TCE exposure has strengthened since 2001, the committee found.  It pointed out that research, including studies of human populations, supports the conclusion that TCE is a potential cause of kidney cancer.  Research shows that the chemical may cause other kidney problems as well, but the level of exposure needed to produce kidney damage is not clear.  Animal data indicate that relatively high doses of TCE are needed to induce liver toxicity and cancer.  Some epidemiology studies indicate a higher incidence of liver cancer among populations exposed to TCE, but the evidence is inconsistent.  Studies of people exposed to TCE at work do not show a strong association between exposure and lung tumors, the report notes.

Animal research and human population studies suggest that TCE exposure may also be associated with other health effects, such as reproductive and developmental problems, impaired neurological function, and autoimmune disease.  The committee recommended studies to advance understanding of the mechanisms by which TCE causes cancer and other health problems; which populations are most sensitive to TCE's effects; and how exposure to a mixture of TCE and other chemicals affects human health.

A large body of epidemiological data on TCE and cancer is available, but a new analysis of that data is needed to better characterize the hazard that TCE presents to humans, the committee said.  It found several weaknesses in the analysis that EPA used in its draft risk assessment, as well as in an analysis developed by researchers since the draft was issued.  To overcome these weaknesses, the new analysis should establish clear criteria for including epidemiological studies based on objective characteristics, the committee said.  It added that it would be appropriate for EPA to use a model jointly developed with the U.S. Air Force to simulate how the body metabolizes TCE, although the model does not resolve uncertainty about the mechanisms by which the chemical causes cancer.

A model is being used to extrapolate from animal studies an estimate of the cancer risk posed by TCE at low doses.  The risk is extrapolated below a "point of departure," which is associated with an incremental effect, such as 5 percent more cancers.  EPA should consider a range of points of departure in its risk assessment, the committee recommended.  Because there is not enough evidence on how TCE triggers cancer to choose the best model for relating the body's response to different dose levels -- a so-called dose-response model -- it is appropriate under EPA's cancer guidelines to extrapolate the risk using a linear model, in which cancer risk rises in proportion to dose.

The committee's report was funded by the U.S. Environmental Protection Agency, U.S. Department of Defense, U.S. Department of Energy, and NASA.  The National Research Council is the principal operating arm of the National Academy of Sciences and the National Academy of Engineering.  It is a private, nonprofit institution that provides science and technology advice under a congressional charter.  A committee roster follows.

                                                                                                                                                                                                                      Copies of ASSESSING THE HUMAN HEALTH RISKS OF TRICHLOROETHYLENE: KEY SCIENTIFIC ISSUES will be available from the National Academies Press; tel. 202-334-3313 or 1-800-624-6242 or on the Internet at HTTP://WWW.NAP.EDU.  Reporters may obtain a pre-publication copy from the Office of News and Public Information (contacts listed above).

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[ This news release and report are available at HTTP://NATIONAL-ACADEMIES.ORG ]


NATIONAL RESEARCH COUNCIL
Division on Earth and Life Studies
Board on Environmental Studies and Toxicology

COMMITTEE ON HUMAN HEALTH RISKS OF TRICHLOROETHYLENE

ROGENE F. HENDERSON, PH.D. (CHAIR)
Senior Scientist Emeritus
Lovelace Respiratory Research Institute
Albuquerque, N.M.

SCOTT M. BARTELL, PH.D.
Assistant Professor
Department of Environmental and Occupational Health
Rollins School of Public Health
Emory University
Atlanta

SCOTT W. BURCHIEL, PH.D.
Professor of Pharmacology, Toxicology, and Immunology, and
Associate Dean for Research
College of Pharmacy
University of New Mexico
Albuquerque

DEBORAH A. CORY-SLECHTA, PH.D.
Director
Environmental and Occupational Health Sciences Institute, and
Chair
Department of Environmental and Occupational Medicine
Robert Wood Johnson Medical School
University of Medicine and Dentistry of New Jersey
Piscataway

MARY E. DAVIS, PH.D.
Professor
Department of Physiology and Pharmacology
West Virginia University Health Sciences Center
Morgantown

KELLY J. DIX, PH.D.
Scientist
Toxicology Division
Lovelace Respiratory Research Institute
Albuquerque, N.M.

MARK S. GOLDBERG, PH.D.
Associate Professor
Department of Medicine
McGill University
Montreal

EVAN KHARASCH, M.D., PH.D.
Professor and Director
Clinical Research Division
Department of Anesthesiology
Washington University
St. Louis

SERRINE S. LAU, PH.D.
Professor
Department of Pharmacology and Toxicology, and
Director
Southwest Environmental Health Sciences Center
University of Arizona
Tucson

JOSE MANAUTOU, PH.D.
Associate Professor of Toxicology
Department of Pharmaceutical Sciences
University of Connecticut
Storrs

D. GAIL MCCARVER, M.D.
Associate Professor
Departments of Pediatrics and Pharmacology, and
Co-director
Birth Defects Research Center
Medical College of Wisconsin
Milwaukee

HARIHARA MEHENDALE, PH.D.
Professor and Kitty DeGree Endowed Chair in Toxicology
School of Pharmacy
University of Louisiana
Monroe

PETER MUELLER, PH.D.
Professor
Department of Biostatistics
M.D. Anderson Cancer Center
University of Texas
Houston

JOHN M. PETERS, M.D., M.P.H., SC.D.
Hastings Professor and Director
Division of Occupational and Environmental Health, and
Director
Southern California Environmental Health Sciences Center
Keck School of Medicine
University of Southern California
Los Angeles

THOMAS J. SMITH, PH.D., M.P.H.
Professor of Industrial Hygiene
Harvard School of Public Health
Boston

LESLIE STAYNER, PH.D.
Professor and Director of Epidemiology and Biostatistics
University of Illinois School of Public Health
Chicago

ROCHELLE W. TYL, PH.D.
Director
Center for Life Sciences and Toxicology
Research Triangle Institute
Triangle Park, N.C.

JACK P. VANDEN HEUVEL, PH.D.
Associate Professor of Molecular Toxicology and Carcinogenesis
Department of Veterinary and Biomedical Sciences
Pennsylvania State University
University Park

JANICE W. YAGER, PH.D., M.P.H.
Senior Scientist
Environment Division
Electric Power Research Institute
Palo Alto, Calif.


RESEARCH COUNCIL STAFF

SUSAN N.J. MARTEL
Study Director