[CPEO-BIF] NAS TCE report

[Lenny Siegel <lsiegel@cpeo.org>]

[Please excuse redundant postings. - LS]


FOR IMMEDIATE RELEASE
July 27, 2006
The National Academies

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.


                                                                        ...

#       #       #

For the original press release, see
http://www8.nationalacademies.org/onpinews/newsitem.aspx?RecordID=11707

To download or order the report, go to
http://www.nap.edu/catalog/11707.html

--


Lenny Siegel
Director, Center for Public Environmental Oversight
c/o PSC, 278-A Hope St., Mountain View, CA 94041
Voice: 650/961-8918 or 650/969-1545
Fax: 650/961-8918
<lsiegel@cpeo.org>
http://www.cpeo.org


_______________________________________________
Brownfields mailing list
Brownfields@list.cpeo.org
http://www.cpeo.org/mailman/listinfo/brownfields