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Aug. 6, 2002 – No. 413
Photo note: To download photos, see bottom of release.
Long Island Breast Cancer Study Project uncovers small risk from hydrocarbons, not organochlorines
By DAVID WILLIAMSON
UNC News Services
CHAPEL HILL -- Exposure to air-polluting polycyclic aromatic hydrocarbons (PAHs) in the environment appears to elevate women's risk of breast cancer by a modest 50 percent in Suffolk and Nassau counties, N.Y., a new much-anticipated study indicates.
The Long Island Breast Cancer Study Project, one of the largest and most comprehensive environmental epidemiologic studies ever done on that cancer, uncovered no increased rate of the illness among area women who might have been exposed to organochlorine compounds.
"Starting with more than 3,000 women in this federally mandated research, we looked at blood samples taken from hundreds of new breast cancer patients and comparable women without breast cancer who served as controls," said principal investigator Dr. Marilie D. Gammon.
Gammon is associate professor of epidemiology at the University of North Carolina at Chapel Hill School of Public Health.
In their work on polycyclic aromatic hydrocarbons, which are known to cause mammary tumors in laboratory rats, researchers focused on PAH-DNA "adducts" -- chemicals attached to the genetic material known as DNA, she said. PAHs are inhaled through air pollution, including automobile and airplane exhausts and cigarette smoke, and are ingested by eating selected foods, including grilled and smoked foods. PAH-DNA adducts are evidence of exposure and suspected evidence of tissue damage in humans.
Except for the possible 50 percent increase in the risk of breast cancer associated with the highest levels of hydrocarbon adducts, "there was no increasing elevation in the risk of breast cancer with increasing adduct levels, nor was there a positive association between adduct levels and two of the main sources of PAHs," she said. "Those are active or passive cigarette smoking and consumption of grilled and smoked foods. Our data indicate that PAH-DNA adduct formation may influence breast cancer development, although the association does not appear to be dose dependent and may have a threshold effect.
"These ambiguous findings shed some doubt on a clear cause-and-effect association," Gammon said. "The study team is continuing to investigate this issue on Long Island through additional research focused on the possibility of individual responses to environmental exposures."
In their research on organochlorines, including the pesticide DDT, its metabolite DDE and industrial compounds known as PCBs, the scientists found no evidence supporting an association between those environmental toxins and heightened risk of breast cancer, she said. Analyzing blood samples from 646 patients and 429 control subjects, they showed such factors as breastfeeding, weight, menopausal status, length of residence on Long Island and form of breast cancer made no difference. Nor was there any increase in breast cancer associated with individual PCB variations, known as congeners. Not excluded was the possibility that such chemicals played an earlier, more subtle role in tumors.
"Recent research by other investigators suggests that organochlroine compounds may be related to the type of breast cancer that has clinical characteristics that are associated with worse survival. This is an important issue that we are continuing to investigate among the women in our study," Gammon said.
A report on the results appears in the August issue of Cancer Epidemiology, Biomarkers & Prevention. Besides Gammon, scientists involved include Drs. Regina M. Santella and Alfred I. Neugut of the Mailman School of Public Health at Columbia University, Mary S. Wolff of Mount Sinai School of Medicine and 24 other scientists from such institutions as Columbia, the State University of New York at Stony Brook, Cornell Medical Center and Long Island hospitals.
"The goal of this population-based, case-control study was to determine whether breast cancer incidence in women in these two counties was associated with exposures to environmental contaminants," said Gammon, deputy director of UNC's Environmental Health and Susceptibility Center and a UNC Lineberger Comprehensive Cancer Center member. "What we observed did not support that possibility strongly."
Because of circumstantial evidence, many experts believe certain pollutants increase women's exposure to the hormone estrogen, which boosts cell turnover so that it's harder for the body to repair damage before cells replicate and pass the damage to new cells, she said. Breast cancer victims are known to have more estrogen in their blood on average than other women.
"We know too, for example, that if a woman's ovaries, which produce estrogen, are removed before she is 35, her risk of breast cancer drops by half," Gammon said. "Men, who have little estrogen, rarely get breast cancer." The increase in breast cancer risk associated with PAH was restricted to women with breast tumors that were either estrogen receptor and progesterone receptor positive or who were negative for both, she said. This means the link was stronger for women with cancers that are considered hormone sensitive. Why is unclear.
"Our findings with polycyclic aromatic hydrocarbons suggest that women's individual responses to similar PAH exposures might be more relevant to breast cancer development than the absolute amount of PAH exposure," Gammon said. "A lot more work needs to be done to sort out exactly what and how environmental exposures may promote breast cancer."
The National Cancer Institute and the National Institute of Environmental Health Sciences paid for the research, which Congress mandated in 1993. The study came in response to concerns by Long Island cancer activists that Nassau and Suffolk counties showed disproportionately high breast cancer levels compared with other parts of New York state.
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Photo note: To download a photo of Gammon, click on http://www.unc.edu/news/pics/faculty/gammon_marilie.jpg
Note: Gammon can be reached at (919) 966-7421. On Tuesday (Aug. 6) she can be reached at the Garden City Hotel at (516) 747-3000. Copies of the papers are available from Kathy Case at (215) 440-9300. For more information on the study, click on the National Cancer Institute World Wide Web site at http://epi.grants.cancer.gov/LIBCSP.
UNC News Services Contact: Deborah Saine, (919) 962-8415
UNC School of Public Health Contact: Lisa Katz, (919) 966-7467
National Cancer Institute Press Office: (301) 496-6641
National Institute of Environmental Health Sciences Office of Communications: Tom Hawkins, (919) 541-1402