Long-awaited results from Long Island study. (Cancer).
The study is unusual in having been mandated by Congress after women's activist groups such as the Baldwin, New York-based 1 in 9: The Long Island Breast Cancer Action Coalition pressured local politicians for an investigation into why area rates of breast cancer were going up. In 1993, Congress passed a bill for the National Cancer Institute to study the possible environmental causes of breast cancer on Long Island.
The first paper reports on PAH-DNA adducts (chemicals attached to the genetic material) as a measure of exposure among 646 breast cancer patients and 429 controls, and found no evidence of a dose-response relationship, nor of any association with the main sources of PAHs, cigarettes and grilled and smoked foods. Principal investigator Marilie D. Gammon, an epidemiologist at the University of North Carolina at Chapel Hill, says these results may be due to a threshold effect, or that the relationship between PAHs and breast cancer may not be causal. Breast cancer, however, correlated strongly with nonenvironmental factors such as age, alcohol consumption, number of pregnancies, and weight.
The second paper reports on blood serum levels of several organochlorine compounds among the same group of women. No dose-response relations were apparent, nor was organochlorine-related risk noted among women with several other breast cancer risk factors.
The results disappointed the activists whose lobbying spawned the LIBCSP. Many believe the studys should have looked at currently used pesticides rather than the long-banned organochlorines. Ruth Allen, former program director for the LIBCSP at the U.S. Environmental Protection Agency and now an agency environmental epidemiologist, says the study's focus was logical at the time it was funded (1993) because a series of papers had implicated organochlorines in excess breast cancers in New York State.
Many media outlets have taken the results as evidence that pollutants contribute little to the Long Island breast cancer rate, which is only slightly above the national average of 114.3 cases per 100,000 women. Allen counters, "It's an epidemic any way you look at it." The rate of breast cancer incidence on Long Island and in many other communities throughout the Northeast has doubled over the past 50 years.
It is premature to absolve pollutants of blame, says Allen; negative results on a few chemicals do not constitute a not-guilty verdict. Three million people live above the aquifers that supply Long Island's drinking water, and, she says, "whatever they put in the soil goes right into the groundwater." Seventy-eight air strippers run continuously to strip volatile organics from the water supply aquifer as a precautionary step to reduce human exposure to chemical residue from past polluting activities.
The studies themselves are first steps--not final results--in the effort to pinpoint causes of breast cancer. An earlier study published in the March 2000 issue of the Journal of Clinical Epidemiology implicated organochlorine pesticides, especially dieldrin, in breast cancer. Gammon plans to test for this association among the Long Island cohort. Women with defective detoxifying genes may be highly susceptible to breast cancer, and the Long Island researchers are investigating this and other possibilities.
Geri Barish, president of 1 in 9, says a geographical information system would enable the correlation of cancer prevalence with exposure to pesticides and other pollutants as documented by various agencies. The National Cancer Institute developed such a system specifically for this study to integrate air pollution, water pollution, hazardous and municipal wastes, electromagnetic fields, and other factors into the study. The system will soon be available for further studies of cancers on Long Island.