Breast cancer and the Long Island study
Results from the long-awaited Long Island Breast Cancer Study were
released this summer, and they dismayed many activists. Most reporters
interpreted the results as proof that pollutants did not cause breast
But a closer look at the study reveals its limits. And taking a step back from the debate that the Long Island study has engendered will help point us toward policies that will alleviate the toxic burden imposed on all of us.
The Long Island Breast Cancer Study looked at approximately 1,500 women with breast cancer diagnosed between 1996 and 1997 (the cases) and an equal number of women without breast cancer (the controls). Blood samples from each group were examined for evidence of several organochlorine pesticides and PCBs. Other samples were examined for evidence that their DNA had undergone changes from exposure to polycyclic aromatic hydrocarbons (PAH).
Researchers found no association between breast cancer and exposure to pesticides or PCBs. They identified a 50 percent elevated risk of breast cancer from PAH exposure, a risk the researchers characterized as "modest" when compared with, for example, the risk of lung cancer from smoking.
The study's limitations bear remembering. As breast cancer develops over many years, most researchers believe a case-control study is unlikely to reveal how environmental exposures are related to the disease. Instead, a study that follows subjects over a long period of time -- a longitudinal study -- is much more likely to help us understand the environmental factors contributing to breast cancer. The case-control approach was chosen for Long Island because the activists pushing for this research in the early 1990s wanted answers fast.
Another major limitation of the Long Island study is that it examined substances -- like PCBs and the pesticides dieldrin and chlordane -- that have long been banned from production and use in the United States. More than 85,000 chemicals are in daily use in this country, most of which have never been evaluated for their effects on human health.
But the most challenging limitation of the study is that scientists have not yet figured out how to measure the combined effects of multiple, long-term exposures to environmental toxins. The strongest conclusion we can draw from Long Island is that these things do not appear to increase the risk of breast cancer by themselves. But we're all exposed to many pollutants, all the time.
Rather than minimize the PAH effect as "modest," we ought to be educating the public about ways to control their exposure to PAH and about the essential political work needed to reduce everyone's exposure to these kinds of substances.
That means working for the implementation of the precautionary principle of public health, or "better safe than sorry." That work must move forward because it will be a long time, if ever, before science can give us the answers we need.
So as we use the lessons of Long Island to push for better environmental research, we need to realize that reliable answers that develop through that research will be many years in arriving. We cannot let the process of science hold us back from working now toward policies that will reduce the chemical exposures that we all experience, all the time.
When I was diagnosed with breast cancer at the age of 41 (nearly 10 years ago) I quickly learned that what happens to me is out of my hands. I'm one of the lucky ones; I'm still here. But the fate of those who follow rests in our hands. We don't have time to despair. There's work to do. We cannot, and will not, give up. Our daughters' lives are at stake.
Brenner is executive director of Breast Cancer Action. For more information, see www.bcaction.org, or write 55 New Montgomery, Suite 323, San Francisco, CA 94105