Researchers Probe Cape Cod's Breast Cancer Rate

Women on Cape Cod experience a 20 percent higher rate of breast cancer than the rest of the country. A new software program for tracking exposure to pesticides could help researchers understand the link between chemicals, genes and breast cancer.

Julia Brody

CAPE COD, Mass. (WOMENSENEWS)-For residents and summer travelers, Cape Cod's bright red cranberry bogs and heron-studded marshlands define the landscape. For researchers at the Silent Spring Institute, Inc., in Newton, Massachusetts, however, Cape Cod's marshes and bogs-or more importantly, their history of contact with pesticides and weed killers-may hold information about the high incidence of breast cancer patients.

The Cape Cod peninsula is a breast cancer hot-spot, a region where women are diagnosed with the disease at a rate 20 percent higher than the rest of the country. In response to these statistics, the Silent Spring Institute along with a software company Applied Geographics, Inc., has created the Spatial Proximity Tool, a computer program that can reconstruct decades of exposures to pesticides and weed killers, house by house.

Breast cancer is the leading cause of death among women in the United States between the ages of 35-54, with 180,000 new cases reported annually. While there are no easily identifiable causes of the disease, scientists generally believe the disease is the result of various factors-genetic, environmental and personal-all subtly working in tandem.

Julia Brody, executive director of the Silent Spring Institute, said the mapping project is the first of its kind and represents a major development in the study of exposure pathways in the environment. Using the software, researchers are able to estimate relative intensities of exposure to pesticides and similar chemicals, creating individual exposure portraits for the 2,100 Cape Cod women-some who have cancer and others who don't-involved in the study.

The institute's mapping database represents the most comprehensive source of information about health and the environment on Cape Cod.

Silent Spring researchers culled data about nearly 50 years of pesticide and similar chemicals used on the Cape from 1948 to 1995, contacting federal, state, and local sources as well as private pesticide-spraying companies, cranberry growers and golf course superintendents. During the period studied, more than two dozen chemicals, including DDT, dieldrin and Sevin, were used as insecticides, herbicides and fungicides on cranberry bogs, wetlands, golf-courses and municipal areas such as telephone and power line sites. People living near these sites may have been exposed at the time of spraying, or over the years, as the chemicals leached into soil, food crops, or drinking water, researchers say.

The Spatial Proximity Tool evaluated the “likely exposure” of each woman's residence to potentially hazardous chemicals. It did this by considering, for example, whether a nearby forest acted as a “buffer” protecting a particular residence from nearby pesticide spraying or whether a house was built on land that had once been used for farming, in which case pesticides would have been used in high concentrations.

While the initial map has produced no obvious link between pesticide exposure and breast cancer incidence, institute researchers plan to overlay the map with other types of information, such as maps of Cape Cod's drinking water supply wells, septic systems and private wells, as well as information gleaned from interviews with the 2,100 participants, such as their exercise habits, use of household products and personal medical histories. Eventually researchers hope to be able to trace associations between contaminated areas and patterns of breast cancer incidence.

Research and Theory Indicates No One Cause of Cancer

Most breast cancer researchers believe there is a combination of influences-environmental and genetic-that trigger the disease. Until recently, scientists have only been able to study links between cancer and the environment from atomic bombs or other direct, massive doses of radiation.

Dr. Deborah M. Winn, acting associate director of Epidemiology and Genetics Research Program of the National Cancer Institute, says the need for further research connecting environment to breast cancer risk is urgent.

“Environmental and lifestyle factors and personal susceptibility factors interact in complex ways in the development of disease. There is an increasing interest in how environmental and lifestyle and genetic factors jointly affect diseases such as breast cancer. Genes can affect how DNA is repaired in response from environmental risk factors, how hormones and nutrients are metabolized or how cell growth is affected.”

Last year the U.S. Centers for Disease Control and Prevention issued the National Report on Human Exposure to Environmental Chemicals. For the first time, environmental exposure to 27 chemicals was documented from urine and blood samples of 5,000 study participants. While the Centers for Disease Control does not perform toxicological risk assessments for these compounds, the report gives environmental health experts important information for further study by identifying what chemicals are routinely found in the human body. This study provided for the first time national exposure levels for 24 of the 27 chemicals tested

Brody believes the national report represents a necessary step toward a national understanding of which chemicals are prevalent in the environment and which ones need further study.

Many Believe that Chemicals Are Safe Because They Are For Sale

“People believe that because something is sold on the market or sprayed in populated places that it must be safe. That's the wrong assumption,” Brody said. “There is a wide mixture of chemicals in our environment. This is really a right-to-know issue.”

The Center for Disease Control and Prevention's report, however, shows the “burden of chemicals on our bodies.” Brody said. “We can now observe concentrations of these chemicals as they rise and fall in different geographic areas.”

No study of environmental causes can offer a complete picture of a person's actual exposure. Brody admits that the Silent Spring's mapping project contains necessary “data gaps.” For example, the software could not factor in how long each woman was exposed to any one contaminant, nor could it determine the type of exposure she was subjected to – direct contact or contact through soil or drinking water, for example.

In addition to the mapping project, the Silent Spring scientists have recently collected and analyzed samples of air and dust from homes of 120 of the 2,100 study participants, testing for the presence of 86 chemical compounds. In an earlier study of seven homes, workplaces and stores, scientists found 33 out of the 86 chemicals tested for, including phthalates (agents found in soaps, shampoos and nail polishes) and estrogenic phenols (agents found in pesticides and personal care products such as cosmetics and spermicides).

Phthalates are known endocrine disruptors, or chemical estrogen-mimics, and researchers believe they could be involved in increased breast cancer risk. Naturally occurring estrogen has been linked to high incidence of breast cancer. Women who have not had children or were younger at menarche or older at menopause are at greater risk because each menstrual cycle results in continual and uninterrupted exposure to estrogen.

The institute also has begun testing wastewater, groundwater and drinking water for endocrine-disrupting compounds, trying to detect how these compounds get into and travel through aquifers.

“Ideally, we would like to know exactly how much of each compound women were exposed to, how multiple exposures interact and when in each woman's life cycle exposure occurred,” Brody said.

Regan Good is a writer based in Brooklyn, New York.

For more information:

Silent Spring Institute, Inc.: The Web site of the National Cancer Institute:

Pesticide Education Office at the University of Nebraska, Lincoln: