The chemical burden we all carry from our increasingly polluted world continues to grow heavier. Not even the newest members of society are safe: One study found the umbilical cord blood of 10 newborns to contain an average of 200 contaminants—including a range of pesticides, flame retardants, and other pollutants—a chemical inheritance from time spent in the womb.
To help clarify the chemical risks for breast cancer, Silent Spring Institute has compiled the most comprehensive review to date of scientific research on environmental factors that may increase risk of the disease. The study findings—entitled “Environmental Factors in Breast Cancer”—appeared in the June 15, 2007, issue of the American Cancer Society’s journal Cancer.
The research team synthesized data from national and international sources and identified 216 chemicals that cause mammary tumors in animals. They then used that information to create a searchable online database featuring detailed information on the carcinogens. The Mammary Carcinogens Review Database offers summary assessments of the carcinogenic potential of each chemical, data on mutagenicity, opportunities for exposure in the general population and for women at work, and other characteristics of chemical use, sources, and regulation.
The database reveals that among those 216 compounds identified as causing breast tumors in animals, 73 have been present in consumer products or as contaminants in food, 35 are air pollutants, and 25 have been associated with occupational exposures affecting more than 5,000 women a year. Twenty-nine of the compounds are produced in the United States in large quantities, often exceeding one million pounds a year. The database includes references to 900 studies.
The Silent Spring Institute project also examined lifestyle influences on breast cancer, such as physical activity and diet. The result of this portion of the research—the Epidemiology Reviews Database—is composed of critical reviews of approximately 450 primary epidemiologic research articles on breast cancer and diet, environmental pollutants, physical activity, and body size.
“The overwhelming majority of chemicals identified as animal mammary carcinogens or endocrine-disrupting compounds have never been included in an epidemiologic study of breast cancer,” says Julia Brody, executive director of Silent Spring Institute. “Just as alarming, most chemicals that Americans are exposed to have never been included in an animal cancer bioassay.”
The review of epidemiology related to environmental pollutants reveals research in this area to be still relatively sparse. Results in recent years, however, have begun to show evidence of increased risk associated with exposure to polychlorinated byphenols (PCBs)—banned chemicals previously used in electrical equipment and other products—in genetically susceptible women and to polycyclic aromatic hydrocarbons (PAHs), which are ubiquitous air pollutants from vehicle exhaust and other sources of combustion byproducts. Results of studies of organic solvents and dioxins suggest possible associations with breast cancer and support additional research on those compounds.
For Further Information
The National Report on Human Exposure to Environmental Chemicals provides information about body burden in a representative sample of U.S. residents.