The role of environmental factors in the pathogenesis of breast cancer
Abstract:Breast cancer amongst women is the most common malignancy in the world, especially in the United States and Western Europe. In 1999, upwards of 175,000 women in the United States and 800,000 women worldwide are estimated to develop cancer of the breast; nearly 30% of cancers in women in the US and 21% of cancers worldwide are of the breast. The rate of breast cancer in the US has steadily increased from roughly 80/100,000 population in 1973 to nearly 115/100,000 in 1995. However, mortality from breast cancer in the US seems to have flattened and slightly decreased in the 1990s, especially among younger women. These decreases are probably the result of earlier detection and improved treatment. Nonetheless, each year more than 43,000 women in the US and 314,000 worldwide will die of breast cancer. The cause or causes for the overwhelming majority of breast and other cancers remain largely unknown. In this commentary, we suggest the influence of environmental chemicals on the occurrence of breast cancer, and the need to consider chemicals in epidemiology investigations. The current emphasis seems to center on pesticides, especially those that are biologically persistent and that mimic natural hormones. The concentration of epidemiologic effort on these chemicals ‐ most often DDT and metabolites and PCBs ‐ may in fact be missing other potential carcinogenic or co‐carcinogenic effects of many other environmental factors that may influence the occurrence of breast cancer. Clearly there are hundreds of chemicals in our environment ‐ workplaces, consumer products, schools, homes, restaurants, taverns, foods, water, air, soil, pollution, contaminants ‐ that we are constantly and routinely being exposed. In some cases we are exposed to certain chemicals in relatively large amounts, especially in workplaces, occupations, avocations, or hobbies. In the absence of epidemiological evidence, long‐term bioassays using laboratory animals continue to be the most common, reliable, and accepted method for identifying carcinogens. Most often epidemiological data are not available on chemicals and cancer, or in many cases if they are available the findings are frequently inconclusive. Hence for public health and regulatory actions one must typically rely on a blending of epidemiological results and animal data, or on experimental chemical carcinogenesis data alone. Biologically and mechanistically we have little scientific evidence to suggest that chemicals causing cancer in animals will not likewise cause cancer in humans Consequently, by reducing exposures to chemicals, the incidence, suffering, and mortality of environmentally associated diseases will be reduced or eliminated. And this is an attainable and befitting goal we must continue to strive.
Document Type: Research Article
Affiliations: Division of Intramural Research, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina USA 27709
Publication date: 2001-07-01