Devra Lee Davis Talk Summarized

BREAST CANCER AND THE ENVIRONMENT: WHAT WE KNOW… WHAT WE SUSPECT… WHAT WE CAN DO IN THE MEANTIME

Tuesday May 14, 2002, 7 PM in the Benedictine Hospital Senior Residence Center, Kingston NY

The effects of the environment on breast cancer risk are controversial and complicated. Dr. Devra Davis, Ph.D., M.P.H., is an internationally renowned epidemiologist and toxicologist, and Professor in the H. John Heinz III, School of Public Policy and Management, at Carnegie Mellon University.

She has held presidential appointments, a number of distinguished visiting professorships, and chaired several major international symposiums and other professional activities.

Dr. Davis is also an advisor to the Benedictine Hospital Breast Cancer/Pesticide Study started by Sheldon Feldman, MD several years ago.

On May 14, 2002 at 7PM, Dr. Davis discussed various environmental risk factors of cancer, specifically when conclusive evidence is not available.

For more than three decades, scientists have consistently identified a number of risk factors that are generally believed to account for up to 40 percent of all cases of breast cancer.

Among the established risk factors for breast cancer are: having menstrual periods that begin before age 12 and end after age 55, having no children or bearing children late in life, not nursing children, early and repeated exposures to relatively high doses of radiation, obesity after menopause, and a family history of breast cancer occurring in a close relative before age 40.

Other factors are suspected of increasing risk, although the data are less clear. These include: drinking alcohol daily, lack of vigorous exercise, low intake of vitamin D and fiber, active and passive smoking, and living near chemical facilities.

However, while many risk factors have been suggested, not many have been sufficiently ‘proven’ to merit elimination.

So, although certain risk factors for breast cancer, such as age at menarche, diet, and genetic predisposition, have been well known for years, many breast cancer cases occur in women with no known risk factors for disease. Scientists cannot explain why there are more new cases of breast cancer today.

However, a growing and complex array of evidence suggests that the general external environment including behavior, diet, and physical and chemical exposures plays a major role in fostering breast cancer. The general environment can induce breast cancer by two distinct mechanisms. Environmental exposures may damage genes directly or they may affect the overall production of growth-regulating hormones, such as estrogen, progesterone, and other such naturally produced substances

Abundant evidence exists that a woman’s cumulative exposure to estrogen plays a role in increasing breast cancer risk. The longer a woman is exposed to estrogen over the course of her lifetime, the greater her risk for developing breast cancer.

Women who start menstruating at an earlier age and enter menopause at a late age, for example, are more vulnerable to breast cancer than women who are menstrual for a shorter period of time. Reduction of estrogen by surgical removal of ovaries can lower cancer risk substantially; breast-feeding, which lowers cumulative estrogen exposure by disrupting regular menses, also reduces the risk of breast cancer somewhat.

In addition, women who have toxemia during pregnancy have lower hormone levels. One recent study suggests that their daughters have a reduced risk of breast cancer, possibly because their developing breast cells were subjected to lower prenatal levels of circulating hormones.

Such evidence of the role of naturally occurring hormones in cancer risk has led to the hypothesis that synthetic hormones could be involved as well. Over the past three decades, several lines of evidence have converged indicating that a number of commonly used synthetic compounds can modify or mimic the actions of natural estrogen in the body. Some of these hormone-mimicking compounds may be beneficial, such as those generally found in plants and fish. In contrast, other hormone-mimicking compounds appear to be generally harmful, such as those often found in pesticides, plastics, and fuels. Experimental, wildlife, and some human studies have found higher levels of some of these damaging compounds in organisms with altered hormonal functioning or other health problems, including developmental and behavioral defects These mechanisms would suggest that strict measures ought to be taken to eliminate any bad xenohormones from the environment, but this has yet to be achieved.

The Precautionary Principle A new approach to thinking about environmental regulations and how we evaluate and control exposures to toxic chemicals has been emerging over the past few years. This approach, called the "precautionary principle," states that "when an activity raises threats of harm to the environment or human health, precautionary measures should be taken even if some cause and effect relationships are not fully established scientifically." Stated differently, when significant risks to public health exist, efforts should be made to reduce those risks, especially avoidable risks, even when scientific knowledge is inconclusive. The precautionary principle shifts the burden of proof from the general public to a proponent who creates a public health or environmental risk. Instead of the public having to show that they have been harmed, a proof that is virtually impossible because of the lack of scientific information, a proponent has to prove that the activity, process, or chemical exposure is harmless.

With regard to potential risk factors, Dr. Davis suggests that it is "better to be approximately right than precisely wrong." It seems absurd that we continue to expose ourselves to potential risk factors, merely because we lack the "proof" necessary to eliminate them from the environment. Rather, Dr. Davis suggested proactive policies such as the promotion of workplace safety, pollution prevention, subsidization of healthy agriculture, and integrated pest management. Through measures such as these we cannot assure the elimination of cancer, but we can promote a safer environment. Here, we can take positive steps towards encouraging a healthy lifestyle and eventually eliminating the risk of cancer.

Thanks to Hope Nemiroff for this summary. More to come (possibly)


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Reviews of Devra Lee Davis' book

Devra Lee Davis - Information from Env Activist

LINK to site with articles (long-time environmental activist Devra Lee Davis)


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