Breast Cancer: Downplaying The Environmental Risks

This week, the New York Times ran an article under the headline ‘Reducing Your Risk For Breast Cancer,’ encouraging readers to lose weight, exercise more, shun alcohol and avoid hormone therapy in order to lower their risk of developing breast cancer (Rabin, NYT).

Of course it makes good sense for women to take what practical steps they can in order to lessen their risk of breast cancer. The Times article makes many valid points and gives some sound suggestions. But in general terms, the article is yet another example of the media’s tendency to over-simplify what is in fact an extremely complex disease. Ultimately it does women no service to focus so single-mindedly on the role of personal responsibility as the primary preventive strategy while omitting to mention the much larger influence of environmental risk factors such as pollution and radiation. Apart from giving a free pass to those who are silently contributing to the burden of breast and other cancers, the media’s tendency to dwell on personal responsibility while largely ignoring known environmental contributions to the disease feeds the notion that breast cancer is at least in part a consequence of poor personal choices. This may have the unfortunate effect of fostering a ‘blame the victim’ mentality.

Genetic and Environmental Triggers

North America has the highest breast cancer rate in the world. Every year in the US, about 182,000 women are newly diagnosed with breast cancer, and about 40,500 women die from the disease. Although the incidence of breast cancer has dropped slightly every year since 2003 - the year that the widespread use of hormone replacement therapy began to decline sharply - the disease remains the second leading cause of cancer death among American women.

Inherited risk plays a part, to be sure, but its influence is relatively minor: having a close relative with the disease only accounts for 5 to 7 percent of a woman’s risk. The large majority of women diagnosed with breast cancer have no immediate family history of the disease. The fact that American women are more likely than their counterparts in most other countries to develop the disease points strongly towards environmental triggers. This is borne out by the observation that women who immigrate to the US from other countries where there are lower breast cancer rates quickly assume the same risk as American-born women.

Identifying the many potential environmental contributors to cancer risk is an enormously complicated task. One group of environmental pollutants that has earned closer scrutiny for its potential role in the development of breast cancer is pesticides.

Pesticides can influence the development of breast cancer in three main ways: They can act as a "complete carcinogen" - i.e., they can cause normal tissue to undergo irreversible changes that lead to invasive malignancy. Very few pesticides are complete carcinogens. Far more common are pesticides that can act as tumor promoters, encouraging unruly growth in an existing tumor or area of abnormality. Finally, many pesticides can act as what are called "endocrine disrupters" - that is, they are capable of mimicking hormones such as estrogen that are known to drive cancer growth, or they may interfere with normal hormonal regulation of cell growth, encouraging uncontrolled cell division. Endocrine disruption is potentially the most serious contributor to breast cancer risk.

According to the Environmental Protection Agency, more than one billion pounds of pesticides are used every year in the US. Eighty percent of this total is used in agriculture, representing an enormous environmental burden. The pesticide atrazine - a known endocrine disruptor - is one of the most widely used. Although it was banned by the European Union after studies demonstrated its endocrine disrupting capacity, atrazine continues to be the second most widely used pesticide/herbicide in the US. More than 70 million pounds of atrazine are used annually in this country, the vast majority (98 percent) for agricultural purposes, as a weed killer.

Sounding the Alarm

Although the environmental movement has long harbored concerns about the endocrine disrupting ability of atrazine, the mainstream media have on the whole been very slow to pay attention to the threat posed by this extensively used compound. But a study published on May 7 in the science journal PLoS One has directly demonstrated the ability of atrazine to interfere with the hormonal signaling mechanisms in human placental cells, once again raising questions about the possible role of atrazine in the development of breast and other hormone-driven cancers (Suzawa, 2008).

The same researchers have shown in a related study that the fish population becomes feminized in water with atrazine concentrations equivalent to those found in runoff from agricultural fields (the female to male ratio is approximately doubled). Interviewed by the online journal Science Daily, the lead author of the study, Holly Ingraham, PhD, a professor of Cellular and Molecular Pharmacology at the University of California, San Francisco, urged scientists to pay more attention to atrazine’s potential dangers. "These fish are very sensitive to endocrine disrupting chemicals, so one might think of them as ’sentinels’ to potential developmental dangers in humans," she said.

The degree of alarm within the scientific community concerning the dangers of hormone disrupting environmental pollutants is also apparent in a report released last month by the Health and Environment Alliance (HEAL), a European umbrella group of non-governmental research organizations. This report directly questions the growing tendency to label breast cancer a lifestyle and genetic disease. "We will not be able to reduce the risk of breast cancer without addressing preventable causes, particularly exposure to chemicals," said the author of the paper, Andreas Kortenkamp, who heads the Center for Toxicology at London University’s School of Pharmacy (Kortenkamp, 2008).

The advocacy group The Breast Cancer Fund, whose mission is specifically focused on the identification and elimination of the environmental and preventable causes of breast cancer, has also done a great deal to influence public awareness concerning the dangers of endocrine disrupters and environmental pollutants. The group publishes an annual review of the evidence - State of the Evidence 2008: The Connection Between Breast Cancer and the Environment - which is available from the organization’s website (www.breastcancerfund.org).

Scientists and advocacy groups are leading the way on this important issue. It’s time for the news media to follow suit and focus more attention on the contribution of environmental risk factors to breast and other cancers.

Ralph W. Moss, Ph.D.
www.CancerDecisions.com

References

The Breast Cancer Fund: http://www.breastcancerfund.org.

Kortenkamp A, Breast Cancer and Exposure to Hormonally Active Chemicals: An Appraisal of the Scientific Evidence. Available from
http://www.chemicalshealthmonitor.org

Rabin, Roni. Reducing Your Risk For Breast Cancer. New York Times May 13, 2008. Accessed May 15 at:
http://www.nytimes.com/2008/05/13/health/13breast.html?ref=health

Science Daily: Common Herbicide Disrupts Human Hormone Activity In Cell Studies. Science News May 8, 2008, Accessed May 15 at:
http://www.sciencedaily.com/releases/2008/05/080507084013.htm

Susawa M, Ingraham H. The herbicide atrazine activates endocrine gene networks via non-steroidal NR5A nuclear receptors in fish and mammalian cells. PLoS One. 2008 May 7;3(5):e2117.