DDT Quadruples Breast Cancer Risk, First-of-Its-Kind Study Shows

Exposure to DDT in the womb significantly increases breast cancer risk years later, scientists say.

June 16, 2015
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The U.S. government banned DDT more than 40 years ago, but this potent insecticide is still haunting us. Women exposed to higher levels of DDT while in their mother's womb were nearly four times more likely to be diagnosed with breast cancer as women exposed to lower levels in the womb, according to a new study published in the Journal of Clinical Endocrinology & Metabolism.

This decades-long study looked at 20,000 woman and nearly 10,000 of their daughters and provides more strong evidence that coming in contact with hormone-disrupting chemicals like DDT during crucial stages of development could trigger disease decades later in life. "This 54-year study is the first to provide direct evidence that chemical exposures for pregnant women may have lifelong consequences for their daughters' breast cancer risk," says one of the study's authors, Barbara A. Cohn, PhD, of the Public Health Institute in Berkeley, California. "Environmental chemicals have long been suspected causes of breast cancer, but until now, there have been few human studies to support this idea."

More: The Other Food Contaminant Linked to Breast Cancer

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Cohn says that many women who were exposed in utero in the 1960s, when the pesticide was used widely in the United States (including the highly estrogenic commercial DDT, o,p'-DDT), are now reaching the age of heightened breast cancer risk. DDT and similar chemicals tamper with the body's natural estrogen hormone functioning, also increasing a person's risk of birth defects, infertility, and type 2 diabetes. Another recent study even linked DDT exposure to Alzheimer's disease

In this latest study, researchers looked at DDT levels in the mothers' blood while they were pregnant or just after delivery. They then studied the daughters to see how many developed breast cancer by age 52 (118 had). Scientists found that regardless of family history of breast cancer, higher levels of commercial DDT in the mother's blood were associated with a nearly fourfold increase in the daughters' risk of breast cancer. 

According to the U.S. Centers for Disease Control and Prevention, DDT persists for a very long time in soil; half the DDT in soil will break down in 2 to 15 years. While DDT was sprayed on food crops, in barns, and even along roadsides while it was still legal to use, today, people's main source of exposure comes from food, including fatty meats, poultry, fish and shellfish, and imported foods from countries that still allow the use of DDT to control pests. (It's still allowed in many Asian and African countries.)

"This study calls for a new emphasis on finding and controlling environmental causes of breast cancer that operate in the womb," Cohn said. "Our findings should prompt additional clinical and laboratory studies that can lead to prevention, early detection, and treatment of DDT-associated breast cancer in the many generations of women who were exposed in the womb. We also are continuing to research other chemicals to see which may impact breast cancer risk among our study participants."

More: 7 Ways to Lower Your Risk of Cancer

Eating lower on the food chain (fewer animal products) and eating domestically produced food can lower your exposure to DDT. If you are concerned or curious, you can learn more about testing for DDT or DDT breakdown materials in your body. Recent research also suggests maintaining a healthy gut can also lower your breast cancer risk. 

Investigating environmental hormone disruptors and the impacts they have on the body is an increasingly important area of research. "Puberty is of interest when studying breast cancer because early onset of menstruation in girls has been linked to higher risk for breast cancer and other reproductive cancers in adult women," explains Julie Deardorff, PhD, coauthor of The New Puberty. "Many researchers are interested in whether there are common causes or environmental exposures early in life that might lead to early puberty and also increase risk for breast cancer later in life, like chemicals that act as endocrine disruptors."