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DDT exposure in utero increases risk for breast cancer in adulthood
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A nearly four times higher risk for breast cancer in adulthood was found among women exposed to higher levels of DDT compared with those exposed to lower levels before birth, according to recent study findings published in The Journal of Clinical Endocrinology & Metabolism.
Further, the more estrogenic DDT, o,p’-DDT, was largely responsible for the results.
“This 54-year-study is the first to provide evidence that chemical exposures for pregnant women may have lifelong consequences for their daughters’ breast cancer risk,” Barbara A. Cohn, PhD, of the Public Health Institute in Berkeley, California, said in a press release. “Environmental chemicals have long been suspected causes of breast cancer, but until now, there have been few human studies to support this idea.”
Cohn and colleagues conducted a 54-year follow-up of 9,300 daughters from the Child Health and Development Studies pregnancy cohort to determine the risk for breast cancer after in utero exposure to DDT.
The researchers found that elevated exposure to o,p’-DDT was associated with a four times higher risk for breast cancer. A lower risk for breast cancer was found with maternal overweight early in the pregnancy.
For a doubling of o,p’-DDT, there was an estimated OR of 2.2 (95% CI, 1.1-4.2) for diagnosis at an advanced stage, as well as an OR of 2.1 (95% CI, 1-4.8) for a human epidermal growth factor receptor 2-positive tumor.
“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 chemical 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.” – by Amber Cox
Disclosure: The researchers report no relevant financial disclosures.
Perspective
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Miquel Porta, MD, MPH, PhD
We very much needed a study like this. Human and animal evidence suggest that during certain “windows of exposure” the developing breast is more vulnerable to the toxic effects of xenoestrogens, such as the pesticide DDT and its metabolites, DDE. Of these windows, by far the less explored quantitatively in humans is the in utero period. The present study is the first to quantify concentrations of DDT and DDE in utero and to prospectively assess their contribution to breast cancer.
The 54-year follow-up of more than 20,000 pregnancies, which occurred in 1959 to 1967, peak years of DDT use in the United States, is a feat, truly impressive. Certainly, the slightly more than 100 cases of breast cancer and 350 controls are modest figures; they should increase as follow-up of the cohort continues.
The study findings are highly relevant from the mechanistic, clinical and public health perspectives. In the U.S., as in most countries worldwide, DDE is detected in nearly 100% of newborns, and DDT is commonly detected in more than 70% of the general population, even today — although, fortunately, at lower concentrations than those common when the study pregnancies occurred. Although banned for some 40 years, DDT continues to be present in animal and human food webs worldwide.
Future studies should also measure other chemicals, such as PCBs and dioxins, and quantify their joint and separate effects with DDTs on the risk of breast cancer.
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