Women who were exposed to higher levels of the pesticide DDT in the womb were nearly four times more likely to be diagnosed with breast cancer as adults than those who were exposed to lower levels before birth, a 54- year study suggested on June 16.
Despite being banned by many countries in the 1970s, DDT, an endocrine disruptor, remains widespread in the environment and continues to be used in Africa and Asia, according to the study published in the U.S. Endocrine Society's Journal of Clinical Endocrinology and Metabolism.
"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," said one of the study's authors, Barbara Cohn of the Public Health Institute in Berkeley, California.
Cohn and colleagues tracked more than 20,000 pregnancies among women who were members of the Kaiser Foundation Health Plan from 1959 through 1967, a time when the pesticide was used widely in the United States. The women gave birth to 9,300 daughters during that period.
The researchers looked at DDT levels in the mother's blood samples during pregnancy or in the days immediately after delivery. They also used state records and a survey of the women' grown daughters to determine how many were diagnosed with breast cancer by age 52.
During the 54-year follow-up period, the researchers measured DDT levels in mothers of 118 women who were diagnosed with breast cancer and compared these women to 354 women who did not develop cancer.
The researchers found that independent of the mother's history of breast cancer, elevated levels of DDT in the mother's blood were associated with a nearly four-fold increase in the daughter's risk of breast cancer.
The researchers also determined that exposure to higher levels of DDT was associated with women being diagnosed with a more advanced stage of cancer.
Among the women who were diagnosed with breast cancer, 83 percent had estrogen-receptor positive breast cancer, a form of cancer that may receive signals from the hormone estrogen to promote tumor growth.
"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."
Past studies have found DDT exposure is linked to birth defects, reduced fertility and increased risk of Type 2 diabetes.
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