Study: DDT exposure prenatally increases risk of breast cancer by four times

DDT was banned from the United States in 1962 for being a ‘possible carcinogen’ – but it’s deadly affects are coming to light only now. A recent study found that increased levels of DDT in the mother’s blood were linked to an almost fourfold increase in her daughter’s risk of breast cancer and that this was independent of the mother’s history of breast cancer. They also determined that those with higher levels of exposure were diagnosed with more advanced breast cancer.

Bestseller science book ‘Silent Spring’, written by Rachel Carson, was the first book to raise the alarm about the detrimental effects of DDT on the environment—particularly on birds—of the indiscriminate use of pesticides. Carson accused the chemical industry of spreading disinformation and public officials of accepting industry claims unquestioningly. At the time, Silent Spring was met with fierce opposition by chemical companies, but it spurred a reversal in national pesticide policy. Since then numerous studies have linked it to birth defects, miscarriage and reduced fertility.

The Environmental Protection Agency classifies DDT as a “probable” carcinogen. However, a new study published Tuesday in the Journal of Clinical Endocrinology and Metabolism is going to change that as it found a shocking connection between pregnant women exposed to DDT and the breast-cancer risk to their daughters.

The study tracked down the daughters of women who were part of a study at the Kaiser Foundation Health Plan from 1959 to 1967 near the city of Oakland, Calif. During that time, DDT was use on a wide scale and tended to accumalate in the fat cells of animals that we eat and was found in milk, butter, cheese and other products in the food supply. It was also in a number of other products, including the wallpaper.

The research at that time found that the participants gave birth to 9,300 daughters. Every mother had some measurable level of DDT in her blood. Researchers determined the level of exposure to DDT in utero by analyzing stored blood samples that were taken from the mothers during pregnancy or shortly after they delivered their babies.

By using state records and surveying the daughters, who are now in their late 40s and early 50s, they were able to figure out which ones developed breast cancer.

About 83 percent of those who got breast cancer had estrogen-receptor positive breast cancer and were more likely to develop HER2-positive breast cancer, in which a genetic mutation produces an excess of a protein. In previous studies, DDT has been found to interfere with the function of estrogen and, separately, to activate the HER2 protein, which may explain the link.

Barbara Cohn, one of the study’s authors and the director of Child Health and Development Studies at the Public Health Institute in Berkeley, Calif., said the 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.”

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 Tuesday.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 US 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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