A new study published by the Public Health Institute in Berkeley California has determined that DDT has a significant impact and increases the risk of breast cancer. The study analyzed the level of DDT prenatal exposure. DDT has been banned in a number of countries including the US in 1972. The chemical was widely used to prevent insects from destroying agricultural crops or spreading diseases, such as malaria and typhus; acts as an endocrine disruptor as it interferes with the function of the hormone estrogen.
The research study analyzed the risk of breast cancer among 9,300 women in the US born between 1959 and 1967. The women were born to mothers who were part of the Child Health and Development Studies (CHDS), and they were tracked for 54 years beginning during pregnancy. The study is based on the exposure of the fetus and the subsequent detrimental health impact and the women were born to mothers who were part of the Child Health and Development Studies (CHDS).
Previous research has also linked prenatal exposure to the pesticide with developmental problems in childhood, greater risk of birth defects, reduced fertility and increased risk of high blood pressure in women.
The researchers examined the levels of DDT exposure in utero, and they assessed stored blood samples that were taken from their mothers during pregnancy or within a few days after birth. State records and health questionnaires completed by the daughters during the 54-year follow-up allowed the scientists to identify how many daughters were diagnosed with breast cancer.
The research findings revealed that 118 daughters were diagnosed with breast cancer during follow-up. The blood samples of their mothers were assessed for DDT levels and compared with blood samples from the mothers of 354 daughters who were not diagnosed with breast cancer. Daughters of mothers who had a higher level of commercial DDT in their blood samples were 3.7 times more likely to develop breast cancer, compared with daughters of mothers who had lower levels of this DDT in their blood. Eighty three percent of breast cancers identified in the study were estrogen-receptor positive.
Exposure to higher levels of DDT in utero increased the risk of being diagnosed with a more advanced form of breast cancer and women with greater exposure to DDT were more likely to develop HER2-positive breast cancer; in which breast cancer cells contain a mutation that makes excess human epidermal growth factor receptor 2 (HER2) protein. The researchers note that past studies have found DDT can activate HER2.
“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 Barbara Cohn. “We also are continuing to research other chemicals to see which may impact breast cancer risk among our study participants,” she said.
DDT exposure in utero and breast cancer, Barbara A. Cohn et al., Journal of Clinical Endocrinology and Metabolism, doi: 10.1210/jc.2015-1841, published online 16 June 2015.