For many years, the insecticide DDT was widely sprayed throughout the U.S. to reduce insect damage to crops. It still is used in some parts of the world to help control malaria. DDT was banned in the U.S. in 1972, but that doesn’t mean we aren’t still exposed to it. According to the U.S. Centers for Disease Control and Prevention (CDC), DDT has been found in snow and in the body tissues of animals in the Arctic and Antarctic regions, far from where it was ever used.
The latest findings show that women in the U.S. exposed to high levels of DDT early in life are at increased risk of breast cancer through age 54. Women born before DDT was banned could not have avoided exposure – they would have come into contact with it via dust and food.
A study published in February (2019) found that women exposed to DDT before age 14, particularly in infancy and early childhood, were most likely to develop breast cancer before menopause. Those exposed after infancy were at increased risk of developing breast cancer between the ages of 50 to 54. The study authors wrote that many women and girls in the United States were exposed to DDT in the middle of the 20th century when the pesticide was widely used and that the youngest of these women are now reaching the ages of increased breast cancer risk. The study found that the period of time between a woman’s first exposure to DDT and her greatest breast cancer risk is approximately 40 years.
The highest risk for premenopausal breast cancer is in women whose first DDT exposure occurred before age 3, although exposure through puberty (until the age of 14) is also associated with increased risk. Those exposed after age 14 are At increased risk of developing breast cancer after menopause.
The researchers followed 15,528 women participating in the non-profit Public Health Institute’s Child Health and Development Studies for nearly six decades. The team tracked the women’s age at first DDT exposure, their DDT levels during pregnancy, and the age when breast cancer was diagnosed. To determine levels of DDT exposure, they analyzed stored blood samples that had been collected from 1959 to 1967 during the women’s pregnancies at each trimester and early after childbirth. They used state records to identify 153 cases of breast cancer diagnosed from 1970 to 2010 in women age 50-54. They then matched each of these cases with comparable women who did not develop cancer.
Lead author Barbara A. Cohn, Ph.D., notes that while almost everyone has been exposed to DDT, only some develop cancer. We do not know why.
Here’s where you can learn more about breast cancer and my advice on how to reduce your risk.
Andrew Weil, M.D.
Barbara A. Cohn et al, “DDT and Breast Cancer: Prospective Study of Induction Time and Susceptibility Windows.” JNCI: Journal of the National Cancer Institute, February 13, 2019; DOI: 10.1093/jnci/djy198