Barbara Cohn, Ph.D.
University of California, Berkeley
An NIEHS study found that women exposed to high levels of the pesticide DDT early in life were at increased risk for breast cancer through age 54 years, with differences in risk depending on timing when they were first exposed. Women exposed during infancy were most likely to develop breast cancer before the age of 50 years, whereas those who were exposed after infancy were at increased risk of developing cancer later, at ages 50-54 years.
The researchers conducted a study within the Child Health and Development Studies cohort, which followed 15,528 women for nearly 60 years. Age at first DDT exposure was calculated by subtracting the woman’s birth year from 1945, the year DDT was first introduced into the United States. DDT exposure levels were estimated from stored cohort blood samples collected from 1959 to 1967. Researchers used state records to identify cases of breast cancer.
DDT exposure during childhood was a risk factor for both early and later breast cancer, but a higher risk for each of the outcomes was associated with exposure timing. Overall, they observed that the induction period from first exposure to breast cancer was about 40 years. According to the authors, measuring environmental exposures during windows of susceptibility are much more consistent in supporting a positive association with breast cancer risk.
Citation: Cohn BA, Cirillo PM, Terry MB. 2019. DDT and breast cancer: prospective study of induction time and susceptibility windows. J Natl Cancer Inst; doi:10.1093/jnci/djy198 [Online 13 Feb. 2019].