Barbara Cohn, Ph.D., Michele La Merrill, Ph.D.
Public Health Institute; University of California, Davis
NIEHS Grants U01ES019471, R00ES019919
A new study, funded in part by NIEHS, found that women exposed to higher levels of the pesticide dichlorodiphenyltrichloroethane (DDT) in utero were nearly four times more likely to develop breast cancer as adults than women exposed to lower levels before birth. During the 1960s, DDT was used widely in the U.S., and women prenatally exposed during this time are now reaching the age of increased breast cancer risk.
The researchers conducted a follow-up of 9300 daughters of women who participated in the Child Health and Development Studies, which tracked Kaiser Foundation Health Plan members who received obstetric care in Alameda County, California, from 1959 to 1967. The researchers studied 118 breast cancer cases diagnosed by age 52 and 354 controls matched by birth year.
Independent of the mother's history of breast cancer, elevated levels of the DDT isomer o,p'-DDT in the mother's blood were associated with a nearly four-fold increase in the daughter's risk of breast cancer (odds ratio for fourth quartile vs. first = 3.7, 95 percent; confidence interval = 1.5–9.0). Levels of o,p-DDT in fourth quartile participants were double or triple that of women in the first quartile. Among the women diagnosed with breast cancer, 83 percent had estrogen-receptor positive breast cancer.
The authors point out that experimental studies are necessary to confirm these findings and to understand the mechanisms involved. If confirmed, this research could lead to biomarkers and interventions targeting DDT- associated breast cancer.
Citation: Cohn BA, La Merrill M, Krigbaum NY, Yeh G, Park JS, Zimmermann L, Cirillo PM. DDT Exposure in Utero and Breast Cancer. J Clin Endocrinol Metab; doi:10.1210/jc.2015-1841. [Online 16 June 2015].