Prenatal DDT exposure tied to nearly 4-fold increase in breast cancer risk

Women who were exposed to higher levels of the pesticide DDT in utero were nearly four times more likely to be diagnosed with breast cancer as adults than women who were exposed to lower levels before birth, according to a 54-year case-control study.

2015 Study Abstract

Context:
Currently no direct evidence links in utero dichlorodiphenyltrichloroethane (DDT) exposure to human breast cancer. However, in utero exposure to another xenoestrogen, diethylstilbestrol, predicts an increased breast cancer risk. If this finding extends to DDT, it could have far-reaching consequences. Many women were heavily exposed in utero during widespread DDT use in the 1960s. They are now reaching the age of heightened breast cancer risk. DDT exposure persists and use continues in Africa and Asia without clear knowledge of the consequences for the next generation.

Hypothesis:
In utero exposure to DDT is associated with an increased risk of breast cancer.

Design:
This was a case-control study nested in a prospective 54-year follow-up of 9300 daughters in the Child Health and Development Studies pregnancy cohort (n = 118 breast cancer cases, diagnosed by age 52 y and 354 controls matched on birth year).

Setting and Participants:
Kaiser Foundation Health Plan members who received obstetric care in Alameda County, California, from 1959 to 1967, and their adult daughters participated in the study.

Main Outcome Measure:
Daughters’ breast cancer diagnosed by age 52 years as of 2012 was measured.

Results:
Maternal o,p′-DDT predicted daughters’ breast cancer (odds ratio fourth quartile vs first = 3.7, 95% confidence interval 1.5–9.0). Mothers’ lipids, weight, race, age, and breast cancer history did not explain the findings.

Conclusions:
This prospective human study links measured DDT exposure in utero to risk of breast cancer. Experimental studies are essential to confirm results and discover causal mechanisms. Findings support classification of DDT as an endocrine disruptor, a predictor of breast cancer, and a marker of high risk.

Sources and more information

• DDT Exposure in Utero and Breast Cancer, The Journal of Clinical Endocrinology & Metabolism, doi/10.1210/jc.2015-1841, June 16, 2015.
• Prenatal DDT exposure tied to nearly 4-fold increase in breast cancer risk, THE ENDOCRINE SOCIETY, eurekalert, 16-JUN-2015.

Press releases

• Prenatal DDT exposure linked to increased risk of breast cancer, medicalnewstoday, 17 June 2015.
• Startling link between pregnant mother’s exposure to DDT and daughter’s risk of breast cancer, washingtonpost, June 17 2015.
• DDT Linked to Fourfold Increase in Breast Cancer Risk, nationalgeographic, JUNE 16, 2015.
• DDT in Pregnancy May Raise Breast Cancer Rates in Daughters, nbcnews, JUN 16 2015.