Some, but not all, epidemiological studies have suggested that dichlorodiphenyltrichloroethane (DDT) may play a role in the development of breast cancer.

These investigations have been conducted in countries where this substance has been banned for at least 20 years.

We conducted a study in Mexico, a country in which DDT is still being used to control malaria.

In a hospital-based case-control study, we compared 141 histologically confirmed cases of breast cancer with 141 age-matched controls (±3 years).

All subjects were identified at three referral hospitals of Mexico City between March 1994 and April 1996.

Reproductive histories and other variables were obtained by structured interviews, DDT/DDE levels were determined in serum by gas-liquid chromatography.

The arithmetic mean of serum DDE in lipid basis was 562.48 ± 676.18 ppb (range, 10.24-4661.44) for the cases and 505.46 ± 567.22 ppb (range, 0.004 to 4361.75) for the controls, but this difference was not statistically significant.

The age-adjusted odds ratios for breast cancer regarding the serum level of DDE were 0.69 (95% confidence interval, 0.38-1.24) and 0.97 (confidence interval, 0.55-1.70) for the contrasts between tertile 1 (lowest level) and tertiles 2 and 3, respectively.

These estimates were unaffected by adjustment for body mass, accumulated time of breast-feeding and menopause, and other breast cancer risk factors. (...)