Warner, M; Eskenazi, B; Mocarelli, P; Gerthoux, PM; Samuels, S; Needham, L; Patterson, D; Brambilla, P
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD or dioxin), a widespread environmental contaminant,
has been shown to disrupt multiple endocrine pathways. The International Agency for
Research on Cancer classified TCDD as a known human carcinogen, primarily based on occupational
studies of increased mortality from all cancers combined. Using data from the Seveso
Women’s Health Study (SWHS), we examined the association between individual serum TCDD
levels and breast cancer risk in women residing around Seveso, Italy, in 1976, at the time of an
industrial explosion that resulted in the highest known population exposure to TCDD. The
SWHS cohort comprises 981 women who were infants to 40 years old in 1976, resided in the
most contaminated areas at the time of the explosion, and had archived sera that was collected
soon after the explosion. For each woman, serum TCDD exposure was measured by high-resolution
mass spectrometry. Cancer cases were identified during interview and confirmed by medical
record. At interview, 15 women (1.5%) had been diagnosed with breast cancer and serum TCDD
levels for cases ranged from 13 to 1,960 ppt. Cox proportional hazards modeling showed that the
hazard ratio for breast cancer associated with a 10-fold increase in serum TCDD levels (log10
TCDD) was significantly increased to 2.1 (95% confidence interval, 1.0–4.6). Covariate-adjusted
results were not different. Individual serum TCDD is significantly related with breast cancer incidence
among women in the SWHS cohort. Continued follow-up of the cohort will help shed
light on the possible role of TCDD in the pathogenesis of breast cancer.
