Dietary Exposure to Dioxins and Risk of Breast Cancer among Women from the French E3N Prospective Cohort

摘要

Background: Breast cancer incidence increased in France during the past thirty years, which cannot only be explained by population ageing or organised breast cancer screening. It has thus been hypothesized that some of the increase could be related to environmental exposure to endocrine disrupting chemicals such as dioxins. Dioxin emissions occur during combustion of chlorinated products (fires, municipal waste incinerators, production of herbicides, or metal industry). Seventeen dioxin congeners are toxic and one of them, tetrachlorodibenzo-p-dioxin, has been classified as a human carcinogen Group 1 by the International Agency for Research on Cancer. Dioxins can contaminate and accumulate in the food chain; therefore diet is considered the main source of exposure to dioxins in humans. Objective: We aimed to estimate the association between dietary exposure to dioxins and risk of incident breast cancer among women from the French E3N prospective cohort. Methods: The E3N prospective cohort involves nearly 100,000 French female volunteers, adherent to a single health insurance plan and followed since 1990, with the aim of identifying cancer risk factors. Our study focused on 68,995 women of the E3N study who responded to the self-administered food frequency questionnaire (FFQ) in 1993. We used dioxin contamination data in foodstuffs consumed in the general French population collected by the French High Council on Public Health in 1998. Dietary exposure to dioxins was calculated by multiplying concentrations of dioxins (pg TEQ/g fat content) in each food group with the amount reported in the FFQs. We used Cox proportional hazard models to estimate breast cancer risk associated with dietary exposure to dioxins, adjusting for known breast cancer risk factors. Results: Analyses are under way and results will be presented at the ISEE 2013 Annual Conference.