Estimation of the dietary exposure to chemical compounds in the French E3N prospective cohort: a study protocol

Diet is an important source of exposure to chemical compounds and estimating individual exposure is challenging and essential to study the association with long term health effects. This project aims to estimate the dietary exposure to more than 400 chemical compounds in the E3N cohort (Etude Epid?miologique apr?s de femmes de la Mutuelle G?n?rale de l?Education Nationale). In order to do so we developed a new database obtained by merging measures of chemical levels in commonly consumed food, from the second French Total Diet Study (TDS2), with the consumption data for food items of the E3N participants. E3N is a prospective cohort enrolled from 1990 with nearly 100,000 women aged between 40 to 65?years at inclusion. Participants complete a follow-up questionnaire every 2?3?years and dietary data were collected in 1993 and in 2005 using validated semi-quantitative food questionnaires developed according to the French meal pattern, collecting consumption information for 238 food items. The TDS2 analysed 445 different chemical substances in 186 core foods prepared as consumed. We attributed an occurrence value for each substance measured in the TDS2 study to all foods items included in the E3N food questionnaires. We identified 146 food items with a direct correspondence between the two databases. Alternatively, we attributed the weighted average of single foods using an a posteriori partition for 19 E3N food items. For 37 E3N food items not considered in the TDS2 we attributed the value of the most similar food measured in the TDS2. Overall 36 food items were excluded from the E3N-TDS2 database because no similar food was available. This study will allow estimating the dietary exposures to more than 400 chemical substances, either individually or as mixtures, in the E3N cohort, and therefore investigating their effect on the risk of chronic diseases, including cancers, diabetes, thyroid abnormalities, or ageing.