Theoretical design and practical implementation of the food sampling for the 3^rd French total diet study

Based on composite food samples representative of the whole diet, prepared as consumed, total diet studies (TDSs) are amongst the most cost-effective approaches to assess population dietary exposure to chemicals residues and contaminants, and to provide representative data for health risk assessment. The third French TDS was launched in 2018. From the most recent French dietary survey, 276 foods were selected based on consumption and contamination levels, thus covering over 90% of the French diet. Stratification by season (3, 6 or 12-month-periods) and agricultural type (organic vs. conventional) led to collecting 719 composite samples. Each sample was made up of 12 pooled subsamples of the same food, representative of the food supply and habits of the French population and prepared as consumed according to the typical household practices. Food collection took place in 2021-2022 in three French departments. Substitution rules were applied when necessary to increase the likelihood of finding a product or to replace unavailable items (e.g. from supermarket, retailed shop…), that allowed collection of 98% of the expected subsamples. It is intended that the food composite samples will be analyzed for approximately 300 chemicals to update concentration levels, estimate dietary exposure, and support health risk assessment in France.