The challenge of assessing exposure to fast-elimination endocrine disruptors: When collecting? Which matrix? How many samples?

Abstract

Background and Aim The assessment of human exposure to fast-elimination endocrine disruptors (FEED) such as phthalates, bisphenols or pesticides is usually based on urinary biomarkers. The variability of biomarkers concentration, due to rapid elimination from the body combined with frequent exposure is however pointed out as a major limitation to obtain reliable information. Collecting samples at specific times of the day, or increasing the number of samples have been suggested to improve the quality of exposure assessment. In parallel, the use of hair, less sensitive to short-term variations in the exposure, have also been proposed as a possible alternative. No consensus has however been reached yet on these points and providing a reliable information on exposure to FEED remains highly challenging. Methods Urine and hair samples were repeatedly collected from 16 volunteers over a 6 months follow-up. 92 hair samples and 805 urines samples were collected and analyzed for 16 phthalate metabolites, 4 bisphenols and 8 pesticides metabolites. Results 21 biomarkers were more frequently detected in urine, 6 in hair, and 1 was equivalent. Biomarkers were much more variable in urine, with intraclass correlation coefficients (ICC) ranging from 0.09 to 0.51, compared to 0.1 to 0.8 in hair. No preferred moment between first urine of the day, morning, afternoon and evening could be identified for urine collection. Algorithms demonstrated that between 10 (for monobenzyl phthalate) and 31 (for bisphenol S) samples were necessary to correctly classify 87.5% of the subjects into quartiles according to their level of exposure. Conclusions The study illustrates the complexity of assessing exposure to FEED and documents the respective advantages and limitations of urine and hair. These results provide new insights in exposure assessment based on biological matrices and will help to better design future biomonitoring strategies. Keywords: Exposure Biomarkers, Endocrine disruptors, Exposure assessment, Phthalates, Pesticides