Exposure assessment of pregnant women to Di(2-ethylhexyl) phtalate by reverse dosimetry : variability in repeated spot sample

Abstract : Phthalates are a family of chemicals that can be found in a wide array of consumer products, and are suspected to induce reproductive and developmental toxicity. Among all phthalates, Di(2-ethylhexyl) phthalate (DEHP) have the strongest reproductive and developmental effects observed in animal studies. Large-scale human biomonitoring surveys typically gather biomarker measurements from single time points. For non-persistent compounds, such as DEHP, the biomarker levels are known to greatly vary within the same individual over a relatively short period of time. Thirty women from two countries (Spain and Norway) were followed over a week during the second trimester of pregnancy. A protocol was designed specifically to assess the intra-individual variability over the week. Two spot samples per day (first and last voids) and the pool of the urines collected over the week were analysed. A toxicokinetic model proposed by Lorber et al., (2010) was applied to back-calculate the exposure levels to DEHP from the urinary metabolites concentrations. Individual data were collected from questionnaires and integrated in the model such as the bodyweight, the times of urination, time of meal and the time of sampling. This model that integrates all the DEHP metabolites has also the capability of considering the temporal variability of concentration. Our results showed a reduced variability of daily intake estimates compared to biomarkers measurement. Daily intake estimates were performed for first and last sample separately. Our study highlights the major influence of time data in reverse dosimetry and point out major information that should be obtained in future survey to better characterize non-persistent pollutant exposure.