Exposure assessment for pregnant women to a non persistant chemical based on human biomonitoring data by reverse dosimetry modelling
Résumé
Background: Large-scale human biomonitoring surveys typically gather biomarker measurements from single time points. For non-persistent compounds, such as Di(2-ethylhexyl) phthalate DEHP, the biomarker levels are known to greatly vary within the same individual over a relatively short period of time. The aim of this work was to evaluate between-day variability for biomarkers, to estimate the exposure to DEHP based on toxicokinetic model and to evaluate the input considering data from questionnaire (meal, urination time) in the daily intake estimates. Methods: Thirty women from 3 countries (France, 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) over the week were analyzed. Intraclass correlation coefficients (ICCs) were calculated using a one-way random effect model to estimate between- and within- subject variability throughout the week. A toxicokinetic model proposed by Lorber et al., (2010) was applied to back-calculate the exposure levels to DEHP from the urinary metabolite concentrations. Individual data such as the bodyweight, the times of urination, time of meal and the time of sampling were collected from questionnaires and integrated into the model. Results: Significant differences in urinary concentrations were observed between the morning and evening voids. In general, the ICCs calculated are low to moderate indicating a high within-women variability. Overall the ICCs calculated for the morning sample are higher than the evening sample indicating a less within-women variability for the morning sample. Our results obtained by reverse dosimetry showed reduced variability of daily intake estimates compared to biomarker measurements. The estimated daily intakes based on morning measurements were significantly impacted by the exposure time (meal time). Short discussion/conclusions: Our study highlights the major contribution of toxicokinetic modelling towards investigating exposure biomarker variability and points out information that should be obtained in future surveys to better characterize exposure to non-persistent pollutants.