Benzene Low-Level Personal Exposure Assessed Repeatedly and Fetal Growth: Are Effects Observed in the General Population?

Context: Benzene is a recognized reprotoxicant but its effects on fetal growth in humans at levels encountered in the general population are poorly known. A study reported decreases in head circumference and possibly birth weight in association with maternal benzene exposure.Aim: To study the possible effect of airborne benzene pregnancy exposure on fetal growth using personal monitoring.Methods: We relied on SEPAGES, a cohort of pregnant women recruited before gestational week 20, who carried personal benzene monitors for two to three 8-day periods. Offspring weight and head circumference were related with benzene levels at each measurement week and averaged over all weeks through adjusted linear regression models.Results: Median (25-75th centiles) benzene 8-day exposure at the first measurement was 1.4 (0.8; 2.2) µg/m3. The correlation of benzene 8-day levels between the first and last measurement periods was 0.25 (p<5.10-4), while for exposure averaged over all measurement periods, benzene levels had a correlation of 0.05 (p=0.4) with nitrogen dioxide and of 0.23 (p=0.001) with PM2.5 personal exposures. Each unit increase in benzene mean exposure was associated with a mean birth weight change by -18 g (95% confidence interval, CI, -43; 7 g, n=402), while mean head circumference changed by -1.0 mm (95% CI, -1.9; -0.2). Across measurement periods, the strongest association was observed with the first benzene measurement, both for birth weight (change, -30 g; 95% CI, -56; -3) and head circumference (-1.7 mm, 95% CI -2.6; -0.8, p<5.10-4). There was no strong attenuation after adjustment for personal NO2 or PM2.5 exposure.Conclusion: This study is the first to characterize possible effects of benzene on birth weight using personal repeated measurements. It provides a confirmation of an association of benzene exposure with head circumference, and suggests that the association is stronger for exposures in the 1st (as opposed to 2nd) half of pregnancy.