Assessing Children's Exposure to Organophosphate Flame Retardants in the Home Environment

Organophosphate flame retardants (OPFRs) are increasingly being used in the home environment as replacements for the phased out polybrominated diphenyl ethers (PBDEs). Several studies utilizing hand wipes and dust samples in concert with urine samples have illustrated that human exposure is occurring in the home environment. While exposure has been measured across age groups and locations, few epidemiological studies have investigated the potential health effects of these individual compounds and their mixtures. Preliminary animal research indicates their potential for endocrine disruption, with a particular emphasis on thyroid hormone dysregulation. Additionally, particular OPFRs may bind with the PPARγ, a nuclear receptor involved in adipogenesis, or the formation of fat cells. The present study uses passive air and urine samples collected from a central North Carolina toddler cohort to explore, for the first time, associations between air and biomarkers of OPFR exposure (i.e. urinary metabolites). This will help to assess inhalation as a potentially important exposure pathway for OPFRs. In addition, associations between levels of OPFR metabolites measured in urine and growth measures are assessed. Few epidemiological studies have explored OPFRs and health outcomes such as weight; therefore, this study provides relevant and new information about specific metabolites and their relationship with BMI percentile. Univariate analyses revealed statistically significant differences in urinary metabolite concentrations between children whose mothers had a college degree compared to those that did not. The urinary metabolites DPHP and tbutylDPHP were significantly correlated with OPFR compounds measured in indoor air. One urinary metabolite, ip-DPHP, was found to have a statistically significant relationship with BMI percentile, suggesting exposure might be affecting growth. Limitations of the present study include the measure of exposure being limited to one time point, and the cohort being limited to the central North Carolina area.