Early-life exposure to organophosphate esters and child neurodevelopment in the French national birth cohort

Organophosphate esters (OPEs) are ubiquitous flame retardants and/or plasticizers, raising concerns regarding their possible neurodevelopmental toxicity. We aimed to explore association between pre- and post-natal exposure to OPEs and cognitive abilities among 3.5-year-old children. We included 381 mother-child pairs from the French ELFE national birth cohort. Pre- and post-natal exposures were estimated using concentrations of 9 OPEs measured in the hair of mothers collected at birth and children at age 3.5. Children's cognitive development was evaluated using the Picture Similarities Test (PST) from the British Ability Scale. Analyses were weighted in order to transpose results to French births in 2011. For each OPE, the association with PST scores was assessed by linear regression accounting for DAG-selected adjustment covariables. The only observed association between prenatal exposure to OPEs and PST score was a decrease of 4.5 points (95 %CI: -8.8, -0.3) among the 25 % of mothers having the highest hair-concentrations of tri-n-butyl phosphate (TBP) versus the 25 % having the lowest ones. Regarding childhood exposure, we observed a decrease (-1.9 points, 95 %CI: -3.0, -0.8) in PST score per twofold increase in children's hair-concentrations of ethylhexyl diphenyl phosphate (EHDPP). Decreased scores were also observed for higher childhood exposure levels for triphenyl phosphate (TPHP). An increase in the PST score was observed for the intermediate category of childhood exposure levels for tris(2-chloropropyl) phosphate (TCPP). While no adverse associations were observed for several OPEs, neurodevelopmental health concerns were raised in the present study for three ubiquitous OPEs, TBP, TPHP and EHDPP.