Association between Exposure to Pyrethroids and Chlorpyrifos at Age 5 Years and IQ at Age 7 Years Among Children from the Odense Child Cohort, a Prospective Birth Cohort Study

Abstract

BackgroundOver the past decade, the use of organophosphate insecticides including chlorpyrifos has faced increasing restrictions due to health concerns, leading to a rise in use of pyrethroids. There are however also concerns about neurodevelopmental insults following exposure to pyrethroids and only few studies have examined the long-term effects of childhood exposure to chlorpyrifos and pyrethroids on IQ.ObjectiveTo investigate the prospective associations between pyrethroids and chlorpyrifos exposure at age 5 years and IQ scores assessed at age 7.Materials and methodsA total of 1083 children from the Odense Child Cohort (OCC), born between 2010-2012, were included in this study. The chlorpyrifos metabolite chlorpyrifos-methyl, 3,5,6-trichloro-2-pyridinol (TCPy) and pyrethroid metabolite 3-phenoxy-benzoic acid (3-PBA) were measured in urine collected at age 5 years. An abbreviated version of the Danish Wechsler Intelligence Scale for Children fifth edition (WISC-V) was administered by trained psychologists at age 7 years.ResultsMedian urine concentrations of 3-PBA and TCPy at age 5 years were 0.18 μg/L and 1.15 μg/L, respectively. Higher childhood urine TCPy concentration was associated with a reduction in child IQ at 7 years (-0.80 (95%CI: -1.29, -0.31)) for each doubling of TCPy. The association was slightly more pronounced in girls (-1.09 (95%CI: -1.80, -0.38)) than in boys(-0.54 (95%CI: -1.21, -0.14)). No association was observed for 3-PBA.ConclusionsEven in this low exposed cohort exposure to chlorpyrifos during early childhood was associated with lower IQ at age 7-years. Our results are in line with previous reports in both animals and humans suggesting that exposure to chlorpyrifos may adversely affect neurodevelopment.

Keywords: Insecticides IQ Children Pyrethroids