Over 15% of children worldwide suffer from neurodevelopmental disorders and diagnoses of autism spectrum disorder and attention-deficit/hyperactivity disorder have been increasing over the past several decades.Widespread use of synthetic pesticides has concurrently grown, raising concerns that pesticide exposure may be contributing to the rise in prevalence of these disorders.Synthetic pesticides are toxic to biological systems by design, with neurotoxicity and disruption of central nervous system signaling as the primary mode of action for many. Early-life pesticide exposures during periods of rapid development are of particular concern for neurodevelopment because of the potential for long-term effects.China is the world’s largest consumer of pesticides, but despite a potentially highly exposed population, very little is known about the levels of prenatal pesticide exposure or predictors of those exposures in China.Organophosphate insecticides (OPs) are used worldwide, and account for more than a third of all pesticide use in China, yet despite nearly ubiquitous exposure in the general population, few have been studied for neurodevelopmental effects. Laboratory studies indicate that OPs negatively affect a host of neuronal processes and epidemiological studies report associations between prenatal OP exposure and increased prevalence ofneurological disorders in childhood.Little is known about how OP exposure during sensitive developmental periods may affect infant development of motor, visual or auditory pathways.Alterations to the developmental timing or function of these pathways could potentially have profound effects on behavior and cognition in childhood.Therefore, the goals of this work were three-fold.First, characterize the prenatal exposure of Chinese newborns to pesticides of all classes and identify predictors of those exposures. The second objective was to explore the effects of prenatal OP exposure on motor function in infancy, as measured by the Peabody developmental motor scales and infant neurological international battery.The final goal was to examine the extent to which prenatal OP exposure affects infant visual and auditory function, as measured by grating visual acuity and auditory brainstem response.We found that season of birth was the strongest predictor of overall pesticide detects in cord blood.We also found deficits in global motor function, visual acuity, and head circumference in 9-month-old infants prenatally exposed to OPs. Chlorpyrifos was associated with statistically significant decrements in global motor function and visual acuity, as well as reduced head circumference. Naled was significantly inversely associated with fine motor function.Methamidophos was consistently associated with lower global motor function and slower auditory signal transmission across the entire study period.Phorate was not associated with the neurodevelopmental outcomes examined here, but was significantly associated with reduced head circumference.Of these commonly used OPs, only chlorpyrifos had been studied for neurodevelopmental effects in humans prior to this study. Early motor skill acquisition in infancy provides the foundation for non-verbal communication in infancy and cognitive and socio-emotional development in childhood. Similarly, visual and auditory system development in infancy is crucial for the development of language and other forms of communication, as well as reading skills in childhood.Therefore, disruption of motor or sensory systems maturation, possibly as a result of prenatal OP exposure, could potentially have detrimental long-term effects on learning or other cognitive functions in childhood. Even small, subclinical changes, that may seem negligible on an individual level, could have potentially detrimental effects at the population level.
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Prenatal Pesticide Exposure and Infant Neurodevelopment in China
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