Early childhood adversity potentiates the adverse association between prenatal organophosphate pesticide exposure and child IQ: The CHAMACOS cohort

• Prenatal exposure to OPs was previously found to be adversely related to child IQ.
• We show that certain life stressors are negatively associated with children’s IQ.
• Prenatal OP exposure has stronger association with IQ in youth with more life stress.
• The types of stressors that interact with prenatal OP exposure vary by child sex.
• This is the first human study of interaction of pesticides and social stressors.

BackgroundPrevious studies have observed an adverse association between prenatal exposure to organophosphate pesticide (OPs) and child cognition, but few studies consider the potential role of social stressors in modifying this relationship.ObjectiveWe seek to explore the potential role of early social adversities in modifying the relationship between OPs and child IQ in an agricultural Mexican American population.MethodsParticipants from the Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS) study, a prospective longitudinal pre-birth cohort study, include 329 singleton infants and their mothers followed from pregnancy through age 7. Dialkyl phosphate metabolite concentrations (DAPs), a biomarker of organophosphate pesticide exposure, were measured in maternal urine collected twice during pregnancy and averaged. Child cognitive ability was assessed at 7 years using the Wechsler Intelligence Scale for Children – Fourth Edition. Demographic characteristics and adversity information were collected during interviews and home visits at numerous time points from pregnancy until age 7.ResultsAmong low-income Latina mothers and their children in the Salinas Valley, total adversity and specific domains of adversity including poor learning environment and adverse parent-child relationships were negatively associated with child cognition. Adverse associations between DAP concentrations and IQ were stronger in children experiencing greater adversity; these associations varied by child sex. For example, the association between prenatal OP exposure and Full-Scale IQ is potentiated among boys who experienced high adversity in the learning environment (β = −13.3; p-value <0.01).ConclusionsGreater total and domain-specific adversity modifies negative relationships between prenatal OP exposure and child IQ differently among male and female children. These findings emphasize the need to consider plausible interactive pathways between social adversities and environmental exposures.