Chlorpyrifos Exposure and Urban Residential Environment Characteristics as Determinants of Early Childhood Neurodevelopment

摘要

Objectives. We evaluated whether neighborhood characteristics correlated with early neurodevelopment and whether these characteristics confounded the previously reported association between exposure to chlorpyrifos (an organophosphate insecticide) and neurodevelopment. Methods. We obtained prenatal addresses, chlorpyrifos exposure data, and 36-month Psychomotor Development Index (PDI) and Mental Development Index (MDI) scores for a birth cohort in New York City (born 1998–2002). We used data from the 2000 US Census to estimate measures of physical infrastructure, socioeconomic status, crowding, demographic composition, and linguistic isolation for 1-kilometer network areas around each child's prenatal address. Generalized estimating equations were adjusted for demographics, maternal education and IQ, prenatal exposure to tobacco smoke, caretaking environment quality, and building dilapidation. Results. Of 266 children included as participants, 47% were male, 59% were Dominican, and 41% were African American. For each standard deviation higher in neighborhood percent poverty, the PDI score was 2.6 points lower (95% confidence interval [CI] = ?3.7, ?1.5), and the MDI score was 1.7 points lower (95% CI = ?2.6, ?0.8). Neighborhood-level confounding of the chlorpyrifos-neurodevelopment association was not apparent. Conclusions. Neighborhood context and chlorpyrifos exposure were independently associated with neurodevelopment, thus providing distinct opportunities for health promotion. Developmental delays in early childhood have long-term implications for educational and occupational attainment. 1 , 2 Environmental characteristics within the household affect neurodevelopment in early life, 3 – 5 frequently to the disadvantage of vulnerable populations. 6 , 7 Neighborhood-level environments may also affect neurologic development; indicators of socioeconomic deprivation have been linked to mental or physical health deficits, and these indicators may signal the presence of psychosocial and physical environment risk factors. 8 – 13 Aspects of neighborhood composition, such as a higher percentage of foreign-born residents, may likewise be associated with the presence of other physical and social environment characteristics relevant to developmental outcomes. 14 Other characteristics with potential relevance to mental development or test performance include crowding of housing units within the neighborhood, exposure to discrimination, and sources of stress that may affect parental caretaking behaviors or parent–child interactions. 15 – 17 Studies of environmental effects have identified a number of specific toxic exposures linked to neurodevelopmental deficits, 4 , 18 – 20 but the degree to which such associations might be confounded by neighborhood social–environment factors is unknown. Previous studies have reported that exposures to organophosphate pesticides, including chlorpyrifos—which was commonly used in residential settings before the US Environmental Protection Agency banned it for domestic use in 2001—are associated with indicators of poor neurodevelopment in diverse settings 21 – 28 ; however, the association remains controversial 29 , 30 and may be subject to confounding. Potential confounders of the association between pesticide exposure and neurodevelopment include building dilapidation and poor neighborhood conditions, because both building and neighborhood deterioration are associated with increased pest levels and subsequent increases in pesticide usage. 31 , 32 We used data from a birth cohort established by the Columbia Center for Children's Environmental Health in New York City, New York, to explore whether neighborhood conditions and indicators of building dilapidation are independently associated with early childhood neurodevelopment. We hypothesized that exposure to neighborhood-level disadvantage (based on socioeconomic and composition measures, crowding, and psychosocial hazards) or to building dilapidation would be associated with lower psychomotor and mental development scores in this population of inner-city children. We also considered whether neighborhood context could confound the previously reported association of chlorpyrifos with lower psychomotor and mental development scores. 26 .