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BACKGROUND: Although growing evidence suggests that early-life excess manganese (Mn) impairs neurodevelopment, data on the neurodevelopmental effects of mancozeb, a fungicide containing Mn, and its main metabolite ethylenethiourea (ETU) are limited. OBJECTIVE: We examined whether prenatal mancozeb exposure and excess Mn were associated with neurodevelopment in 355 1-y-old infants living near banana plantations with frequent aerial mancozeb spraying in Costa Rica. METHODS: We measured urinary ETU, hair Mn, and blood Mn concentrations in samples collected 1-3 times during pregnancy from mothers enrolled in the Infants' Environmental Health (ISA) study. We then assessed neurodevelopment in their 1-y-old infants using the Bayley Scales of Infant and Toddler Development, 3rd edition (BSID-III). We estimated exposure-outcome associations using linear regression models adjusted for maternal education, parity, gestational age at birth, child age, Home Observation for Measurement of the Environment score, and location of neurodevelopmental assessment. RESULTS: Median (P25-P75) urinary ETU, hair Mn, and blood Mn measured during pregnancy were 3:3 lg=L (2.4-4.9; specific gravity-corrected), 1:7 lg=g (0.9-4.1), and 24:0 lg=L (20.3-28.0), respectively. Among girls, higher ETU was associated with lower social-emotional scores [b per 10-fold increase= -7:4 points (95% CI: -15:2, 0.4)], whereas higher hair Mn was associated with lower cognitive scores [-3:0 (-6:1, 0.1)]. Among boys, higher hair Mn was associated with lower social-emotional scores [-4:6 (-8:5, -0:8)]. We observed null associations for blood Mn, language, and motor outcomes. CONCLUSIONS: Our findings indicate that maternal exposure to mancozeb and excess Mn during pregnancy may have adverse and sex-specific effects on infant neurodevelopment. [ABSTRACT FROM AUTHOR]

• Caregiver-infant interactions were assessed with a standardized observational task. • Quality of caregiving interactions is associated with expressive language in infants. • Stimulation and growth-fostering behaviors may be important areas to target. Early caregiving is one of the strongest influences on children's development, and among the most significant modifiable environmental factor. The aim of this study was to explore the association between quality of caregiver-infant interactions and neurodevelopment of infants living in banana-growing communities in rural Costa Rica characterized as having environmental toxic exposures. Home visits were conducted with 94 caregiver-infant dyads from the Infants' Environmental Health Study (ISA), living within Matina county, Limón province. One-year infant neurodevelopmental outcomes were assessed using the Bayley Scales of Infant and Toddler Development®, Third Edition (Bayley-III). Quality of caregiver-infant interaction was assessed with a standardized observational task: Nursing Child Assessment Satellite Training Teaching scale (NCATS) at around two years of age. Multiple regression analyses examined associations between components of caregiver-infant interactions and neurodevelopmental outcomes, adjusting for mancozeb and manganese exposure and other potential confounders. Compared to NCATS normative data for U.S. Hispanic mothers, 35% of the sample had overall caregiving interaction scores ≤10th percentile cut-off, indicating less than optimal interactions. Higher quality of caregiver-infant interaction was associated with higher expressive communication ability in infants [ß = 0.03 (95% CI: 0.01, 0.06)], controlling for pesticide exposure and confounders. Aspects of caregiving such as stimulation and growth-fostering of infants were most strongly associated with language outcomes. Results suggest an association between positive caregiving on language development for infants living in a rural agricultural area in Costa Rica, and highlight aspects of caregiving that could be targeted to improve resilience of these children who live in vulnerable conditions. [ABSTRACT FROM AUTHOR]