Organophosphate pesticides (OPP) cause acute toxicity by inhibiting acetylcholinesterase, however neurodevelopmental effects have been found at relatively low exposure concentrations. Contamination of conventionally-grown produce with OPPs remains an important exposure route for the general population due to agricultural spraying. Previous research suggests a relationship between prenatal exposure and executive functions (EF), but no studies have performed a detailed assessment inclusive of rater and performance-based measures. Methods: We used data from the preschool ADHD sub-substudy of the Norwegian Mother, Father, and Child Cohort Study. 262 preschool children with clinical or subclinical ADHD symptoms and 78 typically developing children underwent an on-site evaluation including the Stanford-Binet nonverbal and verbal working memory (WM), the NEPSY-II statue test, and the cookie delay task. Rating-based assessments were the parent-rated Child Behavior Questionnaire (CBQ) and the parent- and preschool teacher-rated Behavior Rating Inventory of Executive Function (BRIEF). Non-specific OPP exposure was estimated by measuring total diethyl (∑DEP) and dimethylphosphate (∑DMP) metabolites in urine collected at 17-18 weeks’ gestation. Change in EF z-score (β) and 95% confidence intervals (CI) per log-unit increase in specific gravity standardized exposure was estimated using multivariable linear regression with adjustment for dietary factors and other covariates. Results: There was no consistent pattern of association between log-∑DEP or ∑DMP and performance-based assessments and parent CBQ and BRIEF measures. However, log-∑DMP was associated with more adverse scores on teacher BRIEF scales among preschool children with symptoms of ADHD (emotional control: β=-0.27, 95% CI: -0.53, 0.00; inhibition: β=-0.21, 95% CI: -0.48, 0.05; WM: β=-0.14, 95% CI: -0.41, 0.13) and typically developing children (emotional control: β=-0.27, 95% CI: -0.63, 0.10; inhibition: β=-0.31, 95% CI: -0.68, 0.06; WM: β=-0.34, 95% CI: -0.68, 0.00). Conclusion: We found some evidence that prenatal log-∑DMP was associated with more adverse EF in a population experiencing primarily dietary exposure.
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