Prenatal exposure to mirex impairs neurodevelopment at age of 4 years.

Background: Some studies have suggested that certain organochlorine (OC) compounds may impair neurodevelopment in animals and humans. The objective of this study was to investigate the association between prenatal exposure to an OC pesticide, mirex, and cognitive development in children at age of 4 years.

Methods: A population-based birth cohort in Granada (Spain) recruited between 2000 and 2002 was studied between 2005 and 2006, when the children were 4 years old. Complete data for analyses, including mirex determination in placentas, were gathered on a random sample of 104 children. A standardized version of the McCarthy Scales of Children's Abilities (MSCA) was used to assess children's motor and cognitive abilities. Multivariate analyses were performed to evaluate the relation between MSCA scores and prenatal exposure to mirex, adjusting for potential confounders.

Results: The presence of mirex in placenta was inversely associated with cognitive development at 4 years of age: children with prenatal exposure to mirex (>or=limit of quantification: 26%; median: 1.4 ng/g placenta) showed a decrease of 5.15 points in working memory and of 7.33 points in the quantitative area with respect to children of the same age not prenatally exposed to mirex.

Conclusion: The deficit found in intellectual function during early childhood suggests that prenatal exposure to mirex may have a significant impact on school performance.