Prenatal exposure to chlorpyrifos, a widely used organophosphate insecticide, is associated with neurobehavioral deficits in human and animal studies. Magnetic resonance imaging (MRI) was used to study brain morphology in children (ages 5.9 to 11.2 years) with high prenatal exposure to this compound. All participants had minimal prenatal exposure to environmental tobacco smoke and polycyclic aromatic hydrocarbons.

Children exposed to high levels of chlorpyrifos prenatally (upper tertile of chlorpyrifos concentrations in umbilical cord blood) showed frontal and parietal cortical thinning. There was an inverse dose–response relationship between chlorpyrifos and cortical thickness. Other changes in brain morphology included enlarged superior temporal, posterior middle temporal, and inferior postcentral gyri bilaterally, and enlarged superior frontal gyrus, gyrus rectus, cuneus, and precuneus along the mesial wall of the right hemisphere. Exposure – IQ interactions were also reported. Thus prenatal exposure to a widely used environmental pesticide at standard use levels is associated with structural changes in the developing human brain.

Rauh VA, Perera FP, Horton MK, Whyatt RM, Bansal R, Hao X, Liu J, Barr DB, Slotkin TA, Peterson BS: Brain anomalies in children exposed prenatally to a common organophosphate pesticide.  Proc. Natl. Acad. Sci. USA [Epub ahead of print, April 30, 2012; doi: 10.1073/pnas.1203396109]

http://www.pnas.org/content/early/2012/04/25/1203396109.abstract