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Brain imaging study may link prenatal pesticide exposure to cognitive deficits

A small study using neuroimaging explored a possible association between prenatal exposure to organophosphate pesticides (OPs) and deficits in certain brain functions in adolescents.

A small study using neuroimaging indicates that there may be an association between prenatal exposure to organophosphate pesticides (OPs) and deficits in certain brain functions in adolescents. The findings, published in PNAS, were reported by researchers from California.

According to the Centers for Disease Control and Prevention, OPs are the most common insecticides in the United States. These endocrine-disrupting compounds are used in agriculture, the home, gardens, and veterinary practice, and the predominant route of exposure to them is residue on produce.

The population studied by the authors was a subset of Mexican American youth from the Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS) study. CHAMACOS is a longitudinal mother-child cohort living in the Salinas Valley, an agricultural area in California which has been the subject of studies since 1999 on the impact of pesticides on childhood growth and development.,

For the new research, the investigators used functional near-infrared spectroscopy (fNIRS) to perform neuro-imaging in 95 adolescents in the CHAMACOS cohort. fNIRS is a noninvasive optical imaging technique that measures changes in hemoglobin concentrations within the brain and the study authors said it correlates well with functional magnetic resonance imaging.

The objective of the study was to investigate OP-related effects on cortical brain activation and localize them. They wanted to assess neural activity during tasks involving cognitive flexibility, working memory, attention, social cognition, and language comprehension in relation to exposure to OP applied to agricultural crops in close proximity to mothers’ homes during pregnancy.

The authors found that for every 10-fold increase in total OP use within a 1-km radius of mothers’ homes during pregnancy, there was a bilateral decrease in brain activation during tasks of executive function, including cognitive flexibility and working memory. Prenatal OP exposure also was associated with sex differences in brain activation during a language comprehension task. Total OP use was associated with increased activation in males and reduced activation in females across nearly all of the 15 localization clusters (P for sex interaction < 0.05 for 7 of 15 clusters and < 0.20 for all but 1 cluster) but was particularly marked for the frontal and temporal regions.

The researchers said use of fNIRS is “an inexpensive and easily accessible technology” and that it “enhances…efforts to assess the impact of environmental exposures on brain function.” Their findings, they asserted, suggest that “OPs may be impacting cognitive function at the neural level.”