Pregnant women may want to switch to organic produce – exposure to specific pesticides in the womb is linked to a reduced IQ among children.

The finding comes from three studies conducted in New York City and California’s Salinas Valley – known as “America’s salad bowl” because of its intensive cultivation of lettuce and other vegetables.

Metabolites of organophosphates were measured in the urine of pregnant women or in blood from the umbilical cord. In the Californian study, the women were divided into five groups according to these measurements. At the age of seven, the IQ scores of children of the women in the group with the highest pesticide exposures were on average seven points lower than those of women with the lowest exposures.

City or farm?

There was no relationship between the children’s IQ scores and pesticide metabolites in their own urine, suggesting that the brain is particularly vulnerable during its growth in the womb.


The children from the Salinas Valley were mostly from Latino farm-working families – almost half of the women worked in agriculture at some point in their pregnancy, says Brenda Eskenazi of the University of California, Berkeley, who led the study.

However, given that the New York City studies found similar results, it seems exposure to sprays on farms is not the main problem. “We believe most of the exposure is occurring through pesticide residues on food,” says Eskenazi.

Journal reference: Environmental Health Perspectives, DOI: 10.1289/ehp.1003185