Negative Effects on Birth Outcomes.

• Position: PESTICIDES

Although common opinion holds that exposure to pesticides increases adverse birth outcomes, the existing body of scientific evidence is ambiguous. Logistical and ethical barriers--pesticide use data is not widely available and randomized control trials are impossible--have gotten in the way of more-accurate conclusions.

One study addresses the issue by analyzing birth outcomes in California's San Joaquin Valley. With more than one-third of the country's vegetables and two-thirds of its fruits and nuts produced there, the Valley not surprisingly is a heavy pesticide-use region.

The research team investigated the effect of exposure during pregnancy in this agriculturally dominated area and observed an increase in adverse outcomes accompanying very high levels of pesticide exposure. Their findings appear in the journal Nature Communications.

"For the majority of births, there is no statistically identifiable impact of pesticide exposure on birth outcome," says environmental scientist and lead author Ashley Larsen. "Yet, mothers exposed to extreme levels of pesticides--defined here as the top five percent of the pesticide exposure distribution--experienced between five and nine percent increases in the probability of...