The insecticide chlorpyrifos is a powerful tool for controlling various pests, making it one of the most widely used pesticides during the latter half of the 20th century. Like many pesticides, however, chlorpyrifos lacks precision. In addition to harming non-target insects like bees, it has also been linked to health risks for much larger animals " including us. Now, a new US study suggests those risks may begin before birth. Humans exposed to chlorpyrifos prenatally are more likely to exhibit structural brain abnormalities and reduced motor functions in childhood and adolescence. Progressively higher prenatal exposure to chlorpyrifos was associated with incrementally greater deviations in brain structure, function, and metabolism in children and teens, the researchers found, along with poorer measures of motor speed and motor programming. This supports previous research linking chlorpyrifos with impaired cognitive function and brain development, but these findings are the first evidence of widespread and long-lasting molecular, cellular, and metabolic effects in the brain. Subjects in this urban cohort were likely exposed to chlorpyrifos at home, since many were born before or shortly after the US Environmental Protection Agency banned residential use of chlorpyrifos in 2001. The pesticide is still used in agriculture around the world. "Widespread exposures ... continue to place farm workers, pregnant women, and unborn children in harm's way," says senior author Virginia Rauh.