Smog might be just as bad for your brain as it is for your lungs, a study finds. Researchers monitored the air pollution 249 mothers were exposed to during pregnancy, then monitored their children. They found that high pollution levels corresponded to a four-point drop in the kids’ IQ scores by age 5, Time reports.
The relationship holds even when other factors—including exposure to lead, pesticides, secondhand smoke, and the mother’s level of education—are taken into account. “It’s surprising the effects are so persistent,” said one epidemiologist. The reason for the difference is less clear, though the study’s lead author hypothesizes that the pollutants could cause genetic damage, and notes that fetal brains are especially vulnerable to neurotoxic chemicals.