Exposure to above average levels of common air pollutants can lower IQ levels in un-born babies. Scientists as Columbia University have been studying 400 pregnant women in New York City and Krakow, Poland to determine the cognitive effects of pre-natal life. After a decade of tracking children they found a 4 point IQ deficit in children living in air polluted areas. The pollutants stunt brain development in the womb are polycyclic aromatic hydrocarbons, or PAHs. These compounds, created by burning fossil fuels, are prevalent in urban areas where traffic is thick.
Read more at Environmental Health News.