![](https://www.motherjones.com/wp-content/uploads/nycpollution2.jpg?w=990)
by flickr user tracyxxx used under Creative Commons license
It doesn’t take a fancy public health study to convince us that urban pollution—the kind that welcomes you to Los Angeles like a stifling hug from a dirty old uncle—is bad. But it helps.
According to a new study released by Columbia, a common form of air pollution called polycyclic aromatic hydrocarbons (PAH) may be to blame for diminished intellectual ability in children. (PAH has also been linked to astronomical rates of chronic asthma and other respitory problems.)
The Mailman School of Public Health found that 5-year-olds in my old ‘hood of Washington Heights, Harlem, and the South Bronx who were exposed to high levels of the stuff in utero scored an average of 4.5 points lower on a standard IQ test than peers who weren’t. According to the authors, that’s comperable to low-level lead exposure—and we all know how toxic lead is.