A Swedish study that used relatively clean Stockholm as the laboratory shows that Particulate Matter and Ozone in the air does more damage to developing fetuses than if the mother were a cigarette smoker. "If we add up the effects of being exposed to high exhaust levels and ozone it has an even greater effect than smoking, said one researcher. Specifically, the pollution raised the risk of premature birth above that of smoking moms. This is the latest in a series of studies confirming that levels of air pollution considered "safe" are in fact not for the unborn.