Exposure to ozone at levels sometimes present in the world’s most polluted cities can trigger potentially dangerous changes to human cardiovascular systems, according to a new study. In a series of tests conducted 
on 23 healthy adults, scientists found evidence of cardiac inflammation and heart rhythm disturbance after exposure to air containing ozone at 0.3 parts per million for two hours — about the same dose they would receive if exposed to ozone levels exceeding the U.S. standard of 0.075 parts per million over eight hours. According to the findings, published in the journal Circulation, the blood levels of several inflammatory agents increased — more than doubling in some cases — after ozone exposure. This finding “caught us by surprise,” said Robert Devlin, a toxicologist with the U.S. Environmental Protection Agency and lead author of the study. “We think it’s one of the more important and significant findings.” Heavily polluted cities such as Beijing and Mexico City often have extremely high ozone levels, and ozone in U.S. cities such as Los Angeles and Houston can reach levels equal to those used in the experiment.
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Mexico City smog