As the weather gets better, we see more and more people jogging, bicycling, and rollerblading through the City streets. And when we see these same people coupled with an iPod, we just cringe and hope that Rocky soundtrack doesn’t distract from the yellow cab bearing down on them. But as it turns out, street athletes might want to be more careful with what comes out of the cab rather than the cab itself.

Despite the new “cleaner” running buses that the MTA boasts of, exercising outside exposes one to the particulates spewed by buses, cabs, and cars. And this can irritate the lungs causing the airways to clamp down and fill with mucus - actually making your workout harder. And more importantly, polluted air can also worsen underlying medical conditions like asthma, bronchitis, emphysema, or heart troubles. Two other ingredients of dirty air, ozone and carbon monoxide, can cause the airways to further clamp down and steal precious oxygen, respectively.

Dr. Joseph T. Cooke of NY-Presbyterian Hospital/Weill Cornell Medical Center suggests that anyone with the mentioned health problems should exercise early in the morning or in the evening when it is cooler and ozone levels are at their lowest. He also recommends working out indoors when possible.