Nobody wants to be outside when it’s smoggy. Even so, it can still be tempting to escape the house or office and go outdoors for some exercise despite the smog alerts. If that sounds like you, you may want to reconsider: According to the New York Times, exercisers may be at the greatest risk when air quality drops. That’s because, by some estimates, exercisers draw in 10 to 20 times more air compared to those sitting still, which means they also inhale more pollutants on bad air quality days.

For example, in one study conducted in a lab, participants exposed to diesel fumes while exercising moderately for an hour had far more chemical particles in their lungs than when they were exposed to the same amount of fumes while resting. Other studies have shown that, for athletes such as figure skaters and hockey players, long hours of exposure to pollution (caused by exhaust from ice resurfacing machines) may contribute to higher rates of asthma, and that, for healthy bikers, exposure to diesel exhaust may cause abnormal changes in their veins and arteries—possibly indicating a heightened risk for cardiovascular disease. Bottom line? Try not to exercise outside when smog levels are high. But, if you have to, venture out early when smog levels tend to be lower.

Source: New York Times