Question: When is it unhealthy to exercise?
Answer: When you're exercising in polluted air.
With a heat wave blanketing much of the U.S. this week, it's a good time to remind joggers, bikers, hikers and others who exercise outdoors that hot sunny summer afternoons, and evenings, are not good times to exert yourself outdoors. Ozone pollution, a major component of smog, forms when heat and sunlight interact with smokestack and tailpipe emissions. The result is ground-level ozone, which can damage lung tissue and even affect the heart and circulatory systems. Elevated air pollution levels can linger well into the evening, even past midnight during a heat wave.
Generally, exposure is a concern primarily for the elderly, the very young and people with pre-existing lung conditions, like asthma or emphysema. Those who have jobs that require strenuous outdoor activity are also cautioned to take heed of air pollution forecasts. And then there are those who are paying the most attention to their health, the joggers, bikers and hikers who take to the streets and parks of their communities after work. In general, The Daily Green encourages outdoor activities of all kinds: exercising outdoors is a great way to get healthy while connecting with the great outdoors. But on hot summer days, you may be doing as much harm as good.
Before exercising outdoors on a hot summer day, check the air pollution concentrations at airnow.gov. The nationwide side, run by the Environmental Protection Agency, provides a map that you can click to get state- and community-level forecasts and real-time air monitoring data in a user-friendly way. If there's an advisory for your region, consider taking your exercise routine indoors for the afternoon, or plan to exercise in the morning, before temperatures and air pollution levels rise.
Related: 5 Air Pollution Facts and Myths
Enter your city or zip code to get your local temperature and air quality and find local green food and recycling resources near you.