The Straight Dope - Is paying attention to the air quality index crazy?

My brother refuses to go running on days the air quality index tells him not to because he doesn’t want to die sooner. My idea: How do we go about proving him insane?
— littleWaki
 
We’re always hearing about how much damage smoking does to our bodies. My question is, how much damage does smoking do to the environment?
— Jay
 
Let me get this straight. Your brother is trying to keep fit and avoid air pollution, and you think he’s the crazy one?
 
The air quality index, or AQI, was developed by the Environmental Protection Agency as a simple way of indicating how bad the air is at a given moment. Five major pollutants are measured: carbon monoxide, particulates (dust, soot, etc.), ozone, and sulfur and nitrogen oxides. Whichever is worst determines the AQI for the day. Ozone and particulates tend to be the leading offenders. The results are color-coded, from green (little or no health risk) through yellow, orange, red, purple, and finally maroon (hazardous). The local AQI is often shown on TV weather maps or the newspaper weather page, and you can see a map of current and predicted conditions for the entire U.S. at airnow.gov.
 
I’m looking at that map right now. Here’s what I see:
 
• Maybe three-quarters of the country is green, including most of the West and South. Your brother can safely compete in triathlons or otherwise go nuts under such conditions.
 
• Most of the Midwest and Northeast is yellow, which according to the EPA means acceptable except for a few unusually sensitive individuals. We’ll assume your brother is a hardy soul and needn’t be concerned here.
 
• A few spots are orange. South Chicago, northwest Indiana, and points east, for example, look like bad places to be for much of the day. (Having done my share of driving through northwest Indiana, I venture to say this is true most days.) These areas are “unhealthy” for entire “sensitive groups,” such as children, people with lung disease, and adults exerting themselves outdoors, possibly including your brother. Some local environmental agencies declare “air pollution action days” in code-orange conditions. However, according to the EPA, only 18 percent of active adults experience even moderate breathing problems at such times. If your brother feels fine, chances are he is.
 
Here’s what I don’t see:
 
• Red (unhealthy). That’s when things get serious. Anybody active outdoors in such conditions risks breathing problems, so your brother would want to keep his run short. Red is seen mostly in warm-weather months.
 
• Purple (very unhealthy). This is uncommon in the U.S. Half of moderately active adults will have some difficulty breathing and 20 percent will have major problems. Your brother would be smart to skip the run altogether.
 
• Maroon (hazardous). This extreme condition is rare in the U.S. — the only time I’ve seen it reported is downwind of a forest fire. It means no unnecessary exercise for anybody; those with asthma or lung disease are at serious risk.
 
I’m not seeing what’s so insane about heeding such warnings, Waki, and wonder what you’re up to. Did you encourage your brother to play in traffic as a kid? On the assumption you’re merely clueless, be advised the World Health Organization estimates air pollution results in about 2 million early deaths each year. That your brother presumably is healthy and active doesn’t mean he’s immune. On the contrary, the better shape his lungs are in, the faster he’ll suck in pollutants.
 
Ultrafine particles that primarily come from cars and trucks are especially problematic. Called PM2.5, meaning they’re 2.5 micrometers (1/10,000th of an inch) or smaller, these particles can be inhaled deep into your lungs and stay there. Particulate pollution can trigger asthma attacks and allergies. Stress tests on both healthy men and those with mild heart disease show breathing diesel exhaust during exercise reduced blood flow to the heart and increased the risk of blood clots.
 
Exposure to high levels of ground-level ozone causes respiratory problems during exercise, and even light exposure can significantly impair physical performance in adults. In children, ozone is blamed for causing asthma. Carbon monoxide can also set off asthma attacks and aggravate congestive heart failure.
 
Here’s one thing you needn’t worry about, though: outdoor air pollution due to cigarettes. Smoking is plenty dangerous, but it’s an indoor problem. When I had my assistant Una run the numbers, she found an astonishing 357 billion cigarettes are smoked each year in the U.S. Assuming an average of 14 milligrams of fine particle emissions and 200 milligrams of carbon monoxide per cigarette, U.S. smokers produce about 5,500 tons of particles and 78,500 tons of carbon monoxide annually. That sounds like a lot, but it’s roughly 0.1 percent of U.S. totals for those pollutants. The real environmental issue here, in my opinion? The 357 billion cigarette butts.
 
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