In many parts of the country, when summer temperatures sizzle, air quality plummets. Forecasters warn people that it's a "code orange" or a "code red" day. But the Environmental Protection Agency says the air is unhealthy, and even deadly, even when the ozone — commonly known as smog – is at levels that are now considered safe.
That isn't news to many people with lung problems or weakened immune systems. Many Americans have to plan their days around the air quality.