Special report: Environment
of Americans wake up summer mornings to news about how unhealthy their
Where we live
The pollution problem is caused, in part, by expanding cities and suburbs. Many cities in the U.S. are overcrowded, forcing housing builders to start new communities on land outside city limits. This spread of housing developments and strip malls is called urban sprawl.
In places like Atlanta, Washington, New York, people who live in these suburban communities drive almost everywhere, including their jobs. And as more people move to the suburbs and commute to the city, the levels of traffic and pollution increase.
Quality of air
As cars sit in traffic, they burn gasoline and give off pollutants called hydro-carbons and nitrogen oxides. When sunlight hits these compounds, they form ozone, a dangerous form of oxygen. Ozone creates smog and makes daily life difficult for people across the country.
Every day, the Environmental Protection Agency (EPA) measures the levels of ozone and other pollutants in the air with the Air Quality Index (AQI).
The index has colors
to show how high the pollution is that day. An AQI below 100 means the
air pollution poses little risk. If the AQI registers red days
(from 100-150 or above), people may notice a change in how well they
can breathe outside.
A study published in the Journal of the American Medical Association said that long-term exposure to the air pollution in some of Americas biggest cities greatly raises the risk of dying from lung cancer and can be as dangerous as living with a smoker. Almost 400 cities in the U.S. have smog levels above the legal limits.
The worst areas
The EPA lists the Los Angeles metro area as the most heavily ozone-polluted metropolitan area in the country. In fact, the five smoggiest counties in the country are all in California.
However, Los Angeles and many other areas of the country have made significant progress in cleaning up their air. Los Angeles has had 85 percent fewer red days in the late 1990s than in the early 1980s. Other places known for dirty air, like Houston, Texas, have also had fewer red days in the past two decades.
Even the worst days in Los Angeles are nothing compared to some cities in China, where the AQI can rise above 250. Lanzhou, the city with the worst air quality, plans to remove the top of a local mountain to try to bring fresh air into the city.
The United States has laws aimed at making the air cleaner. The Clean Air Act, and additional measures passed in 1997, set tough emission standards. And California's governor just signed a law with even tougher pollution guidelines that he hopes will catch on as other leaders feel political pressure to address an issue as important as the air we breathe.
-- By Samara Aberman, NewsHour Extra
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