America's Most Polluted Cities

 In March the California Supreme Court upheld a massive water transfer system that would likely cut off the agricultural runoff that replenishes California’s biggest lake, the Salton Sea. If the lake dries up, environmentalists and health advocates fear it will kick up toxic dust laced with selenium and arsenic that could spread across Southern California. “As water has been siphoned off for agricultural and urban use, dust emissions have increasingly threatened public health,” warns the California Audubon Society website.

It’s troublesome news for the Sunshine State, where air pollution already plagues many cities. In fact, five California cities have the worst air quality of all major U.S. metropolitan areas, according to the American Lung Association. 

The ALA ranks the air quality of 900 counties and more than 200 Metropolitan Statistical Areas and Combined Statistical Areas–cities and their surrounding suburbs–based on ozone pollution, short-term particle pollution and year-round particle pollution.