Environmental issues - Los Angeles

The name given by the Chumash tribe of Native Americans for the area now known as Los Angeles translates to "the valley of smoke" because of the smog from native campfires. Owing to geography, heavy reliance on automobiles, and the Los Angeles/Long Beach port complex, Los Angeles suffers from air pollution in the form of smog. The Los Angeles Basin and the San Fernando Valley are susceptible to atmospheric inversion, which holds in the exhausts from road vehicles, airplanes, locomotives, shipping, manufacturing, and other sources. Unlike other large cities that rely on rain to clear smog, Los Angeles gets only 15 inches (380 mm) of rain each year: pollution accumulates over many consecutive days. Issues of air quality in Los Angeles and other major cities led to the passage of early national environmental legislation, including the Clean Air Act. More recently, the state of California has led the nation in working to limit pollution by mandating low-emission vehicles. Smog levels are only high during summers because it is dry and warm. In the winter, storms help to clear the smog and it is not as much of a problem. Smog should continue to drop in the coming years due to aggressive steps to reduce it, electric and hybrid cars, improvements in mass transit, and other pollution reducing measures.

As a result, pollution levels have dropped in recent decades. The number of Stage 1 smog alerts has declined from over 100 per year in the 1970s to almost zero in the new millennium. Despite improvement, the 2006 and 2007 annual reports of the American Lung Association ranked the city as the most polluted in the country with short-term particle pollution and year-round particle pollution. In 2008, the city was ranked the second most polluted and again had the highest year-round particulate pollution. In addition, the groundwater is increasingly threatened by MTBE from gas stations and perchlorate from rocket fuel. With pollution still a significant problem, the city continues to take aggressive steps to improve air and water conditions.