section_path: Geography/Environmental issues
section_name: Environmental issues
paragraph_text: Environmental issues
  
  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.
  
  The smog season lasts from approximately May to October. While other large cities 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. When the act was passed, California was unable to create a State Implementation Plan that would enable it to meet the new air quality standards, largely because of the level of pollution in Los Angeles generated by older vehicles. More recently, the state of California has led the nation in working to limit pollution by mandating low-emission vehicles. Smog is expected to continue to drop in the coming years because of aggressive steps to reduce it, which include electric and hybrid cars, improvements in mass transit, and other measures.
  
  The number of Stage 1 smog alerts in Los Angeles 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. The city met its goal of providing 20 percent of the city's power from renewable sources in 2010. The American Lung Association's 2013 survey ranks the metro area as having the nation's worst smog, and fourth in both short-term and year-round pollution amounts.
  
  Los Angeles is also home to the nation's largest urban oil field. There are more than 700 active oil wells within 1,500 feet (460 m) of homes, churches, schools and hospitals in the city, a situation about which the EPA has voiced serious concerns.