LOS ANGELES (CBSLA.com) — The cancer risk from air pollution in Southern California has dropped by more than 50 percent since 2005, according a study released Thursday by the South Coast Air Quality Management District.

The district’s Multiple Air Toxics Study IV found that the average cancer risk from air pollution across the region declined from 1,194 in 1 million in 2005 to 418 in 1 million in 2012-2013. The risk reduction follows a trend of declining toxic emissions in the region since the first study was conducted in 1987, according to the SCAQMD, which is the air pollution control agency for Orange County and major portions of Los Angeles, San Bernardino and Riverside counties.

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“Air pollution controls on everything from cars to trucks to industrial plants have dramatically reduced toxic emissions in our region,” said Barry Wallerstein, the district’s executive officer. “However, remaining risks are still unacceptably high in some areas. We need to maintain our commitment to reducing toxic emissions so that everyone can breathe healthful air.”

The study’s latest results show emissions from trucks and other diesel-powered vehicles and equipment was responsible for 68 percent of the total cancer risk.

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There continues to be pockets of bad air around Southern California. The area of highest cancer risk – about 1,050 in 1 million – is in and around the ports of Los Angeles, a hub powered by ships, trucks and locomotives. Central Los Angeles and transportation corridors that included freeways and rail lines also had high risks.

The lowest cancer risks were found in central and south Orange County, southwest Riverside County and the Coachella Valley.

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