LOS ANGELES (CNS) – Reductions in toxic emissions have cut the cancer risk from air pollution in the Southland by more than 50 percent since 2005, according to a study released today by the South Coast Air Quality Management District.

“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 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 2012-13.

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.

The latest results show that diesel particulate emitted from trucks and other diesel-powered vehicles and equipment was responsible for 68 percent of the total cancer risk. About 90 percent of the risk is due to mobile sources, including everything from cars and trucks to ocean-going ships, locomotives, aircraft and construction equipment, according to the study.

The study found the highest cancer risk — about 1,050 in 1 million — in and around the ports of Los Angeles, the hub powered by ships, trucks and locomotives.

Central Los Angeles and transportation corridors including freeways and rail lines also had some of the highest risks. The lowest cancer risks were found in central and south Orange County, southwest Riverside County and the Coachella Valley.

For several years, the greatest reductions in cancer risk have occurred in areas with the highest overall risk, including the ports, the district reported.

The study measured levels of about 37 gaseous and particulate air toxics, from benzene to lead to diesel particulate, at 10 permanent monitoring stations across Los Angeles, Orange, Riverside and San Bernardino counties. Toxics were monitored every sixth day from July 1, 2012, to June 30, 2013.

In addition to the permanent monitoring sites, SCAQMD used mobile monitoring platforms to assess local impacts in several locations including near airports, rail yards and warehouses.

According to the report, air quality data and economic trends between 2004 and 2013 indicate that the reduction in toxic emissions and cancer risk was not due solely to the recession. From 2010 to 2013, for instance, the number of containers shipped through the ports of Los Angeles and Long Beach — a key indicator of goods movement activity — has rebounded, and yet toxic emissions during that period continued to decline, according to the SCAQMD.

Although toxic emissions and the resulting cancer risk have been significantly reduced over time, a recent assessment by the California Office of Environmental Health Hazard Assessment has found that the actual magnitude of cancer risk has been significantly underestimated by state guidelines.

During the past decade, scientists have found that children’s sensitivity to air toxics has been underestimated, officials said.

When the Environmental Health Hazard office approves and implements its revised cancer risk guidelines, expected during the first quarter of 2015, cancer risk estimates will increase by an average factor of 2.7. SCAQMD’s risk numbers for the current study, and risks posed by mobile sources, businesses and industrial plants, will be revised upward accordingly.

This revision in the cancer risk calculation methodology does not change the fact that actual emissions and risk have declined by more than 50 percent since 2005, according to the agency.

The complete report will be posted online Friday at www.aqmd.gov.

SCAQMD is the air pollution control agency for Orange County and major portions of Los Angeles, San Bernardino and Riverside counties.