On the campus of Salesian High School in Boyle Heights, boys play soccer on a turf field a block away from the East LA Interchange. Four freeways converge here, and diesel trucks hauling containers are visible crawling along the overpass that towers over the neighborhood.

Boyle Heights has some of the highest levels of black carbon, or diesel pollution, near schools in greater Los Angeles, according to recent measurements by Google and Aclima. Which is why Salesian’s principal Alex Chacón is glad that the South Coast Air Quality Management District voted Friday to continue funding an air filter in his school that removes 90 percent of vehicle pollution.

“Because we are so close to traffic and congestion, any little bit helps,” he said.

Google Street View cars equipped with air pollution sensors measured diesel soot levels near L.A. schools. Higher pollution levels (indicated by dark purple) were found near Downtown L.A. and Boyle Heights. Aclima

Salesian is one of 71 schools across Southern California to receive AQMD grant money for air filters in recent years. The money comes from settlements with local polluters who violate environmental laws. To date, the agency has directed $13 million into filters at local schools from San Pedro to San Bernardino. Additional funds also come from state and federal regulators pursuing other settlements.

"It would make sense to install air filters for all the schools in L.A.," said Adrian Martinez, an environmental lawyer with the law firm Earthjustice.

Diesel exhaust is a known carcinogen. Children are most at risk because they breathe faster than adults and have greater lung surface area for their body size, which means their lungs are exposed to a greater share of pollution. Exposure to diesel pollution is largely a factor of distance: the closer you are to a freeway or idling truck, the more pollution you will inhale.

The East L.A. interchange is visible from the soccer field behind Salesian High School in Boyle Heights. Emily Guerin

“In a perfect world, we just wouldn’t allow schools in dense areas right next to roadways,” said Matt Miyasato, the deputy executive officer for science and technology advancement at AQMD.

In California, new schools cannot be built within 500 feet of freeways. But most are already constructed, so air filters are the only solution – that is, until internal combustion engines are gone from California’s roadways.

Gov. Jerry Brown has a goal of five million electric vehicles on the road by 2030. And by 2023, all heavy duty trucks registered in California must meet 2010 emission standards, which will eliminate most of the oldest, most polluting diesel trucks on the road today.