The air near L.A.’s freeways: How dangerous?


You know something is off base when the regional air district monitors and regulates emissions from fire pits on Southern California’s beaches, which affect a handful of homeowners, before it gets around to the 24/7 blasts of pollution along the area’s freeways. That’s not entirely the fault of the South Coast Air Quality Management District, though. Unhealthful emissions from cars and especially trucks along the freeways have fallen into a regulatory black hole until now.

The AQMD regulates only stationary polluters — industrial plants, residential fireplaces, fire pits and the like. But while the freeways are stationary, the cars and trucks that cause the pollution are mobile. So even though the freeways are emitting pollutants all the time — a never-ending source of ultra-fine particulate matter and other noxious emissions that repeated studies have linked to health problems among the people who live closest to them — they are not in fact regulated by the AQMD. In the four counties covered by the South Coast AQMD, that’s more than 1 million people. The air district has done occasional spot monitoring, but none of its 35 permanent stations is near a freeway because such stations are supposed to measure regional, not localized, pollution levels. That’s an outdated way of gauging the damage caused by air pollution, from before the health dangers of particulates were well understood.

A lawsuit filed last year by the nonprofit public law group Earthjustice forced the U.S. Environmental Protection Agency to stop procrastinating on new rules for particulates. The recently adopted standards include requirements for permanent air monitors near freeways; the AQMD will install four of them by 2015.


University research over the years has found substantially worse air pollution adjacent to freeways, and worse health among nearby residents as well. A 2005 USC study concluded that children who lived within a quarter of a mile of a freeway were 89% more likely to have asthma than those living a mile away. The closer they lived to freeways, the higher the asthma rates. But these university studies, though they added to our collective knowledge, did not affect government regulations.

If the new AQMD monitoring stations find pollution levels that far exceed federal standards, the law will require that measures be taken. The question is, what measures? It would be far more complicated and difficult to regulate freeway pollution than, say, to require better filters at an industrial plant. Forcing older diesel trucks off the road would be hugely expensive for a very localized problem. Perhaps sealed windows and air filtration in nearby homes would help, although that wouldn’t do much for kids who are playing outdoors. Two things are certain, though. Authorities can’t make the situation better by ignoring it, and they have ignored it for too long.