One reason Southern California’s air has been so dirty recently is a big increase in diesel emissions from the ports of Los Angeles and Long Beach.

Supply chain problems, a backup of container ships and record cargo volumes have caused a surge in lung-damaging pollution, worsening smog from the harbor area to the Inland Empire. Fine-particle pollution in downtown L.A. in November jumped to levels more than 40% higher than in previous years.

The pandemic-fueled boom in shipping activity has only exacerbated long-standing health risks from the massive hub for diesel trucks, container ships and cargo-moving equipment. The port complex is Southern California’s largest source of smog-forming pollution, responsible for more than 10% of its nitrogen oxide emissions. Though port emissions improved dramatically under a 2006 clean-air plan that banned the dirtiest diesel trucks, progress has tapered off in recent years. L.A. Mayor Eric Garcetti and Long Beach Mayor Robert Garcia pledged in 2017 to transform the ports into largely zero-emission operations by 2035, but the few actions they’ve taken to date fall far short.

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