Roughly a quarter of the diesel-related air pollution in Los Angeles comes from the region's two immense ports – the nation’s busiest ocean shipping complex, which community groups have dubbed "the diesel death zone."
While environmentalists have praised the plan it is drawing criticism from shippers who say the associated fees will increase supply-chain costs just as higher fuel prices and lower volumes are eating into their profits.
The two ports handle about 40 percent of the US's containerized imports, everything from sneakers to electronics coming from Asia to the shelves of Wal-Mart Stores, Home Depot and other retailers.
Experts say the two ports – already known for their relatively high container fees, existing environmental regulations and occasional labour strife – risk losing market share to ports in Canada and on the US East Coast.