California Air Is Cleaner, but Troubles Remain - New York Times

"A major study sponsored by the South Coast district in 1998 showed that the cancer risk for residents of Long Beach, to the immediate northeast of the ports, was twice as great as the risk for people in west-central Los Angeles and four times as high as the risk for those near Topanga Canyon. Diesel particulates from trucks, ships and locomotives, the study said, accounted for 70 percent of the risk.

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California Air Is Cleaner, but Troubles Remain - New York Times