There’s an ongoing effort to clean up the air around the busiest port in America, in San Pedro. Ships that run on diesel fuel spew so much pollution, the cancer rates for nearby residents are more than double the rates are for people living in other coastal communities. So a decade ago, port officials spent millions of dollars to convert Chinese ships to electric power. But once the ships received that upgrade, many of them stopped using the port. They went elsewhere, and the ships that replaced them still run on diesel. Now what?