For years, California has led the nation in the war on air pollution. The state’s emission standards for cars and trucks are among the toughest in the country. But the large commercial ships that travel up and down the California coast pose a growing threat to air quality. In this radio report, heard on 23 public radio stations across California, CIR associate reporter Diane Solomon reports that many of the vessels are foreign-owned, making it tough for regulators to crack down.