Air pollution from cars and factories has been regulated in much of the world since the 1970s. When it comes to the smoke-belching ships that carry global trade, the rules have been a lot looser.
Big changes start next January, though, when long-debated standards from the International Maritime Organization mandate steep cuts of sulfur emissions associated with respiratory disease and acid rain. Much tougher rules are supposed to take effect in 2050, when the IMO will require ships also reduce carbon dioxide emissions by at least half.