Operators of some of the world’s biggest cruise ships are facing calls to bring their fuel emissions while at Asia-Pacific ports into line with stricter air-quality standards in the U.S. and Europe. Many popular destinations, including Singapore, Australia and several of the Pacific Islands, apply international maritime guidelines restricting ships’ emissions of sulfur—a pollutant associated with acid rain—to 3.5% of fuel volume. But that is 35 times the U.S. and European limit. Responsibility for regulating sulfur emissions—found by a number of air-quality studies conducted by the World Health Organization and the U.S. Environmental Protection Agency to cause conditions ranging from breathing difficulties to premature death—rests with local authorities. Activists […]