About 15 percent of the world’s nitrogen- and sulfur-based pollution is produced by ships — some 30,000 of them worldwide — yet the vessels are among the least controlled pollution sources on the planet. That wouldn’t change much under rules proposed by the U.S. EPA yesterday. The new regulations, modeled after a five-year-old international accord that has been widely criticized as too lax, would require some ships to reduce their emissions by about 11 percent. But the rules would cover only new ships (although ships sail the seas for four decades) and only U.S. ships (although nine out of every 10 ships entering U.S. ports are foreign). The EPA has admitted that even if the rules were fully in force across the globe, pollution from ships would increase by about 13 percent in the U.S. in the next 30 years. State and local air quality officials say the lack of strict regulations would make it nigh-impossible to meet air-quality standards, and enviros are threatening to go to court over the issue. The Bush administration is expected to finalize the rules by the end of January, after a public-comment period.