Eastman Kodak has closed a film plant that employed more than 500 workers in China, claiming that new environmental policies in the country have made it unprofitable to keep the plant running. Kodak has made several environmental improvements to the facility since acquiring it in March 1998, including a new water-recycling system and an updated wastewater-treatment process. But it announced this week that a new Chinese policy to restrict manufacturing emissions to help preserve Lake Tai, which borders the Kodak plant, would make it impossible for the plant to meet its financial goals.