To increase its chances of hosting the 2008 Olympic Games, Beijing has ordered some of its biggest polluters to clean up their acts. A $1.25 billion cleanup project is aimed at helping Beijing, notorious for having some of the dirtiest air in the world, approach World Health Organization air standards by 2006. A visit to Beijing from an International Olympic Committee delegation is expected in February, and the committee will decide on a host city in July. Throughout China, industrial firms have made progress in cleaning up their emissions in recent years — 93 percent of 238,000 firms have met government clean air and water standards set in 1996. The country’s State Environmental Protection Administration is threatening to shut down 16,600 companies if they don’t meet the standards by the end of this year.