Forty multinationals are among some 4,000 firms on an air pollution blacklist released Thursday.

Top companies such as Michelin China, Sina-Mars Group APP in China, the joint ventures of Toyota and Ford, and subsidiaries of Sinopec figure on the list of the China Air Pollution Map (http://air.ipe.org.cn), compiled by the Beijing-based non-governmental Institute of Public and Environment Affairs (IPEA).

"We started collecting the records of polluters in 2004," said Ma Jun, director of the institute.

Besides information about the polluters, the institute's latest database also records air quality and air pollution sources in 150 cities in the southern parts of the country.

Ma said the institute gets polluters' information from local and central environmental protection departments' websites or from news reports.

The air pollution map is the second such blacklist launched by the group. The China Water Pollution Map has made public details of about 9,400 water violations since last year, including those involving up to 280 foreign firms.

The water map has led 50 companies, including two local players, to respond; and two have cleared their names so far. To get their names removed from the blacklist, the companies need to comply with the rules and undergo a third-party audit.

Ma expressed the hope that the lists will pressure polluters to make improvements and encourage more people to join in the clean efforts.

The blacklisted companies should move to "provide the public with an open explanation and mend their ways," Ma told China Daily.

He said the air pollution map is only partial and more information about northern China will be released.

"Access to information is a pre-condition for public participation," said Ma. "And China has progressed in disclosing environmental information."