BEIJING -- Beijing launched its first census of pollution sources for accurate statistics on Friday, amid a green drive to improve environment ahead of the Olympics.

The survey will cover 90,000 sources of pollution, among which 24,000 are industrial sources, 45,000 residential, 21,000 agricultural and 128 facilities for centralized treatment of pollutants, according to the city's bureau of environmental protection.

Information collected from the census would help the government formulate policies and plans for environmental protection, said Zheng Jiang, vice director of Beijing's environmental protection bureau.

Beijing authorities had identified the 90,000 sources through their registrations with the industrial and commercial administration and from an informal survey conducted earlier by the local government.

Local companies and institutions must provide accurate and detailed information about the control, discharge and treatment of pollutants, energy consumption and the use of fertilizer, pesticides and feedstuff.

"The success or failure of the census depends largely on whether the questionnaire is filled out truthfully and carefully," Zheng said.

Those who fail to comply could be fined up to 50,000 yuan (US$7,000), he said.

The survey started at Beijing Electric Power Transmission and Transformation Company (BEPTTC) as well as Beijing Yanshan Petrochemical Co., Ltd (BYPC). Each of the two companies, based in Fangshan District, had to fill in a 58-page questionnaire due at the end of the April when the survey was expected to end.

BEPTTC was a source of sulfur dioxide, ammoniate and nitride, while BYPC mainly discharged waste water and exhaust gas.

The survey of residential pollution would not necessarily cover every household but would target larger polluters such as hotels, restaurants, hair salons and hospitals.

About 7,400 surveyors have been trained for the large-scale census.

The statistics would be publicized next year.

Beijing authorities said last month that major pollutants in Beijing were down and air quality in the city had improved for a ninth consecutive year, but experts warned that the government should prepare for a long and tough fight against air pollution, citing inhalable particles and ozone as major obstacles for Beijing to achieve its "Green Olympics" goal.

China started its first national census of pollution sources on February, focusing on industrial sources including metallurgy, chemistry, construction materials. power plants, paper-making, pharmaceuticals and mining.

The central government planned to finish data collection and analysis this year and approve the findings in the first half of 2009.