(Clarifies translated comment from ministry spokesman)
By Ben Blanchard
BEIJING, June 5 (Reuters) - A senior Chinese official demanded on Tuesday that foreign embassies stop issuing air pollution readings, saying it was against the law and diplomatic conventions, in pointed criticism of a closely watched U.S. embassy index.
The level of air pollution in China's heaving capital varies, depending on the wind, but a cocktail of smokestack emissions, vehicle exhaust, dust and aerosols often blankets the city in a pungent, beige shroud for days on end.
Many residents dismiss the common official readings of "slight" pollution in Beijing as grossly under-stated.
The U.S. embassy has installed a monitoring point on its roof which releases hourly air-quality data via a widely followed Twitter feed. The U.S. consulates in Shanghai and the southern city of Guangzhou provide a similar service.
While China tightened air pollution monitoring standards in January, the official reading and the U.S. embassy reading can often be far apart.
Chinese experts have criticised the single U.S. embassy monitoring point as "unscientific".
Deputy Environment Minister Wu Xiaoqing went a step further, saying such readings were illegal and should stop, though he did not directly name the United States.
"According to the Vienna Convention on Diplomatic Relations ... foreign diplomats are required to respect and follow local laws and cannot interfere in internal affairs," Wu told a news conference.
"China's air quality monitoring and information release involve the public interest and are up to the government. Foreign consulates in China taking it on themselves to monitor air quality and release the information online not only goes against the spirit of the Vienna Convention ... it also contravenes relevant environmental protection rules."
Chinese Foreign Ministry spokesman Liu Weimin called on foreign diplomatic missions to respect China's laws and regulations and to stop issuing the readings, "especially over the Internet".
"If the foreign embassies want to collect this kind of information for their own staff and diplomats, I think it's up to them," Liu told reporters. "They can't release this information to the outside world."
The U.S. embassy acknowledges on its website (http://beijing.usembassy-china.org.cn) that its equipment cannot be relied upon for general monitoring, saying "citywide analysis cannot be done ... on data from a lone machine".
Despite his criticism, Wu acknowledged that China's air quality and overall environmental situation remained precarious, with more than one tenth of monitored rivers rated severely polluted, for example.
"What needs saving is the country's air quality, not the government's face," Zhou Rong, an energy campaigner for Greenpeace, said in emailed comments. "The environmental authorities must stop finger pointing and start taking actions that really address the issue." (Additional reporting by Sui-Lee Wee; Editing by Nick Macfie)
Top 10 Most Polluting Countries
We look at which 10 countries have the most CO2 emissions. Figure are preliminary 2010 numbers from the U.S. government's <a href="http://cdiac.ornl.gov/trends/emis/perlim_2009_2010_estimates.html" target="_hplink">Carbon Dioxide Information Analysis Center. </a> (Photo Getty Images)
#10 - Saudia Arabia
Estimated CO2 Emissions in 2010 (in thousands of metric tonnes): 493,726 (Photo MARWAN NAAMANI/AFP/Getty Images)
#9 - Canada
Estimated CO2 Emissions in 2010 (in thousands of metric tonnes): 518,475 (Photo MARK RALSTON/AFP/Getty Images)
#8 - Korea
Estimated CO2 Emissions in 2010 (in thousands of metric tonnes): 563,126 (Photo CHOI JAE-KU/AFP/Getty Images)
#7 - Iran
Estimated CO2 Emissions in 2010 (in thousands of metric tonnes): 574,667 (Photo FRED DUFOUR/AFP/Getty Images)
#6 - Germany
Estimated CO2 Emissions in 2010 (in thousands of metric tonnes): 762,543 (Photo JOHANNES EISELE/AFP/Getty Images)
#5 - Japan
Estimated CO2 Emissions in 2010 (in thousands of metric tonnes): 1,138,432 (Photo YOSHIKAZU TSUNO/AFP/Getty Images)
#4 - Russia
Estimated CO2 Emissions in 2010 (in thousands of metric tonnes): 1,688,688 (Photo KIRILL KUDRYAVTSEV/AFP/Getty Images)
#3 - India
Estimated CO2 Emissions in 2010 (in thousands of metric tonnes): 2,069,738 (Photo ROBERTO SCHMIDT/AFP/Getty Images)
#2 - USA
Estimated CO2 Emissions in 2010 (in thousands of metric tonnes): 5,492,170 (Photo by Kevork Djansezian/Getty Images)
#1 - China
Estimated CO2 Emissions in 2010 (in thousands of metric tonnes): 8,240,958 (Photo PETER PARKS/AFP/Getty Images)
EARLIER ON HUFFPOST: