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City's air 'good' or 'unhealthy?'

OFFICIALLY, Shanghai's air quality was "good" yesterday. But at the American consulate it was a different story. Readings there indicated that the city air was "unhealthy for sensitive groups" throughout most of the day.

The consulate yesterday began publishing hourly readings of PM2.5, or particles less than 2.5 micrometers in diameter, on its official website and Twitter account.

Monitoring data from the consulate was in accordance with that from the Shanghai Environmental Monitoring Center, but the different interpretations were mainly because of the different standards between the two countries.

Data from the consulate, based on a monitoring machine installed in its offices on Huaihai Road M., showed the PM2.5 density began rising from 10am yesterday to a peak of 70 micrograms per cubic meter when the air condition was defined as "unhealthy," and remained at around 60 throughout the afternoon.

China's acceptable daily limit for PM2.5 is 75 micrograms per cubic meter, compared with about 25 in the United States.

The consulate's air quality index has six levels - "Good, Moderate, Unhealthy for Sensitive Groups, Unhealthy, Very Unhealthy, Hazardous."

The city's readings showed that PM2.5 reached a high of 68 at 11am in Putuo District and 82 in Zhangjiang in the Pudong New Area, the only two spots whose readings are made public.

Limited area

But the watchdog defined the air quality as "good" or "moderate" according to China's Air Pollution Index.

PM2.5 particles, about 1/30th of the width of a human hair, are a risk to health because they are small enough to lodge deep in the lungs and even enter the bloodstream.

"The data from the consulate will be able to indicate the air quality of the limited area around the consulate," said Wang Qian, a forecaster with the city's monitoring center.

The consulate also said on its website that "the monitor is an unofficial resource and for the health of the consulate community, and citywide analysis of air quality cannot be done using readings from a single machine."

Shu Jiong, an environmental professor at East China Normal University, said: "The data from the center should be similar to that from the consulate, because all the city's machines were imported from the United States, but the US standards are tougher than the current Chinese standards."

Shanghai has been installing monitoring equipment at more sites to add to the previous 24 spots monitoring PM2.5 and is said to be ready to release readings of fine particle pollution next month.

Shu questioned whether it was proper for the consulate to use the US standard to evaluate Shanghai's air quality.

"The two countries have different demographic situations and are at different steps of development, so it will be more suitable to use the Chinese standard to evaluate the air quality in Shanghai," Shu said.

Last year, the US Embassy in Beijing began making PM2.5 data available to the American community in the capital.


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