Air assessments differ due to separate criteria

Assessments of air quality done by the Chinese government do not match those of the US consulate in Shanghai because they use different standards, environmental officials said on Tuesday.

The US consulate on Monday began publishing PM2.5 readings, which measure particulate matter 2.5 microns or less in diameter.

The PM2.5 reading was 152 at noon on Tuesday, according to the consulate, compared with 122 at the Pudong monitoring site and 155 at the Putuo site, two stations run by the Shanghai Environmental Monitoring Center.

However, the US consulate appraised air quality as "very unhealthy" based on the calculated air quality index, while the assessment from the Shanghai center was "favorable".

"The divergence lies in the different bases for evaluation," said Luo Hailin, deputy chief engineer at the Shanghai environmental protection bureau.

"Our evaluation is based on the air pollution index, which looks at sulfur dioxide, PM10 and oxynitride, while their assessment is based on the air quality index, which focuses on PM2.5," he said.

The US consulate said its readings are based on the air quality in the area around its downtown offices, and are published to make health data available to the US citizens living in the municipality.

"The monitor is an unofficial source for the health of the consulate community. Citywide analyses cannot be done on data from a single monitor," read a notice on the consulate's micro blog on Monday.

Fu Qingyan, chief engineer at the Shanghai Environmental Monitoring Center, said Shanghai may become the first city in the country to announce PM2.5 monitoring data in June, and it will begin using the air quality index.

"But the assessments may still show a discrepancy," she said, although Shanghai's official monitoring data for PM2.5 in the past two months shows little inconsistency with that from the US consulate.

The difference comes from the evaluation standards adopted by the two countries, which are at different stages of economic development and environmental protection, experts said. The United States uses the standard for the third stage suggested by the World Health Organization, while China uses that of the first stage.

"Productivity of countries is in different stages, and the level of science and technology is varied. It's hard to abide by a unified standard," said Qian Hua, director of the research institute of atmospheric environment under the Shanghai Academy of Environmental Sciences.

Shanghai authorities are stepping up efforts to improve air quality in addition to making preparations for building dozens of PM2.5 monitoring sites.

"The monitoring cannot help clear up the days of hazy weather, so we are focusing on actions to control the pollution and expectations of the public," said Zhang Quan, director of the Shanghai Environmental Protection Bureau, during an interview with eastday.com on May 8.

The bureau is mulling policies to tighten dust control at transportation and building construction sites and to prevent pollution from vehicle exhaust, Zhang said.

"Shanghai will adopt harsher standards for automobile emissions in the coming year to curb air pollution, which may be ahead of the nation's regulations," he said.

zhouwenting@chinadaily.com.cn