Different standards leave air quality grades divided

The environmental protection bureau of Shanghai municipality said Tuesday that the bureau and the U.S. consulate in the city have given different assessments for the city's air quality because of different standards.

An official speaking on condition of anonymity said China has adopted the Air Pollution Index (API) as its air quality rating system, while the U.S. Consulate General in Shanghai rates air quality based on the Air Quality Index (AQI), leading to differing grades.

The official made the statement after the consulate released air quality data online on Monday, rating the city's air quality as "unhealthy." The city's environmental protection bureau rated the air quality as "good" on the same day.

The consulate said the concentration of PM2.5 particles at 6 p.m. Monday was 67 micrograms per cubic meter, while official data from two monitoring stations operated by Shanghai Environmental Protection Bureau set the concentration at 58 and 59 micrograms, respectively, according to data released by both sides.

"The data released were basically consistent, but the U.S. has adopted a stricter air quality rating standard than we are currently using," the official said.

The U.S. consulate clarified on its website that the data released is only an indicator of overall air quality near its offices and cannot represent city-wide air quality.

The PM2.5 gauge is considered stricter than the PM10 standard previously in China, as it monitors "fine" particulate matter 2.5 microns or less in diameter.