ShanghaiI will soon be among Chinese cities pioneering a stricter air-quality monitoring standard - in line with countries such as Japan and the US.

The new standard requires the air-quality watchdog to monitor airborne PM2.5 particles, meaning those measuring less than 2.5 microns in diameter, and publish the findings. The practice requires finer technology and monitoring facilities.

The new urban air standard is expected to be extended to other parts of China, according to the Ministry of Environmental Protection.

Compared with China's current practice, which requires monitoring only of the larger PM10 air particles, the new standard will yield more accurate readings about harmful pollution and health threats.

Health experts say PM2.5 particles pose great health risks. About 1/30th the width of a human hair, they are small enough to lodge deep into the lungs and even the bloodstream, causing long-term problems and premature deaths for some people.

Shanghai environmental officials and experts have said the city is ready for the new practice.

Zhang Quan, director of the local environmental protection bureau, said the city launched preparatory trials and research years ago regarding PM2.5 monitoring.

Once the tougher standard is adopted, results of air-quality reports will be much closer to the real feelings perceived by residents, Zhang said.

Fu Qingyan, chief engineer with the local environmental bureau, said yesterday that local stations would follow the technical guidelines provided by the national watchdog to practice PM2.5 monitoring.

The news came amid heated public discussions about sharp differences in air-pollution readings announced by the Beijing authority and the US Embassy.

The embassy used its own equipment to check PM2.5 particles and released results indicating worse pollution levels than reports by the Beijing environmental watchdog.

On Tuesday when many parts of the capital was blanketed by heavy smog, the official air-quality report suggested only slight pollution while the US Embassy rated it as "hazardous."

Websites and blogs helped spread news of the measurement gap quickly. Netizens have urged the authorities to publish PM2.5 statistics in its daily environmental report.