SHANGHAI has failed to meet a national air quality standard for the past five years according to their pilot monitoring of PM 2.5 from 2005, the city's environment watchdog said last Friday.

PM2.5 refers to small particles that affect air quality and visibility. Health experts say they pose major risks as they are small enough to lodge deep in the lungs and even enter the bloodstream, leading to premature death and long-term diseases.

Shanghai Environmental Monitoring Center (SEMC) said on Friday that they have had 24 monitoring spots in Shanghai. Monitoring results showed that the level of PM 2.5 failed to reach the national standards for grade II air quality.

A daily report on PM 2.5 level in Shanghai will likely be published from next year.

Weather experts say the smaller particles are to blame for worsening air pollution in a number of China's major cities. Last year, for example, both Shanghai and Beijing experienced "hazy" days for up to six months.

The national standards refer to a draft standards released by the Ministry of Environmental Protection in November, which includes a five-grade classification of air quality on the basis of pollution indices, with grade I being the best and grade V the worst.

According to monitoring statistics released by SEMC, since 2005 to 2010, the average annual density of PM 2.5 was 0.044 - 0.053 milligrams per cubic meter, failing to reach the level of grade II air quality, which is 0.035 milligrams per cubic meter. The statistics also showed PM 2.5 density in Shanghai was about the same or down slightly in the last five years.

Currently, Chinese cities adopt the less sensitive PM10 standard in reporting air quality.

The Ministry of Environmental Protection said it has been considering revising the present standards, and a new index standard, including the measuring of PM 2.5 and ozone density, was scheduled to be fully implemented nationwide in 2016, with pilot projects conducted in certain regions ahead of the national deadline.