BEIJING, May 25 (Xinhua) -- The Ministry of Environmental Protection has required 74 cities to apply a more comprehensive air quality monitoring standard and publish daily reports on PM2.5, a hazardous airborne pollutant, by the end of 2012.

Cities in the Beijing-Tianjin-Hebei region, Yangtze River Delta and Pearl River Delta, as well as southwest China's Chongqing municipality and all provincial capitals fake ray ban sunglasses, have been asked to monitor for PM2.5 starting in October and publish monitoring results before the year's end, according to a notice posted on the ministry's website.

China currently classifies air quality according to a five-tier system, with grade I being the highest quality and V the lowest. Current standards call for monitoring for PM10, sulfur dioxide and nitrogen dioxide.

The new standard will include monitoring for more pollutants, including ozone, carbonic oxide and PM2.5.

PM2.5 refers to fine particulate matter 2.5 microns or less in diameter. The particles are considered to be more hazardous than larger particles, as they can penetrate more deeply into the lungs.