East China's Zhejiang Province on Sunday began releasing the PM2.5 index in seven of its cities' air quality readings, local authorities said.

Based on the average data for Saturday, which was released Sunday via the website of the provincial environmental protection department, the indices released for all of the cities fell within the upper limit of 70 micrograms per cubic meter as regulated by the newly-enforced national air quality standard, said Zhang Fujian, an official with the department.

The seven cities are the provincial capital of Hangzhou, Ningbo, Wenzhou, Huzhou, Jiaxing, Shaoxing and Zhoushan. Among them, the highest index was monitored in Ningbo at 49 micrograms per cubic meter, and the lowest in Zhoushan at 30 micrograms per cubic meter.

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

To monitor the data, 16 stations have been established in the seven cities, and the number will increase to 153 by the end of 2014, covering every county in the province, according to Zhang.

The province will also cooperate with neighboring Jiangsu Province and Shanghai Municipality on pollution control and improving air quality, he said.