Ningbo's air quality met national standards on 86.7 percent of days in 2019, ranking sixth in Zhejiang province. [Photo/cnnb.com.cn]

Ningbo's air quality met national standards on 86.7 percent of days over the last year, ranking sixth in Zhejiang province, according to a recent report released by the Ningbo municipal bureau of ecology and environment.

In 2019, the average PM2.5 level in 14 counties and districts administered by Ningbo was 29 micrograms per cubic meter, 6.5 percent lower than the previous year.

PM2.5 readings are a measure of the density of hazardous particulates in the air. The World Health Organization recommends an annual PM2.5 level of 10 micrograms per cubic meter.

Experts from the Ningbo municipal bureau of ecology and environment noted that ozone is a prime air pollutant in the city, whose appearance is closely linked to the seasons.

The density of ozone in the air is at its peak from May to August.

The report also showed that the air quality in Xiangshan county, Daxie Development Zone and Ninghai county is relatively good, while in Cixi city, Yuyao city and Jiangbei district it is relatively poor.