Ozone air pollution in Shanghai has worsened since last year, according to a report issued by the environment authority yesterday.
Ozone O3 pollution is created near the Earth's surface by the action of daylight ultra violet rays, and therefore occurs more often in summer.
Pollutants of volatile organic compounds and nitrogen oxide resulting in part from manufacturing processes can cause an excess amount of ozone, which can harm lung functions and irritate the respiratory system.
According to the 2016 Shanghai Environmental Bulletin, the average concentration of ozone monitored daily in the eight peak hours of a day last year reached 164 micrograms per cubic meter, a 1.9 percent increase on 2015.
Ozone has become the second major air pollutant for Shanghai after PM2.5, the tiny particles that are hazardous to health.
About 10 percent of the days in the first five months of this year reported an excess level of ozone, a slight increase on the same period last year, according to a report issued by Shanghai Environmental Protection Bureau yesterday.
"The warmer weather in April was one of the factors that caused more ozone pollution this year," said Liu Dailing, deputy director of the bureau's pollution emission control division. "The formation of ozone is more complicated than other air pollutants," she added. "Nitrogen oxide and volatile organic compounds are two major sources of ozone pollution, and the control of them will be one of our major priorities."
Zhou Jun, deputy director of the environmental bureau's pollution control division, told Shanghai Daily that the bureau would introduce strengthened measures this year to control the discharge of nitrogen oxide and volatile organic compounds.
According to the bureau's report, the index of other major air pollutants in Shanghai fell in the first five months of the year. The average density of PM2.5 was 43 micrograms per cubic meter, a 24.6 percent decrease compared to the same period last year. The nation's yearly average is 35.
The average density of PM10, SO2 and NO2 also saw a decrease of 16.4 percent, 23.5 percent and 2.1 percent respectively.
In the first five months, 78.8 percent of the days recorded an excellent or good air quality, an 8.4 percent increase compared to the same period last year. No severe air pollution was reported.
Shanghai's surface water quality also saw some improvement in the first five months.