Author: Li Rongde
Posted on: Caixin Global, May 19th, 2017
Beijing and parts of neighboring Hebei province and Tianjin were blanketed by smog infused with high levels of ozone late Thursday and Friday amid a heat wave sweeping across parts of northern China.
Air quality in the affected areas is expected to fluctuate between moderately and heavy polluted, largely due to a high concentration of ground-level ozone, the Ministry of Environmental Protection (MEP) said in a statement on Thursday.
The ozone level in the Chinese capital had risen to 141 micrograms per cubic meter of air by 2 p.m. on Friday and was expected to reach 225 micrograms per cubic meter later in the day, according to the Beijing Municipal Environmental Protection Bureau.
Ozone is an unstable blue gas whose molecules comprise three oxygen atoms instead of the two in molecular oxygen. Ozone can cause asthma and chronic respiratory illnesses and exacerbate other breathing problems, according to the World Health Organization (WHO).
Low-altitude ozone is produced through a chemical reaction between nitrogen oxides and volatile organic compounds, the WHO said. Ozone can also damage crops and is a major source of greenhouse gases.
When the concentration of ozone rises to 200 micrograms per cubic meter of air, it can cause headaches, irritate the throat and create a burning sensation in the eyes, the WHO said.
Much of northern China has been hit by a heat wave since Tuesday, with maximum temperatures around 35 degrees Celsius for four days in a row, while the wind was too weak to blow away the pollutants.
Ozone pollution has been on the rise in China in recent years, particularly in the Pearl River Delta, the southern manufacturing heartland known as the “world’s factory,” according to Ma Jun, the director of the Institute of Public and Environments Affairs, a Beijing-based nongovernmental organization. The government can better control ozone levels by targeting motor vehicles, power generators and coal-fired boilers as well as cement plants whose pollutants include nitrogen and other volatile organic compounds, Wang Qifeng, a scientist of environmental studies in Beijing, told Science and Technology Daily.
Ozone can choke cities for days even when the levels of fine particulate matter in the air are low and the sky appears to be clear, he said.
It remains an invisible health hazard because no concrete research can quantify the damage from ozone pollution, Ma said.
The average ozone levels in the Chinese capital has been rising steadily until 2015, the latest year for which data is available from the Beijing Municipal Environmental Protection Bureau. It rose from an annual average of 183.4 micrograms per cubic meter of air in 2013 to 197.2 in 2014 and jumped to 226, a peak for 2015. Ozone levels under 160 micrograms per cubic meter of air is considered safe in China, and the 2015 figure was 27% higher than the national standard. Ozone levels rose to unsafe levels mostly from April to October, the city’s Environmental Protection Bureau said.
The bout of ozone pollution will start to weaken on Saturday as strong winds blow through Beijing and its surrounding areas, the MEP said.
The bad-air spell follows weeks of clear skies in Beijing, Tianjin and Hebei partly due to traffic and manufacturing curbs ahead of a major international forum on China’s ambitious trade plan, the Belt and Road initiative.