China could prevent 330,000 premature deaths a year by 2050 by cutting its ozone-forming gas emissions by 60 per cent, according to a joint study by American and Chinese researchers.
The research, led by scientists at Columbia University in New York, also found that more cuts in greenhouse gas emissions would further reduce premature deaths of adults caused by surface ozone.
Following the country's progress in recent years in combating air pollutants, especially fine particulates PM2.5 and PM10, surface ozone has emerged to be the top air pollutant in some Chinese cities, according to government data.
Surface ozone is formed by the photochemical reactions of other air pollutants like nitrogen oxides and volatile organic compounds (VOCs), and scientists have found that a warming climate accelerates such reaction.
According to the US Environmental Protection Agency, ozone can affect the muscles in a person's airways and increase the frequency of asthma attacks, make lungs more susceptible to infection and cause chronic obstructive pulmonary disease.
Previous research estimated that in 2015 alone, 67,000 premature deaths in China were attributed to ozone, but more recent studies suggest that figure might have been understated.
In the new study published on Tuesday in Environmental Research Letters, a peer-reviewed scientific journal, the researchers simulated different scenarios for comparison with the situation in 2015. They found that ozone increases due to climate change alone would cause an additional 62,000 premature deaths a year by 2050.
Once the growth of ozone-forming pollutants like nitrogen oxides and VOCs was also taken into account, the forecast for the number of additional premature deaths rose to 80,000 a year.
But researchers found that if China could instead cut these ozone precursor emissions by 60 per cent, it would result in more than 330,000 annual premature deaths being avoided by 2050.
In comparison, a Peking University study published in 2016 estimated that PM2.5 caused 1.37 million premature deaths in China in 2013.
"Compared with PM2.5, the premature deaths caused by ozone pollution are fewer, but they can't be ignored," said Wang Shuxiao, professor at the school of environment at Tsinghua University and a co-author of the new study.
She said that in recent years in many regions, the concentration of ozone pollutants had increased in the troposphere - the lowest layer of the atmosphere - and that it had an important influence on human health and crops.
According to the study, curbing ozone precursors would have the most significant impact on premature deaths in eastern China, where both population and ozone concentrations are highest.
But Zhang Yuanhang, a professor at the College of Environmental Sciences and Engineering at Peking University, said the challenge of cutting ozone could be greater than reducing PM2.5 particulates, which do not involve the complication of photochemical reactions.
A separate study by Peking University in 2018 showed that even though PM2.5 concentrations in 33 northern cities fell in the 2013-17 period, the average daytime ozone levels jumped sharply.
In 20 of the cities monitored, the average concentration of the pollutant in summer exceeded the World Health Organisation's standard of 100 grams per cubic metre, and in 10 of these cities, the concentration rose even by 40 per cent.
Daniel Westervelt, the lead author of the new study and an associate research scientist at Columbia University's Lamont-Doherty Earth Observatory, said that was important to think about what changes could be made to tackle the ozone problem.
"It's worth it to address these emissions now, so that you don't have to deal with all the health problems in the future," he said. "You could save 330,000 … that's a lot of lives."
Copyright (c) 2019. South China Morning Post Publishers Ltd. All rights reserved.Artikel Asli