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# Mathematical Model Shows How COVID-19's Impact On Emissions In China Could Save Lives

A researcher from Stanford University posted a mathematical model in a blog post this week on G-FEED demonstrating the impact of the coronavirus pandemic on China’s air pollution. The outbreak and subsequent sanctions on the economy and travel triggered a drop in pollutants so significant it could be seen from space, and it’s thought this effect could save the lives of as many as 77,000 people in the region.

Air pollution is a pressing issue in densely packed cities across the globe. The related pollutants such as nitrogen dioxide are known to trigger a wealth of potentially life-threatening health conditions, having been linked to respiratory and cardiovascular disease as well as cancer. Busy roads, backed-up air traffic, and exhaust from factories all contribute to the problem, which is why measurements of certain pollutants in China saw such a sudden dive when daily life was brought to a standstill by the spread of COVID-19.

A blog post from Stanford University Professor Marshall Burke asked whether the lives saved spared from deaths linked to air pollution could outweigh the total fatalities from the virus itself and found “the answer is a clear 'yes.'”

It's important to note that Burke makes clear this finding does not downplay the threat of COVID-19 or suggest it is a good thing, rather that a reduction in pollution results in benefits for human health.

To calculate approximately how many lives have been saved, Burke gathered data from US government sensors in Chengdu, Shanghai, Guangzhou, and Beijing measuring levels of PM2.5, particulate matter linked to death from air pollution. He calculated an average daily figure for January and February 2020 and compared this to the average daily figures for the same months from 2016 to 2019. The comparison can be seen in this graph that shows overall reductions for 2020 in all cities except Beijing.

His next task was to determine how these reductions in pollution translated into reductions in premature mortality. For this, he leaned on existing research from Guojun He, who studied the implications of the Beijing Olympics (which improved air quality in the region) on mortality rates. His team found improved air quality resulted in large reductions in mortality for children aged five and under and for adults over 65. For the under 5s, mortality increased 2.9 percent for every 1ug/m3 increase in PM2.5 and by around 1.4 percent for people over 70.

These values were considered against baseline age-specific mortality rates in the context of how much of the population was likely to be affected by air pollution, which has a localized impact so will be considerably worse in busy cities compared to more rural areas.

Burke's calculations found that a 2-month reduction of 10ug/m3 in PM2.5 will likely save the lives of 4,000 children under 5 and 73,000 adults over 70 in China, bringing the total to 77,000 people. Even in using the most conservative estimations possible, Burke’s findings put the minimum lives saved at over 53,000, almost 20 times the 3,100 lives lost in China, according to figures taken on March 8th, 2020.

“None of my calculations support any idea that pandemics are good for health,” Burke writes on his blog post. “The effects I calculate just represent health benefits from the air pollution changes wrought by the economic disruption, and do not account for the many other short- or long-term negative consequences of this disruption on health or other outcomes; these harms likely vastly exceed any health benefits from reduced air pollution.”

Burke’s model, however, does support tackling air pollution as a means to preserving human life, and should his predictions come to fruition, it asks big questions about whether as a global community we’re doing enough to monitor and reduce harmful pollutants in our cities.