The World Health Organization on Wednesday updated its guidelines on air quality for the first time in over 15 years.
WHO Global Air Quality Guidelines (AQGs) provide clear evidence of the damage air pollution inflicts on human health, at even lower concentrations than previously understood. The guidelines recommend new air quality levels to protect the health of populations, by reducing levels of key air pollutants, some of which also contribute to climate change.
In New Delhi, the concentration of PM2.5 in 2020 was nearly 17 times higher than the recommended levels. In Mumbai, pollution levels were eight times higher, in Kolkata, over nine times higher, and in Chennai, over five times higher.
Since WHO’s last 2005 global update, there has been a marked increase of evidence that shows how air pollution affects different aspects of health. For that reason, and after a systematic review of the accumulated evidence, WHO has adjusted almost all the AQGs levels downwards, warning that exceeding the new air quality guideline levels is associated with significant risks to health.
At the same time, however, adhering to them could save millions of lives.
Every year, exposure to air pollution is estimated to cause 7 million premature deaths and result in the loss of millions more healthy years of life. In children, this could include reduced lung growth and function, respiratory infections and aggravated asthma.
In adults, ischaemic heart disease and stroke are the most common causes of premature death attributable to outdoor air pollution, and evidence is also emerging of other effects such as diabetes and neurodegenerative conditions. This puts the burden of disease attributable to air pollution on a par with other major global health risks such as unhealthy diet and tobacco smoking.
“The burden of disease attributable to air pollution is now estimated to be on a par with other major global health risks such as unhealthy diet and tobacco smoking, and air pollution is now recognized as the single biggest environmental threat to human health,” says (pdf) the United Nations agency’s new Global Air Quality Guidelines (AQGs).
A study published in February estimated that fossil fuel-related air pollution alone killed about 8.7 million people in 2018, accounting for 18% of global deaths that year.
“Air pollution is a threat to health in all countries, but it hits people in low- and middle-income countries the hardest,” WHO Director-General Tedros Adhanom Ghebreyesus said in a statement announcing the AQGs Wednesday.
“WHO’s new Air Quality Guidelines are an evidence-based and practical tool for improving the quality of the air on which all life depends,” Tedros added. “I urge all countries and all those fighting to protect our environment to put them to use to reduce suffering and save lives.”
Laura Corlin, an epidemiologist at Tufts University who studies the health effects of air pollution, detailed some of the changes in the AQGs for The Conversation on Wednesday:
The WHO cut in half its recommended limit for exposure to PM2.5, tiny particles commonly produced by cars, trucks, and airplanes, and a major component of wildfire smoke, lowering the average maximum exposure from 10 micrograms per cubic meter per year to 5.
It also tightened the limits for gaseous air pollutants like nitrogen dioxide that are produced when fossil fuels are burned by vehicles and power plants. The WHO now recommends limiting nitrogen dioxide to one-quarter of the previous level, from 40 to 10 micrograms per cubic meter.
Corlin also highlighted the health benefits of limiting PM2.5 levels in line with the new guidance.
Along with helping to prevent low birth weights, research shows cutting pollution levels decreases the chances of heart attacks and cardiovascular-related deaths, lung cancer, and Alzheimer’s disease, she explained. Further, the World Bank estimates that reducing the health burden related to air pollution exposure could save $225 billion in labour productivity and $5 trillion in health-related costs each year.
“Countries can improve their air quality by moving to cleaner sources of energy and cutting out fossil fuels, which are a major source of PM2.5. Electric vehicles can help reduce traffic-related air pollution,” the expert wrote, encouraging governments to take action.
In a Wednesday tweet, Dr Aaron Bernstein, interim director of the Center for Climate, Health, and the Global Environment at Harvard T.H. Chan School of Public Health, similarly called on governments to commit to a “healthier future” by agreeing to phase out fossil fuels at COP 26, a U.N. climate summit for world leaders that’s set to kick off in Scotland on October 31.
Aidan Farrow, a Greenpeace International air pollution scientist based at the United Kingdom’s University of Exeter, also demanded urgent action, noting a Greenpeace India analysis (pdf) that found last year air quality in all of the world’s 100 biggest cities didn’t meet WHO’s new guidelines.
“The science is unequivocal—exposure to air pollution, even at low levels, shortens lives and has serious implications for public health,” Farrow said. “The WHO has strengthened its guidelines incorporating new advances in research, but these targets for clean air are meaningless if they aren’t addressed with government action.”
“At this point, addressing air pollution is a question of political will, not technology.”—Avinash Chanchal, Greenpeace India
“What matters most is whether governments implement impactful policies to reduce pollutant emissions, such as ending investments in coal, oil, and gas and prioritizing the transition to clean energy,” he said. “The failure to meet the outgoing WHO guidelines must not be repeated.”
Emphasizing that “there is no safe level of air pollution exposure,” because even at low levels it can lead to lung cancer, stroke, diabetes, and death, Farrow argued that policies “must prioritize health and strive for continuous air quality improvements in all places.”
Greenpeace India air pollution campaigner Avinash Chanchal noted that “we have all the economically viable tools we need to solve the air pollution crisis.”
“In most parts of the world, it is more cost-effective to develop renewable energy sources, such as wind and solar, than to keep burning coal, oil, or gas, even before taking the economic burden of air pollution into account,” Chanchal said. “At this point, addressing air pollution is a question of political will, not technology.”