(CNN)New air quality guidelines published on Wednesday by the World Health Organization could prevent millions of deaths globally each year, the UN agency said.
Fine particulate matter, or PM 2.5, is the tiniest pollutant yet also among the most dangerous. When inhaled, it travels deep into lung tissue where it can enter the bloodstream and can contribute to asthma, cardiovascular disease and other respiratory illnesses.
The new guidelines, which hadn't been updated in 15 years, recommend the concentration of this harmful substance be halved in the world's air, from 10 micrograms per cubic meter to 5.
In 2016, around 4.1 million premature deaths — more than half of the total deaths attributable to air quality issues — were associated with fine particulate matter. If the new 2021 air quality guidelines had been applied then, there could have been a nearly 80% reduction in PM 2.5-related premature deaths, or 3.3 million fewer deaths, according to the UN agency.
The guidelines, which are designed to help governments craft air quality regulations, also include other major health and climate-damaging pollutants, both outdoor and indoor, such as PM 10 — particulate matter larger than PM 2.5 — as well as ozone, nitrogen dioxide, sulfur dioxide and carbon monoxide.
The report comes as world leaders meet in New York for the 76th United Nations General Assembly to tackle the twin crises of the Covid-19 pandemic and climate change. Dorota Jarosińska, the international agency's technical lead, who helped develop the new global guidelines, called the new update a "triple-win scenario," as it not only protects public health and improves air quality, but also mitigates the climate crisis.
"These guidelines reinforce the need for urgent action that would benefit the health of all, including vulnerable populations," Jarosińska told CNN. "This creates a triple-win scenario for the benefit of air quality, climate action and health, and is one of the elements postulated by WHO Manifesto for a healthy recovery from Covid-19."
The latest guidelines also support recent research that found air pollution is most likely a contributing factor to health burden caused by Covid-19. Fine particulate matter comes from sources like the burning of fossil fuels, wildfires and agriculture, and is linked to a number of health complications including asthma, heart disease, chronic bronchitis, and other respiratory illnesses — all underlying conditions that make people vulnerable to severe outcomes from Covid-19.
People with these underlying medical conditions are at greater risk of developing the most severe outcomes from Covid-19 infection, the research showed. Researchers have already seen a particularly strong connection between the rise in Covid-19 cases and air pollution from wildfires. A recent study published in August found that increases in PM 2.5 from wildfire smoke in 2020 led to a surge in Covid-19 cases and deaths across the Western US.
Tarik Benmarhnia, a climate change epidemiologist at Scripps Institution of Oceanography who studied the health impacts of wildfire smoke, said the new guidelines could have been more ambitious than just reducing air quality threshold levels, calling the scope of the new update "a bit underwhelming."
"There are a lot of evidence that's been produced in the last few years showing that even at the lowest levels of air pollution, including PM 2.5 and nitrogen dioxide, there is still a huge impact at the population level," Benmarhnia told CNN.
Global assessments of ambient air pollution alone suggest hundreds of millions of healthy years of life lost, with low and middle-income countries the hardest hit. Still, many countries don't meet the WHO's recommended guidelines. In India, where the air in vast parts of the country is often clogged by smoke from industries, recent research showed people could achieve nearly six years of life expectancy if they strictly met air quality guidelines.
In the US, people of color and low-income communities suffer disproportionately from air pollution. A recent study found that 78% of Black Americans are exposed to higher-than-average concentrations of pollution from every type of source, including industry, agriculture, construction and vehicles.
These same communities also face the greatest impacts of the climate crisis. Some air pollutants including methane — a potent greenhouse gas — as well as the components of soot and urban smog are short-lived climate pollutants, which have been linked to the near-term warming of the planet. They are described as "short-lived" because they persist in the atmosphere for as little as a few days to months.
Despite this, Benmarhnia said the new guidelines could have widened the scope and included more types of sources of emissions in the context of tackling the climate crisis. Still, he adds it gives governments an opportunity to identify more pollution sources and push for more robust policies on their own based on these guidelines.
"This is just one tool, among many others, and it should not be taken for granted," he said. "It should be some kind of advocacy tool to show that we need to reduce more and more exposure to air pollution."
The new guidelines reflect the conclusions of the major UN state-of-the-science report on climate change released in August, which calls for strong, rapid cuts on short-lived climate pollutants, particularly methane emissions, to improve air quality and mitigate the worst effects of climate change.
"Much of air pollution comes from the same sources that are driving climate change, mainly from burning of fossil fuels," Jarosińska said. "Therefore, addressing air pollution goes hand in hand with the global climate action — efforts to improve air quality will contribute to climate change mitigation. In turn, climate change mitigation efforts also improve air quality."
With clearer insights on pollution or emissions sources, WHO is also calling on world leaders to phase out fossil fuels, particularly coal and biomass-fuel combustion. The disparities in air pollution exposure have been stark and are increasing worldwide due to large-scale urbanization and economic development that has recently been largely reliant on burning fossil fuels unsuitable for the planet.
And as the world's top leaders gather in the chambers of the UN General Assembly this week to address the warming planet ahead of the critical UN climate change conference in Glasgow, Scotland, in November, the new air quality guidelines underscore the need for countries to rapidly reduce emissions for healthier air and to mitigate the climate crisis.
Benmarhnia said it's also important for leaders to note that the new update is not a "one size fits all" solution since countries are not made equal in terms of air quality and the different climate disasters they face.
"Registering inequalities in terms of exposure but also in terms of susceptibility impacts associated with air pollution is important," he said. "Hopefully, the next guidelines will be a little bit more comprehensive in taking into account the heterogeneity of sources of emission and the composition of particulate matter in the context of climate change."