In its largest release of data on air quality ever, WHO has found that most of the world’s population are breathing unsafe levels of air pollutant – particularly fine particulate matter (PM2.5)  and Nitrogen dioxide (NO2) – which cause excess illness and premature death from respiratory disease, as well as from cardiovascular disease and cancers. 

“Air Quality is poorest in specific regions, like the Eastern Mediterranean Region, the Southeast Asian region and also Africa, said Sophie Gumy, WHO technical officer of the updated data at a press briefing on Monday.  

Of the 117 countries now monitoring air quality, only 17% of cities and settlements, in mostly high-income areas, have air that meets WHO’s recently-updated Air Quality Guidelines for particulate matter.    

In low- and middle-income countries, less than 1% of settlements that measure air quality comply with WHO recommended thresholds for small particles – the pollutant most closely associated with air pollution-related premature mortality.  

Globally, only about 1% of the world’s population breathes air that meets WHO air quality standards, according to the new WHO assessment, which also analyzed air quality data from satellite images and measurements, along with the ground monitoring data collected from 6,000 cities and settlements across the world.

Compared to the last analysis of air quality data by WHO in 2018, the proportion of cities and settlements compliant with WHO air quality guidelines, has in fact dropped sharply. That is due to the fact that WHO tightened its limits for key pollutants like PM 2.5 and NO2  in 2021. 

The 2021 WHO guidelines cut the annual average limit for safe PM2.5 by one-half, from 10 to 5 micrograms per cubic meter of air (10µg/m3 to 5µg/m3). The limit for safe NO2 levels was reduced by three-quarters. The WHO update was based on over a decade’s worth of new evidence that has strengthened the link between death and illness from key air pollutants.   

In terms of air pollution levels, China, once considered the world’s air pollution hot spot still has dozens of cities with annual PM2.5 air pollution levels that are 15-30 times higher than WHO’s new guideline average of 5µg/m3.  But it is now outpaced by India where Delhi reported an average annual PM2.5 level of 105 µg/m3, 21 times higher than WHO’s new guideline limit for PM2.5, according to 2019 data. 

However, the latest data published by WHO on Delhi hearkens back to 2014. Although more recent Indian data is available, a lack of endorsement from government officials can leave WHO unable to publish more recent synthesis of the numbers.

In the Eastern Mediterranean region, which stretches from Afghanistan as far west as Morocco, cities in Pakistan, Iran, Iraq, Egypt and Gulf States like Saudi Arabia and Bahrain were among those with the biggest air quality problems – with some cities exceeding WHO guidelines by a factor of 20 or more. However, there are comparatively fewer settlements measuring air pollution at all.  In Africa, only about 200 cities have reported data, with South Africa among the few countries consistently reporting. Bamenda, Cameroon and Kampala, Uganda were among the continent’s hot spots, with 132 µg/m3 and 104 µg/m3 of average annual PM 2.5 respectively.

Some politicians in arid parts of the Middle East, Asia and Africa argue that dust storms drive up measured levels of particulate air pollution in many cities of the region, distorting the data. However, the fact that NO2 levels, produced by both gasoline and diesel vehicles, also are very high, reflects the fact that overall, air pollution is still largely a product of humans, said Gumy.  In addition, WHO measurements are based around annual averages of air pollution, and not peaks that occur during dust storms.  

Rich regions fare much better

In WHO’s European region, the highest air pollution concentrations are several orders of magnitude lower than Asia and Africa.   Major hotspots were in Tajikistan, Bosnia and Herzegovina, Turkey, Poland and Czechia, where PM2.5 concentrations ranged from 8-14 times higher than WHO Guideline limits – while the United Kingdom, Israel, Spain  and France also showed mediocre results – although in the case of many European cities, as well, data is five years or more out of date.  On the other end of the spectrum,  cities in Scandanavia, Germany,  Finland and Estonia, Spain  were among the lucky ones with the best air quality, meeting WHO recommended limits.

In the Americas, cities and towns in North America’s Canada and the US boast the cleanest air, with hundreds meeting the WHO guidelines for PM2.5 – while those in Latin America generally fare worse.

Globally, NO2 pollution levels much more evenly distributed between rich and poor regions of the world – reflecting perhaps the lower priority that has been placed in curbing emissions of this pollutant -heavily emitted by diesel and gasoline vehicles – and even those newer models.

NO2 had been receiving more and more notice, however, from both health and climate activists. It is a leading ingredient in the development of ground-level ozone, which is in turn a short-lived climate pollutant. It now understood as a major factor in childhood asthma. And ozone also stunts crop growth as it drifts from cities across nearby rural areas – which in turn lowers economic outputs and creates risks for food security.

Unprecedented number of cities collecting air pollution data 

The new WHO report is the first to capture data on NO2.  It found that about 4,000 cities/human settlements in 74 countries are now collecting and publicly reporting on nitrogen dioxide levels.   Among those, only 23% of cities and communities meet WHO  annual average concentrations for NO2, now set at 10 µg/m 3.  The WHO guideline limit for NO2 was also sharply last year reduced from its previous limit of 40 µg/m3  – based on new data about the associations between nitrogen dioxide exposures and chronic respiratory illnesses, including childhood asthma. 

The new WHO reflects the unprecedented number of cities worldwide that are now collecting data on air quality, which is a good thing – despite the results that the data reveals, WHO officials said.  

“This report shows that some 6000 cities are now monitoring the quality of the air that we are breathing,” said Maria Neira, Director of WHO’s Department of Environment, Climate Change and Health.

“Maybe we can say that 6000 is not enough. We have many cities around the world but compare with what’s happening previews here. This is a very important increase in the willingness by cities to measure the quality of that we are breathing.” 

Speed up clean energy transition – WHO Director General 

Along with traffic, other major sources of ambient (outdoor) air pollution include: industry, waste incineration, particularly in open areas in low- and middle-income countries, and the use of highly polluting coal, kerosene and biomass for heating and cooking in poor households.  

Together, air pollution is estimated to kill some 7 million people a year, WHO says.  

Particulate matter, especially PM2.5, is capable of penetrating deep into the lungs and entering the bloodstream, causing cardiovascular, cerebrovascular (stroke) and respiratory impacts.  There is emerging evidence that particulate matter impacts other organs and causes other diseases as well.

NO2 is associated with a range of chronic respiratory diseases, including asthma, leading to respiratory symptoms (such as coughing, wheezing or difficulty breathing), hospital admissions and visits to emergency rooms. 

Most of the sources of air pollution are also climate drivers, particularly fossil fuels used in transport, heating and electricity production. And that highlights further the urgency of transitioning to cleaner and greener energy, WHO stressed in a press statement.

“Current energy concerns highlight the importance of speeding up the transition to cleaner, healthier energy systems,” said Dr Tedros Adhanom Ghebreyesus, WHO Director-General.  “High fossil fuel prices, energy security, and the urgency of addressing the twin health challenges of air pollution and climate change, underscore the pressing need to move faster towards a world that is much less dependent on fossil fuels.”

WHO also called for policymakers to accelerate adoption and enforcement of national air quality standards in line with the latest WHO Air Quality Guidelines. Many countries that suffer from air pollution, such as India, still have air pollution limits that far exceed those deemed safe by WHO – although those, too, are regularly exceeded during peak air pollution periods such as the late autumn.

Countries and cities also need to do more to identify key sources of air pollution and then support transition to cleaner alternatives for energy, transport and waste management in particular, WHO said.  Those include: 

• Support the transition to exclusive use of clean household energy for cooking, heating and lighting; 
• Build safe and affordable public transport systems and pedestrian- and cycle-friendly networks
• Implement stricter vehicle emissions and efficiency standards; and enforce mandatory inspection and maintenance for vehicle
• Invest in energy-efficient housing and power generation
•  Improve industrial and municipal waste management;
• Reduce agricultural waste incineration, forest fires and certain agro-forestry activities (e.g. charcoal production).

–Updated 14 April, 2022, with 2019 value for air PM2.5 pollution in Delhi, replacing the older 2014 value.

Image Credits: Rashed Shumon, V.T. Polywoda, World Health Organization , Flickr, World Health Organization , Flickr – joiseyshowaa.