Explained | WHO’s air quality database and its latest update

According to the 2022 update to the World Health Organisation’s air quality database, almost all of the world’s population breathes air that is polluted beyond the accepted limits. 

April 11, 2022 09:41 pm | Updated April 13, 2022 06:56 pm IST

The story so far: The World Health Organisation (WHO), in a report last week, said that nearly 99% of the global population is breathing air that contains pollutants beyond the accepted air quality limits. The WHO made the observation after the 2022 update to its air quality database.

More than 6,000 cities spread across 117 countries are monitoring air quality and people living in low- and middle-income countries suffer the most exposure to unhealthy levels of fine particulate matter and nitrogen dioxide, the global health body said in its report. It also highlighted the need to reduce usage of fossil fuels and other steps for reducing air pollution. 

What is the air quality database ?

The air quality database is a compilation of data on air quality and the concentrations of particulate matters in the air. It was started in 2011 and has since then been periodically updated. The database intends to help in studies about diseases due to air pollution by providing robust estimates of population exposure, according to the WHO.

Each year, the WHO has been publishing the database with ground measurements of air quality and particularly the concentration of particulate matters PM 2.5 and PM 10. In 2011, observations from almost 1,100 cities across 91 countries were represented by the database for the period of 2003 to 2010. 

What is new in the current update ?

Following the fifth update to the database this year, for the first time, the database contains the ground measurements of annual mean concentrations of nitrogen dioxide, which the WHO calls “a common urban pollutant and precursor of particulate matter and ozone.” However, this data was not recorded in the previous versions of the database in 2011, 2014, 2016 and 2018. 

Also, close to 2,000 more cities/human settlements were recording the data for PM 2.5 and PM 10 since the last update in 2018. The fifth and current update to the database makes it “most extensive yet in its coverage of air pollution exposure on the ground,” the WHO said. 

Thus, the 2022 version will contain data about the annual means for PM 2.5, PM 10 and nitrogen dioxide for the years between 2010 and 2019 from 6,743 human settlements in 117 countries. The averages in the database are usually for a whole city/town and not at individual monitoring stations.

Contaminants and their effect

The database records the levels of three contaminants namely, particulate matters PM 2.5 and PM 10 and nitrogen dioxide. PM 2.5 and PM 10 represent particulate matters that have a diameter equal to or less than 2.5 microns and 10 microns respectively. The pollutants originate largely from human activities related to fossil fuel combustion, the WHO said. 

Further, the WHO warns of growing evidence pointing to the dangers of air pollution to the human body and says that even low levels of many air pollutants could cause significant harm. 

While particulate matter, especially PM 2.5, could enter deep into the lungs and the human bloodstream, causing cardiovascular, cerebrovascular and respiratory impacts, nitrogen dioxide is associated with respiratory diseases, particularly asthma. 

Key observations

Among countries in the high-income group, 17% of cities had levels of PM 2.5 and PM 10 below the WHO’s threshold, whereas in low- and middle-income countries less than one per cent of the cities were found compliant. However, the nitrogen dioxide levels in the cities showed less difference, the WHO said. 

Notably, only about 4,000 cities/human settlements across 74 countries collect nitrogen dioxide data at the ground level. Overall, 23% of people in these cities breathe levels of nitrogen dioxide that are accepted by WHO’s guidelines. 

2021 air quality guidelines

The WHO, in its latest guidelines released in 2021, specifies the annual average of the concentration limits for major pollutants. Accordingly, an annual average of 5 µg/m3 is accepted for PM 2.5 and for PM 10, the accepted level is 15 µg/m3.For nitrogen dioxide, the accepted annual average is 10 µg/m3.

Moreover, the guidelines also specify accepted 24-hour averages for the pollutants. The levels are 15 µg/m3, 45 µg/m3 and 25 µg/m3 for PM 2.5, PM 10 and nitrogen dioxide respectively. 

Steps for improving air quality

In light of the air quality data available, the WHO also prescribed some steps to be taken by governments to improve the air quality and health. It urged countries to implement national air quality standards in line with the WHO’s guidelines, usage of clean household energy, implementation of stricter vehicle emissions and efficiency standards among other measures. 

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