WHO launches new air quality guidelines after 16 yrs; recommends new AQ levels

Geneva: The World Health Organisation (WHO) released a revised Global Air Quality Guidelines on Wednesday, announcing more stringent limits for six pollutant categories —particulate matter (PM), ozone (O3), nitrogen dioxide (NO2) sulfur dioxide (SO2) and carbon monoxide (CO).

The latest WHO guidelines 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. 

“Air pollution is a threat to health in all countries, but it hits people in low- and middle-income countries the hardest,” said WHO Director-General Tedros Adhanom Ghebreyesus said at the virtual launch of the guidelines. 

“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. I urge all countries and all those fighting to protect our environment to put them to use to reduce suffering and save lives,” he further said.

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. Taking cognisance of these factors, the WHO has adjusted almost all the air quality norms 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.

"Since the last update in 2005, a substantial new body of evidence has accumulated, further demonstrating the degree to which air pollution affects all parts of the body, from the brain to a growing baby in a mother’s womb, at even lower concentrations than previously observed,” the WHO Director-General stressed.

WHO’s revised guidelines prescribe annual PM2.5 average at 5 ug/m3, bringing it down from 2005 limits set at 10 ug/m3. PM10 annual average is now 15 ug/m3 in comparison to the earlier norm of 20 ug/m3. NO2 levels, which are primarily attributable to vehicular emissions, have been revised to 10 ug/m3, in comparison to 40 ug/m3 in 2005. 

"These new guidelines will have major implications for public health. They provide a practical tool for improving air quality around the world, and a robust evidence-base for developing national and local air quality standards,” Ghebreyesus said.

While these guidelines not legally-binding, the WHO recommendations on air quality are an evidence-informed tool for policymakers to guide legislation and policies, in order to reduce levels of air pollutants and decrease the burden of disease that results from exposure to air pollution across the world.

“It is common knowledge that lesser the exposure, the healthier is the outcome. WHO by reducing the PM2.5 and 10 exposure levels under the new air quality guidelines has reemphasised the need for putting in more efforts to control particulate matter concentration in air. But for countries like India, it is a huge challenge to meet these guidelines. Nonetheless I hope that efforts by all stakeholders will be intensified so as to make honest efforts to aim towards the revised levels,” Dr Arun Sharma, director of ICMR’s National Institute for Implementation Research of Non-Communicable Diseases said.

As low-and-middle-income countries like India experience increased disparities in air pollution exposure due to large-scale urbanisation and economic development which has largely been driven by fossil fuels, it has resulted in an unequal burden of disease and mortality for its population. 

India last revised its National Ambient Air Quality Standards in 2009 —setting annual averages for PM2.5 (40 ug/m3), PM10 (60 ug/m3) and NO2 (40 us/m3) — which were more relaxed in comparison to WHO's 2005 guidelines and other South Asian countries like Bangladesh, Pakistan and Nepal. The WHO guidelines, also often referred to as ‘safe levels’, ring the assumption that they will lower the risk of disease or death. In 2013, outdoor air pollution and particulate matter were classified as carcinogenic by WHO’s International Agency for Research on Cancer (IARC).

An analyst at Centre for Research on Energy and Clean Air, Sunil Dahiya stressed the need for India to revise it air quality standards in view of the elevated pollution level in the country. 

“It’s been more than a decade that India notified the national ambient air quality standards in 2009 and lot of new evidence on impacts of different pollutants on human health at lower pollution levels have come into existence necessitating it for Indian government to revise the standards similar to WHO’s action,” Dahiya said, adding, “The good thing is that India is already working on revising the standards, we just need to make sure we make use of evidence gathered by WHO and others on increasing and severe health impacts of pollutants at lower levels and try to aim towards moving closer to WHO prescribed levels for pollutants.”

Both PM2.5 and PM10 are capable of penetrating deep into the lungs but PM2.5 can even enter the bloodstream, primarily resulting in cardiovascular and respiratory impacts, and also affecting other organs. PM is primarily generated by fuel combustion in different sectors, including transport, energy, households, industry, and from agriculture. While these guidelines are not legally binding for countries, the new recommendations for air quality standards, if adopted by nations, can save millions of lives and contribute to climate change. 

Out of 100 global cities in 2020, 92 exceeded WHO's revised 2021 air quality guidelines, which include 5 Indian cities as well. Delhi's annual PM2.5 trends in 2020 was 16.8 times more than WHO's 2021 guidelines of 5 ug/m3, while Mumbai's exceeded 8-fold, Kolkata 9.4, Chennai 5.4, Hyderabad seven-fold and Ahmedabad exceeded 9.8-fold.

Professor SN Tripathi of Indian Institute of Technology Kanpur and a steering committee member of the National Clean Air Programme said there is no two ways about the need for revising India's air quality standards to make them more stringent. 

“Even at the current relaxed standard of 40 ug/m3 for annual PM2.5 averages in India vs WHO's 2005 annual limit of 10 ug/m3, most Indian cities failed to meet even those levels. In parallel, we have to strengthen our health data and revise the National Ambient Air Quality Standards accordingly. Raw health data is required to conduct a large range of health studies vis-a-vis air pollution impacts for India's varied demography, exposure and differing PM2.5 composition. A single exposure prevention response will not suit the Indian population,” he said.

Air pollution is considered the greatest environmental threat to health, and it disproportionately affects vulnerable populations:91% of deaths from ambient air pollution occur in low-income and middle-income countries. In India, 116,000 infant deaths in 2019 are attributable to air pollution, while burning coal combustion resulted in 100,000 deaths and ambient air pollution killed 16.7 lakh Indians. Children are also especially vulnerable, as exposure to air pollution in early childhood can lead to reduced lung capacity. Globally, approximately 15% of deaths from Covid-19 are linked to PM2.5 air pollution.

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. 

Air pollution is one of the biggest environmental threats to human health, alongside climate change. Improving air quality can enhance climate change mitigation efforts, while reducing emissions will in turn improve air quality. By striving to achieve these guideline levels, countries will be both protecting health as well as mitigating global climate change.