The World Health Organization (WHO) on Wednesday revised its more than a decade old Global Air Quality Guidelines (AQGs), making them further stringent, prompting the experts to suggest India too should revise its guidelines.

The new WHO AQGs provide a 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.

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The new AQGs recommend annual average of PM 2.5 to just 5 from the 2005’s 10 Ig/m3. Similarly, PM10 has been recommended down to 15 from the previous 20 Ig/m3.

The guidelines focus on Particulate Matter (PM 2.5 and PM 10), Ozone (O3), Nitrogen Dioxide (NO2), Sulphur Dioxide (SO2) and Carbon Monoxide (CO). When action is taken to reduce these classical pollutants, it also has an impact on other pollutants, the guidelines said.

For the AQGs, more than 500 papers were identified for systematic review and synthesised to get the most up-to-date evidence for establishing the new AQG levels.

“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,” the WHO said in a global release.

“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.

Exposure to air pollutants is heavily dependent on their ambient concentrations. For example, ambient PM 2.5 concentrations vary substantially between and within regions of the world. More than 90 per cent of the global population in 2019 lived in areas where concentrations exceed the 2005 AQG level of 10 Ig/m3. Now, with the 2021 AQG level being lower, there will subsequently be an increase in the attributable health burden in all countries.

Data shows that in 2019, annual population-weighted PM 2.5 concentrations were highest in the WHO South-East Asia Region and then in the Eastern Mediterranean Region.

Based on the extensive scientific evidence currently available, the guidelines identify the levels of air quality necessary to protect public health worldwide. The AQGs also serve as a reference for assessing if, and by how much, the exposure of a population exceeds levels at which it might cause health concerns.

Air pollution is considered the greatest environmental threat to health, and it disproportionately affects vulnerable populations: 91 per cent of deaths from ambient air pollution occur in low-income and middle-income countries.

In India, 1,16,000 infant deaths in 2019 were attributable to air pollution, coal combustion was attributable for 1,00,000 deaths while ambient air pollution killed 16.7 lakh Indians, data released by the Indian Council for Medical Research (ICMR) showed.

India’s National Clean Air Programme (NCAP) has a target to reduce 20-30 per cent of PM 2.5 and PM 10 concentrations by 2024, taking levels in 2017 as the base year. Integrating the top 10 cities from WHO’s most polluted cities’ list, 122 non-attainment cities were identified for NCAP, which did not meet India’s National Ambient Air Quality Standards (NAAQS) for the period of 2011-15.

NAAQS standards were notified by the Central Pollution Control Board (CPCB) to ensure “protection of health”, among other reasons.

“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 PM 2.5 averages in India vs WHO’s 2005 annual limit of 10 ug/m3, most Indian cities failed to meet even those levels,” said S.N. Tripathi, a professor at the Indian Institute of Technology-Kanpur, and steering committee member, NCAP.

“In parallel, we have to strengthen our health data and revise the National Ambient Air Quality Standard 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 PM 2.5 composition,” Tripathi added.

Poornima Prabhakaran, Deputy Director, Centre for Environmental Health, Public Health Foundation of India, said: “India’s existing NAAQS were already less stringent compared to previous air quality guidelines by WHO, allowing cities to consider an incremental approach to achieving interim targets through assessment of local sources of air pollution. More stringent guidelines by WHO necessitates a greater focus on health impacts of air pollution during the proposed revision of India’s NAAQS in 2022.”

And it is not just India that needs to relook at its actions vis-a-vis air pollution. Experts have pointed out that entire South Asia and South-East Asia need stringent measures.

“This is a public health emergency, affecting the lives of people all over the world, with the worst impacts in South Asia. Governments across South Asian countries need to urgently align their national air quality standards with the latest WHO guidelines,” said Arvind Kumar, Founder, Lung Care Foundation, and Chairman, Institute of Chest Surgery, Chest Onco Surgery and Lung Transplantation.

Achieving the recommended AQG levels will deliver substantial health benefits globally. The WHO has performed a rapid scenario analysis to assess the health gains attributable to improved annual ambient particulate matter concentrations, if the AQG levels were achieved. Around 80 per cent of deaths attributed to PM 2.5 exposure in the world could be avoided if countries attain the annual AQG level for PM 2.5.

Reaching the interim targets also offers substantial benefits for health. For example, attainment of interim target 4 for PM 2.5 (the same level as the AQG from 2005) would result in a nearly 48 per cent decrease in total deaths attributed to PM 2.5 exposure. The highest impact would be observed in the South-East Asia and African regions (57 per cent and 60 per cent reduction, respectively), the WHO said.

Results clearly demonstrate a major reduction in the estimated burden of disease, even if other analyses may yield different estimates due to different assumptions made. The WHO scenario analysis showed that if the interim targets were achieved, the greatest benefit in terms of reduced burden of disease would be observed in countries with high PM 2.5 concentrations and with large populations. Results are significantly different for high-income countries, as in most cases the PMa 2.5 ambient concentrations in these areas are already below the interim target.

Among the number of recommendations, Greenpeace said the actions needed include encouraging national governments to urgently seek alternatives to burning fossil fuels for power, transport and industry because burning coal, oil and gas are major sources of the global burden of disease and mortality from air pollution and also encourage national governments to prioritise provision of transport infrastructure that revolves around walking and cycling — or for longer distances and people with additional needs, electric buses, trams and trains — and stop using fossil fuelled modes of transport.