Context: Recently, the World Health Organisation (WHO) has released new Global Air Quality Guidelines (AQGs). This is WHO's first-ever update since 2005 that has tightened global air pollution standards.

• It warned that air pollution is one of the biggest environmental threats to human health, causing seven million premature deaths a year.

Key highlights of the new air quality guidelines

• Harms from air pollution begin at much lower levels than previously thought, hence, lowered acceptable thresholds for several pollutants, including ultrafine PM2.5.
• These guidelines are not legally binding on countries, but are meant to provide guidance to help reduce levels of air pollution.
• It does not include recommendations about pollutant mixtures or the combined effects of pollutant exposures.

Thresholds
Average 24-hour exposure

• PM2.5 must remain below 15µg/m³, down from 25µg/m³.
• PM10 particles has been lowered from 50 to 45µg/m³.

Exposure over a year-long period

• PM2.5 has been brought down from 10 to 5µg/m³.
• PM10 has been brought down from 20 to 15µg/m³.

In comparison, India’s thresholds are many folds higher.

• According to the 2009 National Ambient Air Quality Standards still in force, the acceptable PM2.5 exposure limit over 24 hours is 60µg/m³ (four times the new WHO limit) and for exposure over a year-long period, 40µg/m³ (eight times the revised WHO threshold).
• There are also standards for a host of chemical pollutants including sulphur dioxide, lead and nitrogen dioxide.

Improvements in air quality

• Despite some improvements in air quality, the global toll in deaths and lost years of healthy life has barely declined since the 1990s.
• Air quality has markedly improved in high-income countries, it has generally deteriorated in most low- and middle-income countries, in step with large-scale urbanization and economic development.

Important observations

• As per the new guidelines, among 100 global cities, Delhi’s annual PM2.5 trends in 2020 was 16.8 times more than WHO’s revised air quality guidelines.
• Annual average PM2.5 levels in Delhi ranged from 114-145µg/m³ in 2020.
• Mumbai’s exceeded 8-fold, Kolkata 9.4, Chennai 5.4, Hyderabad 7 and Ahmedabad exceeded 9.8 fold.
• Large parts of the Indo-Gangetic Plains region, including several cities in Uttar Pradesh, West Bengal, Punjab, Haryana, had very high concentrations of PM2.5 and PM10.

Significance of WHO’s AQG
It sets the stage for eventual shifts in policy

• WHO move sets the stage for eventual shifts in policy in the government towards evolving newer stricter standards.
• This will soon become part of policy discussions — much like climate targets to reduce greenhouse gas emissions keep getting stricter over time.
• Once cities and States are set targets for meeting pollution emission standards, it could lead to overall changes in national standards.

Challenges for India

• The current challenge in India is to meet its national ambient air quality standards in all the regions.
• The hard lockdown phases during the pandemic have demonstrated the dramatic reduction that is possible when local pollution and regional influences can be minimised.
• This has shown that if local action is strengthened and scaled up at speed across the region, significant reduction to meet a much tighter target is possible.
• The influence of geo-climatic attributes is quite pronounced in all regions of India, which further aggravates the local build-up of pollution.
• This is further worsened due to the rapid proliferation of pollution sources and weak air quality management systems.
• India may require a more nuanced regional approach to maximise benefits and sustain air quality gains.

Air pollution impacts in India

• 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- reduced lung growth and function, respiratory infections and aggravated asthma.
• In adults- ischaemic heart disease and stroke, other effects such as diabetes and neurodegenerative conditions.
• State of Global Air (SOGA 2020) estimated that over 116,000 infants in India died within a month after their birth due to exposure to severe air pollution in 2019.
• India had the highest burden of infant deaths due to air pollution followed by Nigeria, Pakistan, Ethiopia and the Democratic Republic of Congo.
• India released National Clean Air Programme (NCAP) in January 2019 which aims to achieve a 20% to 30% reduction in PM 2.5 concentrations over 2017 annual levels in over a hundred cities by 2024.
• NCAP does not have a legal mandate.

Other Facts

• 90% of the entire global population is breathing polluted air.
• 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.
• PM is primarily generated by fuel combustion in different sectors including transport, energy, households, industry and from agriculture.
• In 2013, outdoor air pollution and particulate matter were classified as carcinogenic by WHO’s International Agency for Research on Cancer (IARC).