Emergent need of drastic actions to control air pollution

Debapriya Mukherjee
Delhi has been ranked as the most polluted capital city globally despite air quality improvements during 2019–2020 according to a report from IQ Air, a Swiss air quality technology company. The progress is only marginally attributable to India's flagship National Clean Air Programme (NCAP) introduced in January 2019, which targets PM2.5 reductions between 20-30% in 122 selected cities by 2024 from a 2017 baseline. The 'World Air Quality Report, 2020', shows that Bangladesh, China, India, and Pakistan account for 49 of the 50 most polluted cities worldwide. In the world capital city ranking, Delhi fares the worst.  Delhi, the world's second-most populous city, is located southeast of India's agricultural breadbasket, where open burning is common. Notably, India showed an overall improvement in several cities, with 63% reporting direct improvements over 2019 averages.
Polluted air is a public health hazard  and  long-term exposure to air pollution enhances the risks of cardiovascular and respiratory diseases. Scientists have linked air pollution with many health conditions including asthma, heart disease, lung cancer and premature death. Among air pollutants, fine particulate matter is especially harmful because the tiny particles (diameter of 2.5 micron or less) can penetrate deep within the lungs with a low probability to be exhaled. Obviously, there remains concern that ultrafine particles with a diameter of smaller than 0.1 micron (PM0.1) could be particularly harmful, as they can directly pass into the bloodstream and affect other organs. Researchers reported that specifically the smallest fraction of PM0.1 can directly translocate into the circulatory system and accumulate at sites of vascular inflammation.
The mortality caused by ambient air pollution is highest in East Asia (35 percent) and South Asia (32 percent), followed by Africa (11 percent), Europe (9 percent) and North- and South America (6 percent). Lowest mortality rates are found in Australia (1.5 percent) associated with the strictest air quality standards of all countries.  Among the different types of air pollution, PM2.5 consisting of particles smaller than approximately 2.5 microns  is responsible for an estimated 4.2 million premature deaths every year globally. This includes over a million deaths in China, over half a million in India, almost 200,000 in Europe, and over 50,000 in the United States. India continues to dominate annual PM2.5 rankings by the city as 22 of the top 30 most polluted cities globally.  Major sources of India's air pollution include transportation, biomass burning for cooking, electricity generation, industry, construction, waste burning, and episodic agricultural burning. Transportation constitutes one of India's leading PM2.5 emission sources, responsible for emitting pollutants and re-suspending road dust.
The  loss of life expectancy caused by air pollution is higher than many other risk factors such as smoking, infectious diseases or violence. Air pollution caused 8.8 million premature deaths worldwide in 2015. This corresponds to an average reduction in life expectancy per capita of 2.9 years. In comparison, tobacco smoking reduces the life expectancy by an average of 2.2 years (7.2 million deaths), HIV/AIDS by 0.7 years (1 million deaths), parasitic and vector-borne diseases such as malaria -- by 0.6 years (600,000 deaths). Air pollution exceeds malaria as a cause of premature death by a factor of 19; it exceeds violence by a factor of 17 and HIV/AIDS by a factor of 9. With reference to PM10 pollution it is pertinent to mention that researcher reported significant linear  relationship between long-term exposure to PM2.5 and the rapidity of COVID-19 spread. The presence of secondary inorganic components in PM2.5 only aggravates severity of human suffering.
According to the researchers, the viral entry of SARS-CoV-2 uses Angiotensin-converting enzyme 2 (ACE2) as its co-host receptor that  plays a crucial role in lung protection by cleaving and converting angiotensin II (Ang II) to the cardio protective angiotensin1–7 . Viral loads of SARS-CoV-2 depleting residual ACE2 activity and impairing host defenses. This causes an imbalance between Ang II and Ang 1–7, resulting in high circulating levels of Ang II, which induces pulmonary vasoconstriction, inflammation, and oxidative stress. Thereby long-term exposure to pollutants had rendered the Nationwide population susceptible to the virus spread plausibly via the “double hit phenomenon”. The huge adverse impact on public health and the global population is the indication of  “air pollution pandemic”.

(To be contd)