Air pollution is the second largest risk factor affecting public health in India; it is estimated to have contributed to ~1.67 million (or about 18% of all) premature deaths in 2019 and 11.5% of all the disability-adjusted life years lost (India State-Level Disease Burden Initiative Air Pollution Collaborators 2019). It increases the risk of a variety of adverse health outcomes, including but not limited to cardiorespiratory diseases, lung cancer, and diabetes in adults and acute lower respiratory infections, low birthweight, and cognitive impairment in children (GBD MAPS Working Group 2018); with each passing year, we discover how it is more harmful than previously understood. It is also a national crisis; an estimated 76% of the Indian population is exposed to air quality levels that are worse than the national standards for fine particles (Apte and Pant 2019). Furthermore, the air pollution crisis is particularly complex in India, with an unusually diverse group of polluting sources necessitating a whole of government response going well beyond the traditional regulatory instruments and spanning administrative boundaries.
Several air pollutants that impact health are: coarse and fine particulate matter (designated based on the size in micrometre as PM10 and PM2.5), carbon monoxide, oxides of nitrogen and sulphur, ammonia, and ground-level ozone. Some of these are emitted directly from various anthropogenic activities, while others are formed from precursor pollutants in the atmosphere. Considerable health evidence has accumulated on both the short- and long-term impacts of PM2.5 exposure, making it the focal point of recent debates. PM2.5 comprises a mixture of chemical substances, attributed to multiple sources such as fossil fuel combustion in industries, power plants and vehicles, biomass burning in households, waste burning, construction, and road dust, crop residue burning, and ammonia emissions from excessive fertiliser use.