Air pollution is a global environmental threat, and a cause of significant proportions of diseases and premature deaths. The threat is massive in India, which continuously fails to meet World Health Organization (WHO) standards and is home to 21 of the 30 most polluted cities of the world. Air pollution is caused by particulate matter, oxides of carbon, nitrogen and sulphur, and other pollutants. The primary sources of ambient particulate matter (PM) in India are biomass burning by both commercial and residential establishments, windblown mineral dust, coal burning, industrial emissions, and transport emissions. In rural regions, the main source of air pollution is the burning of organic matter; in urban areas, it is industrial and vehicular emissions. Poor air quality led to over 1.6 million deaths in the country in 2019 alone; the 2020 State of Global Air report named air pollution the single largest death risk factor in India.