India was the world's eighth most polluted country in 2022, dropping from fifth place the previous year. While PM 2.5 level dipped to 53.3 micrograms/cubic metre, that is still over 10 times the World Health Organisation's safe limit. The ranking was decided by Swiss firm IQAir in its "World Air Quality Report" and is based on the level of PM 2.5, a pollutant closely tracked by scientists and health experts. Significantly, the report indicates that 39 of the 50 most polluted cities in the world are in India. In broad terms, what can this potentially mean for millions of residents of major Indian cities?