In this article, published in October 2017 on HuffPost India, Prof. McNeill and Dr. Julia Nunes break down the data for particulate air pollution in cities across India. Air pollution is at an unhealthy level for a large part of the year, in most Indian cities.
The pie charts show the number of days in the past year that the average PM2.5 level fell into the following three categories: Green days (PM2.5 < 35.4 μg m-3) are healthy or moderate, yellow days (35.5 μg m-3 to 55.4 μg m-3) are unhealthy for sensitive groups such as children, the elderly or those with lung disease, and red days (PM2.5 > 55.5 μg m-3) are unhealthy for all. For more information on the data sources: https://aire.mcneill-lab.org/india-aq-2016-2017/