India's air pollution comes mostly from coal-fired power plants, crop burning, domestic cooking with firewood or cow dung, and vehicles burning diesel fuel. The incomplete burning of these fuels produces black carbon, which constitutes most of the tiny particulate matter known as PM2.5, and can lodge and fester in human lungs. Black carbon is also blamed for up to 20 percent of global warming.

Anxious to grow its economy, India has made building electricity capacity a top priority. It plans to boost solar and wind power, but also plans to triple its coal-fired electricity capacity to 450 gigawatts by 2030.