The champions of clean air [http://www.thehindu.com/sci-tech/energy-and-environment/the-champions-of-clean-air/article22838900.ece]Clean air is turning into a rare commodity as India’s towns and cities become the dumping ground for a variety of pollutants. In this seemingly bleak scenario, the author profiles five Indians whose courageous battle for cleaner air offers a ray of hope to fellow citizens. In November 2017, when pollution was at its peak in New Delhi, 38-year-old Brikesh Singh, a runner, decided to run the Delhi Half Marathon 10 days before the event. He had a purpose: to record with a device the pollution level on the route to be taken by the runners.