The Yamuna, the main source of water for Delhi’s 19 million residents, is one of the most polluted rivers in India. At this year’s Hindu religious festival of Chhath Puja, where people dress in colorful clothing and pray at the riverbanks, celebrants were knee-deep in clouds of stinky, toxic foam that floated on the water.

At the same time, Delhi was suffering under the worst air pollution the city has seen in several years. For two weeks, car travel was rationed, schools were shut and construction was banned, but observers said these measures did little to remedy pollution at its sources.

“Yamuna is not a river anymore,” Manoj Mishra of Yamuna Jiye Abhiyaan, a group that campaigns to clean up the river, told CBS News. “It’s a collection of 18 drains flowing into it, carrying a toxic cocktail of sewage, chemicals, detergents, industrial waste, and excreta.” Less than 10 percent of the sewage discharged into the river is treated, putting millions of people who use the water at risk of disease, CBS reported.

Despite several official plans and promises to address widespread pollution, little action has been taken, Mishra said.