The Yamuna, along with India’s holiest river, the Ganges, are considered among the most polluted in the world. Activist Brij Khandelwal once described the Yamuna as "ecologically dead." Sewage from Delhi and other cities, chemical waste from manufacturing plants and pesticide runoff are all part of the problem.

Himanshu Thakkar, an engineer who coordinates the South Asian Network on Dams, Rivers and People, told the Guardian, “There are already 1.5 billion liters of untreated sewage entering the river each day and 500 liters of industrial waste.”

Hindu devotees cross the Yamuna river, surrounded by industrial effluent, on a boat during Karthik Purnima in Delhi, India, Nov. 28, 2012.

Holy rivers are meant to be purifying. Indians perform religious ceremonies, bathe and drink from the 855-mile Yamuna. The river provides three quarters of Delhi’s water needs, posing a serious health threat to its 12 million residents and many other Indians who depend on it, according to The Associated Press.

A man immerses himself in a large amount of toxic foam formed along the banks of the Yamuna on July 12, 2015, in Noida, India. The pollution is caused in part to high ammonia levels emanating from the high discharge of industrial pollutants in the river.

A Ganesh idol is seen on the banks of the polluted Yamuna river, Sept. 24, 2018, in Noida, India. Lord Ganesh is considered the remover of obstacles and the idols are immersed on the last day of the Ganesh Chaturthi festival.

A Hindu devotee offers prayers after a dip in the Yamuna River, surrounded by industrial effluent, during Kartik Purnima festival in New Delhi, Nov. 28, 2012.

Toxic waste and trash are seen in the Yamuna river in New Delhi, India, Nov. 20, 2015.

Boys sit in a boat before immersing an idol of Hindu god Lord Ganesh in the polluted Yamuna river on the ninth day of the eleven-day long festival Ganesh Chaturthi in New Delhi on Sept. 21, 2018.