NEW DELHI , One of India’s most sacred rivers seems to have a thick snow layer. It isn’t.

White toxic foam covers a large stretch of Yamuna River, which is partly due to pollutants released from New Delhi’s industries.

On Wednesday, hundreds of Hindu devotees sat knee-deep in the frothy, poisonous waters. Sometimes, they even took a holy dip to celebrate Chhath Puja.

One of the most sacred rivers for Hindus is the 1,376-kilometer (855 mile) Yamuna. It is also one of the most polluted rivers in the world.

It supplies more than half the water in New Delhi and poses a serious threat to residents’ health. It has been getting dirtier as more of New Delhi’s sewage, pesticides from nearby states, and industrial effluents have flooded into it despite strict laws against pollution.

A dangerously unhygienic waterway in a city with the world’s worst air is a problem. It is still visited by thousands of devotees every year for the festival dedicated to the solar deity.

Rajesh Kumar Verma joined those offering prayers on Yamuna’s banks Wednesday. He is aware that the water can be harmful, but he did not hesitate to stand in the water, undeterred by the danger.

“What fear?” He said, “What fear?”

To disperse the toxic foam, authorities deployed motorboats. To keep the toxic foam from reaching the banks of rivers, they also constructed bamboo sticks barricades.

India’s capital is home to over 20 million people and is among the most polluted in the world. Winters are particularly dangerous because of the toxic haze that covers the city and obscures the sky. This can lead to severe health problems.

Pollution levels soar after farmers from neighboring regions set ablaze their land to clear the way for next year’s crop.

“Delhi is full polluted, but people live on. Rajendra Mahto, another devotee, said, “We will also pray like that.”

According to SAFAR (India’s principal environmental monitoring agency), New Delhi’s air quality index was “very low” on Wednesday.