In photos: Thick toxic foam covers sacred river in Indian capital

One of India’s most sacred rivers, the Yamuna in New Delhi, is covered with white toxic foam, with vast sections frothing as a result of pollutants discharged from industries around the city. The pollution poses a severe health threat to residents since the river provides more than half of the Indian capital's water.

New Delhi also has some of the world’s most polluted air every year, and the current festival season is exacerbating the situation.

On Tuesday, the air-quality index deteriorated to “a very poor” reading of 273, 18 times more than the World Health Organization’s quality guidelines. The tiny PM 2.5 particulate matter can enter deep into the lungs and cause diseases.

Still, Hindu devotees have not given up their religious practices at the Yamuna. On Tuesday morning, a young couple was among a group that visited the river bank, had a dip, and then left.

Jasraj, a 70-year-old retired government clerk, said he has been visiting the river for a bathing ritual since 1980.

"I worship the river as a mother, and there is no question of its being clean or dirty. It's dirty on the surface but clean below the top," said Jasraj, who uses one name.

Imran Khan, a student, said one can't breathe properly in Delhi's polluted air.

"People are here for jogging, and they are facing problems, too. Our environment should be cleaner," he said.

Shishupal Kumar, a contract worker, said people visit the river from far-off places to perform religious rituals.

"The river has become completely dirty. It is full of chemicals. It looks like snowfall has happened here, like it happens on mountains," Kumar said.

The 1,376-kilometer Yamuna is one of the holiest rivers for Hindus. It is also among the most polluted in the world. Dangerously unhealthy waterways are a concern for many, especially with pollution expected to worsen during the upcoming Chhath Puja, a Hindu festival.

The river has become dirtier over the years as sewage, farm pesticides and industrial effluents flow into the waterway despite laws against polluting and authorities setting up dozens of sewage treatment plants.

The New Delhi government said officials were using defoamers to tackle the problem. Authorities have deployed dozens of motorboats to disperse the toxic foam and erected bamboo barricades to keep people away from the river banks.

The officials worry that thousands of Hindu devotees next month will stand knee-deep in its frothy, toxic waters, sometimes even immersing themselves in a holy dip to mark Chhath Puja.

Winters, in particular, have become a time of health woes in India’s capital, which is home to more than 20 million people. The city during winter is covered with a toxic haze that obscures the sky. Pollution levels soar as millions of Hindus celebrate “Diwali,” the festival of light, amid emissions from massive firecrackers. Diwali will be celebrated on Thursday.

Farmers in neighboring agricultural regions also set fire to their land after harvests to clear it for the next crop season.

India's Supreme Court earlier this month slammed northern Indian states for not taking stricter action against people burning crop residues ahead of the winter season and aggravating the region's air pollution.

Authorities each year shut construction sites, restrict diesel-run vehicles and deploy water sprinklers and anti-smog guns to control the haze and smog enveloping the skyline of the capital region.