On the banks of the Ganges in northern India, tanneries that have poured effluent into the holy river for decades are closing.

For environmentalists, it's a victory over filthy companies with no regard for nature and a rare example of pollution legislation being enforced.

They say the closures point to a willingness to tackle serial polluters even at the expense of jobs.

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But the mostly Muslim workers and tannery owners in the city of Kanpur, home to more than 400 of the estimated 2,100 tanneries in the country, smell a religion-tinged vendetta against them and a political conspiracy.

"Since we are Muslim, there is more pressure from the government for us to control pollution," said Hafizur Rahman, president of the Small Tanners Association in Kanpur.

"There are many industries in Kanpur, and some of them use harsher chemicals than ours. We have taken steps to treat effluent. Why are we constantly being singled out?"

The issue is linked to the religious significance of the Ganges, Rahman added, referring to India's majority-Hindu population who believe water from the river to be sacred.

Muslims have traditionally dominated India's leather sector because of their willingness to work with cow carcasses - considered taboo by Hindus.

According to the Uttar Pradesh Leather Industries Association, 65 tanneries have closed in the last two years, with 19 more ordered to shut.

The Allahabad High Court in 2008 ordered all industries accused of discharging effluent directly into the Ganges - including tanneries - to establish special treatment plants, move elsewhere, or risk being sealed.

Around Kanpur is one of the most heavily polluted stretches of the river, where frothy brown wastewater can been seen pouring into the main channel from storm drains or other pipes.

Rubbish forms into solid floating islands and a foul smell wafts over the water's murky surface.

Despite this, the belief that the Ganges washes away sin entices millions of Hindus into the river each year.

Rakesh Jaiswal, the founder of a Kanpur-based environmental lobby group called Eco Friends, has little time for the protestations of the tannery owners.

"Everybody knows that tanneries are polluting the river," he told AFP. "One can see tannery waste water that is a cocktail of chemicals going into the river untreated through drains."

The heavy metals and other pollutants kill river life and get into the food chain through fish consumed by local people and via crops that are irrigated with water from the river.

"It is a very easy excuse to say that they are being targeted because they are the Muslim minority. That's not the reality," said Jaiswal, who wants more stringent curbs on pollution from tanneries and other industries.

Irfan Ali, a Muslim worker, is caught in the middle of the struggle between pollution fighters, local authorities and the tannery owners. He eats and sleeps on the grounds of a leather factory that has been marked for closure.

Employees here spend long days using heavy machinery amid the stench of chemicals and raw hide. Pay is low and protection from workplace dangers even lower.

"The tannery's electricity supply was cut a few days back and I don't know when it will be running again," said Ali.

"It doesn't matter why we are being targeted. My wife and three children are dependent on me. If the tannery is closed I will be forced to move back to my village."

The crackdown comes at a bad time for the industry in Kanpur as a whole.

Last year, India's Council for Leather Exports warned that the sector was already in trouble due to the global economic downturn.

It said Kanpur was "near-idle" with tanneries operating at about 50 percent of normal levels.

The leather sector in Uttar Pradesh is worth almost 890 million dollars annually and exports products all over the world, according to the state's Leather Industries Association.

A large-scale shutdown would spell disaster for the city, which employs roughly 50,000 people directly and thousands more indirectly in sectors such as shoe-making and textiles.

Rahman called the high court judgments "one-sided" and said compliance reports submitted by the state Pollution Control Board had cleared tanneries of any negligence.

"This is a planned way to close the industry," he said.