One of humanity’s most private and pervasive hygiene habits is changing. And Sal Scapelito’s job is a sign that the trend may not be sustainable.

Every two minutes, the 31-year-old sewage treatment worker cleans off a five-foot-wide device designed to prevent tree branches from entering north Brooklyn’s Newtown Creek Wastewater Resource Recovery Facility.

But it’s not just filtering sticks. Instead, it’s strung with spongy stalactites of whitish tissue. Scapelito jabs a pole at the quivering mass, swooshing it into a bin, where its composition is clear to him: “It’s majority wipes,” he says.

Wipes, as in those moist towelettes used to clean the bottoms of babies and, increasingly, adults. People have been using toilet paper since the 1850s but have turned to wet wipes over the past decade. That’s been a boon for makers of so-called flushable wipes, such as Kimberly-Clark Corp., Procter & Gamble Co. and Nice-Pak Products Inc. But it’s come at a big cost for cities, who say the wipes often don’t dissolve and form sewage blockages, the largest of which have earned a nasty moniker: fatbergs.

Now, a watershed moment may be approaching, as cities from Melbourne to Baltimore to Detroit finger flushable wipes for a growing number of blockages. In February, New York City launched a $2 million campaign, complete with subway ads, telling residents to “respect the flush” and trash even wipes labelled flushable. It has also commissioned a study showing that leading brands don’t dissolve and is close to unveiling a legal strategy intended to try and force wipe makers to change their flushable labels. Lawsuits from consumers may also reshape the market—if startups selling what they say are truly flushable wipes don’t get there first.

“We have to get in front of this; it’s just going to get worse and worse,” says Michael DeLoach, deputy commissioner of public affairs for New York City’s Department of Environmental Protection, as he checks out Scapelito’s bin, full after just three hours.

Companies and an industry group, the International Nonwovens and Disposables Association, or INDA, deny responsibility and say people using cheaper baby wipes for a job meant for flushable wipes are the main culprit—along with disinfectant wipes and makeup removal towelettes. P&G spokesman Damon Jones says the company stands behind the performance of Charmin Freshmates, while Kimberly-Clark says its Cottonelle and Scott wipes are made to break down after flushing. Kimberly-Clark is working with water treatment experts to determine “what exactly is causing sewer and pump blockages,” says spokesperson Sarah Lary.

London has infamously suffered the largest fatberg specimens, one about 15 semi-trucks long, mostly made up of cooking grease and now partly exhibited in a museum. New York City has largely avoided the monstrosities by removing unwanted items before they enter the plant—with work done by those like Scapelito. The city estimates that out of more than 53,000 tons of refuse collected in 2017 from its 14 treatment plants, 95 percent was wipes. That’s almost doubled since 2007, as has the price of disposing it in landfills—to at least $19 million a year.

New York officials commissioned a study in September—calling it the “slosh box disintegration test”—that tested wipes by their tendency to disintegrate enough to pass through a sieve after 30 minutes. All six “flushable” brands failed. Only 9.4 percent of a flushable P&G Charmin brand wipe passed through and just 45 percent of a flushable Kimberly Clark Cottonelle wipe did, according to results, obtained under New York’s Freedom of Information Law. The companies both referred questions about the study to the INDA, which says its own studies found all flushable wipes broke down—with standards that soaked them for 3 hours, and oscillated them faster.

The rise in reports of fatbergs and other blockages mirrors the growth in flushable wipes. From 2013 to 2018, the moist toilet wipes market grew 36 percent globally, worth around $1.1 billion today. About half of the market is in the U.S., according to Euromonitor International.

U.S. municipalities shoulder at least $1 billion a year to deal with them, which gets passed on to taxpayers. Methods include grinder pumps that break up the wipes, says Cynthia Finley, director of regulator affairs for the National Association of Clean Water Agencies. But that just forces the problem further into the system, she says, creating micro-plastics that may turn up in marine life.

Cities and consumers have had mixed legal results in trying to blame blockages on the wipes. After Washington, D.C., enacted a law in 2017 to prevent manufacturers from labeling wet wipes as flushable, Kimberly-Clark turned around and sued D.C.’s mayor and attorney general. It contended the measure would violate the company’s right to free speech. The case is on pause while regulations are drafted.

Consumers got a significant win in January, when P&G settled a potential class action in San Francisco. The company agreed not to use polyester fibers and let class members claim 60 cents a pack for flushable wipes they bought from 2011 to 2018. The suit claimed that consumers had paid a premium for wipes labeled flushable that didn’t live up the claims.

New York State consumers made similar claims in a suit that won class action designation in 2017. P&G and Kimberly-Clark appealed, and are expected to argue April 10 to overturn the ruling. The case could come down to semantics. P&G, outlining its arguments in court papers, said the plaintiffs haven’t shown “that a common understanding of ‘flushable’ exists.”

Meanwhile, innovators are stepping in, such as U.K.-based Natracare, which just launched a wipe it says is the first to achieve a “fine to flush” standard. Jerry and Alissa Staub, a married couple, self-funded their startup Fohm Co., which markets a foam that consumers apply directly to toilet paper. They noted that wipes are used increasingly by middle-aged men who want to feel cleaner, and people with digestive disorders like Irritable Bowel Syndrome.

In the ultimate irony, consumers’ desire for cleaner bottoms may reduce the long-term cleanliness of the water that they use to wash themselves in the first place. “Water quality is better than it’s been in 140 years,” says Mikelle Adgate, a senior adviser for New York’s DEP. “But people flushing away wipes is making our job of protecting it so much harder.”