How about a cold glass of pond water after a hard day of work? Or a sip from a stream after brushing your teeth?

That may sound like the frightening circumstances faced by families in hurricane-ravaged Puerto Rico or poor rural villages in India, but it’s also the latest craze promoted by Silicon Valley startups and companies across the US that have begun packaging and selling so-called “raw water.”

Even as roughly 2 billion people around the world lack access to clean water, one child every minute dies from preventable waterborne diarrheal disease, and countries contend with devastating waterborne cholera epidemics, an untreated water trend has emerged among some Americans wary of water treatment and purifying processes.

Scientists and public health experts, however, say the mysterious “raw” water could actually contain raw sewage and other dangerous contaminants.

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Like the anti-vaccine trend, the movement away from clean water contradicts near-universally accepted science. The Centers for Disease Control (CDC), for example, has long warned against drinking untreated water.

“While the water flowing in the streams and rivers of the backcountry may look pure, it can still be contaminated with bacteria, viruses, parasites, and other contaminants,” CDC states on its website. “[D]rinking contaminated water can increase the risk of developing certain infectious diseases.”

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If you need an ad for your raw water business I have some great old-timey graphics. pic.twitter.com/Wz1Bb6S42n

— John Coulthart (@johncoulthart) January 2, 2018

Though raw water purveyors say their water flows from “pure” springs, the contents and source of the water remain a mystery to consumers.

Public health experts say that removing contaminants and testing water systems throughout the US has virtually eliminated deadly waterborne illnesses like typhoid fever and cholera, which routinely killed children a century ago.

“[Water treatment] was truly instrumental in improving public health in the United States,” Johns Hopkins Univesity Water and Public Health Professor Kellogg Schwab told Time Magazine. “Having a central treatment process of our drinking water and then distributing it out to the individual homes and businesses is a tremendous asset that we, as a country, take for granted.”

Global Citizen campaigns on ensuring everyone around the world has access to clean water to prevent the spread of deadly infectious diseases. You can take action here.

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To: Anybody who drinks or is considering drinking "raw water." From: Everybody who has ever died of cholera, dysentery, typhoid fever, or tooth decay. Message: Do! Not! Be! A! F! -ing! Idiot! https://t.co/6HmYfgGbTb

— Laura Helmuth (@laurahelmuth) December 31, 2017

Among some consumers, the desire for untreated water flows from a distrust of water treated with fluoride, which they say is part of government-sponsored mind-control conspiracy.

“Tap water? You’re drinking toilet water with birth control drugs in them,” one man told the New York Times. “Chloramine, and on top of that they’re putting in fluoride. Call me a conspiracy theorist, but it’s a mind-control drug.”

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In fact, fluoride has been added to drinking water — in safe, tiny amounts — for decades to help prevent tooth decay and cavities, the American Dental Association and various public health organizations report.

In other cases, people say they drink dirty water because they think municipal treatment removes important minerals. But public health experts scoff at that notion, explaining that individuals get nutrients from their diet and that the risk of contamination outweighs any potential benefit from leftover minerals.

“In some respects,” Harvard Medical History Professor David Jones told the Washington Post, “the fact that people are worried filtration is removing necessary minerals is really an extreme case of one of these First World problems.”