Backpackers, Don’t Listen To Slate: Science Does Support Stream Water Treatment

By Christie Wilcox | February 8, 2018 8:00 am
The risk might be low, but the alternative is maybe months of debilitating diarrhea. It's your choice. Photo Credit: Timothy Epp/Shutterstock

The risk might be low, but the alternative is maybe months of debilitating diarrhea. It’s your choice. Photo Credit: Timothy Epp/Shutterstock

While we like to think of ourselves as rational creatures, there’s no doubt that human beings are actually quite awful at assessing risk. So I can understand why Ethan Linck thought to contextualize the risk of drinking from backcountry streams with data. “Life is triage, a constant series of negotiations between risks of varying severity,” he wrote. “And how we talk about those risks matters.”

Yes, it does—which is exactly why his piece in Slate last week was so damaging. It was anything but a careful, scientific evaluation of the risks. Wes Siler over at Outside Magazine already pointed out a myriad of issues with the article, but I want to zero in on the actual data, because Linck claimed to be looking at the matter scientifically. Instead, he cherry-picked sources to argue against doing one of the simplest things you can do to protect yourself from some truly awful diseases when you’re backpacking: treating your water.

The Bad

Simply put: when you drink water straight from a stream, river, or lake, you have no idea what’s in it. And that’s bad, because, as epidemiologist Tara Smith, PhD, explained for SELF last month, it can be contaminated with all sorts of nasty things. “These include Giardia, a parasite found in streams and rivers that causes “beaver fever” in campers and hikers, and bacteria like Shigella and Campylobacter that can cause bloody diarrhea,” she wrote.

These organisms exist in waters because they exist in our digestive tracts and those of other animals. So anywhere that there’s poop near water, that water could contain pathogenic strains of Escherichia coli, Salmonella, Campylobacter, Aeromonas, Yersenia enterocolitica, Leptospirosis, Listeria, or Vibrio, in addition to a suite of viruses and protozoan parasites like Giardia and Cryptosporidium. Some of these bugs only cause short-term, if severe, gastrointestinal distress. Others can cause issues that last for weeks, months, or even years. 

“Even water that appears pure or clear can be contaminated by people or animals,” explains Jonathan Yoder, MPH, who is deputy chief of CDC’s Waterborne Disease Prevention Branch. I asked Yoder and his colleague, epidemiologist Kathy Benedict, PhD, what their thoughts were on the bold claim that science doesn’t support backcountry water treatment (that “the scientific evidence shows that this mandate [to filter water] rests on a shaky foundation”). Needless to say, they disagreed.

Because appropriately assessing risk requires a clear understanding of what’s at stake, it’s important to point out that with many of these pathogens, we’re not just talking inconvenient cases of the runs. The gastrointestinal symptoms that can occur—intense diarrhea, vomiting—aren’t easily managed by hikers on long trips in the middle of nowhere. “If they have an acute situation, it can actually be quite scary,” says Benedict, “especially if they’re out there by themselves, because they can get themselves into a lot of trouble very quickly.” And people, even people with rapid access to medical care, do sometimes die.

A 3D rendering of Giardia lamblia a protozoan parasite that can set up shop in your intestines and be pretty hard to remove. Image Credit: fotovapl/Shutterstock

A 3D rendering of Giardia lamblia a protozoan parasite that can set up shop in your intestines and get pretty comfortable there. Image Credit: fotovapl/Shutterstock

To his credit, Linck doesn’t exactly downplay the dangers of Giardia or other potential pathogens. But, he argues, that their dangers are not important. It’s totally ok to drink any water you might come across while backpacking (or as the title says, “You Don’t Need to Filter Your Stream Water”) because: “The idea that most wilderness water sources are inherently unsafe is baseless dogma, unsupported by any epidemiological evidence”.

It’s a lovely little straw man that he immediately sets to tearing apart. To paraphrase his argument: everyone says most water is chock full of terrible things. So as long as most water sources are safe, then you’re good to drink from any stream. And look! Here’s a study that says feces contamination was only found in a minority of the sites tested! And one by… a magazine… that says the same thing!

But let’s take a quick look at those sources. The first study examined lakes and streams in Kings Canyon, Sequoia, and Yosemite National Parks looking for feces-associated bacteria (fecal coliform), because where there’s feces, there could be something dangerous in the water. And they found it at 22 of the 55 chosen sites. So yes, that’s a minority, but it’s 40%—and of those, ~16.3% (9) had “higher levels”. And that magazine one? Well, Linck didn’t directly link to it, but Google is a wonderful thing. They surveyed seven locations three times throughout the year for parasites, five of which had at least one test come up positive for either Giardia or Cryptosporidium—just over 71%. But, they claimed, only one had close to dangerous levels. That’s still 1/7—or a little over 14%. It’s a shame that Linck didn’t include the percentages in his article, because for all his talk about appropriately assessing risk, he doesn’t give the information needed to actually do that.

And those studies—if you can really call the magazine investigation that—were conducted in the early 2000s, each testing a miniscule fraction of the waters that are accessed by U.S. hikers every year on a handful of occasions. There is other research he could have cited—like this 2009 study from Georgia, which found 79% of water samples from rivers and streams in southern Georgia over a year tested positive for Salmonella. Or this 2011 one which found “Salmonella, Campylobacter, Staphylococcus aureus, Vibrio vulnificus, and V. parahaemolyticus were widespread—12 of 22 O’ahu streams had all five pathogens.” And even if he didn’t want to count Hawai’i (though it is a U.S. state), then he could have cited this 1987 study in Washington instead, which found Campylobacter at ~36% of sites tested (5 of 14), including a mountain stream. According to the authors, “Campylobacter spp. are widely distributed in central Washington and are present in a variety of aquatic habitats including ponds, lakes, and small mountain streams, which ranged in elevation from 1,460 to 5,400 feet above sea level.” Or this 1982 study, which detected fecal coliform bacteria in ~86% of streams in Great Smoky Mountains National Park, with ~5% testing extremely high (>1 organism per milliliter). They concluded that “it is clear that water in natural streams in the Great Smoky Mountains does not meet standards for safe drinking water.”

Even if he just looked at other papers by the same authors as his study, he’d have found this 2004 study, which found that out of 31 backcountry sites, 45% tested positive for fecal coliforms, and just over 25% had high levels. Or this 2006 study which found fecal coliform at 1/15 sites used by backpackers (~6.7%). Or this one from 2008, which found coliform bacteria  in 18% of human day use areas, and 14% of backpacker sites. But really, they all tell the same story: one-in-five to one-in-ten sites test positive, which means they might get you sick if you drink their water untreated.

Even the cleanest water can harbor these pathogens. Photo Credit: michaeljung/Shutterstock

Even the cleanest water can harbor these pathogens. Photo Credit: michaeljung/Shutterstock

Of course, even counting every sample in every study I just mentioned, only a tiny fraction of potential hiker drinking sources have been tested, so a lot remains unknown. And because these pathogens are associated with human and animal activities, their presence can be as transient as the wildlife. None of these studies really explains just how variable the risks can be, which is actually something that was noted in that Backpacker article:

“Risk in this area is very hard to quantify,” explains Tod Schimelpfenig, curriculum director for the Wilderness Medicine Institute, of the Wyoming-based National Outdoor Leadership School. “Sample a creek at one point in time and you could have a flush of organisms from an animal that just defecated upstream. Sample it 20 feet upstream 2 hours later and you could find nothing. The risk of drinking untreated water in the wilderness depends entirely on when and where.”

If any conclusions can be drawn, it’s that not all areas carry the same risks, and that even remote streams can harbor dangers. Even if you could assume something like 10%-20% of water sources test positive for fecal contamination (and thus may get you sick)—then, yeah, technically, only a minority of sites are ‘unsafe’ (not that anyone was arguing that most of them were). But just imagine going to a buffet and seeing a sign that said “Nine out of ten of our menu items tested negative for fecal bacteria!”—would you want to eat?

Yoder wouldn’t. Of course, he’s had Giardia before, so he knows exactly what he’d be risking. “I think after you have a one of the more severe diarrheal infections—and I speak from my personal experience—I think you understand that even though you know ninety-nine times out of a hundred, if you drank from that water source, you’re not going to get infected, it’s worth it to protect yourself for that one percent chance.”

The Ugly

While Linck’s prevalence analysis is a straw man at best, he goes on to claim something that’s patently false: that “research to date has failed to demonstrate any significant link between wilderness water consumption and infection with these threats.”

Again, he turns to decades-old data, citing a 1993 study where only 5.7% of backcountry travelers in California’s Sierra Nevada had Giardia, and none of them felt sick. Mind you, he failed to note that more than half of the travelers did purify their water, so they’d have been protected from the parasite. And he didn’t mention that 16.7% of them did return with gastrointestinal illnesses—they just weren’t that one. Then he cites a survey of health departments and a meta-analysis from the same researcher looking at Giardiasis in the US, both of which found that the majority of cases came from non-wilderness sources. But again, that’s a straw man—no one was arguing that backcountry streams were the main source of Giardia infections. That’s like saying most house fires aren’t started by deep-frying a frozen turkey, so by all means, it’s totally safe! And Giardia seems like a very specific hill to die on. What about the myriad of other possible disease agents? Nothing about Campylobacter, Leptosporosis, Shigella, Norovirus, E. coli—and the list goes on.

Heck, if we’re going back decades for our data, why not mention this 1977 study of 256 known Giardia cases in Colorado, where they found a significantly higher proportion of cases among people who “visited Colorado mountains (69% vs. 47%), camped out overnight (38% vs. 18%), and drank untreated mountain water (50% vs. 17%), p less than .001” [emphasis mine]. They also found that when they tested 16 Rocky Mountain streams in uninhabited areas, they found unsafe concentrations of fecal coliforms in all of them. Or this 1984 study that found people who drank untreated water taken from a stream, river, or lake were about ten times as likely to have Campylobacter jejuni infections than their neighbors who didn’t? Or this 1983 one, which found both Campylobacter jejuni (23%) and Giardia lamblia (8%) in people who came back from Grand Teton National Park with diarrheal disease. They also found that Campylobacter occurred “most frequently in young adults who had been hiking in wilderness areas and was significantly associated with drinking untreated surface water in the week before illness” [emphasis mine]. They even isolated Campylobacter from one of the mountain streams suspected as a source.

You might not realize what has happened upstream. Photo Credit: Ruud Morijn Photographer/Shutterstock

You might not realize what has happened upstream. Photo Credit: Ruud Morijn Photographer/Shutterstock

Or, Linck could have looked at more recent data—like this 2016 study of Giardia outbreaks in the US from 1971-2011, which found six linked to rivers or streams. Or this 2017 study looking at waterborne illness outbreaks in the US in 2013 and 2014, which found another six outbreaks of Giardiasis affecting 91 people which were “caused by ingestion of water from a river, stream, or spring.” And these are just outbreaks where multiple people got infected and sought treatment—they don’t look at the countless individual cases, many of which are not reported to authorities because we don’t go to the doctor for diarrhea unless it’s really bad (diarrheal diseases are notoriously underreported). And it can take a week or more for signs to show in some cases, so you might not even connect your bowel troubles to your recent hiking experience.

Linck does mention a camping related outbreak of Giardia from 1976 which was thought to be waterborne. But he claims, citing a 2004 editorial, that the analysis was wrong. Instead, “the afflicted campers failed to properly wash their hands after using the bathroom.” (Yet, none of the campers had the parasite in their stool before the trip, so even if poor hand-washing spread it faster, where did the disease come from?)

“I don’t disagree with the author that, in addition to water treatment, there are other very important things that people can do to stay safe in the backcountry,” says Yoder, “and those include the proper disposal of waste and using good hand-washing hand hygiene, particularly after using the bathroom and before eating before preparing food.”

By pointing to hand-washing, Linck is basically making the turkey argument again; the fact that poor hand-washing also causes outbreaks, maybe even more of them or worse ones, doesn’t mean that drinking untreated water never causes any.

And there is a study that compared the two—a paper examining the outcomes of 280 people planning to hike the Appalachian Trail in 1997 for a week or more found that both bad hygiene and drinking untreated water increased the backpacker’s odds of cancelling their trip early. Those that practiced good hand-washing were about 50% less likely to have gotten sick, while those that drank untreated water were almost 8 times as likely to have had to pack it in because of diarrhea. They concluded: “Hikers should purify water routinely, avoiding using untreated surface water. The risk of gastrointestinal illness can also be reduced by maintaining personal hygiene practices and cleaning cookware.”

In fact, the idea that every case reported from backpackers comes from poor hygiene instead of streams is not just hard to believe—it’s unsupported by the science (excellent summaries of the many papers that show this can be found here). “We have data that there is a risk from backcountry water,” says Yoder. “There certainly are waterborne disease outbreaks—more than twenty that have been reported to CDC—where consumption of water in the backcountry has been linked to illness.”

The Good

The simple fact is, if you drink untreated water, you’re taking on a non-negligible amount of risk. The good news is that risk—however large or small it may be—can be mitigated. And no, not just with fancy filters.

Linck is quick to chastise the outdoors industry for “claiming the average hiker or camper needs a $99.95 microfilter pump to avoid illness and death.” Maybe expensive devices are talked up by their makers (are we really blaming companies for wanting to sell their products?), but luckily, the people that study waterborne diseases and pretty much everyone who has had any kind of training in wilderness survival will tell you that decent water treatment can be done a myriad of ways, many of which are dirt cheap. “Boiling water is one of the most effective ways to inactivate parasites, viruses, and bacteria,” Yoder notes. Or you could get chlorine dioxide tablets that treat a liter of water for about $0.50 each.

Boiling water goes a long way if you're going to be off the grid for awhile. Photo Credit: AlisLuch/Shutterstock

Boiling water goes a long way if you’re going to be off the grid for awhile. Photo Credit: AlisLuch/Shutterstock

Ultimately, the choice of what you drink is yours and yours alone. The point of this isn’t to shame you if you choose to drink untreated stream water—it’s to provide you with what is known from scientific research, rather than hyperbolic rhetoric. Now that you have the information, you can decide to trust in your ability to pick safe water sources, or to take precautions.

As for me, I’ll go with the instincts of the guy who studies these things. Yoder has analyzed the data, and his choice is simple: “I think that having that extra level of protection and making your water safer is worth it, because you’re trading that for more enjoyment out of the backcountry and not having to experience an illness that, at least temporarily, is pretty debilitating.”

It seems like the overwhelming majority of Slate’s twitter followers agree. (Ah, the ratio…)


UPDATED 2/8/18 to add additional papers I was alerted to after publication.

  • Cooper French

    Did you reach out to Mr. Linck to seek clarification on any of the points in his piece?

    • Nate

      In a published article giving advice relative to the audience’s health, it had better stand on it own without the need for clarification. Seems the title doesn’t leave much ambiguity

      • Cooper French

        Authors don’t write headlines, editors do. I just wanted to know if there was discourse (the typical journalistic “when reached for comment or clarification…”)

        • Christie Wilcox

          Since you asked: No, I did not ask him for clarification, because this piece isn’t a news story about his opinions; it’s an audit of the piece written in Slate and the sources it cites. He did not provide any clarifications for the people that read his piece. If Slate issues any updates or corrections, then those will be added and analyzed here as well. You can think of it more as a reply letter in a scientific journal. Mr. Linck is always welcome to publish a rebuttal of his own in response.

      • Ken Murray

        ALL scientific articles, which this author seems to hold up at the Holy Grail, allows authors to respond to criticism.

    • sniper74

      Sounds like you didn’t actually read his article and then this one. This article is clearly written by someone who has a science background, the other one is clearly some guy who think’s he knows everything because he once picked up a science book or participated in a 4th grade science fair and won a ribbon for trying.

      • Cooper French

        Christie Wilcox IS an accomplished author and has a PhD in Cell & Molecular Biology. Ethan Linck is also an accomplished author and a PhD student in Evolutionary Biology; he regularly writes for Molecular Ecologist. He is not inherently dumb or dangerous just because you disagree with him.

        • sniper74

          Ah…he is a student studying evolutionary biology. Per his own words, I’m a Ph.D. Candidate in the Klicka Lab at the University of Washington Department of Biology,
          where I study the evolutionary genetics and ecology of mountain birds. He does NOT have any degree in microbiology. Notice that he studies genetics and birds. He doesn’t study anything in water, nor health.

          I work to describe
          patterns of avian biodiversity and the processes responsible for them.

          A member of the Klicka Lab, I’m particularly interested in the birds and ecosystems of the broader New Guinea region and
          western North America.

          If he was really a good candidate in his field, then he would understand how to do some actual scientific research, and not rubish. Read the article you are posting to. They have pointed out a ton of flaws in his article, ranging from the fact that he has ZERO evidence, that he didn’t actually do any other studies related to it, and he only took evidence from ONE study in a very small area. Even someone who doesn’t have a doctorates degree can grasp that you don’t do that.

          That’s like saying that the Honda Civic is the fastest and best car in the world, only because you took it for a test drive.

          He is actually inherently dumb and dangerous. Here let me prove it. I saw a ton of people jumping off the a Bridge near my house with no parachute or bungee cords….therefore jumping off any bridge is safe.

          Now perhaps you will find the world longest and highest bridge and prove to the rest of the world that I am correct.

          • Cooper French

            Christie Wilcox does indeed provide good evidence that pathogens are present in a large number of American waterways. But that same evidence finds waterways that don’t contain pathogens, so not all water is inherently unsafe. What is left then is a decision centered on personal risk. The extremely cautious and risk averse can/may/should choose to never drink any form of untreated water. This is not a guarantee against illness (as you can still get sick from food, unwashed hands,etc…), but will significantly reduce risk. To use your analogy, these people would not jump off any bridge, no matter how tall or how deep or slow-moving the water below. Others might apply a personally responsible (your actions really only affect your own health in these cases) decision process to such circumstances. In the case of backcountry water this might mean drinking from glacial runoff or a spring, but filtering water from larger lakes and low elevation rivers. In your bridge analogy, such a person might enjoy jumping off a 20 foot tall bridge into a clear, deep current but would stay well clear of the George Washington and SF Bay Bridges.

            As for your suggestion that I “find the world [sic] longest and highest bridge and prove to the rest of the world that I am correct.” I don’t see the value in suggesting that anyone,especially an internet stranger, harm themself.

          • sniper74

            I don’t see the value in suggesting that anyone,especially an internet stranger, harm themself.

            Ah…hence the reason why I and many others state that the stupid idiot who is recommending others to not bother filtering water because it’s not necessary.

            Or do you fail to grasp what I am trying to say?

            You stated: He is not inherently dumb or dangerous just because you disagree with him.

            You just stated directly to me, that you don’t see any value in suggesting that anyone, especially an internet stranger, to harm themselves. So then why are you sticking up for Ethan if you are saying that there is no value in suggesting that anyone harms themselves. It’s clear that if you read the article (as I suggested you do) that Ethan clearly has not done enough scientific research to basis his argument off, and thus, publishing his crappy article, it could actually cause some stranger on the internet to harm themselves….something you clearly disagree with.

            So do you really enjoy circular logic that much that you just keep arguing this? Or are you ready to say, “Yes Sniper, you are correct, it’s clear that the guy has no clue as to what he is talking about on a scientific basis, and that the mere suggestion for people NOT to filter their water in the back country is clearly a stupid idea, and thus Ethan is clearly either someone who should be sued the first time someone attempts it and goes to the hospital, or he should be called out on the internet and perhaps even have his PhD revoked, for even suggesting this based upon the poor Scientific evidence and clearly poorly written article?”

          • Cooper French

            I am defending Linck’s position because I know him personally and we have discussed this topic at length. I mentioned this in another comment but I repeat it here b/c it helps explain why I feel so personally vested in this.

            I think where we disagree is I don’t see Linck’s original article as giving advice and others (not just you) clearly do.

            Here’s the closest Linck comes to giving advice in his article: “of course, even if the current absence of evidence were widely discussed, it’s likely many outdoors enthusiasts would continue to treat their water out of an abundance of caution. As a personal choice that’s fine, perhaps even commendable. But life is triage, a constant series of negotiations between risks of varying severity. And how we talk about those risks matters.”

            The title of the article can certainly be taken as advice to not filter water, but editors write titles, not authors. So if you want to lay responsibility at someone’s feet, I would say either an editor at Slate or the current internet economy of more drama = page views = ad revenue.

            Linck shares data and information and encourages discussion. He wants people to talk about the risks. I don’t think the suggestion of skipping filtration is inherently dangerous. There are risks I take like eating street food and drinking from streams and eating sushi that I acknowledge and accept responsibility for. To suggest that an article in Slate is going to kill someone seems to underestimate the critical thinking skills of the public generally and outdoor enthusiasts in particular.

            Sharing data and talking about it is important and good and more of life should involve individual choice and freedom over dogma or conventional wisdom. The more I look at the original article, the more I see how divergent the title and content are. They really do say two different things, and I think I only saw the content because of my previous discussions with Linck. But I can see how everyone else reads the title as the main argument of the piece, because it is right up in front and clearly influences how the rest of the article is perceived.

          • sniper74

            I don’t see Linck’s original article as giving advice and others (not just you) clearly do? Really? Seems to me the opposite…especially when TWO, count them…TWO articles come out specifically saying that he is wrong and WHY.

            Simply put: when you drink water straight from a stream, river, or lake, you have no idea what’s in it. And that’s bad, because, as
            epidemiologist Tara Smith, PhD, explained for SELF last month, it can be contaminated with all sorts of nasty things.

            While we like to think of ourselves as rational creatures, there’s no doubt that human beings are actually quite awful at assessing risk.So I can understand why Ethan Linck thought to contextualize the risk of drinking from backcountry streams with data. “Life is triage, a constant series of negotiations between risks of varying severity,” he wrote. “And how we talk about those risks matters.”
            Yes, it does—which is exactly why his piece in Slate last week was so damaging.

            Hmm…this is just from ONE article…the one above. Did you even take the time to read it? Or did you just gloss over it and with your obvious bias, dismiss it as nonsense?

            There is other research he could have cited—like this 2009 study from Georgia, which found 79% of water samples from rivers and streams in southern Georgia over a year tested positive for Salmonella.

            When you READ his Article…the title even states this:

            Actually, Backpackers, You Don’t Need to Filter Your Stream Water

            Hmm…so in other words, everyone should jump off a bridge….and you stated that was a silly thing to do. Remember when you said this? I don’t see the value in suggesting that anyone,especially an internet stranger, harm themself.

            So right there alone, along with his article…and all the other scientific data and studies done, clearly he is encouraging every backpacker to not filter water, to drink directly from a stream or lake or creek…which, according to something like 6 studies in this article alone, all state could be potentially harmful to oneself.

            So how can you say that you don’t value in suggesting that anyone to harm themselves, yet still back him? That’s called being hypocritical and contradictory.

            In fact, it’s unclear that dangerous protozoans and bacteria occur in very many of North America’s wilderness streams and lakes at all—and where they are present, they are usually found far below levels that should concern humans.

            Ah…yet in this article, clearly his statement is incorrect. Where is his evidence? One or maybe TWO papers? He doesn’t even link to those papers. Yet he calls himself a scientist? Clearly he has no clue how to footnote his work, or give credit where credit is due.

            This is the same issue with Climate Change and why so many people don’t believe in it. To many variables and no solid evidence. And the research that is presented in articles all speculate that their data comes from sources that “MAY” be caused by Humans. In other words…the science is still not 100% certain that humans are causing it.

            So if there are two articles, one in Outside Magazine, and one in Discover Magazine, all show proof that he is actually incorrect, then how can you support that? All the science actually leads to the conclusion that Backpackers SHOULD filter or treat their water in the backcountry.

            Then to go further, he uses race as a reason? How, then, did water treatment become the norm? Because the outdoor recreation community is far whiter, wealthier, and better educated than the U.S. population at large, it’s an interesting case study in how misinformation propagates through privileged communities.

            So now he is saying that it’s because most backpackers are white and privileged? How about all those in Africa or South America that can’t find good clean water and are constantly worried that they might catch some disease? Did he simply ignore those facts? Or did he just simply not include them in his “work”?

            Also, he clearly wrote this with a bias…and even states it. Full disclosure: I’ve also been drinking unfiltered water in the backcountry without incident for a decade, which may have biased my perspective.

            Science isn’t about bias. It’s about facts. He should know better, especially if he is a candidate for a PhD in Biology. Clearly he has no facts to back up his research, it’s written with a bias, he hasn’t done any scientific studies himself, and clearly he hasn’t done any actually research. If you can’t see that, then perhaps you should just stop right now, go back and remove your own bias, read it for the FACTS….ignore your own personal feelings towards him and focus on the science. Then perhaps once you do that, you will realize how stupid he was to suggest this.

            Again, go jump off a bridge if you don’t believe me. See what happens.

          • OWilson

            A life lived without risk is a very poor life indeed!


            Common sense plays a huge part.

            With it you can enjoy an occasional Burger King, bucket of KFC, or even a carbonized bar-b-qued steak, together with a Big Gulp of Soda.

            The inherent problems, come from giving advice. Should I share this advice with loved ones, without a detailed and peer reviewed study showing just what levels of poisons and carcinogenics each member of my family can tolerate. Perhaps a Medical Checkup should be included before such a meal?

            Ban it entirely, because some people abuse it?

            The problem is, when you take self sufficiency and common sense from the curriculum, you finish up with a dependent citizen who looks to authority/government to tell him what choices he should make in life, and a lot of people who gravitate to that authority!

            The problem with that is you have to trust them to be right, and unfortunately they are often wrong!

          • Bruce Nelson

            “But that same evidence finds waterways that don’t contain pathogens, so not all water is inherently unsafe.”

            Even if a surface water source is tested for one pathogen (such as giardia) and found to be free of it, there might be one or more other pathogens present, (viruses, bacteria.) And a surface water source truly free of a pathogen might be contaminated next time it’s tested. As a matter of fact, that’s been shown to be true many times. That’s why municipalities don’t use untreated surface water no matter how many times they’ve been tested and found safe.

            These principles aren’t just rhetorical arguments.

  • OWilson

    Whenever we street urchins could escape the smoke and smog of our steel town we took it. A hike, a weekend camping trip to the coutryside! The cost? A loaf of bread and a can of beans. A few pennies for bus fare to get us to the outskirts of town.

    We knew what and where we could drink, just like the natives in the jungle. No chemistry kit did we carry and nobody got sick, although we got beat up in other ways.

    Some rules I remember, never drink standing water from lakes, rivers, ponds or sluggish steams. Only drink clear fast running water, and always as close to the source of the spring as possible. We ALWAYS found good water.

    For us it was just “common sense!”

  • John C

    Boil your water. Don’t eat any cute looking mushrooms. Don’t try to pet anything.

    • OWilson

      And, of course, don’t eat yellow snow!

  • Bruce Nelson

    Truly a great article. Well done!

  • Elia Sinaiko

    No wild water is safe any more. At 10,000 feet in the Sierra Mountains we thought water would be safe, until we heard of back packers taking a dump in the snow pack above us. Don’t risk Giardia!!

    • Robert Blake Briggs Jr

      I only drink “wild” water from known artesian springs. Any surface run of water risks contamination. I do miss drinking from streams, though, to be honest.

  • Lee Riffee

    There is a good reason that wine (and sometimes other alcoholic beverages like beer) were so important and mentioned so often in antiquity – up until the advent of modern sanitation and water treatment, water has always been rather risky to drink!

  • Marcy Tiffany

    My grandfather died at the age of 32 when he drank from a stream. It turns out an animal had died and fallen in the water upstream. I also have a friend who recently died after several years of pain and suffering from a disease she contracted while swimming in a polluted stream. It is irresponsible of Slate to publish an article that could well cause people to suffer or die.

  • Marshall Gill

    Stream water? You need to filter TAP water! Better filter the bottled stuff too, just in case. You can’t be too safe.

    • sniper74

      Most bottled water these days are nothing more than tap water that some company has decided to call Spring Water.

    • Rob H.

      In the Philippines, maybe. Tap water in the US is incredibly safe. No need to filter it at all.

  • Stinky Taint

    Wipe your butt with fiberglass softened with bear poop…it’s okay. (just giving a Slate-type opinion.

  • Jared

    I think the original article was attempting to attack the myth that every drop of water in natural settings is poison, which is how most people have been trained to think in the last couple decades and is the part I object to as well.
    Saying people should not treat at all was a mistake though, there is
    some risk, but it is pretty difficult to estimate.

    My experience is that the risk of getting sick is far lower than generally assumed, at least here in the US. I don’t treat except in rare cases. I personally know 3 AT through hikers (that’s 2000 trail miles, about 4 months, and a lot of water stops) who did not treat at all. They did not get sick, or it was minor enough they did not notice. In terms of the number of times they pulled from different water sources and drank without getting sick, it is probably 250 times each conservatively. I melt snow without boiling it on my mountaineering trips too.

    People sometimes tell me with great confidence that anyone who does not purify every time is a moron, that it is all toxic, and that confidence is what annoys me given my experience.
    My argument is that people I know who do not purify have a more realistic view of the risk. They know there is a risk, have found it
    to be quite low picking water sources with some awareness, and take
    that risk knowing it could bite them some day. For the most part it
    makes outdoor travel faster and easier.

    I reiterate that I think this quote from the article is the most accurate:
    “Risk in this area is very hard to quantify”
    Most people understandably play it safe. I have not, along with some others I know. Either due to skill, luck, or those factors in combination with the risk being much lower than generally thought, we have not been sick.

    I would be happy to see widespread testing done to establish danger areas/ how likely sickness is to occur. Its not a high enough priority to spend the kind of money on testing to do that though, so we don’t, and it is understandable. So small samples, limited testing, and anecdotes are what we are left with to argue over.

    To comment on some other posters;
    There is plenty of safe wild water, and statement like “there
    is none” are just as silly as saying you can’t possibly get
    sick. A single poop on the ground does not make all water foul.

    Thinking tap water is not safe would explain why
    the bottled water industry that often pulls from tap water sources is
    so successful; the bottle gives a psychological sense of safety even
    when it may literally be tap water.

  • siempre44

    Slate UsedToBe a real news site. Sadly, it has gone left wing propaganda and that has contaminated all the articles ‘ quality. “Raw water” is all the liberal rage so Slate puts in a literally dangerous but politically correct article about drinking untreated water. Sad fake news…which is all Slate is now.

  • Rob H.

    A lot of people don’t take very simple precautions while hiking. For example, if you’re in an area with bears, it’s important to make noise so they can hear you coming, because bears are usually afraid of humans. So wear little bells on your person, and have some pepper spray, just in case. It’s important to know which kind of bears are in the area, and you can tell this from their scat. Black bear scat is usually dark and compact. Grizzly bear scat is larger, smells like pepper spray, and has little bells in it.

  • Captain Obvious

    It’s okay to play Russian Roulette because only one chamber has a bullet so the chances of losing are small.

  • Ray Mainer

    I’ve been drinking water straight out of streams in the Sierras for ten years now and haven’t had a touch of diarrhea, of course I am careful of what streams I choose. I have drunk untreated water out of Adirondack lakes for over 50 years and even drank untreated water out of Lake Champlain for years. (I thought it was treated.)

    • Veritas

      I had a friend who smoked everyday from the time he was 16. Died at age 85. He claimed smoking was safe and he was the proof…so go ahead and light up

  • Cooper French

    This comment is written largely in response to the other comments already offered. Disclosure: I know and work with the author of the Slate piece, Ethan Linck.

    This issue of water purification seems to fall into a prevailing dichotomy: dogmatic adherence to strict safety measures or independent assessment and acceptance of risk.

    A lot of outdoors recreationists were taught by their parents or troop leaders or NOLS instructors to ALWAYS treat drinking water. This is a good, and possibly life-saving rule, for much of the non-municipal water in the USA. But some water is very clean. And some people feel comfortable making an assessment based on their location and experience and what little information we have on backcountry water pathogens. Those people take an the risk and responsibility for those actions.

    Ad hominem attacks (author A is dumb/dangerous), No True Scotsman fallacies (author A isn’t a real biologist/backcountry user), and appeals to authority and anecdote (my NOLS instructor told me, my uncle got giardia) don’t actually address any of the issues in the original article or this response. This is a good dialogue to have that deserves better intellectual engagement than the dogmatic responses here.

    • Bruce Nelson

      This Discover article blows the Slate article out of the water with data, not ad hominem attacks.

      This isn’t that complicated. As Dr. Timothy Welch said: “Published reports of confirmed giardiasis among outdoor recreationists clearly demonstrate a high incidence among this population.”

      All, or nearly all, backcountry giardiasis outbreaks have been traced to water. The EPA says “Cysts have been found all months of the year in surface waters from the Arctic to the tropics in even the most pristine of surface waters.”

      People will be making POORER assessments of risk if the data is as irresponsibly presented as it was in the Slate article, for example: “while giardiasis was prevalent enough to justify concern, there was no connection between recorded cases and drinking backcountry water.” That’s an absolute falsehood. MULTIPLE CDC WATERBORNE GIARDIASIS OUTBREAKS people! And outbreaks are the tip of the iceberg. As in less than 1%.

      My collection of most of the available research was cited in the Discover article. :

  • Ken Murray

    I object to the sensational nature of this article. The author specifically cites the possibility of death. How many PCT hikers have died of diarrhea? 0, AT hikers? 0 CDT hikers? 0

    Where are all these hiker deaths that are suggested that are being risked? There are none.

    • Bruce Nelson

      “you don’t need to filter stream water” THAT’S a sensational, click-bait, irresponsible, scientifically indefensible title.

      It’s not just death that people are concerned about. Being sick for days or weeks or months or years is a significant risk that can’t be dismissed.

      “Our data are based on a waterborne Giardia outbreak, causing
      gastroenteritis in a large population of individuals presumed not to have been exposed to this parasite previously. This unfortunate event made it possible to study the natural course of IBS and CF after giardiasis, and shows a significantly increased risk for both IBS and CF even 6 years after the infection.”

    • disqus_atlq8Zmtsd

      Per the World Health Organization: Contaminated drinking water is estimated to cause 502 000 diarrheal deaths each year

  • Patrick Campbell

    Slate’s article is as irresponsible as telling a child not to look both ways when crossing a street because his chances of getting run over are only 1 in 7.

  • PaulJKrupin

    Excellent analysis. Beware – when it comes to field water purification you get what you pay for. Don’t fall for the advertising and packaging claims and the praise of non-scientists and lay hikers. Retired hydrologist water quality specialist talking. I did original research on giardia in the mid 1970’s. Katadyn and MSR have the best tested equipment. Without naming product names, the data continues to show that anything made with natural or artificial fibers cannot be trusted. I speak at the IMAC Backpacking School every year. Here’s a link to my presentation in a pdf file on Backpacking and Water Purification Remember – science is not the same as the marketing and advertising. The products and the claims they make are poorly regulated. Bottom line. Look for the NSF 53 and 58 accreditation for giardia cyst removal and even then, don’t push the product beyond what it is designed for. Be careful with your life and those you love and care about.


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About Christie Wilcox

Dr. Christie Wilcox is a science writer based in the greater Seattle area. Her bylines include National Geographic, Popular Science, and Quanta. Her debut book, Venomous, released August 2016 (Scientific American/FSG Books). To learn more about her life and work, check out her webpage or follow her on Twitter, Google+, or Facebook.


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