View Full Version : water treatment and illness

11-17-2004, 14:00
I just read a brief review of "Long-Distance Hiking: Lessons from the Appalachian Trail." One paragraph jumped out, to quote:

" Water treatment/purification: 59% of hikers never treated or purified water, or did it rarely. Also, the majority of hikers (57%) simply used iodine. The highest rate of people that became ill used chlorine, while the lowest was the iodine users; in the middle is the filtering, boiling, and no treatment crowd. But, other than the chlorine crowd with a 75% illness rate, the rest all come within a few points away from each other's average at about 29.25%."

Although I haven't read the book, the review says that the author surveyed hikers (136) asking them a variety of questions. From the data collected, the author talks about different variations in hiking, gear, etc.

Leaving aside the puzzling statement that 59% never treated water while the majority used iodine, even if one assumes that there was an even distribution of hikers using iodine, chlorine, and other methods (including no treatment), and even if other related variables were entered, the sampling number itself does not allow for statistically significant results to generalize that chlorine users are more likely to be sick than iodine or "other methods" users (unless I was completely sound asleep on the day sampling size was presented in stats class, which is entirely possible).

All that said, I'm still paranoid enough to wonder if there might be something to the idea that chlorine treatment simply isn't as effective as iodine?

SGT Rock
11-17-2004, 14:14
I think that there maybe something to the chlorine, but who knows. As I remember from that book and other things I have read, water is rarely if ever the cause of illness. I think that hand sanitation and sharing of food has been listed as the key culprit in most cases.

That said, use what you feel most comfortable with and wash your hands before you eat. Personally I like the lightest and simplest method which for me is iodine.

11-17-2004, 14:24
Sometimes I feel like I sounds like a broken record, but here I go again...

Chlorine does not kill giardia when used at a level that is palatable (i.e. doesn't taste like swimming pool water).

Here's a link (http://www.bchealthguide.org/healthfiles/hfile49b.stm) to the canadian ministry of health website that specifically says in part :

" NOTE: Bleach does not work well in killing off beaver fever (Giardia) or Cryptosporidium parasites. The amount of bleach needed to kill these parasites makes the water almost impossible to drink. If beaver fever or Cryptosporidium are in your water, boiling is the best way to ensure safe drinking water. "

Seems pointless to use if this is what you are trying to kill...


11-17-2004, 14:30
I also carry iodine - though I have seldom found need to use it on the southern trail.

However, I am about to do a section hike in the Shenendoah National Park, and the trail stays close to the roads. I may well use iodine more.

I use a variation of Polar Pure, and just this morning made a modification of the way I use it.

I bought the polar pure bottle a year or two ago and put about 10 of the pellets in a one ounce motel shampoo bottle. I have always been careful to not pour the pellets out of the bottle into my platypus water supply, but sometimes this is a little difficult.

So, this morning, I took those pellets and put them on a scrap piece of noseeum netting. I put my finger on them and gathered the netting up around my finger and then formed a little sack, like a minature pot-parie sack.

I took that to the sewing machine and sewed across the top of the little sack, trapping the pellets in the bug net.

Then I put the little sack in the shampoo bottle. (The sack is about a half inch tall) Then I filled the bottle up with water.

This arrangement has a couple advantages.
- It is easy to carry the bottle in a pocket, which warms it and this causes more iodine to be disolved in the bottle.
- The temperature of the bottle is standard (about 80 F) , and I no longer need the the "thermometer" on the side of the standard Polar Pure bottle
- The weight and bulk of the system is much reduced.
- I can easily pour the concentrated iodine solution out of the bottle into my Platypus without worrying or fussing with the possibility of the pellets getting out of the bottle.

I have used the lightweight version of the Polar Pure for more than a year. I hope and believe that this modification will make it even more useful and user friendly.

11-17-2004, 14:48
Why do you feel that you that the 136 hikers is not sufficient to test for differences? That's a relatively large sample.

If you categorize as iodine, chlorine, and all others, and sick yes/no, you have a 3X2 table that you could use a Chi-square test for. Provided there were no low count cells (rough guide, 5 or fewer counts per cell), you could test for an overall statistical difference. However, you can't test the groups one against the other this way.

Alternatively, you could record each person as sick or not (yes/no). This data is then binary and a logistic regression could be used with one independent variable treatment type. You could then compare the groups using a multiple comparisons adjustment.

11-17-2004, 14:49
OK ...so chlorine isn't the answer. But how about chlorine dioxide (aka "Aqua Mira").

I carried Aqua Mira on my thru last year and had no after effects (of which I am aware). At highter elevations I rarely treated my water at all.

Like Sgt Rock, I am a believer that most GI trouble on the trail comes from poor hygene and not from ingested water.

AT 2003

11-17-2004, 15:30
I would say chlorine dioxide is just fine. It's nothing like chlorine. Comparing the two is like comparing Hydrogen (bursts into flames al a the Hindenburg) and dihydrogen oxide - water used to put out a fire...

chlorine dioxide is commonly used in city water treatment.

We will and do treat all our water. It's the old risk verses impact trade. The implimentation of it is so easy, the impact so high, that even with a low risk level it is worth doing in my opinion.


11-17-2004, 16:01
...the sampling number itself does not allow for statistically significant results to generalize that chlorine users are more likely to be sick than iodine or "other methods" users (unless I was completely sound asleep on the day sampling size was presented in stats class, which is entirely possible).

Actually, national polls are based on 800 or so in a nation of 250 million. 136 out of a few thousand is a pretty good ratio, though the fact that the 136 were not statistically chosen, may skew the results.

However, I'm not surprised at the results because there is little evidence that most trail gastro-intestinal problems are caused by drinking water. I think the evidence is overwhelming that hikers with a bit of common sense face very little risk from not treating most of their water. My practice is to either boil or simply not drink suspect water sources from near towns or farm animals and drink the rest untreated. In 75 years I have yet to become sick from drinking untreated water as near as I can tell.


11-17-2004, 17:30
Actually, national polls are based on 800 or so in a nation of 250 million. 136 out of a few thousand is a pretty good ratio, though the fact that the 136 were not statistically chosen, may skew the results.

Good point on the fact that the 136 may not have been randomly selected. In particular, perhaps some folks were too sick to participate in the analysis;) . Small sample sizes and the concurrent low margin of errors (usually around 2-4%) are possible because the questions are typically Yes/No. The statistical power curves for binary data often have easily attainable sample sizes. Sample sizes for estimating other types of responses (i.e. continuous) can inflate much higher, it all depends on population variability.

11-17-2004, 17:43
Looking at Apendix 2 in Long Distance Hiking:

Question 31: Did you purify your water?

Always 14%
Usually 27%
Sometimes 41%
Never 18%

How did you decide? Appearance, nature of source, proximity of farm animals

32. If you purified your water, how did you do it?

Iodine 43%
Boiling 11%
Filter 30%
Cholrine 3%
Never purified 13%

33. Do you believe bad water ever coused you illness? 6% of all hikers contracted Giardia, 30% suffered some kind of gastrointestinal illness. There was no discernible trend indicating wter treatment prevented infection. (Mueser's words, not mine).

But, I'll certainly agree with Rock and others that most illness is probably attributed to poor hygene.

Also, note that this survey was done in the days before Aqua Mira and Miox.

11-18-2004, 10:00
I appreciate all the comments. I don't have the guts not to treat or the knees and money to carry a filter, so iodine it shall be.

Sorry if the question was redundant and for my poor statistical analysis. I should have had a mug of Cafe Buestelo before the class on sample size, confidence intervals, and all the other stuff I've now forgotten...

11-18-2004, 10:12
I appreciate all the comments. I don't have the guts not to treat or the knees and money to carry a filter, so iodine it shall be......................etcetcetc...

i follow my buddy, Model T's rules....

if it comes directly out of the mountain or ground....i dont filter...
if questionable, slow moving, or other variants...iodine tabs.....

i NEVER carry a filter! :D

SGT Rock
11-18-2004, 10:28
True, I hiked for years before I found out about using iodine, but it doesn't hurt to use it and I don't mind the taste. I tried a filter once and hated it.

11-24-2004, 06:58
Be Carefull with poll results-they may not be "skewed" correctly!

I wonder just how many of those hikers polled would have contracted some form of gastrointestinal illness had they just stayed home and not gone hiking at all. If the sample is large enough one is bound to find someone who dies after drinking a glass of water-but you wouldn't infer from it that all water kills.

I suppose we are so accustomed now to getting our water from a spigot at home-water that has just passed through the watchful eye of some municipal waterworks- instead of from a well in the ground- that we have began to distrust all water that doesn't come from a "safe" spigot somewhere. It's a shame that so many will miss the taste of the delicious, untreated water from those cold mountain streams

The Hog
11-24-2004, 08:50
I urge newbies not to make a decision on whether to treat/filter their water based on polls or anecdotal opinions. Base it on science, do your homework, talk to an expert, preferably someone with experience in water microbiology. I spent 16 years working in a water microbiology laboratory. Want some free advice?

Worldwide, water treatment exists to eliminate the threat of cholera, dysentary, typhoid, and hepatitis. Those are the major killers. But they're just the tip of the iceberg. There is a huge array of viruses, protozoans, and bacteria thriving in aquatic environments, even those considered "pristine." If you think it's just giardia, think again. There is a long list of pathogens, including cryptosporidium, adenovirus, coxsackie virus, reovirus, campylobacter, etc. etc. in surface waters. And there is an even longer list of so-called opportunistic pathogens (ready to multiply inside you when your immune system is down).

Those so-called "pristine" sources are not as pristine as you think they are. Remember, even at high elevations, there are plenty of wild and domestic animals regularly visiting these springs and rivulets. I have personally witnessed a deer pooping and peeing into one, an elk peeing into one, and I unwittingly once drank from a source next to a moose carcass (I filtered the water and did not get sick).

In the Rockies and Sierras, horse packing trips and cattle deposit fecal matter everywhere, such that watersheds are contaminated right from the source. On the A.T., wild animals and hiker's dogs traipse thru the springs on a regular basis. I have tested streams emanating from a wildlife management area (almost zero human habitation) and have consistently found proof of fecal contamination. Animal scat is deposited directly in water sources, animals die in the water and decompose, and rain washes scat into those same sources. Are some sources cleaner than others? Sure, but you can't tell by looking at the water (I have tested water that looked absolutely pure but was loaded with bacteria).

I doubt that you would want to drink the organisms that are in poop. Out in the woods, nobody's going to stop you, and yes, you may get away with it. There are plenty of people on this site who claim that they drink without treating or filtering and never get sick. But there's just as many with horror stories (I have personally been thru that hell). What can you conclude from these conflicting opinions? You can safely conclude that drinking untreated water is a roll of the dice.

I've said it before, but it bears repeating: Why would you want to risk your trip of a lifetime?

11-24-2004, 10:20
Don't be so afraid to venture a few steps upon the road less travelled, Hog. I'm sure you'll be pleasantly surprised at what you may find if you do ;)

I'm not suggesting that you drink from a cesspool, either. Just dont immediately assume that all your water sources are such.

11-24-2004, 10:38
Fear of drinking the water has and always will be a problem for many. A guy starting the AT nearly died from dehydration untill he was pulled off the trail at Suches,Ga to get treatment. His problem was fear of drinking too much of the water along the trail. I too am concerned about water quality and so I filter when the water is suspect, especially at low elevations where run-off may have occured. You have got to drink lots of water to stay hydraded so get a filter/chemical and get over any fear of drinking the water. Dehydration will kill quicker than most gut disease.

11-24-2004, 11:09
Fear of drinking the water has and always will be a problem for many. ....

I suspect, one reason the statistics don't show any difference between treating and not treating water is that in my observation very few use the care needed for treatment to do any good.

It takes more care than I've ever used to keep "contaminated" water from filtered water using most of the popular filters.

In cold water (think at least through May in Georgia and North Carolina, and always on the high ridgelines of New England) it takes eight hours for iodine to complete its killing powers and even then some harmful things survive.

When I'm hot and sweaty on the trail and come across an icy cold spring, somehow, I'm never inclined to wait eight hours for iodine to do its thing. I find it best to just leave the filters and the chemicals at home. That way I don't feel guilty when I just indulge.


Mr. Clean
11-25-2004, 09:11
I have 13 years of time in a water filtration plant where I do water microbiology as well, and as Hog says, it's a roll of the dice. I've seen whats in the water, and I'm not drinking it. Thats not to say that if I come upon a spring running right out of the ground that I'm not going to drink straight from it, but I filter 95% of the time. I'm not taking the chance, and I've never gotten sick. (famous last words...)

Lone Wolf
11-25-2004, 09:22
I have 18 years and 16,000 miles on the AT and I've never filtered or treated any water. I'm taking the chance and I've never been sick. :)

The Hog
11-25-2004, 09:47
I've been down the road of no treatment/no filtration and have paid the price. Now, there is no fear, just a lesson learned. I'm glad many of you who don't treat or filter have not gotten sick, more power to you. But others have gotten sick, which says to me that it's still a roll of the dice.