Water contaminates - how much does it take to get sick?

For example, when dipping your bottle into dirty water and treating with chemical or UV, is it correct to assume that you will not get sick from the small amount of untreated water on the brim or outside threads of your bottle?

In other words, a large amount of bacteria is much worse than a tiny amount of bacterial... Or does it only take one contaminate to get sick?

It depends on the person, their tolerance and the particular bug.

In most cases a few drops here or there are harmless, otherwise people would get sick from swimming in lakes.

I wouldn't worry about small amounts of water.

Swimming in lakes is a good example. I figured you should have some natural tolerance to small amounts contaminates, but wasn't sure.

"is it correct to assume?"

No. It seems like we keep going over the same subject, over and over.

First of all, you have to assess the water quality to decide what the likely risks are. Since we aren't carrying instruments, about all we can rely on are the clarity of the water and it's distance from mammal habitations.

There are a few different water risks, so you have to guess what you are up against. A virus can cause disease, and some are pretty nasty, like hepatitis. A poor filter won't touch that. Bacteria can cause disease, and some are pretty nasty, especially some of the tropical types. A poor filter won't touch that. Protozoans can be in the form of microscopic eggs, called cysts. They are not normally lethal, and it may take some number of them to actually make you sick. Or not. A poor filter may not be very successful against them. Then you have chemical contaminants, like agricultural and industrial chemicals. You almost have to go after those with chemical treatment.

There are multiple risks, and there are multiple methods of prevention. You can boil the water. You can filter it. You can treat it chemically. You can treat it with strong UV light. There may be other methods. However, if you don't know what you are up against, you have to make a stab at it. In some of the risks, if you can eliminate 99% of the organisms, then that is probably good enough. There are some rare risks that would almost require you to eliminate 100% of it to feel safe, but those are rare.

With all that in mind, what do I do? I travel mostly high in the Sierra Nevada range, and the snow melt is cold even into the summer. Normally, I carry a tiny 2-micron filter hooked up for gravity flow, and some household bleach. I filter the raw water and then drink it. If I think the raw water looks suspicious, then I pre-treat it with the bleach. If either of those methods is gone, then I boil the water. So, somehow the water gets treated one way or the other, and I have never gotten sick from the water for the decades that I have lived in California. Note that the next person might be more or less sensitive, so they need to adjust their methods.

Yes, it is possible to get sick from a few drops of raw water left on screw threads of a water bottle. Is it likely? Hard to tell. Do you feel lucky?

--B.G.--

> In other words, a large amount of bacteria is much worse than a tiny amount of bacterial...

Basically, correct.

EPA specifications do not require a treatment method to eliminate ALL the bugs. They only require that the filter or whatever reduce the concentration to a low value. This is where the '5-log' reduction comes in. This is because you do encounter these bugs all the time (day to day) in your life, and you do have some natural resistance. You only get sick when your natural defences are over-whelmed.

So a few drops of untreated water will not be significant when diluted by the rest of the litre container of treated water. Sure, take some care, but don't be paranoid.

Bob's comments are technically correct, that there can be bugs and you can get sick. But the probability or risk factor in most cases is very low when up in the mountains. Many of us don't bother to do anything, but that is an individual choice. I carry a Steripen Opti, but I rarely use it.

On the other hand, near 'civilisation' (towns or farms), be a bit more careful. Concentrations of bugs can rise dramatically, and farms (and towns) also discharge nasty dissolved chemicals which can NOT be treated out of the water. I just don't use such sources at all.

Cheers

With giardia, the ingestion of only 10-25 cysts can lead to giardisis. Thankfully it is quite rare. Some bacteria (can't remember which off the top of my head) follow the same rule with just a few cells leading to the disease process, while others like ETEC E. coli (traveler's diarrhea) require 10^8 or more bacterium before clinical disease is apparent so it really depends on the location and which organisms predominate. That small amount of water on the brim of your bottle does carry a theoretical risk, but probably will never give you problems.


sources: Uptodate

Edited by godsfshrmn on 03/30/2011 16:30:58 MDT.

I pour a little clean stuff from inside the bottle over the lip and threads, gravity does the rest.

Don't forget the variable of your own particular well being at the time. Eating well, keeping warm and resting well? Or eating crappy, feeling cold and exhausted? Drinking from that same pond can give you two totally different experiences!