I’ve now read what seems like the 100th post-PCT thru hike gear review where the author states something to the effect of:
“At first, I used a filter (sawyer mini, sawyer squeeze, whatever…), but it quickly clogged and I became tired of the low flow rate and the general hassle of filtering. Once I got to the Sierras, I just used bleach drops instead and it worked great, so I sent the slow filter home!”
This has gotten me thinking about how much we all might just be kidding ourselves with the effectiveness of our chemical water treatment.
The Centers for Disease Control and Prevention (CDC) clearly states here and here that chlorine (i.e. bleach) is ineffective at killing Crypto and has only low to moderate effectiveness at killing Giardia. It’s effectiveness at the actual concentrations used by most backpackers, might be even lower.
Additionally, the CDC also states that chlorine dioxide (i.e. aquamira) has only low to moderate effectiveness at killing Crypto, though unlike bleach is highly effective at killing Giardia.
Let’s be honest, very few of us wait the actual 4 hour period of time prescribed for killing Crypto with aquamira (drops or tablets, it makes no difference, just ask McNett– though this is a common misconception).
Clearly, many of us (at least lots of these PCT hikers I’m reading about) also just use bleach, so effectively killing a real Crypto threat in this scenario is totally out of the question.
So what I’m getting is this:
1) People using the two common chemical water treatment methods (bleach or aquamira) are probably safeguarded quite well against bacterial and viral infections from their treated water.
2) People using aquamira are probably safeguarded quite well against Giardia infections from their treated water.
3) People using aquamira are probably not safeguarded very well against Crypto infections from their treated water.
4) People using bleach are probably not safeguarded very well against Giardia infections from their treated water.
5) People using bleach are definitely not safeguarded against Crypto infections from their treated water.
So in summary, whether using bleach or aquamira, and using it in the way that we all commonly do (i.e. not waiting for hours and hours before drinking and also often treating very cold water), we seem to be opening ourselves up to protozoan infection by either Giardia or Crypto (or both).
These are the pathogens that people seem to worry most about, but we are actually doing the least to protect against them when using chemical treatment.
So my question is, are we just kidding ourselves with our chemical water treatments? If Giardia or Crypto are actually in that water, are we going to get sick anyway?
If so, why even treat?
Is there any actual data on the prevalence of Giardia and Crypto in backcountry water sources where backpackers commonly collect water? I’ve been very frustrated in my own limited search, having come up pretty much empty handed trying to find real data concerning this topic.
Thoughts?

