I saw that study. I'm more curious now as to why the CDC put that warning on their site.

My guess would be that their warning was meant very literally. Their study only applies to filters which use ultraviolet light (many of which are probably gimmicky and do not expose the water to ultraviolet light long enough to kill cryptosporidium oocysts). Since the SteriPEN is not technically a filter, this particular CDC study does not apply to it. Using the SteriPEN according to its own instructions should yield similar results as the studies done specifically on the SteriPEN.

I was thinking along similar lines. I don't think the particular NSF protocols mentioned on that page (53 and definitely not 58, which applies to RO) can accomodate UV products. There's an NSF 55: Ultraviolet Microbiological Water Treatment Systems protocol, however I'm not sure if that applies to personal purification products or just larger products for municipal use. And I'm not sure if NSF 55 mentions crypto.

I looked at the NSF site as well. NSF only tests products submitted to it. The submitter must pay for the cost of the testing. I suspect that Steripen hasn't submitted for testing as of today.

The question I have is re viruses. Does Steripen kill viruses too? Or did I miss that on the site? If Steripen kills viruses, then it might be a really great thing to have while travelling in warm climates, superior to filters.

I don't think I'd depend on anything battery operated in a cold climate, but I suppose one could always take spare batteries, and can warm the batteries by placing them in a pouch around one's neck which will increase performance.

My thought on the CDC is that the SteriPen may not kill the cysts. Basic science, there are cysts (kind of like the microbe version of a spore) and then there's the active microbe. So, killing Crypto would technically be correct, if it's killing the active, mobile form. Leaving the cysts un-treated would thus cause both Steripen's claims and the CDC's claims to be technically correct.

Of course, that still leaves the cysts to wake up in your gut and give you diarrhea.

I've been reading up more on this today. UV irradiation (254nm, like the Steripen) does inactivate the crypto cysts, preventing sporolation or excystation. Although most articles do mention in the discussion section the hypothetical possibility of some DNA repair mechanism eventually reactivating the cyst, all the studies I've read do conclude that the inactivation is irreversible.

Regarding the question about why the CDC says UV may not kill crypto, I ran across one comment for a household UV purification system regarding crypto. The kind of system that works with your kitchen faucet. It mentions that a particular countertop model is not really recommended if you're worried about crypto because at the usual rate that household water pressure flows through the unit, any given volume of water may not be exposed to UV long enough to thoroughly inactivate any crypto cysts. However, with the Steripen, you are thoroughly exposing the water to UV, so I see no reason to think that it won't effectively kill any crypto cysts in the water.

And regarding the lack of a NSF certification, apparently the NSF protocol is rather specific and a UV product like the Steripen doesn't fit into the protocol, therefore it can't readily be tested by NSF. That's why Steripen advertises the fact that it passes the EPA standards for water purification. The EPA protocols require a similar level of purification as the NSF standards, but the protocols are flexible enough to accomodate a product like the Steripen. So, as I mentioned before, as long as the water isn't turbid or full of sediment, limiting the transmission of UV throughout the water to be purified, the Steripen should do a good job.

Actually, looking this stuff up was a good exercise for me since I do have a Steripen myself.

The Steripen does great against viruses.

I used to use one, but my biggest pet peeve was the way it let you know you had filled up a bottle or had a dirty cylinder was to squirt you without warning!

I currently use a PUR hiker and love it. I use the ubiquitous MP-1s as a backup. And of course there is always boiling.

Interesting. Was that on the Steripen site and I missed it? Can you point me to any studies or articles?

I've never carried a full on filter. I've hiked with guys who do and my opinion was always that they were bulky, time consuming, and just not 'hiking' gear.

That's why I picked up the MIOX Pen. I guess had the Steripen been readily available when I made the purchase I could have gone either way but I'm not unhappy with mine in the least. My only beef with the steripen is that the water needs to be clear and you need to have the right bottle to get it inside. I like narrow neck bottles and bladders...seems to me like the Steripen would be awkward with those vessels.

I also carry MP-1s as backup.