Hi everyone,
So I know a lot of us carry iodine for water purification. I did a bit of research today, and found that BOTH iodine AND chlorine are pretty poor at purifying water from giardia or cryptosporidia.

Regarding cryptosporidia:
"For individual use, water can be decontaminated by bringing it to a boil or by passing it through a filter with a 1-μm or smaller pore size. Generally, chlorine and iodine are ineffective."

Regarding giardia:
"Individual water supplies, such as for travelers or backpackers, should be boiled or filtered. Water filters with pores of 1 μm also may be used. Giardia and Cryptosporidium are relatively resistant to chlorine or iodine treatment."

This article came from the journal "Gastroenterology Clinics" Vol 35, No. 2, June 2006. An interesting read if you know your science, though it's pretty basic.

Chlorine Dioxide is NOT chlorine. CLO2 is effective against Crypto and Giardia.
There have been several threads about this subject.

What Bill said. Do not confuse Chlorine and Chlorine Dioxide.

Chlorine = No
Chlorine Dioxide = Yes

A while back someone put a link to an Army web-site that rates water treatment devices, and that web-site rated the "pure" chlorine dioxide treatments highly, but they rated the MSR Miox lower since it creates a "mixed oxidants" solution rather than a pure chlorine dioxide.

I really wish someone would do a independent test of the Miox's effecacy for killing Giardia and Cryptosporidium in comparison to chlorine dioxide, boiling, and the UV "pen" technology.

Yes, thank you. As I said in the original post... chlorine. NOT ClO2. To add another quotation "Incubation of oocysts for up to 2 hours in household bleach failed to decrease infectivity [19]."

Though I'm not sure how ClO2 can be used in the field, since it appears that the gaseous form is used for water purification, and the liquid form for hard surfaces (according to the EPA sheet).

CLO2 is available for use in the field as Katadyn MP1 or McNett Aqua Mira products.

Cool. Looking at how unstable this chemical is, I'm suprised that it's available. Thanks for the heads up.

The other option is a small vial of bleach. But you have to repack, which costs you some effectiveness.

So what does this mean for those who carry iodine for water purification? Should we all switch over to Micropur tabs? How great a threat is Giardia and Cryptosporidium ? Thanks

I am also building my base of knowledge on water disinfecting methods.

My standard practice is to filter the water. If I am unable to filter, I boil it (3+ minutes due to high elevation).

I am trying to come up with option #3.

I purchased "Tincture of Iodine" yesterday. I had to talk to the pharmacist to locate it "behind the counter". (Sounds like it is used to make meth).

Cody Lundin recommended 5 drops per quart.
I always try to get second/third confirmations to information I read. I found good confirmation here:
http://www.cdc.gov/travel/water_treatment.htm
(NOTE: say's safer and might not kill)

As far as effectiveness vs risk studies, any good references for idodine, Chlorine Dioxide, or other recommended chemicals?