[at-l] Water filters vs. Tablets?

[mcdermo at verizon.net (McDermott)]

I found the following on a Potable Aqua web site.  It is the first time 
that I have seen guidelines from  Potable Aqua about how long you can 
use their product.
They say you should not use their product for more than 6 weeks, but 
then go on to say that other studies found no problems when used for 16 
weeks and even up to 6 months. (for what ever that's worth...)
Panzer


HOW LONG MAY I USE POTABLE AQUA?
Potable Aqua tablets are to be used as a short-term, emergency treatment 
for disinfecting drinking water. Potable Aqua should not be used on a 
long-term, continuous basis.

According to label directions, the recommended dosage of Potable Aqua is 
two tablets in one liter or quart of water. This dosage is equivalent to 
16 ppm of elemental iodine in the water. Since this product is intended 
for use in emergency situations, extended daily use should be kept to a 
limited basis and not exceed six weeks.

The recommended dosage of Potable Aqua, as indicated by the directions 
on the label, is two tablets in one liter or quart of water. With the 
recommended dosage of two tablets per liter of water, 16 mg of elemental 
iodine is released in the water. This dosage is equivalent to 16 ppm of 
elemental iodine in the water. Since this product is intended for use in 
emergency situation, extended daily use should be kept to a limited 
basis not exceeding 6 weeks.

Several studies have demonstrated that no evidence exists indicating 
long-term use of iodinated water as being deleterious to the health. 
These studies include A.P. Block's paper in The Journal of America Water 
Works Association, Vol. 60, Number 1 and Donald P. Morgan's study, "Test 
of Chronic Toxicity of Iodine as Related to the Purification of Water," 
which appeared in The United States Armed Forces Medical Journal, Vol. 
4, Number 5.

Subjects in Morgan's study consumed iodinated water for 16 weeks at a 
daily dosage of 12 milligrams per subject per day. During the last ten 
weeks of the study, the iodine concentration was increased to an 
estimated dosage of 19.2 milligrams per subject per day. Analysis of the 
resulting data revealed that subjects did not suffer weight loss, 
failure of vision, cardiovascular damage, altered thyroid activity, 
anemia, bone marrow depression, or renal irritation. It was the opinion 
of the investigators that consumption of iodinated water over a six 
month period did not result in an unusual incidence of any form of skin 
disease. There was no evidence of sensitivity to iodine among the 
healthy subjects, nor was there any indication of impaired wound healing 
or resolution of infections as a result of consumption of iodinated water.

These tests furnish evidence that Potable Aqua contains an iodine level, 
which can safely be used for short-term use.

------------------------------------------

<>(Note: each tablet contains 8 mg/Liter iodine)
Also note that AT hikers may be using as much as 2 pills per liter for 
very dirty water, that would be equal to 16 Mg/Liter Iodine.  However I 
would recommend that you not treat or consume very dirty to start with.

 In another 6 month army study of presumably healthy young soldiers, I 
found:

"Morgan and Karpan added 12-19 mg/L  iodine to the water supply of a 
military base for 26 weeks and reported no evidence of altered thyroid 
activity or other abnormalities. Unfortunately, the only published 
report of their study (50) contains no details of their results, and the 
original data are not available."

50. Morgan D, Karpen R. Test of chronic toxicity of iodine as related to 
the purification of water. US Armed Forces Med J 4:725-728 (1953).