Returning to the Well
A Second Look at Water Treatment Options
Part 1Is It Safe? Is It Legal?
By Farwell Forrest
August 6, 2002
Need a drink? You're not alone, apparently.
Tamia's piece on
the perils of drinking "found" water provoked more comment than any
other recent column. Readers' concerns varied, but most letters fell into
one of three categories. I'll call the first the "Attagirl!" camp, and
while such notes are always welcome, they don't really require any
responsebeyond a heartfelt "Thanks!" that is.
The same thing can't be said of letters in the other categories,
however. (Let's label them the "Wait Just a Second!" and ""Yes, But
camps.) These are perhaps best represented by two letters. The first,
written by Harlan Price, belongs with the "Wait Just a Second!" mail. It
reads, in part:
[O]n the package of Potable Aqua® [one brand of tetraglycine
hydroperiodide "emergency germicidal drinking water tablets"] it says it
is against Federal
law to not follow the explicit directions on the packaging. [But] your
recommendations differ in dosage and contact time.
I loaned my Philosopher's Stone to Harry Potter, I'm afraid, and with it
went my only claim to being an alchemist, but Harlan raises two very
interesting points. The first concerns the "low-dose" iodine treatment
regimen that Tamia described in her original article: Is it safe and
effective? This is an important question, to be sureto my mind, it's
the most important questionbut Harlan's second point is
perhaps more troubling: Is it illegal to deviate from the printed
instructions when treating water with an EPA-registered germicide?
Perhaps I missed something or there is some scientific literature that
defines your recommendations? Do you know what Federal law they are
talking about? I would think from a liability point of view they would not
want the average Joe playing alchemist.
I'll take Harlan's two questions in turn. The discussion will get a
little technical at times. Please bear with me.
Is "Low-Dose" Water Treatment Safe and Effective?
Yesand no. This isn't a very satisfactory answer, I realize, but
it's the only honest one. Tetraglycine hydroperiodide (TGHPI) germicides
should not be used by everyone. Specifically, water treated with
TGHPI should not be drunk by anyone with known thyroid disease or iodine
allergy. Period. Nor is TGHPI equally effective against all microbial
pathogens. Whereas an iodine concentration of 0.5 ppm (parts per million)
is sufficient to kill many organisms, Medicine for Mountaineering,
a standard medical handbook for wilderness travelers, notes that "higher
concentrations are needed
to destroy parasitic cysts."
These "higher concentrations" are in fact the concentrations that
result from treatment according to the directions printed on the
label of bottles of emergency germicidal drinking water tablets. One
fresh tablet in one quart of clear water yields a final concentration of 8
ppm, and according to Medicine for Mountaineering, this
concentration has been "repeatedly demonstrated" to "eradicate" bacteria,
viruses, parasites, and parasitic cysts.
So, is that the last word on the subject? Not quite. Medicine for
Mountaineering is one of the best books of its type, but this
particular claim falls short of the whole truth. No germicide can truly
"eradicate" waterborne pathogens. The best that can be hoped for is to
reduce the numbers of pathogens to some fraction of their original
strength. If all goes well, the surviving organisms will then be too few
to sicken otherwise healthy individuals. That's good news,
obviouslybut only if you're healthy. If you're not, you'll need to
take more stringent precautions to ensure safe drinking water.
And I'm sorry to say that there's worse news to come. Some common
pathogens are apparently largely or wholly resistant to the action of most
germicides. Cryptosporidium parvum is a case in point. A
"ubiquitous" protozoan parasite with a complex life cycle,
Cryptosporidium poses little threat to healthy individuals.
However, in the words of a recent review article by the US Environmental
Protection Agency's Walter Jakubowski, "it can produce severe, chronic,
and life-threatening infections in the immunocompromised," a group which
includes transplant recipients, persons receiving chemotherapy, and AIDS
Unfortunately, research has established that Cryptosporidium is
"much more resistant to inactivation by chlorine and other disinfectants"
than is the better known (and much more benign) Giardia. In the
absence of clear and convincing evidence to the contrary, therefore, it's
reasonable to infer that iodine-based germicideswhose mechanism of
action is similar to that of chlorineare not necessarily
effective against Cryptosporidium.
What can we conclude from all this? Two things, I think: (1) TGHPI is
effective against most non-protozoan pathogens at doses well below that
called for on the label, and (2) even at the label dose, potentially
harmful numbers of cysts of some protozoan pathogens may survive initial
As luck would have it, Tamia and I are reasonably healthy. That being
the case, we worry most about bacterial and viral pathogens, particularly
when paddling in waters contaminated by farm run-off or municipal sewage.
Don't imagine that "wilderness" waters are trouble-free, by the way, or
that popular destinations are necessarily pristine. We've even found
outflow pipes disgorging rivers of raw sewage right on the margin of James
Bay. Closer to home, the Adirondack village of Lake Placid has just been
cited for dumping "partially-treated sewage sludge" into the Chubb River,
a tiny stream whose upper reaches are a favorite paddling destination.
(The lower Chubb drains into the West Branch of the Ausable, a popular
trout stream and spring whitewater run.) It doesn't matter if you're
paddling in your back forty, or back of beyond. Either way, it's a dirty
world. There's pollution even in paradise.
With this in mind, on most outings in temperate waters we balance
risk (little or no control of protozoan pathogens) against
benefit (no iodine taste, reduced cost, minimum "fussiness") and
arrive at an informed decision to treat at a lower dose than that called
for on the label of our bottle of emergency drinking water germicidal
tablets: instead of one TGHPI tablet to each quart of water, we use one
tablet to 2 US gallons, an eight-fold dilution. As Tamia's already
observed, this yields a final iodine concentration of 1 ppm, twice the
concentration which Medicine for Mountaineering deems "adequate"
for non-encysted pathogens. We also extend the contact time well beyond
the recommended 10 minutesto 1 hour or more. Most often, in fact, we
treat water in bulk just before turning in, insuring a contact period of
6-8 hours. Since the rate at which microorganisms are destroyed in clear
water is equally dependent on contact time and iodine concentration,
doubling contact time has the same effect as doubling dose. Think of it as
That said, do we urge others to emulate our example? No!
Following package directions is always the prudent course, and those who
don't must be ready to bear the risks and accept the consequences. We
are prepared to do so, however, and we've used our low-dose
treatment regime at home and afield in North America for more than 20
years. This does not mean that readers should assume their experience will
be equally benign, of course. When in doubt, doubt. That's the best
advice we can give.
OK. Let's look at the next question.
Is the "Low-Dose" Treatment Regimen Illegal?
I don't think so. The controlling statute is the Federal Insecticide,
Fungicide, and Rodenticide Act, as amended (7 U.S.C. §§ 136 et
seq), mercifully abbreviated FIFRA. Under FIFRA, all manufacturers of
pesticidesand a germicide is a pesticide within the meaning of the
lawmust substantiate any claims of efficacy to the satisfaction of
the EPA in order to receive appropriate registration. They must then label
their products accordingly. TGHPI tablets are registered as "emergency
drinking water germicidal tablets," and the label on the bottle on my desk
bears the following cautionary language:
It is a violation of Federal law to use this product in
a manner inconsistent with its labeling.
I understand this rather delphic pronouncement to mean that TGHPI tablets
are not to be used for applications outside the scope of their
registrationthat is, that they are not to be used in municipal
water treatment systems, say, or for the disinfection of surgical
instruments. I do not believe that the law necessarily precludes
adjustments in dosage and contact times, when such adjustments are
indicated by field conditions or special circumstances, and are also
sanctioned by established standards of practice or the scientific
Of course I could be wrong. I'm not a lawyer, let alone a federal
hearing officer. I don't even play one on TV. So I've queried the EPA to
see what they have to say. I've heard nothing yet, but no matter. It's
still early days. Stay tuned. I'll be returning next week to discuss other
questions raised in connection with Tamia's article. In the meantime,
though, whatever you do, always follow the directions on the
Next week, Farwell crunches the numbers and surveys the
state of the mart, attempting to address the concerns of readers who wrote
to say, "Yes, but
." It was thirsty work, he admits, but someone had
to do it.
Copyright © 2002 by Verloren Hoop Productions. All rights