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Paddling Articles In the Same Boat

Returning to the Well

A Second Look at Water Treatment Options
Part 1—Is 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 response—beyond 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.

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 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 sure—to my mind, it's the most important question—but 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?

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?

Yes—and 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, obviously—but 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 patients.

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 germicides—whose mechanism of action is similar to that of chlorine—are 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 treatment.

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 minutes—to 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 insurance.

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 pesticides—and a germicide is a pesticide within the meaning of the law—must 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 registration—that 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 literature.

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 package!

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 reserved.

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