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Thirty years ago, we didn't fret about lake-water microbes. We just drank the water straight or spiked it with iodine. Today, that is changed. Many of us grip our water filters and cautiously take a sip. In fact, Giardia and other water-borne pathogens often star in those scary mind-flicks we conjure from bears, bugs, and huge, wind-swept waves.

Don't get me wrong. I'm not saying that six months of recurring diarrhea isn't something to ponder. Just don't panic if you swallow a mouthful of lake water. The Boundary Waters isn't a New York sewer. Much of the water is clean. The problem is, we can't distinguish the clean sources from the dirty ones.

To Treat or Not To Treat?

That's why I filter, boil, or chemically disinfect the water I use for drinking, washing dishes, and brushing my teeth. On the other hand, canoe-country author Michael Furtman has roamed the Boundary Waters for nearly 40 years, and hasn't treated a drop and has never been sick. He's not alone. Quite a few Boundary Waters old-timers and wilderness guides drink the water. But they are careful about where they collect it. More on that later.

Furtman recently met a canoe party that was rationing bottled water. ''It was warm, humid, and all were sweating profusely,'' Furtman says. ''They needed water, but weren't drinking enough because they were worried about drinking from the lake. I think it's riskier to not drink the water. I see too many people not drinking water on trips.''

Even those who filter tend to be dehydrated because pumping takes time and effort, he says. ''Dehydration is, I believe, a far more common malady among wilderness travelers than Giardia, at least as far as the Boundary Waters/Quetico is concerned.''

Scientists who study wilderness water agree that staying hydrated is important, but say microbes shouldn't be part of the mix. ''When I see a stream, all I see is a toilet,'' says Charles Gerba, a University of Arizona professor of environmental engineering. ''My feeling is you never know who used it as a toilet upstream; and every stream is a beaver's toilet.''

Ryan Jordan, a Montana State University senior research engineer in the Center for Biofilm Engineering, is an avid backpacker who has tested many backcountry water sources. He has found pathogens in clear water in places that would seem least suspect, and tested some nasty-looking sources that turned out to be pathogen-free.

''The bottom line is this: If you play backcountry water roulette for long without using a form of treatment, sooner or later, your number will come up. And that won't mean you're a winner,'' he says.

Patricia Bloomgren agrees. She directs the division of environmental health for the Minnesota Department of Health. ''We would not consider the water safe to drink even in the pristine Boundary Waters,'' she says. Her agency requires that even resorts adjacent to the Boundary waters clean their drinking water to meet the surface water treatment rule of the Safe Drinking Water Act.

Bloomgren says that she has several friends who have contracted giardiasis on Boundary Waters canoe trips. ''Some people can go up there year after year after year and never treat the water and don't get sick,'' she says. ''And someone else goes up there and does. If I did a canoe trip, I would be treating my water.''

What Are the Odds?

So what are the odds that pathogens will find their way into your water bottle?

About 15 years ago, the Superior National Forest conducted a small administrative study that looked for coliform bacteria in BWCA lake water. Not surprisingly, they found more bacteria near the shore than in the middle of the lake, says forest hydrologist Bob Berrisford.

Several years ago, the forest also looked at the incidence of giardiasis in counties adjacent to the Boundary Waters. During a three-year period, two counties had one reported case and another had two or three. But many cases might go unreported because most visitors aren't from the area and are back home when the illness hits.

''We haven't gotten much feedback from the public indicating there is a problem,'' he adds. ''If a lot of folks thought it was, I think we would be hearing about it.''

Still, Berrisford endorses the forest service recommendation that Boundary Waters visitors treat or filter all their drinking water. Those with compromised immune systems should particularly heed the forest service advice, says LeRoy Halberg, registered sanitarian for Cook County in Grand Marais, Minnesota. This can include diabetics or anyone with an illness. It also includes anyone over age 55 or under age two, Gerba says. ''If you're over 55, you should take full precautions. This is a major susceptible group.''

Start With the ''Cleanest'' Water!

Start with the cleanest water you can find. There's no way to tell by looking whether a source has disease-causing pathogens, but there are ways to play the odds.

''I consider water sources near heavily used locations to be suspect, particularly if those locations are near a road and thus easily accessible by folks not normally aware of good backcountry practices,'' Jordan says. '' In April, I was camped on the Appalachian Trail near the Big Spring Shelter (North Carolina), and found a pile of human feces about five yards upstream of a presumably pristine spring.''

Beaver are notorious Giardia carriers, so stay away from beaver ponds or areas downstream, Gerba adds.

Also, avoid places where people swim, such as areas near campsites. Gerba, who studies stuff like this, says the average person carries a quarter-peanut-sized bit of fecal matter in his or her shorts. When they go swimming, microbes spread from this material into the water.

''Any activity that causes untreated water to be ingested (swimming, fishing and so on) could be an avenue for infection,'' Jordan adds. ''You have to use common sense here. One person swimming in a remote mountain lake is probably not going to infect the lake for the rest of the summer.''

And pass on stagnant water, Jordan advises. ''Stagnant water, standing water with no influent or effluent streams to replenish the source, is certainly a candidate for chemical treatment. So are waters that are rich in suspended solids, like algae-rich and silt- or clay-rich waters.''

Deep areas of large lakes may be one of the safest places to fill your bottles. Furtman recommends staying away from shorelines or streams, unless the water is going to be boiled for cooking, because beavers travel there and moving water can suspend Giardia.

Jordan notes, however, that Giardia cysts still can be found in the middle of a deep lake. Conventional wisdom has it that cysts sink to the bottom in these areas but Jordan says microbes don't settle in the same way that sand particles do.

''A lake harbors convection currents induced by both thermal gradients in the water and surface chop from the wind, and there are few places in a lake that are truly quiescent,'' he says. These currents are strong enough to suspend microorganisms.

Cysts also can be found on algae and other organic matter that forms a film on the lake's surface, which is held in place by surface tension. To keep lake film out of your bottle, plunge it into the water mouth-down at arm's length. Let the air escape only when it's beneath the surface to avoid taking in surface debris.

Filter, Treat or Both?

Gerba recommends filtering the water and then treating it with a disinfecting agent such as iodine, Aquamira™ or Pristine®. (Aquamira™ and Pristine® are chlorine dioxide disinfectants. More about them later.)

He advises using filters and chemicals together because filters stop bacteria that cause diarrhea, but they don't block viruses, which are much smaller. Meanwhile, iodine alone can kill Giardia, bacteria, and viruses, but doesn't stop Cryptosporidium, which causes a 7-day-long cholera-like diarrhea. At the proper concentration Aquamira™ and Pristine® kill just about everything. However, disinfectants won't remove silt, so cloudy water needs to be filtered, unless you like grit. Microorganisms also cling to particles in the water, making them harder to kill.

''There is no question that a filter in combination with chemical methods provides one of the best combinations of treatment for backcountry water,'' Jordan says. ''But there are limits to patience and you have to define for yourself what level of acceptable risk you want to take. If I'm drinking out of a riparian stream frequented by cattle, you can bet that I'm going to combine a chemical treatment like Aquamira™ with my filter. But if I'm dipping out of the headwaters of a mountain creek at 12,000 feet, the chances of encountering a deadly virus or bacterium are probably pretty slim.''

When using both the filter and a disinfectant, filter first, and then add the chemical treatment, Jordan advises. The residual disinfectant helps protect the water from pathogens, such as those from dirty hands, that might later contaminate it.

Boiling is a third alternative. ''We boil water at night before we go to bed,'' Halberg says. ''By morning, the water is at 45 degrees, and we make some of it into juice, and use the rest to fill our water bottles.''

What To Buy

Not all filters are created equal. Anyone can slap together a filter element and a couple hoses, but that doesn't mean it will work properly.

''You need a good engineer to design these,'' Gerba says. If the seals don't hold up or water leaks past the filter element when pressure builds up, the microbes get a free ride into your glass.

So make sure the filter is registered with the EPA. Gerba's lab does EPA certification testing for point-of-use water filters and the procedure is rigorous. In fact, one technician in his lab does nothing but test filters. ''These are really mini water treatment plants and we have to make sure the units perform throughout their lifetime,'' Gerba says. ''The EPA tests give these filters some rough challenges.''

REI and L.L. Bean require testing before they will sell a product, so those are good places to buy a filter, Gerba adds.

Most backpacking water filters require hand pumping, which can turn into real work if you're supplying a group. Some backpackers have recently switched to gravity-fed systems in which a water bag is filled, hung from a tree, and attached to the filter by a hose. Another hose below the filter goes to the clean water bag. The water flows through the filter while you set up camp. (See ''Additional Resources'' below for more information on gravity filters.)

Iodine was the standard water treatment method for wilderness travelers until filters came along. Today, it's less popular because it doesn't kill Cryptosporidium. However, the new disinfectants, such as Aquamira™ and Pristine®, are much more effective than iodine and will kill Cryptosporidium. They use chlorine dioxide to kill pathogens, and, in foul-smelling water, can significantly improve the taste and odor. (Aquamira™ is available from Campmor. Pristine® can be purchased from the company's web site. See the ''Additional Resources'' listing below.)

Cloudy water tends to neutralize treatment chemicals, so try to start with clear water, says George Farkas, of McNett Corp, which makes Aquamira™ . Just running the water through a coffee filter before treatment will help significantly.

Although water treated with Aquamira™ is ready to drink in as little as 15 minutes, it's best to allow as much time for disinfection as possible. Some wilderness guides will treat a gallon or two in the evening, let it stand overnight, and then fill water bottles in the morning. ''This enhances the safety margin, especially when using lake water, which is often teeming with microscopic life,'' Farkas says.

Although microbes can be a problem, the Boundary Waters is protected from municipal and industrial pollutants by its topography and remote location. Furtman notes that no watersheds flow into the Boundary Waters or Quetico from outside. So no large concentrations of municipal and industrial pollutants can flow into canoe-country waters. And airborne pollutants are present in such low levels that ''you'd have to drink the water the rest of your life for there to be any chance at all of accumulating significant amounts of mercury, PCBs, and so on,'' he says.

It's Not Just the Water

In Long Distance Hiking: Lessons from the Appalachian Trail, Roland Mueser interviewed thru-hikers who spent months walking the entire 2,150-mile-long trail. He asked about their water treatment strategies and illnesses, and found no difference in the rate of illness between those who treated or filtered the water, those who sometimes did and those who didn't filter or use disinfectants.

The sample was small and the results were based on what people said they did, rather than direct observation. So the results aren't scientifically rigorous. But they do raise some interesting questions. Why did those who faithfully treated their water still get sick? It could have been poor filtering or treating technique, but Mueser speculates that some illnesses might have come from other hikers, not the water.

Stomach illness can be transmitted by sharing cups, dishes or food, such as a bag of gorp. Other illnesses can result from spoiled food and dirty dishes.

Gerba says Shigella, which lives in human intestines, is easily spread through a camping group. This happens when a person doesn't wash after defecating and prepares or shares food with others. Shigella causes diarrhea that is often bloody and accompanied by fever and stomach cramps.

To test how bacteria spreads in camping situations, Gerba took a group into the Santa Catalina Mountains north of Tucson, Ariz. He split the campers into three subgroups: those who didn't wash their hands, those who washed with soap and water, and those who used alcohol gels. The hands of those who didn't wash were soon covered with E. coli bacteria. Those who used soap and water had some E. coli, and those who used alcohol gels had the cleanest hands.

''You can use either the disinfectant wipes or gels,'' Gerba says. ''I would use this as an adjunct to washing hands.'' He recommends washing for at least 30 seconds and rinsing well. And he cautions that sharing anything such as food, dishes, or water bottles can transmit disease.

Dishes that aren't properly washed also can spread disease. Gerba recommends rinsing dishes with boiling water. Rinsing with water straight from the lake and letting the dishes dry won't eliminate Giardia and Cryptosporidium, Jordan notes. Many species of bacteria and protozoa retain water in their cell structures and can remain viable for a long time on dry surfaces.

Go Out and Have Fun

OK, lets put all this into perspective. Remember that more than 200,000 people visit the Boundary Waters each year and most have a great time and stay healthy. So consider the experts advice and do your best to keep your drinking water, hands, and dishes clean. Then forget about the microbes and enjoy yourself. After all, we don't stop driving because people die in cars. Instead, we drive defensively, use our seat belts, and trust our luck. The same goes for the water.

--article courtesy of BoundaryWatersMagazine.com

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