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Water FiltersFrequently Asked Questions
Why do I need to be concerned? Is the water contamination really that bad?
In a word, yes. The most recent figures out estimate that 90% of surface water in the United States fails to meet EPA standards for acceptable drinking water. That's almost enough to make your stomach turn right there. Figures for other countries are harder to come by, but in many developing countries, even water that flows from the tap can be loaded with Montezuma and his marauders. Attack rates for Traveler's Diarrhea for instance, have been reported as high as 50% in some areas. The upshot of these figures is that unless you carry a testing lab with you and you have the luxury of waiting 3 or 4 days for the results to come in, you've got to assume that the untreated water you find in the backcountry, in recreation areas, and in many travel destinations is not safe to drink.
What are the most common contaminants?
Though many people worry about inorganic pollutants such as lead or pesticides, microbial contaminants are by far the greater threat. This may be a good time to define a few terms. Pathogen is the umbrella term that describes all disease-causing microbes. There are three basic categories of pathogen that can be found in untreated water:
The first is protozoa. Protozoa include the well-known Giardia, and the not-so-well-known Cryptosporidium, or Crypto for short. These two scoundrels have been detected in 90% of U.S. surface water and very common in Canada. Protozoa are the largest organisms of the three categories, ranging in size from 1-16 microns. They are more resistant to disinfection by iodine or chlorine than either bacteria or virus, but can be effectively filtered. Giardia is relatively large and easy to catch, but Crypto is a sneakier, smaller felon, "more likely to pass through units which depend upon filtration for parasite removal. To know whether or not a filter will protect you against Crypto, find out if it's been tested with Crypto and proven to remove 99.9% of this organism.
The second category is bacteria. Bacteria include such commonly-known organisms as Campylobacter, E. coli, Vibrio cholera, and Salmonella. Bacteria are intermediate-sized organisms, ranging from 0.2 to about 10 microns. They respond well to disinfection, and can be effectively filtered by any filter that is proven to remove 99.9999% of bacteria.
The third category is viruses. Commonly known viruses include Rotavirus, Hepatitis A, Norwalk, and Polio. Viruses are truly tiny; they range in size between 0.02 and 0.085 microns, which makes them extremely difficult to filter. Viruses respond well to disinfection, and can be effectively inactivated using a purifier proven to remove or inactivate 99.99% of virus.
What are the incubation periods of common pathogens?
For bacteria, these are the most common waterborne pathogens and their incubation periods: Campylobacter jejuni, 3-5 days; Ecoli, 24-72 hrs; Salmonella, 12-36 hrs; Shigella, 12-96 hrs; Vibrio cholerae, 2-3 days; Yersinia enterocolitica, 3-7 days. For viruses, these are the most common waterborne pathogens and their incubation periods: Adenovirus, 5-12 days; Enterovirus (Polio), 7-14 days; Hepatitis A, 15-50 days; Norwalk, 1-2 days; Rotavirus, 1-3 days; Coxsackievirus, 3-5 days; Hepatitis E, 15-64 days. For protozoa, these are the most common waterborne pathogens and their incubation periods: Giardia, 5-25 days or longer; Crypto, 1-12 days. (From Control of Communicable Disease in Man. 1990. Abram S. Benenson, editor. 15th edition. American Public Health Association. Victor Graphics, Inc. Baltimore, MD.)
How do these contaminants get in the water?
The vast majority of pathogens are introduced by animals, but human beings are also carriers. Feces wash into drainages, carrying with them the disease-causing pathogens. Water moving through the drainages spreads pathogens downstream. Waterborne viruses are unique in that they are species-specific; i.e. human fecal matter must be present for there to be a viral threat to humans.
What happens if I drink bad water?
Reactions range from no symptoms at all, to desperate illness, to death for some immune-compromised individuals. Your reaction will depend on the pathogen and on your immune system. Immune systems vary from individual to individual, based on genetic make-up and medical history. You may be one of the lucky few who experiences few, mild, or no symptoms. It is estimated that up to 30% of the population of the U.S. is resistant to Giardia, for instance. For the rest of us, after drinking contaminated water, there will be an incubation period of between a few hours and a couple of months, during which no symptoms will be evident. During this time, the pathogen is invading your system and multiplying. Crypto can produce up to 100 million oocysts each day in your gut! How's that for a party you don't want to host?) When concentrations of the pathogen reach a certain threshold, you enter the manifestation period during which you begin to feel symptoms. That is the tidy medical description. Reality is not so tidy: infection by waterborne pathogens often leaves you looking like a dog's dinner and feeling like you have been hit by a truck. Fever, cramps, fatigue, diarrhea, nausea, dehydration, and general malaise can either sneak up on you slowly, or slam you all at once. During the manifestation period, being more than 10 seconds away from the nearest bathroom is often a bad idea. Some people bounce right back, some are hit so hard they're bed-ridden or even hospitalized, and a very few can't shake the disease at all. (For instance, over 1000 people were hospitalized in Milwaukee's 1993 Crypto outbreak, and over 100 immune-compromised individuals died.)
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