What’s in the Water?
Chemicals in water could include inorganic contaminants (arsenic and other heavy metals) or organic toxins (pesticides, for example). In general, it is a bad idea to drink from natural water sources before the water has been purified. Even a small amount of these chemicals ingested into your body can make your camping, hiking or outdoor adventure a real bummer. The good news is that water sources in the backcountry are seldom contaminated with appreciable levels of toxic chemicals. Still, it’s better to be safe than sorry. So make sure you purify the water you drink on your next backpacking or camping trip either through a filter system or through chemical germicidal tablets such as Potable Aqua.

Parasites
There are a number of parasites which live in water. The most common ones in North America are Giardia lamblia and Cryptosporidium. Boiling water will kill both and so will a good filter. An iodine-based product, like Potable Aqua, will kill Giardia but has not been proven effective against Crypto. In third world countries, the number of parasites in the water is staggering. Take heed the advice, "don’t drink the water." Dysentery, diarrhea and roundworms are just a few of the unpleasantries you can take home with you from an outdoor trip if you’re not careful. In some areas, such as the Philippines and Africa, you should avoid any contact with river water, including swimming or washing in unpurified water as Schistosoma is prevalent in these areas. These tiny parasites bore directly into the skin, enter the bloodstream and eventually set up shop in either the intestine or the bladder. If left untreated or incorrectly diagnosed, the complications can be severe.

Bacteria
Bacteria are the second smallest pathogens in water, but can be removed from water by boiling, filtration (0.2 micron filter) or iodine treatment. While strains of bacteria such as Escherichia coli (E. coli) can be pathogenic, the vast majority are not and are actually needed for our digestive process. This is not to say, however, that all bacteria strains are good for us. In fact, there are plenty of other bacteria which are happy to live in the intestine to the detriment of the host. Again, make sure you purify the water you are about to drink.

Viruses
The smallest parasites are viruses. In true wilderness areas, pathogenic viruses are seldom found in water, but the odds increase with population density and poor sanitation practices. Ordinary filters do not remove viruses. You will need a filter with an iodine matrix or use an iodine treatment, such as Potable Aqua, to ensure viruses are no longer present. Boiling water is also a reliable way to do away with viruses. The specific viruses you should worry about in water are hepatitis A, rotaviruses, polioviruses and echoviruses. All of these will cause diarrhea, intestinal cramps and discomfort about 48 to 72 hours after contact, and complications could range from liver damage (for hepatitis) to aseptic meningitis and encephalitis (for echoviruses), and paralysis or death (for polio). Make sure you take extra precautions in the backcountry to ensure you don’t pick up a virus when drinking from a natural water source.