Water of Life
Each American drinks about a half gallon of water a day. Where does all that water come from, and how is it made safe to drink? By Rear Adm. Joyce Johnson, D.O.

About two-thirds of Americans get their drinking water from rivers, lakes, and reservoirs, via their public water systems. The more than 170,000 public water systems in the United States are regulated by the EPA, which has set standards for about 90 contaminants, including lead, radon, and pesticides.

Public water systems treat water in several steps. The first step, flocculation, involves adding alum and other chemicals so unwanted particles “flock” together. The next step, sedimentation, allows the water to sit so the flocked particles will sink. This clarifies the water. The water is further clarified by passing through a series of filters — sand, gravel, and charcoal. Next, disinfectants such as chlorine are added. Many communities add fluoride to help children develop strong teeth. This treated water is stored and piped to your home.

Underground water, such as from a household well, doesn’t usually require as many steps because the water is filtered through the ground. However, care must be taken that contaminants don’t enter the well-water supply. It’s a good idea to have home wells checked annually for nitrates and coliform bacteria. Depending on where you live, checking for pesticides and radon also might be advisable. If you have children, consider adding fluoride. Some people install water-treatment units at home.

Severe storms and other incidents can contaminate drinking water. Water contaminated with microorganisms can be made safe by boiling it or adding chlorine bleach. Diarrhea and other gastrointestinal illnesses from unsafe drinking water generally are caused by the bacterium E. coli or other fecal coliforms or, less often, the parasite Giardia lamblia. In Third World countries, amoebic dysentery is common.

People who are severely immune-compromised (people with HIV/AIDS or receiving chemotherapy, steroids, or immunosuppressant drugs) are particularly susceptible to Cryptosporidium and other infectious agents in water. They often are advised to boil their drinking water or take other precautions.

Some people prefer the taste of bottled water. Both bottled and tap water are generally safe. Bottled water is a good alternative if your home has lead pipes or a contaminated well. Artesian, ground, spring, and well water are from underground sources and may or may not be treated. Mineral water is ground water that has at least a certain concentration of minerals, which contribute to the taste. Bottled water labeled “drinking water” is similar to tap water and might have fluoride added. Purified water has few minerals and sometimes has all the microbes removed. Distilled water has all minerals removed; it should not be routinely used for drinking, because some minerals are required by the body.

— Rear Adm. Joyce Johnson, USPHS-Ret., D.O., M.A., is vice president, Health Sciences, Battelle Memorial Institute, Arlington, Va. Find more health and wellness resources online at www.moaa.org/wellness.