Where Does Your Water Come From?
Your tap water has been many places before it fills your glass or runs over your hands. Tap water starts out in lakes, streams and reservoirs, or, in the case of well water, as the ground water that supplies the well. Public water suppliers treat surface water by adding chemicals to it to remove dirt and other contaminants, and then filter the water and add chlorine to eliminate viruses and bacteria. (Well water, which is often privately owned, may be treated differently, or not require treatment.) The water then runs though the pipes in your community and home and out your taps. Contamination can occur at each of the steps in the water-supply process.
"Our biggest concern is with microbial contamination that can have acute health effects," says Veronica Blette, special assistant to the director in the office of ground water and drinking water at the Environmental Protection Agency (EPA), in reference to viruses, bacteria, such as E-coli, and parasites such as Cryptosporidium.
What Lurks?
Besides viruses, bacteria and parasites, the water in your home or workplace may contain other types of contaminants associated health risks if they are above a certain level. Other major contaminants include manmade chemicals such as degreasers and pesticides; bi-products of the chemicals used to disinfect water at the treatment plant; and inorganic chemicals such as lead—pipes may also contain lead—arsenic, nitrate and chromium, which can occur naturally or be introduced into the water supply through activity such as mining.
While microbes and parasites can cause nausea, vomiting and diarrhea, ongoing exposure to water with certain chemicals, such as arsenic and disinfection bi-products, are associated with cancer, infertility, liver and kidney problems. People with compromised immune systems, such those with HIV/AIDS, children, pregnant women and older people may be particularly vulnerable to contaminants in water.
