Most community water suppliers deliver high quality drinking water to millions of people every day. Of the more than 55,000 Community Water Systems in the United States, only 4,769 or 8.6 percent reported a violation of one or more drinking water health standards in 1996.

Nationwide, drinking water systems have spent hundreds of billions of dollars to build drinking water treatment and distribution systems, and they spend an additional $22 billion per year to operate and maintain them. Additional monies became available in 1997 to upgrade drinking water systems and implement local source water protection activities.

In addition, there is a network of government agencies whose job is to ensure that public water supplies are safe. Nonetheless, problems with local drinking water can, and do, occur.

Why Allow Any Contaminants in Drinking Water?

All sources of drinking water contain some naturally occurring contaminants. Because water is the universal solvent, many materials are easily dissolved upon contact. At low levels, these contaminants generally are not harmful in our drinking water. Removing all contaminants would be extremely expensive and in nearly all cases would not provide greater protection of health. A few of the naturally occurring substances may actually improve the taste of drinking water and may have nutritional values at low levels.

Problems That Can Occur

As development in our modern society increases, there are growing numbers of threats that could contaminate drinking water. Suburban sprawl has encroached upon once-pristine watersheds, bringing with it all of the by-products of our modern life style. Actual events of serious drinking water contamination occur infrequently, and typically not at levels posing near-term health concern. Nonetheless, with the threats of such events increasing, we cannot take drinking water safety for granted. Greater vigilance by you, your water supplier, and your government is vital to ensure that such events do not occur in your water supply.

Microbiological and chemical contaminants can enter water supplies. These materials can be the result of human activity or can be found in nature. For instance, chemicals can migrate from disposal sites and contaminate sources of drinking water. Animal wastes and pesticides may be carried to lakes and streams by rainfall runoff or snow melt. Human wastes may be discharged to receiving waters that ultimately flow to water bodies used for drinking water. Coliform bacteria from human and animal wastes may be found in drinking water if the water is not properly treated or disinfected. These bacteria are used as indicators that other harmful organisms may be in the water.

The potential for health problems from drinking water is illustrated by localized outbreaks of water-borne disease. Many of these outbreaks have been linked to contamination by bacteria or viruses, probably from human or animal waste. In 1993 and 1994, for example, there were 30 reported disease outbreaks associated with drinking water, 23 associated with public drinking water supplies and 7 with private wells.

Certain pathogens, such as Cryptosporidium, may pass through water treatment filtration and disinfection processes in sufficient numbers to cause health problems. Cryptosporidium is a protozoa that causes the gastrointestinal disease cryptosporidiosis. The most serious, and sometimes deadly, consequences of cryptosporidiosis tend to be focused among sensitive members of the population, such as individuals with immune system deficiencies.

A 1993 outbreak of cryptosporidiosis in Milwaukee, Wisconsin, is the largest outbreak of waterborne disease in the United States. Lake Michigan is the source of Milwaukees water, which is treated by filtration and disinfection. Due to an unusual combination of circumstances during a period of heavy rainfall and runoff the treatment plant was ineffective, resulting in an increase in the turbidity of the treated water. Increased turbidity can be, and was in this case, an indicator of higher levels of Cryptosporidium. Over 400,000 persons were affected by the disease, more than 4,000 were hospitalized, and over 50 deaths (some counts are as high as 100) have been attributed to the disease. The original source of contamination is uncertain.

Nitrate in drinking water at levels above the national standard poses an immediate threat to young children. Excessive levels can result in a condition known as "blue baby syndrome." If untreated, the condition could be fatal.

Naturally occurring contaminants also are being found in drinking water. For example, the radioactive gas radon-222 occurs in certain types of rock and can get into ground water. People can be exposed to radon in water by drinking it, while showering, or when washing dishes. The primary source of exposure to radon in the home is radon seeping out of the soil and into the basement air.

Who Makes Sure That My Water Supply Is Safe?

Local governments, public water systems, the states, and EPA work together towards the goal of ensuring that all public water supplies are safe. For households on private wells, state and local health departments usually have some standards for the drinking water, but it is generally up to the homeowner to maintain the quality of the drinking water.

Local governments have a direct interest in protecting the quality of their drinking water source, be it ground water or surface water. They may be responsible for overseeing land uses that can affect the quality of untreated source water. Public water systems have a responsibility to maintain sound treatment works and water distribution networks. They are responsible for ensuring that the water they supply does not contain contaminants at levels higher than the law allows.