Tap Water - Where Does It Come From and Is It Safe to Drink?

Water is one of our most valuable resources. Water covers about 70% of the Earth's surface and is one of the most important resources needed for maintaining life (1). In 2000, the United States alone used 408 billion gallons of water per day (2)! Ground water, which is obtained by drilling wells, is water located below the ground surface in pores and spaces in the rock, and is used by approximately 40%–45% of the US population as its drinking water supply (3–5). People use ground water every day for a variety of reasons, including drinking, recreation, agriculture, and industry. Most of the time this water is completely safe and not a cause for worry. However, during 2003 and 2004, 30 waterborne-disease outbreaks related to drinking water were reported to CDC. These outbreaks resulted in 2,760 cases of illness and 4 deaths. Seven of these outbreaks (23%) and 1,830 cases of illness could be attributed to improperly treated or untreated ground water used for drinking purposes; two of these outbreaks involved private wells (6).

National Ground Water Awareness Week*, sponsored by the National Ground Water Association (NGWA), is March 9–15. The primary focus during this week is to stress the importance of ground water as a valuable resource and to focus attention on yearly water testing and well maintenance to prevent waterborne illness.

Ground Water and Pollution

Drinking water supplies in the United States are among the safest in the world. However, even in the U.S., drinking water sources can become contaminated, causing sickness and disease. Ground water can become unusable if it becomes polluted and is no longer safe to drink. Certain contaminants, such as arsenic and radon, can occur naturally in the environment and their concentration in ground water depends highly on the geology of the land around the water source. Other ground water contaminants are the result of local land use practices (fertilizers and pesticides), microbial contamination, manufacturing processes, and problems with the integrity of nearby onsite septic systems. For example, nitrate contamination of ground water may occur as a result of nitrate-containing fertilizer used in agricultural areas, fecal contamination from feedlots, and leaking onsite wastewater systems contaminating the ground water source.

The presence of these toxic substances in our water can lead to health issues, including gastrointestinal illness, reproductive problems, and neurological disorders. Infants, young children, pregnant women, the elderly, and people whose immune systems are compromised because of AIDS, chemotherapy, or transplant medications, may be especially susceptible to illness from some contaminants. The U.S. Environmental Protection Agency (EPA) sets maximum concentration levels for many water pollutants and chemicals and regulates drinking water quality in public water systems. With careful use and by reducing sources of pollution, ground water can continue to be an important natural resource in the future.

For More Information on Ground Water and Pollution

• EPA - Water Pollution

• Water Health Connection - Recognizing Waterborne Disease and the Health Effects of Water Pollution (Clinicians)*

• EPA - Surf Your Watershed

Community or Municipal Water System

If you get your tap water from a system that uses ground water, your water could come from a community/municipal water system or a private ground water well.

In 2005, 89.5 million Americans got their tap water from a community or municipal water system that used ground water (7). EPA has laws that regulate the levels of contaminants allowed in drinking water supplied by public water systems, such as public water utility companies. More information about these laws can be found on EPA's National Primary Drinking Water Regulations Web page. Every water utility company is required to provide Consumer Confidence Reports (CCR) to their customers each year. This report provides information on local drinking water quality, including the water's source, the contaminants and levels found in the water, and how customers can get involved in protecting their drinking water.

For More Information on Public Drinking Water Quality and Your Local Drinking Water CCR

• CDC – Health Topic: Water Quality

• EPA – Public Drinking Water System Programs

• EPA – Local Drinking Water Information

• EPA – Consumer Confidence Reports (CCR)

• EPA – What Contaminants May Be Found in Drinking Water?

• EPA - Drinking Water Standards

• EPA Water Quality

Private Ground Water Well

Spring is a great time to have your well water tested, before the beginning of peak water-use season! Between 40 and 45 million Americans regularly depend on private ground water wells (8–9). EPA rules that protect public drinking water systems do not apply to privately owned wells. Private well owners are responsible for ensuring their well water is safe from contaminants of health concern. See the box for rules to help ensure safe drinking water from your well.

For More Information on Ground Water Quality, Well Maintenance, and Well Water Testing

• CDC - Private Well Resources

• EPA - Private Drinking Water Wells

• Wellowner.org*

What CDC Is Doing

CDC has initiated prevention activities to help protect public health and prevent diseases associated with exposures to drinking water contaminants. Activities include:

• Investigating waterborne disease outbreaks, their causes, and their environmental
conditions that set the stage for the outbreak to happen

• Investigating the health effects of exposure to contaminants in ground water

• Investigating drinking water exposures among households without access to potable water

• Collaborating on investigations of the impact of household water filtration systems on public health

• Tracking waterborne disease outbreaks at the national level

• Providing recommendations on how to prevent waterborne disease

• Evaluating community-level interventions to reduce drinking water contamination

For additional information about these activities, see:

• Surveillance for Waterborne Disease and Outbreaks Associated with Drinking Water and Water not Intended for Drinking – United States, 2003-2004

• Text

• Appendix

• Glossary

• Outbreak Investigation of Gastrointestinal Illness Associated with Contaminated Ground Water on South Bass Island

• Clinical Infectious Diseases Journal Article

• Ohio Department of Health Summary

• MMWR 2008: XX(XX):XX. Notice to Readers: Ground Water Awareness Week, March 9-15, 2008

• CDC - Water-Related Environmental Public Health

• CDC - Chemical Contaminants in Drinking Water and Public Health

• CDC - Water-Related Diseases

For More Information

Ground water in general

• USGS- What is Ground Water?

• EPA- Drinking Water & Ground Water Kids' Stuff

• CDC- My Water's Fluoride

References

1 USGS. How much water is there on, in, and above Earth? Available at http://ga.water.usgs.gov/edu/earthhowmuch.html.

2 USGS. Estimated Use of Water in the United States in 2000. Available at http://pubs.usgs.gov/circ/2004/circ1268/.

3 US Census Bureau. Annual estimates of the population for the United States, regions, and states and for Puerto Rico: April 1, 2000 to July 1, 2007 (NST-EST2007-01). Available at http://www.census.gov/popest/states/NST-ann-est.html

4 US Environmental Protection Agency. Private drinking water wells. Available at http://www.epa.gov/safewater/privatewells/index2.html.

5 US Environmental Protection Agency.  Factoids: Drinking Water and Ground Water Statistics for 2005. Available at http://www.epa.gov/safewater/data/pdfs/statistics_data_factoids_2005.pdf.

6 CDC. MMWR - Surveillance for Waterborne Disease and Outbreaks Associated with Drinking Water and Water not Intended for Drinking --- United States, 2003--2004.  Available at http://www.cdc.gov/mmwr/preview/mmwrhtml/ss5512a4.htm.

7 US Environmental Protection Agency. Factoids: Drinking Water and Ground Water Statistics for 2005. Available at http://www.epa.gov/safewater/data/pdfs/statistics_data_factoids_2005.pdf.

8 US Environmental Protection Agency. Private Drinking Water Wells. Available at http://www.epa.gov/safewater/privatewells/index2.html.

9 U.S. Census Bureau. National and State Population Estimates. Available at http://www.census.gov/popest/states/NST-ann-est.html.