Drinking Water Contaminants

Drinking water, including bottled water, may reasonably be expected to contain at least small amounts of some contaminants. The presence of contaminants does not necessarily indicate that water poses a health risk.  EPA sets standards for approximately 90 contaminants in drinking water. EPA's standards, along with each contaminant's likely source and health effects, are available at www.epa.gov/safewater/mcl.html . More detailed information on specific contaminants is available below:

Microbes ~ Radionuclides ~ Inorganics ~ Volatile Organics ~ Synthetic 
Organics ~ Disinfectants ~ Disinfection Byproducts ~ MTBE ~ Health Advisories

Microbes

Coliform bacteria

are common in the environment and are generally not harmful. However, the presence of these bacteria in drinking water is usually a result of a problem with the treatment system or the pipes which distribute water, and indicates that the water may be contaminated with germs that can cause disease.

Fecal Coliform and E coli are bacteria whose presence indicates that the water may be contaminated with human or animal wastes. Microbes in these wastes can cause short-term effects, such as diarrhea, cramps, nausea, headaches, or other symptoms. 

Turbidity has no health effects. However, turbidity can interfere with disinfection and provide a medium for microbial growth. Turbidity may indicate the presence of disease causing organisms. These organisms include bacteria, viruses, and parasites that can cause symptoms such as nausea, cramps, diarrhea, and associated headaches.

Cryptosporidium is a parasite that enters lakes and rivers through sewage and animal waste. It causes cryptosporidiosis, a mild gastrointestinal disease. However, the disease can be severe or fatal for people with severely weakened immune systems. EPA and CDC have prepared advice for those with severely compromised immune systems who are concerned about Cryptosporidium . 

Giardia lamblia is a parasite that enters lakes and rivers through sewage and animal waste. It causes gastrointestinal illness (e.g. diarrhea, vomiting, cramps).

Radionuclides

Alpha emitters.

Certain minerals are radioactive and may emit a form of radiation known as alpha radiation. Some people who drink water containing alpha emitters in excess of  EPA's standard over many years may have an increased risk of getting cancer.

Beta/photon emitters. Certain minerals are radioactive and may emit forms of radiation known as photons and beta radiation. Some people who drink water containing beta and photon emitters in excess of EPA's standard over many years may have an increased risk of getting cancer.

Combined Radium 226/228. Some people who drink water containing radium 226 or 228 in excess of EPA's standard over many years may have an increased risk of getting cancer.

Radon gas can dissolve and accumulate in underground water sources, such as wells, and in the air in your home. Breathing radon can cause lung cancer. Drinking water containing radon presents a risk of developing cancer. Radon in air is more dangerous than radon in water.

Inorganic Contaminants

Technical fact sheets on Inorganic Contaminants

Arsenic . Some people who drink water containing arsenic in excess of EPA's standard over many years could experience skin damage or problems with their circulatory system, and may have an increased risk of getting cancer.

Fluoride. Many communities add fluoride to their drinking water to promote dental health. Each community makes its own decision about whether or not to add fluoride. EPA has set an enforceable drinking water standard for fluoride of 4 mg/L (some people who drink water containing fluoride in excess of this level over many years could get bone disease, including pain and tenderness of the bones). EPA has also set a secondary fluoride standard of 2 mg/L to protect against dental fluorosis. Dental fluorosis, in its moderate or severe forms, may result in a brown staining and/or pitting of the permanent teeth. This problem occurs only in developing teeth, before they erupt from the gums. Children under nine should not drink water that has more than 2 mg/L of fluoride.

Lead typically leaches into water from plumbing in older buildings. Lead pipes and plumbing fittings have been banned since August 1998. Children and pregnant women are most susceptible to lead health risks. For advice on avoiding lead, see EPA's lead in your drinking water fact sheet. 

Synthetic Organic Contaminants,
including pesticides & herbicides

Technical fact sheets on Synthetic Organic Contaminants

Volatile Organic Contaminants

Technical fact sheets on Volatile Organic Contaminants

Disinfectants

Many water suppliers add a disinfectant to drinking water to kill germs such as giardia and

e coli . Especially after heavy rainstorms, your water system may add more disinfectant to guarantee that these germs are killed. 

Chlorine. Some people who use drinking water containing chlorine well in excess of EPA's standard could experience irritating effects to their eyes and nose.  Some people who drink water containing chlorine well in excess of EPA's standard could experience stomach discomfort.

Chloramine. Some people who use drinking water containing chloramines well in excess of EPA's standard could experience irritating effects to their eyes and nose.  Some people who drink water containing chloramines well in excess of EPA's standard could experience stomach discomfort or anemia.

Chlorine Dioxide. Some infants and young children who drink water containing chlorine dioxide in excess of EPA's standard could experience nervous system effects.  Similar effects may occur in fetuses of pregnant women who drink water containing chlorine dioxide in excess of EPA's standard.  Some people may experience anemia.

Disinfection Byproducts

Disinfection byproducts form when disinfectants added to drinking water to kill germs react with naturally-occuring organic matter in water.

Total Trihalomethanes. Some people who drink water containing trihalomethanes in excess of EPA's standard over many years may experience problems with their liver, kidneys, or central nervous systems, and may have an increased risk of getting cancer. 

Haloacetic Acids. Some people who drink water containing haloacetic acids in excess of EPA's standard over many years may have an increased risk of getting cancer.

Bromate. Some people who drink water containing bromate in excess of EPA's standard over many years may have an increased risk of getting cancer.

Chlorite. Some infants and young children who drink water containing chlorite in excess of EPA's standard could experience nervous system effects.  Similar effects may occur in fetuses of pregnant women who drink water containing chlorite in excess of EPA's standard.  Some people may experience anemia.

MTBE is a fuel additive, commonly used in the United States to reduce carbon monoxide and ozone levels caused by auto emissions. Due to its widespread use, reports of MTBE detections in the nation's ground and surface water supplies are increasing. The Office of Water and other EPA offices are working with a panel of leading experts to focus on issues posed by the continued use of MTBE and other oxygenates in gasoline. EPA is currently studying the implications of setting a drinking water standard for MTBE.

Health advisories provide additional information on certain contaminants. Health advisories are guidance values based on health effects other than cancer. These values are set for different durations of exposure (e.g., one-day, ten-day, longer-term, and lifetime).

Radionuclides in Drinking Water

EPA has revised the current radionuclides regulation, which has been in effect since 1977, by requiring new monitoring provisions that will ensure that all customers of community water systems will receive water that meets the Maximum Contaminant Levels for radionuclides in drinking water.  EPA also has promulgated a standard for uranium as required by the 1986 amendments to the Safe Drinking Water Act. The current standards are: combined radium 226/228 of 5 pCi/L; a gross alpha standard for all alphas of 15 pCi/L, not including radon and uranium; a combined standard of 4 mrem/year for beta emitters. The new MCL  for uranium is 30 µg/L. This final rule will provide improved health protection for 420,000 persons through monitoring improvements for the combined radium-226/-228 standard (a carcinogen)  and for an additional 620,000 persons through a new standard for uranium (a kidney toxin and carcinogen) in drinking water.

•  Fact sheet about final Radionuclides rule

•  Final Radionuclides Rule (December 7, 2000)
 ( HTML version   ~  PDF version )

•  Notice of Data Availability (April 21, 2000)

•  Stakeholder

Input  

Final Standards

 The regulated radioactive drinking water contaminants are:

Background

Radionuclides emit “ionizing radiation”, a known human carcinogen, when they radioactively decay.  Long-term exposure to radionuclides (see table above) in drinking water may cause cancer.  As described in the Notice of Data Availability, EPA has performed new health effects analyses based on improved models and data.  These new analyses demonstrate that the health effects analyses performed in 1991 generally understated the risks associated with the proposed Maximum Contaminant Level (MCL) changes.  In fact, the new health effects analytical results indicate that radionuclides in drinking water are as risky (in some cases riskier) than originally estimated in 1976.  For this reason, EPA has retained the more stringent 1976 MCLs in the final rule, since the proposed MCL changes were determined to be insufficiently protective of human health.

In addition, exposure to uranium in drinking water may cause toxic effects to the kidney.  In 1991, EPA proposed an MCL of 20 µg/L, which was determined to be as close as feasible to the Maximum Contaminant Level Goal (MCLG).  Based on human kidney toxicity data collected since then and on its estimate of the costs and benefits of regulating uranium in drinking water, EPA has determined that the benefits of a uranium MCL of 20 µg/L do not justify the costs.  Instead, EPA has determined that 30 µg/L is the appropriate MCL, since it maximizes the net benefits (benefits minus costs), while being protective of kidney toxicity and carcinogenicity with an adequate margin of safety.

Provisions of the Final Radionuclides Rule

In addition to the MCLs discussed above, this final rule requires community water systems to ensure that all water served to all customers meets the MCLs for radionuclides in drinking water.  This provision will be accomplished by the requirement that all future monitoring be performed such that all water entering the distribution system is tested.  Under the old rule, community water systems only tested water from a “representative point” in the distribution system.  The old monitoring requirements did not protect every customer, since water quality may vary significantly within the distribution system.

The monitoring frequency requirements have changed to be more consistent with the “Standardized Monitoring Framework” that other drinking water standards use.  This improvement will result in increased consistency in monitoring requirements and will provide monitoring relief for those water systems that have very low contaminant levels.

In addition, the new rule corrects a monitoring deficiency in the 1976 framework for monitoring for combined radium-226 and -228.  Under the old rule, it was assumed that radium-226 and gross alpha levels could be used to screen for radium-228.  Since then, EPA has collected substantial evidence that this assumption is false.  The correction involves separate monitoring requirements for radium-228, further ensuring that drinking water system customers will be protected from harmful radioactive contaminant levels.

This final rule will apply only to community water systems, which are water systems with at least 15 service connections or that serve 25 or more persons year-round.  EPA will further consider a future proposal to regulate radionuclides levels in drinking water served by non-transient non-community water systems, which are water systems that serve at least 25 of the same people more than six months per year, such as schools, churches, nursing homes, and factories that supply their own water.  EPA is consulting with the National Drinking Water Advisory Counci l to determine the best course of action to take with respect to regulating chronic contaminant levels for non-transient non-community water systems, including radionuclides.

Occurrence of Radionuclides in Drinking Water

Most drinking water sources have very low levels of radioactive contaminants ("radionuclides"). These very low levels are not considered to be a public health concern. Of the small percentage of drinking water systems with radioactive contaminant levels high enough to be of concern, most of the radioactivity is naturally occurring. Certain rock types have naturally occurring trace amounts of "mildly radioactive" elements (radioactive elements with very long half-lives) that serve as the "parent" of other radioactive contaminants ("daughter products"). These radioactive contaminants, depending on their chemical properties, may accumulate in drinking water sources at levels of concern. The "parent radionuclide" often behaves very differently from the "daughter radionuclide" in the environment. Because of this, parent and daughter radionuclides may have very different drinking water occurrence patterns. For example, ground water with high radium levels tend to have low uranium levels and vice versa, even though uranium-238 is the parent of radium-226.

Most parts of the United States have very low "average radionuclide occurrence" in drinking water sources. However, some parts of the country have, on average, elevated levels of particular radionuclides compared to the national average. For example, some parts of the mid-West have significantly higher average combined radium-226/-228 levels. On the other  hand, some Western states have elevated average uranium levels compared to the national average. However, in general, average uranium levels are very low compared to the MCL throughout the United States. While there are other radionuclides that have been known to occur in a small number of drinking water supplies, their occurrence is thought to be rare compared to radium-226, radium-228, and uranium.

A very small percentage of drinking water systems are located in areas that have potential sources of man-made radioactive contamination from facilities that use, manufacture, or dispose of radioactive substances. Drinking water contamination may occur through accidental releases of radioactivity or through improper disposal practices. Water systems that are vulnerable to this type of contamination are required to perform extensive monitoring for radioactive contamination to ensure that their drinking water is safe. These radionuclides are regulated under the "beta particle and photon radioactivity" standard.

Costs

For the small percentage of households that are served by water systems that will be required to take corrective actions because of this rule, it is estimated that households served by typical large water systems will experience increased water bills of less than $30 per year and that households served by typical small water systems (those serving 10,000 persons or fewer) will experience increased water bills of $50 - $100 per year. 

Since 1996, EPA's drinking water state revolving fund program has made available $3.6 billion to assist drinking water systems with projects to improve their infrastructure.  EPA has funded over 1000 loans for projects around the country.

Opportunities for Public Involvement 

EPA encourages public input into regulation development. A public meeting took place on 
December 11-12, 1997.  The  meeting summary describes the agenda, the presentations made, and the comments received. 

Notice of Data Availability 

EPA published a Notice of Data Availability (NODA) [ read online in HTML or download PDF file ] to update the public and the regulated community with new information that will be considered in the finalization of the radionuclides rule.  Also available on-line is the Technical Support Document , which provides background information and further describes the analyses discussed in the NODA, and the preliminary Health  Risk Reduction and Cost Analysis , which presents the analyses of projected impacts, costs, risk reductions, and benefits for the uranium NPDWR and the new monitoring requirement for radium-228. 

For More Information 

For general information on radionuclides in drinking water, contact the Safe Drinking Water Hotline , at 1-800-426-4791, or visit the EPA Safewater website at http://www.epa.gov/safewater or the radionuclides website at http://www.epa.gov/safewater/radionuc.html .

Articles on other contaminents;

Asbestos - Lead - Aluminum - Cysts - Chlorine

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