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drinking water quality


The Importance of Our Drinking Water  

Water is the most important element on which all life depends. The average adult body is approximately 55 to 60 percent water. As our population grows, the amount of water used for industry, farming and recreation also grows. Water is our most precious and indispensable resource. The scarcity of water and also its quality are becoming issues. Various chemicals have contaminated both surface and underground waters. Sewage, factory waste and toxins pollute our rivers and lakes and threaten our most important resource.

Collecting Data on Drinking Water Quality

This website gives data and information on contaminants found in our water systems. The data used comes from state drinking water programs that collect it from the water suppliers. The data are routinely collected as part of the monitoring requirements set out by the Environmental Protection Agency (EPA) as well as other state agencies. Community water suppliers are required by law to conduct regular water quality monitoring for impurities and report the results to the state regulatory agency. The data are not collected specifically to measure the level of exposure or to track changes in quality over time. However, these data are the only set of data on drinking water quality that are currently available for scientific research.
EPA sets rules for treating and checking on drinking water delivered by community water systems.
There are quality standards and monitoring requirements for over 90 substances. Treatment and
monitoring rules for these systems will vary from state to state. Programs at both the state and national
levels play an important role in ensuring high quality drinking water. By having  quality standards and
monitoring requirements we protect the public's health.
Drinking water can be polluted by natural sources like bedrock, or from man-made sources like chemicals or farming run-off. Pollution can happen if there are new sources of contamination of the natural water sources that the system uses. Also there are sometimes problems with the water treatment system itself. The risk of developing a specific disease depends on many factors: the specific contaminating substance; the level and potency of that substance; the way that it enters the body, for example, drinking or showering; and the person’s individual susceptibility. Elderly people, children and pregnant women are more likely to suffer ill effects than the rest of the population.
Since pollution in a single system can expose so many people at once, drinking water quality is an important public health issue. People can be exposed to contaminants not only by drinking the water but also by eating foods prepared with the water, breathing water droplets or chemicals released from the water while showering or by absorbing chemicals through their skin while bathing.
Community water systems are required to provide drinking water that meets standards established under the Safe Drinking Water Act. EPA establishes drinking water standards for individual substances and groups of substances. Typically, EPA establishes Maximum Contaminant Levels (MCLs) and associated compliance monitoring requirements. When it is not feasible to measure a contaminant in drinking water, EPA establishes drinking water Treatment Technique Requirements (TTR). These are requirements about the type of treatment required and measures of how well these processes are working. Compliance with MCLs and TTRs is the basis of determining whether the drinking water meets public health standards.
MCLs and TTRs apply to all community water systems; however, the associated monitoring requirements vary. Monitoring requirements are contaminant-specific. Regulations and state drinking water agencies specify sample location and acceptable analytical methods. The frequency of monitoring for a substance may vary based on the type of source water and on the results of previous samples. Monitoring may vary based on service population size and water treatment used.
Drinking water standards and monitoring requirements are not fixed or unchanging. New rules are developed for previously unregulated substances. Also, EPA must periodically review and, if necessary, revise existing regulations based on new information.  

Drinking Water Contaminants

Arsenic is a toxic chemical element that is naturally found in the Earth’s crust. There is a wide variation in the levels of arsenic found in drinking water systems and private water supplies across the country. Arsenic can also be a byproduct of some farming and industrial activities. It can enter drinking water through the ground or as run-off into surface water sources.
All community water systems are required to monitor for arsenic at the entry point to the distribution system; however, the frequency of monitoring varies based on source water type and the level of arsenic observed in past samples. Routine-required monitoring is annual for surface water and once every three years for ground water, with quarterly monitoring once a sample exceeds 10 parts per billion. With a state-granted monitoring waiver, the sampling frequency can be reduced to once every nine years.
Some people who drink water containing arsenic over many years could experience skin damage or problems with their circulatory system, and may have an increased risk of getting cancer. Health effects might include:
     - Thickening and discoloration of the skin, stomach pain, nausea, vomiting, diarrhea and liver
- Cardiovascular, pulmonary, immunological, neurological, reproductive and endocrine effects
     - Cancer of the bladder, lungs, skin, kidney, nasal passages, liver and prostate
If your water comes from a municipal or privately-owned water company that meets the definition of a community water system, they are already testing your water for arsenic. If you have your own household water supply, you are responsible for testing it. Contact your local health department to find out whether arsenic is a concern in your area. Your state’s drinking water agency can give you names of laboratories that are certified to test drinking water.
Public water may contain viruses and bacteria that can cause illness, such as gastrointestinal disorders or diarrhea. Public water suppliers disinfect their water to kill these. Chlorine is the most commonly used disinfectant, sometimes used in combination with other disinfectants such as ozone, chloramine, chlorine dioxide and ultraviolet light.
The risk of illness from disinfectants is much lower than the risk of illness from drinking most surface water or ground water that has not been disinfected. The major health risks from DBPs result from long-term exposures. EPA requires that water systems use treatment methods to reduce disinfection byproducts and protect people from waterborne disease and the harmful effects of disinfection byproducts.
When people consume disinfection byproducts at high levels over many years, they increase their risk of developing bladder cancer. Other health effects include rectal and colon cancer. Adverse developmental and reproductive effects associated with exposure to disinfection byproducts during pregnancy are also a concern.
There are two primary ways that disinfection byproducts can get into your body:
      -  Ingestion through your mouth: drinking water with DPBs
      -  Inhalation through your nose: some DBPs can be released into the air when you use your tap
         water. This can happen when you are taking a shower or washing dishes. And the hotter the
         water is, the more likely it is that DBPs will be released into the air. DBPs can also get into the
         air when you boil your tap water, such as when you make tea or soup.
If your public water system has notified you of a disinfection byproduct violation, it does not mean that the people who consume the system's water will become sick or that your exposure to DBPs has increased. EPA requires that water systems use treatment methods to reduce the formation of disinfection byproducts and protect people from disease and the harmful effects of disinfection byproducts.
Nitrates and nitrites are nitrogen-oxygen molecules which can combine with various compounds. Nitrates are the form commonly found in water, often in areas where nitrogen-based fertilizers are used. Vegetables and meat are the major sources of nitrate exposure. Nitrates and nitrites originate in drinking water from nitrate-containing fertilizers, sewage and septic tanks and decaying natural material such as animal waste. Nitrates are very soluble in water, can easily migrate and do not bind to soils. Nitrates/nitrites are likely to remain in water until consumed by plants or other organisms.
The short-term risks of high levels of nitrates include the potential for serious illness and sometimes death. The serious illness in infants is due to the conversion of nitrate to nitrite by the body, which can interfere with the oxygen-carrying capacity of the child’s blood. This can be an acute condition in which health deteriorates rapidly over a period of days. Symptoms include shortness of breath and blueness of the skin. The long-term risks are being investigated with possible effects including adverse reproductive effects and some forms of cancer.

Tracking Drinking Water Quality

      1.   Contextual Measures - The contextual measures show how many people drink water covered
            under the Safe Drinking Water Act, which regulates contaminant levels in water. The
            proportion of a state’s population served by community water supplies is estimated between
            44 and 95 percent. This proportion provides a measure of the estimated proportion of people
            in the state that are served by water that is being monitored for public health protection.  This
            measure also gives context to how much of the total population is represented by the
            community water supplies included in the level of contaminant and potential population
            exposure indicators.
      2.   Level of Contaminants in Drinking Water - These measures give the level of the
            contaminant in the water served by community water systems showing the extent of
            contamination across water systems. The level of the contaminants is measured in two ways:
            in comparison to a benchmark level, such as the maximum contaminant level (MCL), and in
            terms of average or maximum contaminant concentrations. 
      3.   Potential Population Exposure to Contaminants in Drinking Water - These measures
            portray the potential public exposure to the four contaminants based on the observed levels of
            the contaminants. This potential for exposure is measured in two ways: by the amount and
            proportion of population that is provided water which meets a benchmark, usually the MCL,
            and in terms of average or maximum contaminant concentration.