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Drinking Water Quality and Health – 9.307   arrow

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What is water quality and why is it important?

In its purest form, water is two parts hydrogen to one part oxygen, but the presence of other components determines the quality of water.

Water quality is defined as the suitability for consumption based on physical, chemical, and biological characteristics. Poor water quality can pose health risks for humans and ecosystems.

Across Colorado and the country, the quality and characteristics related to water can vary widely depending on location, environmental exposures, and how the water has been treated and handled. Water covers 71% of the earth’s surface and comprises up to 60% of the human body, so understanding water quality is vitally important for protecting our health and the health of all ecosystems.

How Much Water Should You Drink?

Sufficient daily fluid intake is estimated to be about 15.5 cups per day for men and 11.5 cups per day for women. Someone working outdoors in the summertime without shade may need to consume greater amounts of water to be adequately hydrated. Colorado is an arid, high elevation state, so staying hydrated is crucial for health. Although most of this liquid comes from beverages, food also provides water for us. During digestion, water is released as a by-product in the conversion of fats, sugars, and proteins to energy.

Whether drinking water is bottled or from the tap, there are many factors that may influence the quality. It is important to understand how water quality and composition change due to natural or human causes. Across the state, water quality can vary tremendously, so it is helpful to know characteristics of the water in your area.

Drinking Water Sources

The quality of water is dependent on where it is sourced and other impacting factors. The Safe Drinking Water Act was passed in 1974 to regulate water quality and protect public health. Geographic region plays an influential role in water quality. The Rocky Mountains have helped Colorado earn the reputation of having some of the best tasting tap water in the U.S. Being close to the source of snowmelt and mountain surface water impacts water quality and has several advantages.

To better understand water quality, it is important to be familiar with your water source and how quality is checked.

Municipal Water: Public water supplies in the U.S. are monitored, tested, and treated to meet specific guidelines regulated by the U.S. Environmental Protection Agency (EPA).

Private Well Water: The water from private wells is not subject to federal drinking water regulations. This means it is the owner’s responsibility to have the water regularly tested and treated according to need.

Bottled Water: Commercially bottled water is generally sourced from wells, springs, or tap water. The U.S. Food and Drug Administration (FDA) regulates bottled water products in accordance with the Federal Food, Drug, and Cosmetic Act which requires manufacturers to be responsible for producing safe, wholesome, and truthfully labeled products.

Backcountry Water: The water found in isolated wilderness areas is sometimes used during recreational activities and differs from other sources of drinking water because it is untreated and the safety and quality is unknown. Before consuming, water in the backcountry should always be treated according to guidelines.

Other Types of Water

Graywater: Wash water that has been used in a home or business, except water from toilets. This includes water from kitchen sinks, dishwashers, and non-laundry utility sinks. It is usually considered “relatively clean” compared to black water and may have a secondary application for conservation purposes. Black Water: water from toilets and urinals.

Wastewater: water that has been used domestically, for businesses, or for industrial processes. This can include any process that decreases the water quality. In a municipal water system, this is the water that flows through sewage pipes.

Chemical Components of Water that can Affect Quality

The chemical composition of drinking water can be quite different whether you turn on a tap, unscrew a bottle cap, or filter from a mountain stream. Water can be changed by human activity as well as natural processes, such as weathering and erosion, or by changes in temperature and acidity. Industry and agriculture have a profound effect on the quality of our water supply.

Discharges, whether accidental or intentional, can unexpectedly change the chemical characteristics of our water supply. Some of Colorado’s water sources are affected by the following natural or human-made chemical components.

  • Ammonia/Ammonium
  • Selenium
  • Arsenic
  • Cadmium
  • Uranium
  • Lead
  • Pesticides
  • Nitrates and Nitrites
  • Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS)
  • Salinity
  • Sulfates
  • Radon

Review the Full Water Quality Fact Sheet for in-depth information on more than 10 types of water contamination, along with information on water quality testing.

Hard vs. Soft Water

The concentration of calcium, magnesium, and iron in the water determines its ‘hardness.’ The more minerals present, the ‘harder’ the water. Conversely, soft water contains little calcium, magnesium, or iron.

You cannot tell whether water is hard or soft based on how it looks. Even if water is extremely hard and contains elevated levels of minerals, it may appear clear. However, you may be able to tell if water is soft because it has a different feel during use. For example, soft water makes soap lather better, gets clothes cleaner, and leaves less of a ring around the tub. You may find spots on your dishware or less water pressure in your home if you use hard water.

A common treatment for hard water includes using an ion-exchange water softener. When the similarly charged magnesium and calcium ions bind to the ion exchange resin, sodium ions are released, softening the water.

Although effective for managing the physical effects of hard water, removing calcium and magnesium has drawbacks from a nutritional standpoint since these are both essential dietary nutrients. Elevated sodium intake increases the risk of hypertension, whereas calcium intake may have a protective effect. However, consuming excess calcium could negatively impact health. There are no direct adverse health effects from hard or soft water. However, whether your water is hard or soft may affect other aspects of your water quality.

First, soft water is more likely to corrode toxic metals from outdated piping. This could potentially introduce metals like cadmium and lead into the drinking water. Second, adding sodium to the water supply may be a significant source of sodium for those on a sodium-restricted diet. As stated in the sodium section, the EPA has not set a mandatory upper limit for sodium in drinking water but recommends no more than 20 milligrams per liter to protect individuals on a sodium-restricted diet.

Chlorination of Municipal Water

Public water treatment facilities often add chlorine as a disinfectant. It is favored over other forms of disinfection such as ultraviolet light or ozonation because it prevents the regrowth of pathogens. Most pathogens do not survive treatment with chlorine; it effectively kills the pathogens that cause typhoid fever, dysentery, cholera, and Legionnaire’s disease.

Due to its wide success and application, chlorination of municipal drinking water has been accepted as the common treatment to prevent waterborne disease outbreaks in the United States. Chlorine is used by more than 98% of all water utilities in the U.S. that disinfect drinking water for their communities.

Why doesn’t this potent treatment harm humans? The gastrointestinal tract neutralizes the chlorinated water when it is ingested. The concentration of chlorine is monitored closely and regular testing is performed to measure ’chlorine residual,’ or the amount of chlorine remaining in the water when it reaches the tap (see: Disinfection By-Products).

Water with chlorine levels less than 4 parts per million is unlikely to cause harmful human health effects. Reptiles, fish, amphibians, and other aquatic pets should not be contained in or offered chlorinated water. These species absorb water directly into their bloodstream and may experience toxicity from chlorinated water. Use water purchased at a local pet store or let chlorinated water sit out for a few days to allow the chlorine to dissipate.

Disinfection By-Products

One drawback of using chlorine as a disinfectant is that it introduces the potential for the formation of disinfection by-products, or “DBPs.”

Chlorine is a reactive chemical and can react with many other chemicals in the water, forming hundreds of DBPs. Scientists and regulators do not yet have a clear understanding of how DBPs affect us and the environment, but it is thought that chronic exposure to DBPs may lead to liver, kidney or central nervous system problems and increased risk for cancer and reproductive effects.

To err on the side of caution, the EPA has chosen to monitor commonly detected DBPs as a sum of the highest contributing constituents. This measurement is referred to as “TTHM” or “Total Trihalomethanes.” The DBPs in this family are chloroform, bromodichloromethane, dibromochloromethane, and bromoform.


Fluoride is a naturally occurring mineral. There are trace amounts of fluoride in soil, water, plants, and food. Having some fluoride in your diet is important to prevent dental cavities and tooth decay.

Many municipalities add fluoride to their drinking water so the public has less risk of developing tooth decay. Children can receive fluoride treatment at the dentist if they are drinking water that does not contain the optimal level of fluoride. It is estimated that intervention with fluoride reduces the risk of tooth decay by 30 percent. Evidence suggests that fluoridated drinking water is safe and effective at preventing tooth decay and saves healthcare costs.

In the United States, adverse health effects due to excessive fluoride are unlikely but exposure over many years may cause bone pain, tenderness, and disease. Overall, fluoride treatment has improved the dental health of millions of Americans but children who drink water with excess fluoride may experience tooth staining or pitting.

Home Water Treatment

Depending on the source of water to your home, it may be necessary to choose a water treatment system to improve the quality of the supply.

Municipal systems are typically monitored regularly so water from this source does not require additional intervention. As a consumer, you should pay attention to public advisories that may be applicable to you in instances of contamination or malfunction. To understand what type of treatment system you need at home, it may be helpful to submit samples for testing.

Well water accesses groundwater aquifers, the quality of which can be altered by a multitude of factors. Having some idea of your water’s quality prior to installing a system may help inform your choice. Companies that sell water treatment systems are not required to prove their efficacy. Independent organizations, such as NSF International, test products to document and certify their performance. The results follow voluntary national standards. This information is available at Consumer Resources | NSF International.

Review the Full Water Quality Fact Sheet for additional information on water contamination, water quality testing, algal blooms, microplastics, water conservation, and much more.