There are many potential contaminants that can be found in well water. Some of these contaminants can have a serious impact on human health, while others may just make the water taste or smell bad. It is important to test your well water for contaminants on a regular basis and take steps to reduce the likelihood of contamination. Here we will discuss some of the most common potential contaminants in well water and their impacts.

Potential Sources


The use of arsenic as a poison is widely documented. As a result, many people are alarmed when they hear that their drinking water, either from a public or private water system, may contain an amount of arsenic. What do you do if your water contains arsenic, and can it be removed? This Q&A addresses these questions and more.

Learn more: Arsenic in Well Water


Bacteria, microscopic in size, are the smallest single-celled organisms that can live completely on their own because they have the ability to ingest food and transform it into energy. The vast majority of bacteria found in water do not cause disease; however, some can. These are called pathogens. Bacteria are important residents of groundwater, transforming organic carbon, forms of common elements and minerals such as iron, manganese, sulfur, phosphorus, nitrogen and oxygen.

Learn more: Bacteria in Well Water

Hydrogen Sulfide

Water that is giving off a distinctive smell is most likely contaminated with hydrogen sulfide. Hydrogen sulfide does not usually pose immediate health problems at the levels it is found in domestic drinking supplies. However, it is certainly an inconvenience — especially to one’s nose, as it creates a “rotten egg” smell.

Learn more: Hydrogen Sulfide in Well Water


MTBE has been in the news more and more in recent years. A chemical added to gasoline to help it burn cleaner and aid air quality, it has been showing up in water supplies as a contaminant. In fact it reportedly has been detected in ground water at some levels in 49 states.

Learn more: MTBE in Groundwater


Contamination from nitrates is one of the problems that can arise after severe flooding or heavy rains in rural areas. Nitrates are nitrogen-oxygen chemical units that combine with various organic and inorganic compounds, or may be present in water in ionic form. They are essential nutrients for plants, which absorb them from soil.

Learn more: Nitrates in Well Water


Per- and polyfluoroalkyl substances (PFAS) are human-made chemicals containing carbon and fluorine that are found in groundwater and surface water throughout the world. The two most prominent PFAS (known as PFOA and PFOS) are no longer made in the United States, but remain in the environment.

Learn more: PFAS in Groundwater


Radionuclides contaminating water is a developing issue. Radioactivity in groundwater formerly was limited to natural causes such as radon, radium, or uranium. But releases from nuclear power plants and medical facilities have added the dimension of man-made radioactivity finding its way into drinking water sources. What follows are answers to frequently asked questions about radionuclides.

Learn more: Radionuclides in Groundwater


Radon is a colorless, odorless gas produced by the radioactive decay of the element radium, which has itself been formed by the decay of uranium. All rocks contain some uranium, although most contain a very tiny amount. Just as uranium is present in all rocks and soils, so are radium and radon, due to radioactive decay. Radon is found in groundwater in areas that have high levels of uranium in the underlying rocks, such as granites and shales.

Learn more: Radon in Well Water


Water safety has been in the news again in recent months. This time it is due to trihalomethanes, a water by-product thought to be a possible carcinogen. However, that doesn’t mean all homeowners who use a water well for their daily water supply are at risk.

Learn more: Trihalomethanes in Well Water


Naturally occurring radioactive substances are frequently found in groundwater—including uranium, a heavy metal. It exists in almost all rocks and soils. Everyone ingests or inhales small amounts of natural uranium daily. Learn more about whether your private well is at risk.

Learn more: Uranium in Well Water

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