Arsenic in Well Water

Arsenic in Well Water: A Public Health Concern

Arsenic, a naturally occurring element found in the earth's crust, can infiltrate groundwater and thus, well water, posing potential health risks to individuals who consume it. The presence of arsenic in well water is a concern worldwide and can be particularly prevalent in certain geographical regions where the soil and rock have higher arsenic concentrations.

Health Implications of Arsenic Exposure

  1. Cancer Risk: Chronic exposure to arsenic in drinking water has been linked to an increased risk of various cancers, including skin, bladder, and lung cancer.

  2. Skin Conditions: Exposure to arsenic can also lead to skin conditions, such as pigmentation changes and lesions.

  3. Cardiovascular Issues: Studies have indicated a relationship between long-term exposure to arsenic and the development of cardiovascular diseases.

  4. Developmental Effects: In some cases, exposure to arsenic can impact child development, affecting cognitive function and memory.

  5. Diabetes: There is evidence to suggest that arsenic exposure may be linked to an increased risk of diabetes.

Well Management Program: Mitigating Arsenic Exposure

Given the potential health risks associated with arsenic exposure, implementing a well management program is crucial to safeguard public health. Here are some key components that such a program might involve:

1. Testing and Monitoring

  • Regular Testing: Regular testing of well water for arsenic levels is vital to ensure they remain within safe limits set by health authorities.

  • Monitoring: Continuous monitoring of arsenic levels in well water, especially in areas known for higher natural levels of the element.

2. Public Awareness and Education

  • Awareness Campaigns: Conducting campaigns to raise awareness about the risks of arsenic exposure and the importance of regular well water testing.

  • Educational Programs: Implementing educational programs to inform communities about safe water practices and arsenic mitigation strategies.

3. Treatment Solutions

  • Installing Treatment Systems: Encouraging and facilitating the installation of arsenic removal systems in wells with elevated levels.

  • Maintenance: Ensuring the proper maintenance of installed treatment systems to guarantee their efficacy over time.

4. Regulatory Framework

  • Setting Standards: Establishing and enforcing strict regulatory standards for permissible arsenic levels in drinking water.

  • Legal Framework: Developing a legal framework that mandates regular testing and reporting of arsenic levels in well water.

5. Alternative Water Sources

  • Providing Alternatives: In cases where arsenic levels cannot be effectively reduced, providing access to alternative safe drinking water sources is crucial.

  • Infrastructure Development: Developing infrastructure to supply safe water to affected communities, ensuring no one is left without access to safe drinking water.

Addressing the issue of arsenic in well water requires a multifaceted approach that combines rigorous testing, public education, regulatory enforcement, and the provision of treatment solutions or alternative water sources. A well-structured management program is paramount to mitigate the health risks posed by arsenic exposure and to ensure safe drinking water for all communities.

Well Management Program

Arsenic occurs naturally in rocks and soil across Minnesota and can dissolve into groundwater. Drinking water that contains arsenic can increase your risk of cancer and other serious health effects. Unfortunately, there is no way to know the arsenic level in water before a well is drilled. Arsenic levels can vary between wells, even within a small area. You cannot taste, see, or smell arsenic in your water.

Test your well for arsenic at least once so you know how much arsenic is in your drinking water and you can make an informed decision about whether to take further action.

Drinking Water Standard

The maximum level of arsenic the U.S. Environmental Protection Agency (EPA) allows in community water systems is 10 micrograms per liter (µg/L*). However, consuming water with arsenic at levels lower than the EPA standard over many years can still increase your risk of cancer. As a result, the EPA has set a goal of 0 µg/L of arsenic in drinking water.

*1 µg/L is the same as 1 part per billion (ppb).

Health Risks

Consuming water with even low levels of arsenic over a long time is associated with diabetes and increased risk of cancers of the bladder, lungs, liver, and other organs. Ingesting arsenic can also contribute to cardiovascular and respiratory disease; reduced intelligence in children; and skin problems such as lesions, discoloration, and the development of corns. Health impacts of arsenic may take many years to develop.

Test Your Well Water

Test for arsenic at least once.

Minnesota Department of Health (MDH) recommends you use an accredited laboratory to test your water. Contact an accredited laboratory to get sample containers and instructions, or ask your county environmental or public health services if they provide well testing services.

New wells are tested for arsenic.

As of August 2008, well contractors test each newly drilled well for arsenic and share the results with the well owner and MDH.

Find existing test results: Use the online Minnesota Well Index or contact MDH for test results for a well constructed since 2008.

Consider confirming the arsenic level.

  • If arsenic was NOT detected in the first sample, your water is unlikely to have arsenic later.
  • If arsenic was detected in your new well, you may want to retest your well about six months after construction. MDH research found that when arsenic is detected in a new well, the level may increase or decrease in the first few months after construction. Learn more about this study at Private Well Protection Arsenic Study.

Learn more about testing well water at Well Testing, Results, and Options.

Protect your health! Test your well water for: Coliform Bacteria (every year), Nitrate (every other year), Arsenic (at least once), Lead (at least once), Manganese (before a baby drinks the water). Testing is even more important if young children drink the water.

MDH may recommend you test for additional contaminants based on where you live.

Protect Your Family

If arsenic is detected at any level, consider:

  • Installing a treatment unit or
  • Using a different drinking water source.

Drinking water with arsenic over many years increases the risk of diseases such as cancer.

MDH highly recommends you take action if arsenic levels are above 10 µg/L.

Water Treatment Units that Reduce Arsenic:

  • Reverse osmosis uses energy to push water through a membrane with tiny pores. The membrane stops many contaminants while allowing water to pass through.
  • Distillation uses distillers to boil water, which makes steam. The steam rises and leaves contaminants behind. The steam hits a cooling section, where it condenses back to liquid water.
  • Adsorptive media is a charged media bed that causes ions of the opposite charge (contaminants) to be pulled out of the water and attach to the media.
  • Anion exchange removes dissolved minerals in the water. The owner adds sodium chloride or potassium chloride (salt), which replaces negatively charged minerals in the water.
  • Ozonation and filtration is a system in which ozone (a disinfectant that kills bacteria and viruses) is generated using electricity and then injected into the water. The ozone changes dissolved contaminants into solid particles. The solid particles are large enough to be filtered out of the water.
  • Oxidation filtration has a media bed that changes dissolved contaminants into solid particles. The solid particles are large enough to be filtered out of the water.
  • Chlorination and filtration requires that the owner add chlorine bleach to a holding tank. A pump feeds chlorine into the water, which helps change dissolved contaminants into solid particles. The solid particles are large enough to be filtered out of the water.

Learn more about these treatment options, pros and cons, and general costs at the Home Water Treatment webpage. A water treatment specialist can help you select the best option for your household.

MDH recommends that you choose a treatment system that is certified by an independent certifying organization, such as NSF International, Underwriter’s Laboratory (UL), or the Water Quality Association, that tests water treatment systems to assure their effectiveness in living up to the manufacturer’s claims. In Minnesota, water treatment systems must be installed by a licensed and bonded plumbing or water conditioning contractor, although homeowners may install equipment in homes they own and occupy. After the treatment system is installed, it is important to follow the manufacturer’s recommendations for maintaining the system. Also, have the treated water tested periodically to make sure that the treatment system is working properly.

Remember that while some treatment systems can be useful for other purposes, systems such as conventional water softeners and activated carbon filters will not alone remove arsenic. Also, boiling the water will only concentrate the arsenic, due to evaporation of some of the water.

Using a Different Drinking Water Source

There are a few options for using a different drinking water source to reduce your exposure to arsenic in your drinking water.

Construct a New Well

In some areas, a new well constructed into a different water-bearing formation may produce water with less natural arsenic. Drilling a new well may be a good option if you already want to replace your existing well for other reasons. It can be less expensive in the long run than maintaining a treatment system. However, a new well may still contain natural arsenic even if the well is properly constructed and in an appropriate location.

As our information about the occurrence of arsenic grows, we will learn more about which water-bearing formations in an area have higher or lower levels of arsenic. While there will still be no guarantees, the chances of constructing new wells with lower arsenic levels should improve in some areas. For more information about new well construction, contact a licensed well and boring contractor (Licensed Well and Boring Contractor Directory) or a well specialist at your nearest MDH district office (Contacting the Well Management Section).

Connect to a Community Public Water System

In some cases, connection to a community public water supply system may be possible. All community public water systems are regularly tested for arsenic and other contaminants and must comply with all EPA standards.

Buy Bottled Water

If the level of arsenic in your well water is above 10 µg/L, you could reduce arsenic levels in your drinking water by using bottled water. It is important to note that while all public drinking water systems must meet EPA standards, no single set of standards applies to all bottled water. Instead, bottled water is subject to a variety of standards, depending on the type of bottled water and where it is bottled. These standards may be more or less stringent than those for public water systems. If you are considering switching to bottled water, be sure that levels of arsenic and other contaminants in the bottled water you choose are lower than levels in water from your current water supply. The bottling company should be able to provide testing results for their water. Learn more about bottled water at Bottled Water: Questions and Answers.

Water with Arsenic is Safe to use for Other Things (Unless the Level is Above 500 µg/L.)

Since your skin does not easily absorb arsenic, your water is safe for washing dishes and clothes, brushing teeth, showering, bathing, and watering plants (including vegetables).

Tips for Reducing Other Contact With Arsenic

  • Do not burn wood treated with arsenic.
  • Be aware of ingredients in medications and folk remedies.
  • Seal arsenic-treated wood structures.
  • Make sure children wash their hands.
  • Wash and peel vegetables grown underground (e.g., potatoes, carrots).
  • Eat less rice, cereal grains, or other foods that contain arsenic.
  • Do not use old pesticides and soil supplements if they contain arsenic.

Learn more tips for reducing other contact with arsenic at Arsenic and You.

Arsenic in Minnesota Water

Arsenic has been detected in about 40 percent of new wells drilled since 2008 in Minnesota. (The detection level for arsenic is usually 2 µg/L.) About 10 percent of Minnesota’s private wells have arsenic levels higher than 10 µg/L.

Arsenic is in groundwater throughout the state, but it is more likely in some areas. The map below shows where arsenic is found most often in Minnesota wells. (Map made with MDH data from 2008-2017.) You can learn more about arsenic levels in private wells in your county at MN Data: Private Wells-Arsenic.

Map shows the percent of new wells with arsenic detections in Minnesota. The counties with the highest percentage of new wells with arsenic detections are in central and west central Minnesota.

The way glaciers moved across Minnesota affects where arsenic is found in sediment and groundwater. Arsenic levels can vary between wells, even within a small area. Some wells have arsenic levels as high as 350 µg/L. Learn more about arsenic in private well water through the The Minnesota Arsenic Study (2000).

Background Information

For most people, food and water are the biggest sources of arsenic exposure. There are two forms of arsenic:

  • Inorganic arsenic is the type found in drinking water and is the more harmful type of arsenic. It is also found in rice, cereal grains, and other foods. It forms when arsenic combines with metals and elements other than carbon.
  • Organic arsenic is the most common type of arsenic found in food. It is common in fish and shellfish and is less harmful to health than inorganic arsenic. It is formed when arsenic combines with carbon.

While most arsenic in Minnesota’s environment occurs naturally, some comes from human activity. Arsenic was an ingredient in some pesticides and was used as a wood preservative in the past.

Go to > top.

Should I test my well water for anything besides arsenic?

Yes. Both natural sources and human activities can contaminate well water and cause short- or long-term health effects. Testing your well water is the only way to detect most of the common contaminants in Minnesota groundwater; you cannot taste, see, or smell most contaminants. Minnesota Department of Health recommends testing for:

  • Coliform bacteria every year and any time the water changes in taste, odor, or appearance. Coliform bacteria can indicate that disease-causing microorganisms may be in your water.
    See Bacterial Safety of Well Water.
  • Nitrate every other year. Bottle-fed infants under six months old are at the highest risk of being affected by levels of nitrate higher than 10 milligrams per liter in drinking water.
    See Nitrate in Well Water.
  • Lead at least once. The well and water system may have parts that have lead in them, and that lead can get into drinking water. Lead can damage the brain, kidneys, and nervous system. Lead can also slow development or cause learning, behavior, and hearing problems.
    See Lead in Well Water Systems.
  • Manganese before a baby drinks the water. High levels of manganese can cause problems with memory, attention, and motor skills. It can also cause learning and behavior problems in infants and children.
    See Manganese in Drinking Water.

Other contaminants sometimes occur in private water systems, but less often than the contaminants listed above. Consider testing for:

  • Volatile organic chemicals if the well is near fuel tanks or a commercial or industrial area.
  • Agricultural chemicals commonly used in the area if the well is shallow and is near cropped fields or handling areas for agricultural chemicals or is in an area of geologic sensitivity (such as fractured limestone).
  • Fluoride if children or teenagers drink the water.

Should you be concerned about arsenic?

Yes. While everyone is exposed to some arsenic, certain people are exposed to more arsenic on a regular basis. Find out if you might be exposed to more arsenic, and read on to learn what you can do to reduce your exposure.

Explore this website for details on arsenic in food, water and other sources, and follow the steps outlined on each page to reduce your arsenic exposure. See the Resource links for helpful tools, videos and more detailed information. The Definitions page provides explanations of arsenic-related words and terms.

Why is arsenic a problem?

You can’t see, smell, or taste arsenic. At very high levels, arsenic is poisonous and causes serious and immediate health effects. In the U.S., levels of arsenic in food and water are usually too low to cause obvious symptoms or make you sick right away.

Many people in this country are exposed to low levels of arsenic through food, water and other sources that may increase their risk of diseases like cancer, heart disease and diabetes later in life.

What Can You Do?

  • If you are a private well user, get your water tested.
  • If you eat a lot of rice or other foods that are higher in arsenic, eat them less often or vary with other types of food that are lower in arsenic.
  • If you are pregnant or have infants or children in your home, be sure your family’s diet is as low in arsenic as possible since arsenic may negatively affect growth and development.
  • Eat a varied diet to make sure you’re getting balanced nutrition.
  • Don’t completely stop eating a food if it still provides nutritional benefits.
  • Find out if you could be exposed to other sources of arsenic from pressure treated wood or living near industrial or hazardous waste sites.
  • Stop smoking.
  • Review this site to better understand your total arsenic exposure.
  • Reduce your total arsenic exposure by following the What You Can Do recommendations in this website.

Is Arsenic Regulated?

  • Public water supplies are regulated by the U.S. Environmental Protection Agency and specific state agencies (New Hampshire and New Jersey).
  • If you drink from a private well, it is your responsibility to make sure your well water does not contain arsenic.
  • Right now there are no regulatory limits for arsenic in food, but there is guidance for action levels for arsenic in baby rice cereal and apple juice (scroll to “FDA Regulations and Guidance to Industry to Limit Arsenic in Food”).

Arsenic Exposure: Animated Information

This interactive infographic provides an overview of exposure and health information about arsenic in water and common foods.

Where is the arsenic?

Arsenic is a metalloid naturally found in soil, air, water, plants and animals. As scientists are learning more about the importance of keeping arsenic exposure low, industry and food producers are already taking steps to reduce the amount of arsenic in the environment:

  • The use of pesticides containing arsenic has been banned on food-producing land.
  • Arsenic can no longer legally be used in animal feed.
  • Arsenic is no longer used to pressure-treat wood.
  • The U.S. Food and Drug Administration and international food safety groups are considering maximum limits for arsenic in food.

Since it’s impossible to totally eliminate arsenic from the world, it is up to you to decrease your arsenic exposure by making careful choices about your diet, your drinking water and other arsenic sources.

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Arsenic and Your Health

Arsenic may be harmful to your health in many ways, from causing cancer to potentially disrupting child development, even though the levels of arsenic in the U.S. are rarely high enough to cause obvious symptoms of arsenic poisoning.

What health problems can arsenic cause?

Arsenic is linked to many health problems, such as:

  • Bladder, Lung and Skin cancer
  • Heart and Lung disease
  • Diabetes
  • Lower immune function
  • Poor brain function in children
  • Skin lesions

Who can get sick from arsenic?

Anyone can be harmed by arsenic including:


  • If you use a private well, test your drinking water.
  • If you are a parent, learn about how to protect your baby and kids.
  • Make your diet as low in arsenic as possible. Learn which foods you should limit.
  • Eat a varied diet to make sure you’re getting balanced nutrition.
  • Don’t completely stop eating a food if it provides nutritional benefits.
  • Check out the other sources of arsenic exposure to see if they apply to your family.
  • Review this site to better understand your total arsenic exposure.
  • Talk to your doctor if you think you have had unsafe amounts of arsenic.

How does arsenic affect children?

Young children have very small bodies and eat more food per pound of body weight as they grow. As a result, they get more arsenic from food or drinks compared to adults. Also, babies and young children can be more sensitive to the harmful effects of arsenic because their bodies are rapidly growing and they may not have fully developed systems to get rid of harmful chemicals as well as adults.

If you’re pregnant, your baby could be exposed to arsenic too. Arsenic can cross the placenta, which means that a pregnant woman’s arsenic exposure through food and water may affect her baby’s growth and development or lead to health problems later on.

Expert agencies such as the American Cancer Society, the World Health Organization, and the National Institutes of Health all classify inorganic arsenic, the type found in drinking water and in many foods, as a “human carcinogen,” meaning something that causes cancer in humans.

How does arsenic make you sick?

Arsenic enters your blood stream and is carried to the cells in your body. Unlike other toxins, arsenic leaves your system within a couple of days in your urine. Even though arsenic doesn’t build up inside you, the longer you are exposed to it, the more it affects your cells and over time, can make you sick. As soon as you lower the arsenic you get each day, you are protecting yourself and your family from the harmful effects of arsenic.

“Arsenic is harmful to human health in many ways. It increases the risk of certain cancers and heart disease, and may impact growth, brain development and immune function. Scientists are learning that health effects can occur even at low levels of exposure. ”

Dr. Margaret Karagas, Dartmouth College

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