Arsenic in community water systems

What is arsenic and how does it get in water?

Arsenic occurs naturally in soil and rocks across Minnesota. Small amounts can dissolve into groundwater that may be used for drinking water. Arsenic can be found in groundwater throughout Minnesota but is more likely in some areas than others. West central and northwestern Minnesota tend to have higher levels of arsenic. Arsenic has no smell or taste, so water must be tested in a laboratory to see if it has arsenic.

Health effects of arsenic

Drinking water with 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. Coming in contact with 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 not occur right away and can develop after many years, especially if you are in contact with arsenic at a low level over a long time.

Standard and goal for arsenic in community water systems

All community water systems test for arsenic and ensure levels meet the Environmental Protection Agency drinking water standard, or Maximum Contaminant Level (MCL). The MCL for arsenic is 10 micrograms per liter (µg/L). However, drinking water with arsenic at levels lower than the EPA standard over many years can still increase your risk of cancer. As a result, EPA sets health risk goals. The EPA has set a goal of 0 µg/L for arsenic in drinking water. These goals do not consider the cost of water treatment to reach that level of arsenic in drinking water.

Most community water systems provide drinking water with no or low levels of arsenic

Very few community water systems provide drinking water with levels of arsenic above the federal drinking water standard. Read the most recent Drinking Water Protection Annual Report  for more information.


Mean arsenic levels in Minnesota community water systems

 
The MCL is 10 µg/L. Concentrations are the mean annual levels for community water systems in Minnesota.
 
The MCL is 10 µg/L. Concentrations are the mean annual levels for community water systems in Minnesota.

The percent of systems in violation of the MCL is not equal to the percent of systems shown in the chart because whether a system is in violation is based on a running annual average at each entry point to the system, rather than a system-wide calendar year average. A number of systems in Minnesota are working to bring their arsenic levels below the MCL.


Maximum arsenic levels of Minnesota community water systems

 
The MCL is 10 µg/L. Concentrations are the maximum annual levels for community water systems in Minnesota.
 
The MCL is 10 µg/L. Concentrations are the maximum annual levels for community water systems in Minnesota.

In the chart above, the maximum value of each system shows the highest concentration in any single sample, prior to any blending of water. The level of arsenic in blended water that reaches the consumer's tap may be lower because of dilution.

The number of people served by community water systems with arsenic at levels above the EPA standard is very low.


Population served by community water system mean arsenic concentration, 2017

Arsenic Systems Population served Percent
0 - 5 901 4,370,991 93.7%
5+ - 10 58 34,919 6.0%
10+ - 20 3 571 0.3%
20+ - 30 0 0 0.0%
30+ 0 0 0.0%

Note that the estimates of number of people served by each system are rough calculations periodically updated by water system managers.

What can be done about arsenic in drinking water?

All community water systems test for arsenic and ensure levels meet the EPA standard. If a system’s arsenic level exceeds the standard, the system notifies customers and makes changes to reduce the level.

You can find the level of arsenic your community water system detected by reading their Water Quality Report (also known as a Consumer Confidence Report [CCR]). Call your community water system to get a copy of your CCR, or find it online at Search for Your Consumer Confidence Report (CCR) .

Arsenic is also a concern in private wells. The only way to know if a private well contains arsenic is to have it tested. Private well users are responsible for testing their well water for arsenic. MDH recommends private well users test their water at least once for arsenic. See Well Testing, Results, and Options for information about how to test your well water. For more information about arsenic in well water, see Arsenic in Well Water.

If you want to take additional steps to reduce your exposure to arsenic in drinking water, you can use a home water treatment system. For more information on home water treatment, visit Home Water Treatment.

Related topics:

Arsenic in Drinking Water
• Arsenic in Private Wells
Safe Drinking Water for Your Baby
• Chemicals in People: Biomonitoring - Arsenic
• Arsenic Drinking Water Requirements for States and Public Water Systems


 

Last updated November 2018. Updates are made when data become available; not all data are available annually.