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Arsenic in Drinking Water: Protect Vital Water Systems with Proactive Solutions

A Drop of Knowledge E-Newsletter

Arsenic in Drinking Water


Protect vital water systems with proactive solutions


by Erinn Zindt, Technical Assistance Provider with the Midwest Assistance Program


What is arsenic?

Arsenic is a chemical element that is naturally present in rock and soil.  Arsenic can be released into the environment from volcanic activity, forest fires, agriculture, industrial activity, and mining practices. When arsenic gets into our drinking water it is odorless, colorless, tasteless, and toxic.

What are the health impacts from arsenic?

Arsenic has been linked to many forms of cancer, including cancer of the bladder, lungs, skin, kidneys, nasal passages, liver, prostate, and others.  Along with carcinogenic risks, arsenic may cause skin damage, stomach pain, nausea, diarrhea, vomiting, and liver damage.

How much is too much?

The Environmental Protection Agency (EPA) has set the Maximum Contaminant Level (MCL) for arsenic in public drinking water supplies to be 10 parts per billion (ppb) in an attempt to reduce negative impacts on human health. While the EPA has set the Maximum Contaminant Level (MCL) to be 10 ppb for compliance issues, the Maximum Contaminant Level Goal (MCLG) to ensure drinking water is safe from arsenic health impacts is 0 ppb.  Community and non-transient, non-community public water supplies are required to sample for arsenic annually or every 3 years, depending on the source water. Details on the EPA’s Arsenic Rule and sampling requirements can be found on the EPA website or by contacting your state primacy agency.  Public water systems are required to include arsenic sampling results in the consumer confidence reports provided to customers annually.

What is 10 ppb?

10 molecules of arsenic for every 999,999,990 molecules of water.
To help visualize, 10 ppb would be just a few drops in an Olympic sized swimming pool.

Elevated arsenic? What’s next?

If arsenic is detected, even if it is below the compliance standard of 10 ppb, your water system should look into potential solutions to reduce arsenic levels to protect the health of your water users.  Solutions to reduce arsenic levels in drinking water vary greatly and are specific to each water system. Options may include treatment at the plant using absorptive media, membranes/reverse osmosis, and ion exchange; blending of water sources; changing water sources; point of entry treatment; or point of use treatment.  There are many issues to consider when selecting an arsenic reduction solution, including water chemistry, existing treatment processes, background and target arsenic concentration, waste discharge methods, land and labor availability, flow rate, and much more.



Available Resources


The EPA’s website has a number of resources, including basic arsenic information, details on the Arsenic Rule, compliance help, state to state guidance, funding sources, useful publications, and research that has been done. As always, you can contact your regional RCAP for additional guidance.


A few specific EPA resources include:

In addition, EPA is looking into other treatment techniques, including electrochemical arsenic removal.

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