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Shortlist

Contaminant

Arsenic in drinking water

A naturally occurring carcinogen, common in some wells and groundwater.

This page can’t tell you what’s in your tap water.
Only a test of water from your own tap can. Public-system results describe the system, not your home.
11 sources
01Check your water systemWater Check · system results, not your tap02Test your tapHow to get a reliable result03Treatment approachesWhat can reduce it at the tap
On this page · 10 sections
  1. 01Reference values
  2. 02Is it in my water?
  3. 03Where it comes from
  4. 04Testing
  5. 05Water filters
  6. 06Treatment
  7. 07Evidence
  8. 08Next steps
  9. 09Ask about arsenic
  10. 10References
Reference values

A legal limit — and a lower health goal.

Each value says what kind of reference it is, and they mean different things. A lower or missing number never means water is safe.

Enforceable limit · MCLFederal · public water systems
10 ppb

The highest level allowed in water a public system delivers. A legal limit, not a health goal.

Applies to
Water delivered by public water systems, not private wells
Status
In force
Source
EPA NPDWR MCL (0.010 mg/L) · 40 CFR §141.62
Health-based goal · MCLGFederal · not enforceable
0 ppb

The level below which no known health risk is expected. A goal, not a limit.

Applies to
Set alongside the rule as a public-health goal
Status
Published goal
Source
EPA National Primary Drinking Water Regulations — MCLG zero · 40 CFR §141.51
How they relate
Health-based goalNo known risk expected below itEnforceable limitThe legal maximum

Water between the two isn’t automatically safe. A goal and a legal limit answer different questions. Positions are illustrative, not to scale.

Your stateNot held yetStates may set their own references. We don’t hold a state reference for arsenic yet.
Is it in my water?

Only a test of your own tap can tell.

Choose what you have. We’ll show what it can and can’t tell you.

If you haven’t tested
Nobody can tell without a measurement, including us.

Three things you can do, in this order.

Test water from your tapThis is the only way to know your level. Testing guidance ↓See what your system reportsSystem results aren’t a tap measurement. Open Water Check →On a private well?Public-system reports don’t cover wells. Open Well Water →
Where it comes from

Where it comes from

  1. Arsenic occurs naturally in rocks and soil across Minnesota and can dissolve into groundwater.
  2. 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.
Why it matters
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.
Arsenic can 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.
Testing

How to test your tap water for arsenic

Test your well for arsenic at least once using an accredited laboratory; you cannot taste, see, or smell arsenic in your water.

  1. 01Use a certified labA state-certified lab, or a kit that sends samples to one.
  2. 02Follow the sampling stepsHow and when you collect the water changes the result.
  3. 03Check the reportIt should state units and the detection limit.
Certified labNot sponsored
Use a state-certified labYour state keeps a list of labs certified for drinking water.

Choosing a filter for arsenic

None qualify
No products currently qualify for a arsenic pick here.

Nothing in our database has a arsenic claim for an exact configuration we can verify.

Find a fit in FinderRead treatment approaches
Treatment

How to reduce arsenic in water

Function: ReduceRemoving arsenic requires treatment systems certified by independent organizations to reduce this naturally occurring dissolved mineral from groundwater.
Reverse osmosisUses energy to push water through a membrane with tiny pores that stop arsenic while allowing water to pass through.Before you chooseClaims apply to the exact model and configuration tested.
Activated aluminaA charged media bed that attracts negatively charged arsenic ions, pulling them out of the water and causing them to attach to the media.Before you chooseClaims apply to the exact model and configuration tested.
Ion exchangeAnion exchange removes dissolved arsenic. The owner adds sodium chloride or potassium chloride (salt), which replaces negatively charged arsenic in the water.Before you chooseClaims apply to the exact model and configuration tested.
Whole-house systems and point-of-use filters treat different water. A whole-house system treats water where it enters the home; a point-of-use filter treats the tap it’s installed on. Check which one a claim is for.
Evidence

What the evidence means

We keep evidence types apart. A result for one configuration never stands in for another, and we never average across types.

No product in our database holds a reduction record for arsenic yet.

How we read evidence →

Next steps

Take the next step

Match a system to your homeFinder asks about your home first. It suggests arsenic as a starting point, and nothing counts until you confirm it.
Ask about arsenic

Still have a question?

Answers come only from WaterDecoder’s reviewed sources and show citations. Ask can’t interpret your test result or choose a product. Don’t include personal details.

AI assistant

Ask about Arsenic

Answers draw on cited public-health sources and the filters certified to reduce Arsenic. Every source is linked, and if the sources don’t cover a question, the answer says so.

Questions to start with

Educational information from cited sources. Not medical or professional advice.

References

Where these facts come from

  1. 1Regulatory reference40 CFR §141.62EPA NPDWR MCL (0.010 mg/L)
  2. 2Regulatory reference40 CFR §141.51EPA National Primary Drinking Water Regulations — MCLG zero
  3. 3Knowledge BaseArsenic in Well WaterMinnesota Department of Health
  4. 4Knowledge BaseOverview of Drinking Water Treatment TechnologiesUS EPA (SDWA program)
  5. 5Knowledge BaseGuidelines for Testing Well WaterCDC (Division of Drinking Water Safety)
  6. 6Knowledge BaseArsenic in Your Drinking WaterEPA
  7. 7Knowledge BaseNSF/ANSI 58: Reverse Osmosis Drinking Water Treatment SystemsNSF International
  8. 8Knowledge BaseArsenic Fact SheetWater Quality Association (WQA)
  9. 9Knowledge BaseTreatment Options and TechnologiesUniversity of Maine Cooperative Extension (Arsenic in Maine program)
  10. 10Knowledge BaseArsenic Water TestingDartmouth Toxic Metals Superfund Research Program (Dartmouth College, NIH-funded)
  11. 11Knowledge BaseArsenic (Fact Sheet)World Health Organization (WHO)

Written and maintained by WaterDecoder. A review date appears only once we have confirmed one.

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