Arsenic in Tap Water
Arsenic is a naturally occurring semi-metal that dissolves into groundwater from rock and soil, and can also enter water from mining and legacy agricultural chemicals.
Natural erosion of arsenic-bearing rock into groundwater; also mining, smelting, and past pesticide use.
- 1Natural mineral deposits
- 2Mining and smelting
- 3Legacy agricultural chemicals
Most affected: Anyone on an affected community system or private well; developing children and pregnant people are of particular concern.
A result is read with its context
This contaminant is tracked through federal and state compliance monitoring. Private wells are not covered by the federal rule and should be tested directly. PurityMap does not yet publish a per-system measured value for Arsenic; this page is a reference explainer. To learn what is in your own water, check your utility’s Consumer Confidence Report (CCR) or use a certified home test.
- Above reference
- Evidence exceeds a reference level.
- Detected
- This substance was found in the monitoring record. Being present is not the same as being above a reference level, and this signal does not say which.
- Not detected
- Somebody looked and the laboratory reported nothing above its reporting limit. This is a result, and it is not the same as nobody looking.
- Not monitored
- No sampling for this substance has been reported for this system. Nothing is known either way, and an empty row is not a clean one.
10 cities with a published arsenic result
- NormanOK · 2025 · Utility report0.01 mg/LView city →
- BoiseID · 2023 · Utility report0.009 mg/LView city →
- LincolnNE · 2025 · Utility report0.008 mg/LView city →
- Metropolitan DistrictNE · 2025 · Utility report0.005 mg/LView city →
- OmahaNE · 2025 · Utility report0.005 mg/LView city →
- Los AngelesCA · 2025 · Utility report0.003 mg/LView city →
- BiloxiMS · 2025 · Utility report0.003 mg/LView city →
- Las VegasNV · 2025 · Utility report0.002 mg/LView city →
- FriscoTX · 2025 · Utility report0.001 mg/LView city →
- BuffaloNY · 2025 · Utility report0 mg/LView city →
Latest published value per city, from Utility report. A system-level result, not a measurement of any single home.
16 cities with a health-based violation
A violation is a past event with a status, from the federal compliance record (EPA SDWIS, since 2016). It does not describe the water today.
- MustangOklahomaArchivedView city →
- BelenNew MexicoResolvedView city →
- AndrewsTexasResolvedView city →
- Bay CityTexasResolvedView city →
- Camino RealNew MexicoResolvedView city →
- MooreOklahomaArchivedView city →
- Military Hwy WSC Las RusiasTexasResolvedView city →
- Auburn DistrictMassachusettsResolvedView city →
- Arvin Community DistCaliforniaResolvedView city →
- ColumbusNebraskaResolvedView city →
- Greenfield County WdCaliforniaResolvedView city →
- BellmeadTexasResolvedView city →
- Elkhorn WaterworksWisconsinResolvedView city →
- EspanolaNew MexicoResolvedView city →
- Lamont DistCaliforniaResolvedView city →
- LivingstonCaliforniaResolvedView city →
What can carry a arsenic reduction claim
- Reverse osmosis
Semi-permeable membrane separation removing dissolved minerals, heavy metals, and persistent fluorinated chemicals down to 0.0001 microns.
- Anion exchange
Synthetic polyvalent resin beads that exchange unwanted dissolved ionic contaminants for harmless benchmark ions.
- Activated alumina / adsorptive media
Boiling does not remove a dissolved chemical compound and can concentrate it. Many pitcher and refrigerator filters carry no verified claim for a compound like this at all.
A finding establishes the need, the need names the capability, the capability requires a verified certification. No product appears before that sequence completes. Filter Finder →
Frequently asked
Answers cite the same records as the page. How PurityMap analyzes water data
Arsenic is a naturally occurring semi-metal that dissolves into groundwater from rock and soil, and can also enter water from mining and legacy agricultural chemicals.
The enforceable federal limit is 10 µg/L (MCL). The health-based goal (MCLG) is 0. PurityMap reads every measurement against its stated benchmark and never sets its own.
Natural mineral deposits, Mining and smelting, Legacy agricultural chemicals.
Long-term arsenic exposure is linked to skin, bladder, and lung cancers and to cardiovascular and developmental effects. Because the risk is cumulative, the EPA set the limit near the lowest feasible level. Boiling does not remove arsenic and concentrates it.
Treatment technologies commonly certified to reduce Arsenic include Reverse osmosis, Anion exchange, Activated alumina / adsorptive media. Match the exact certified claim to your water before buying. Holding a format is not the same as holding the claim.
In PurityMap's published record, 10 cities have a published Arsenic value from utility Consumer Confidence Reports. This is the scope of our record, not a national prevalence estimate.
In the federal compliance record (EPA SDWIS, since 2016), 16 cities in PurityMap's record across 7 states had a water system measure Arsenic above the legal limit, most recently in 2026, including Mustang, OK; Belen, NM; Andrews, TX. Each violation is a past event with a published status, not a description of the water today.