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Arsenic in drinking water

Also called As, Arsenic (III), Arsenic (V), Trivalent arsenic, Pentavalent arsenic.

Legal limit
10 ppb
Health goal
Zero

Values in parts per billion (ppb). Comes from the source.

Where the rules stand

Final MCL of 10 ppb (0.010 mg/L), in effect since January 23, 2006. The health goal is zero.

The scale every TapBuff report uses for this contaminant: the legal line at the middle, twice it at the right.

What EPA says about health

EPA lists skin damage, circulatory system problems and an increased risk of cancer from long-term exposure above the MCL.

Where it comes from

EPA lists erosion of natural deposits, runoff from orchards, and runoff from glass and electronics production wastes.

What handles it

  • NSF/ANSI 58

    Claim to look for: Arsenic (Pentavalent)<=50 ppb Reduction

    Also listed as: Arsenic (Pentavalent)<=300 ppb Reduction

    Pentavalent arsenic only. NSF listings say the product fits only water at or below the stated level and valence. WQA wording: "Arsenic (V) (50 ppb influent level)."

    Same valence limit, for water up to 300 ppb. WQA wording: "Arsenic (V) (300 ppb influent level)."

  • NSF/ANSI 53

    Claim to look for: Arsenic (Pentavalent)<=50 ppb Reduction

    Also listed as: Arsenic (III) (50 ppb influent level)

    Non-RO filters, including some pitchers, per NSF. Pentavalent arsenic only.

    WQA listing wording. The only trivalent arsenic claim found. NSF's listings show none.

Filters with that claim on a certifier’s listing

Sources

  1. National Primary Drinking Water Regulations, U.S. EPA. Checked Oct. 4, 2026.
  2. Search for NSF Certified Drinking Water Treatment Units (standards and reduction claims lists), NSF. Checked Oct. 4, 2026.
  3. NSF listings for the NSF/ANSI 58 pentavalent arsenic claim (valence footnote), NSF. Checked Oct. 4, 2026.
  4. Contaminant Reduction Claims Guide, NSF. Checked Oct. 4, 2026.
  5. Find WQA Certified Products (Gold Seal listings by standard and claim), Water Quality Association. Checked Oct. 4, 2026.
  6. SDWA Dataset Download Summary (codes from SDWA_REF_CODE_VALUES.csv, 2026 Q2 extract), U.S. EPA ECHO. Checked Oct. 4, 2026.