EPA — Arsenic in Drinking Water MCL (10 ppb)
Summary
The US Environmental Protection Agency Maximum Contaminant Level for arsenic in drinking water is 10 parts per billion (10 µg/L), established in 2001 under the Safe Drinking Water Act, replacing the prior 50 ppb standard that had been in place since 1942. The 10 ppb MCL applies to both community water systems and non-transient non-community water systems. The MCL is the regulatory implementation of EPA’s risk assessment for arsenic in drinking water and is the operational US federal floor for drinking water arsenic compliance.
| Parameter | Value |
|---|---|
| Current MCL | 10 ppb (10 µg As/L) |
| Prior MCL | 50 ppb |
| Effective date | 2006-01-23 (compliance) |
| Adopting rule | 2001 Final Rule for Arsenic in Drinking Water |
| Authority | Safe Drinking Water Act |
| Coverage | Community water systems and non-transient non-community water systems |
Wiki pages updated on ingest
Page history
The five most recent substantive edits to this page. The full version history lives in git; when DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.
| Commit | Date | Description |
|---|---|---|
| b0f3d38 | 2026-06-12 | batch | corpus rescreen b04 old terminal skips |