Scope
The amended section 64431 table applies primary inorganic-chemical maximum contaminant levels to California public water systems.
Exact limit and units
| Species | Chemical row | MCL mg/L | Structured value |
|---|---|---|---|
| Al | Aluminum | 1.0 | 1,000 ug/kg-equivalent |
| Sb | Antimony | 0.006 | 6 ug/kg-equivalent |
| tAs | Arsenic | 0.010 | 10 ug/kg-equivalent |
| Cd | Cadmium | 0.005 | 5 ug/kg-equivalent |
| Cr-VI | Chromium (hexavalent) | 0.010 | 10 ug/kg-equivalent |
| Cr-total | Chromium (total) | 0.05 | 50 ug/kg-equivalent |
| tHg | Mercury | 0.002 | 2 ug/kg-equivalent |
| Ni | Nickel | 0.1 | 100 ug/kg-equivalent |
How tested
Section 64432 requires public water systems to monitor for the MCLs in Table 64431-A. The excerpt does not list analytical method codes in the table itself.
Enforcement posture
Public water systems must comply with the primary MCLs in Table 64431-A and monitor under the cited sections. These are enforceable drinking-water standards.
History of changes
The regulation text is marked SWRCB-DDW-21-003, Hexavalent Chromium MCL, February 2024. The companion State Water Board resolution adopted a 10 ppb hexavalent chromium MCL.
How it compares
The table records both total chromium and hexavalent chromium as separate rows, preserving species. Arsenic and mercury are not narrowed beyond the element names in the table and are recorded as total arsenic and total mercury.
Sources
Update history
The five most recent substantive edits to this page, classified major (evidence or structure moved), correction (a published value or statement was wrong and has been fixed), or minor (narrative rewritten without changing the underlying evidence). Each description is derived from what the edit did to this page; the linked commit is the authoritative record, routine regeneration passes are excluded, and 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 | Change | Description |
|---|---|---|---|
| a8052bb | 2026-08-09 | major | 1 source added; contamination-profile values revised; 7 sections added |