Cadmium and Mercury MCLs

This rulemaking is in development and has not yet begun.

Inquiries regarding the contents of this regulation may be directed to Melissa.Hall@waterboards.ca.gov.

The current cadmium MCL (maximum contaminant level) is 5 µg/L (0.005 mg/L).

The current cadmium DLR (detection limit for purposes of reporting) is 1 µg/L (0.001 mg/L).

The current cadmium PHG (public health goal) is 0.04 µg/L (0.00004 mg/L).

The current mercury MCL (maximum contaminant level) is 2 µg/L (0.002 mg/L).

The current mercury DLR (detection limit for purposes of reporting) is 1 µg/L (0.001 mg/L).

The current mercury PHG (public health goal) is 1.2 µg/L (0.0012 mg/L).

The tables below summarize the Division of Drinking Water's water quality database's reported findings of cadmium and mercury from 1 January 2014 to 1 October 2024 for community water systems (CWS), non-community non-transient water systems (NTNCWS), and transient non-community water systems (TNCWS) using the highest running annual average for each source. In this case, sources are active wells, springs, infiltration galleries, common headers, and other intakes reporting monitoring results for cadmium and mercury. Data includes both raw and treated sources.

The values above should not be considered to reflect cadmium or mercury in drinking water served to customers, since water from these sources may be blended, treated, or otherwise not used to provide drinking water. For more information about the quality of specific drinking water supplies, see public water systems' annual Consumer Confidence Reports. The sampling results in the table above were obtained from laboratories using one of the following ELAP accredited methods:

• Cadmium
  • SM 3113 B: Metals by Electrothermal Atomic Absorption Spectrometry (2010)
  • EPA 200.5: Determination of Trace Elements in Drinking Water by Axially Viewed Inductively Coupled Plasma – Atomic Emission Spectrometry (2003)
  • EPA 200.8: Determination of Trace Elements in Water and Wastes by Inductively Coupled Plasma – Mass Spectrometry (1994)
  • EPA 200.9: Determination of Trace Elements by Stabilized Temperature Graphic Furnace Atomic Absorption (1994)
• Mercury
  • SM 3112 B: Metals by Cold-Vapor Absorption Spectrometry (2009)
  • EPA 200.8: Determination of Trace Elements in Water and Wastes by Inductively Coupled Plasma – Mass Spectrometry (1994)
  • EPA 245.1: Determination of Mercury in Water by Cold Vapor Atomic Absorption Spectrometry (1994)
  • EPA 245.2: Mercury (Automated cold Vapor Technique) by Atomic Absorption (1974)

• Notice of Proposed Rulemaking Published: TBD
• Close of the 45-Day Public Comment Period: TBD
• Date of Scheduled Public Hearings: TBD
• Date filed with Office of Administrative Law: TBD
• Approved by Office of Administrative Law: TBD
• Filed with the Secretary of State: TBD
• Effective Date: TBD

• California Code of Regulations, Title 22, sections TBD

• TBD