Contaminants in Drinking Water

Regulated Contaminants

• Drinking water standards are called maximum contaminant levels (MCLs). MCLs are found in Title 22 of the California Code of Regulations.
• Primary MCLs address health concerns -- here is a comparison of Federal and California MCLs (PDF).
• Esthetics such as taste and odor are addressed by secondary MCLs (PDF).
• Learn about MCLs and public health goals (PHGs).
• Standards also include detection limits for purposes of reporting (DLRs). DLRs can be found in Title 22 of the California Code of Regulations and can also be found in the Reference Value Tables for analytes associated with the submittal of analytical results through the California Laboratory Intake Portal (CLIP).
• Also, see chemical-specific information on arsenic, 1,2,3-Trichloropropane (1,2,3-TCP), manganese (which has a secondary MCL), MTBE, nitrate and nitrite, and perchlorate; and information about fluoridation by public water systems.

Public Notification and Information about Contaminants

• Water systems: Use these templates -- and contact your Drinking Water Program district office -- when public notification is required because of chemical or microbiological contamination, or because of other conditions.
• Consumers: Information about your drinking water quality is available from your water system in its annual Consumer Confidence Report (CCR). A number of CCRs for California water systems are available on the DDW’s Drinking Water Watch webpage.

Unregulated Contaminants

• Notification and Response Levels: The Division of Drinking Water (DDW) uses these health-based advisory levels for certain chemicals without MCLs. Exceeding them prompts certain requirements and recommendations.
• Also, see chemical-specific information on 1,4-dioxane, hexavalent chromium, NDMA and other nitrosamines, microplastics, and have Perfluorooctanoic acid (PFOA) and Perfluorooctanesulfonic acid (PFOS).
• Unregulated chemicals for which monitoring is required: These regulations were repealed October 18, 2007.
• Emerging contaminants: Information about emerging contaminants pertinent to drinking water and recycled water, along with links.
• Cyanobacteria and Cyanotoxins in Drinking Water: Information about harmful algal blooms and potentially associated toxins in California.

Treatment Technology

• DDW's Water Treatment Technology Approval Process (PDF) - January 16, 2002

Sampling and Analysis

• Monitoring schedules
• EDT - data submittal by laboratories
• Additional information for laboratories
  • Non-Target Volatile Organic Chemicals (PDF) - September 10, 2003 draft
  • Non-Target Semi-Volatile Organic Chemicals (PDF) - September 10, 2003 draft.
  • Characterizing Severely Impaired Water Sources through Elemental Analysis (PDF) - January 26, 2004.

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Email Address

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Contact Us

State Water Resources Control Board
Division of Drinking Water
Regulatory Development Unit

Mailing Address:
P.O. Box 100
Sacramento, CA 95812-0100

Street Address:
1001 I Street
Sacramento, CA 95814

E-mail us at DDWRegUnit@waterboards.ca.gov.