Chemicals and Contaminants in Drinking Water

Last Update: December 1, 2008

Regulated Contaminants

• Drinking water standards [maximum contaminant levels (MCLs)] are in Title 22 of the California Code of Regulations.  Primary MCLs address health concerns (see public health goals, PHGs). The standards for lead and copper are called "action levels" instead of MCLs.  Secondary MCLs (PDF)address esthetics, such as taste and odor. 
• Standards also include detection limits for purposes of reporting (DLRs), included in the chemical list (Excel)that is associated with the submittal of analytical results by electronic data transfer (EDT).
• Here is the process for establishing MCLs in California. 
• Here is a comparison of federal and California MCLs (PDF).
• Also, see chemical-specific information on arsenic (California's MCL became effective November 28, 2008), as well as manganese (which has a secondary MCL), MTBE, nitrate and nitrite, and perchlorate.

Public Notification and Information about Contaminants

• Water systems: Use these templates -- and contact your CDPH district office (PDF)-- 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 US EPA's website.

Other Regulated Chemicals

• Fluoridation by public water systems

Unregulated Contaminants

• Notification Levels:  CDPH uses these health-based advisory levels for certain chemicals without MCLs. Exceeding them prompts certain requirements and recommendations.

• Also, see chemical-specific information on chromium-6  (currently regulated under the total chromium MCL, but a chromium-6 MCL will be developed), NDMA and other nitrosamines and 1,2,3-trichloropropane.

• Unregulated chemicals for which monitoring is required - these regulations were repealed October 18, 2007.

• Emerging contaminants - FAQ for CDPH's draft recharge reuse water, along with pertinent links.

Treatment Technology

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

Sampling and Analysis Issues

• EDT - data submittal by laboratories
• Additional information for laboratories
• Use of extremely impaired sources - CDPH follows Procedure Memorandum 97-005 (PDF)for evaluating of the use of extremely impaired sources for drinking water. 
• For extremely impaired sources and recycled water are analysis and reporting of non-target compounds—including tentatively identified compounds (TICs)—are these documents:  
• Non-Target Volatile Organic Chemicals (PDF)- September 10, 2003 draft.
• Non-Target Semi-Volatile Organic Chemicals (PDF)- September 10, 2003 draft.
• Charaterizing Severely Impaired Water Sources through Elemental Analysis (PDF)- January 26, 2004.