Chemicals and Contaminants in Drinking Water

Last Update: July 1, 2009

Regulated Contaminants

• Primary maximum contaminant levels (MCLs) address health concerns.  MCLs are found in Title 22 of the California Code of Regulations.  (Go to Drinking Water Regulations and Statutes.
• Learn about MCLs and public health goals (PHGs).
• 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)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, chromium-6 (currently regulated under the total chromium MCL), 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  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• Unregulated chemicals for which monitoring is required - these regulations were repealed October 18, 2007.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.
• Characterizing Severely Impaired Water Sources through Elemental Analysis (PDF) - January 26, 2004.

Links