Nitrosamines

• OEHHA releases draft revised NDMA public health goal; comment period closes 20 January 2025 (December 2024)
• ELAP accreditation for EEA-Agilent Method 521.1 for determination of nitrosamines in drinking water now available (September 2024)
• OEHHA initiates process to update NDMA public health goal (March 2020)

N-nitrosamine chemicals ("nitrosamines") are or were formerly produced by numerous industrial sources such as the manufacturing of rocket fuel, rubber products, and other industrial process. Some nitrosamines have been identified by the National Toxicity Program as reasonably anticipated to be human carcinogens. Nitrosamines are among the chemicals known to the state to cause cancer [Title 27, California Code of Regulations, Section 27001], pursuant to California's Safe Drinking Water and Toxic Enforcement Act of 1986 ("Proposition 65"). Furthermore, the U.S. EPA's IRIS Assessments classifies a number of nitrosamines as probable human carcinogens, including N-Nitrosodimethylamine (NDMA). NDMA is a chemical formed in industrial and natural processes and can be found in various foods and alcoholic beverages, as well as in cigarette smoke. It can also form in drinking water as a result of chloramine disinfection, and in chlorinated wastewater used for aquifer recharge. Historically, NDMA has been used in research, in the production of 1,1-dimethylhydrazine for liquid rocket fuel, and in a variety of other industrial uses. Another nitrosamine, N-nitrosomorpholine (NMOR) has been detected in environmental and potable reuse water. Unlike several other nitrosamines, current research suggests that NMOR contamination in drinking water likely occurs from industrial sources, as opposed to being a by-product of certain disinfection processes. Nitrosamines research is ongoing.

NDMA has been detected in some California drinking water supplies. All drinking water occurrence from January 2011 through October 2023 is available on this spreadsheet.

1998

• NDMA was found in a drinking water well in northern California. NDMA was subsequently found elsewhere (including groundwater recharge projects), and was also found to be a by-product of certain drinking water treatment processes (e.g. chloramination, chlorination, ozonation) (see studies).
• NDMA notification level (then called an "action level") of 2 ng/L established

2002

• NDMA notification level revised to 10 ng/L because 2 ng/L was below the capabilities of available analytical methods at the time

2004

• N-nitrosodiethylamine (NDEA) notification level of 10 ng/L established

2005

• N-nitrosodi-n-propylamine (NDPA) notification level of 10 ng/L established
• U.S. EPA publishes Method 521 for the determination of nitrosamines in drinking water.

2006

• OEHHA established a Public Health Goal (PHG) of 3 ng/L for NDMA.

2008 through 2010

• Monitoring of nitrosamines by selected public water systems conducted under U.S. EPA’s Second Unregulated Contaminant Monitoring Rule (UCMR 2), which included NDEA, NDMA, NDBA, NDPA, NMEA, and NPYR.

2018

• U.S. EPA confirmed modifications to EPA Method 521 developed by Eurofins Eaton Analytical and Agilent Technologies, Inc., EEA 521.1, yielded performance equivalent to EPA Method 521. Method modifications allowed for use of newer, more sensitive instrumentation and accurate quantitation of NMOR, which was not a target analyte under EPA Method 521.

2020

• California Department of Public Health’s Drinking Water and Radiation Laboratory commences method validation study for Method EEA 521.1.
• OEHHA announced initiation of process to update the NDMA PHG and noted the following

  "NDMA is not currently produced or commercially used in the United States. Within the last five years, there have been numerous detections of NDMA in California public drinking water supply wells above the NL of 0.01 ppb. The update of the risk assessment for NDMA will consider the toxicology literature since the publication of the PHG in 2006 and will incorporate the application of updated risk assessment methodologies."

2021 through 2023

• Division of Drinking Water staff coordinated a multi-laboratory validation study method validation study of EEA 521.1 to evaluate precision, accuracy, and sensitivity to determine if the method would be fit-for-purpose for regulatory monitoring of drinking water.

Notification Levels and Response Levels have been established for three of the eight nitrosamines listed below and a public health goal has been developed for NDMA. The levels of 1-in-1 million (de minimis) theoretical excess lifetime cancer risk are also presented in the table for comparison.

1 - DDW recommends removing sources from service if they exceed the Response Level. These levels correspond to a one-in-10,000 cancer risk, or 10 times the Notification Level.

2 - Cancer risk levels for nitrosamines in drinking water can be derived from the lifetime cancer risk levels in 27 CCR §25705, which sets forth "no significant risk" levels of carcinogens for purposes of Proposition 65, in terms of daily exposures. These calculations assumed drinking water consumption of two liters per day.

3 – The 1-in-a- million cancer risk level for NDMA was established by OEHHA's public health goal (PHG).

• Environmental Laboratory Accreditation Program (ELAP)
• Division of Drinking Water Method Development and Validation
• U.S. EPA Unregulated Contaminant Monitoring Rule (UCMR) 2 Fact Sheet
• Office of Environmental Health Hazard Assessments (OEHHA) – Water