NDMA in Washington Drinking Water
Ranked by max NDMA detected (ng/L) · UCMR 2 data (2008–2010) · Data from EPA SDWIS & UCMR
NDMA in Washington: what the data shows
Washington has 7 cities with NDMA data from the EPA's UCMR 2 program (2008–2010). NDMA was detected above California's 10 ng/L public health goal in 0 of those cities. The state average max detected level is 4.2 ng/L. N-nitrosodimethylamine (NDMA) is a probable human carcinogen that forms primarily as a disinfection byproduct when chloramines react with organic precursors in source water. Systems using chloramines for residual disinfection are most affected. NDMA can also enter water from industrial discharge — historically from rocket fuel manufacturing and rubber processing. There is no federal maximum contaminant level for NDMA. California's Public Health Goal of 10 ng/L (0.01 µg/L) is the most-protective US benchmark. EPA classifies NDMA as a B2 probable human carcinogen — in animal studies, lifetime exposure at very low concentrations significantly elevates liver cancer risk. UV treatment, granular activated carbon, and reverse osmosis can reduce NDMA, though not all home filters are effective.
Cities exceeding CA PHG: 10 ng/L (no federal MCL)
NDMA data across Washington
Each dot is a city with UCMR 2 NDMA testing data. Cities exceeding California's 10 ng/L public health goal are highlighted. Size reflects population served.
Top 10 cities by ndma level in Washington
Highest NDMA levels (ng/L)
All Washington cities ranked by ndma level
| # | City | Level | Level | Over PHG? | Violations | Grade |
|---|---|---|---|---|---|---|
| 1 | Lacey | 8.2 ng/L | No | 125 | F | |
| 2 | Edgewood | 8.0 ng/L | No | 4 | A- | |
| 3 | Friday Harbor | 4.7 ng/L | No | 153 | F | |
| 4 | Federal Way | 2.3 ng/L | No | 2 | B | |
| 5 | Spokane | 2.2 ng/L | No | 56 | F | |
| 6 | Cashmere | 2.0 ng/L | No | 21 | F | |
| 7 | Bridgeport | 2.0 ng/L | No | 47 | C |
Frequently asked questions about ndma in Washington
What is NDMA and why is it in Washington tap water?
NDMA (N-nitrosodimethylamine) is a probable human carcinogen that forms when chloramine disinfectants react with naturally occurring organic matter in source water. No cities in Washington exceeded California's 10 ng/L public health goal in UCMR 2 testing. Note that this data is from 2008–2010; many systems have since adjusted disinfection practices to reduce NDMA.
Is NDMA in drinking water dangerous?
NDMA is classified by the EPA as a B2 probable human carcinogen. Animal studies show liver tumors at very low chronic doses. There is no federal MCL, but California's Public Health Goal — set at the level associated with one additional cancer case per million over a lifetime of exposure — is 10 ng/L. NDMA was a major focus of the contaminated Camp Lejeune water investigation.
How can I remove NDMA from my drinking water?
NDMA is one of the harder contaminants to remove. Reverse osmosis provides 50–80% reduction depending on the membrane. Granular activated carbon (GAC) works for some NDMA but is variable. UV treatment effectively destroys NDMA but is rarely deployed at the household level. Boiling does NOT remove NDMA. Best protection: choose a water utility that has switched away from chloramination or implements UV/AOP treatment.