Bromate
City of Napa
Bromate is a carcinogenic disinfection byproduct formed when source waters containing bromide are treated with ozonation or sodium hypochlorite. Studies of laboratory animals show that bromate damages DNA and causes cancer in multiple organs. Click here to read more about disinfection byproducts.
Samples
Samples exceeding legal limit (MCL)
Samples exceeding
health guidelines
Testing results - average by year
| Year | Average result | Samples taken | Detections | Range of results |
|---|---|---|---|---|
| 2013 | N/A | 0 | 0 | N/A |
| 2014 | 0.167 ppb | 6 | 1 | ND - 1.000 ppb |
| 2015 | 2.30 ppb | 6 | 3 | ND - 5.50 ppb |
| 2016 | 3.63 ppb | 6 | 5 | ND - 11.0 ppb |
| 2017 | 0.440 ppb | 5 | 1 | ND - 2.20 ppb |
| 2018 | 0.940 ppb | 5 | 3 | ND - 2.10 ppb |
| 2019 | ND | 3 | 0 | ND |
ppb = parts per billion
State and national drinking water standards and health guidelines
EWG Health Guideline 0.1 ppb
The EWG Health Guideline of 0.1 ppb for bromate was defined by the California Office of Environmental Health Hazard Assessment as a public health goal, the level of a drinking water contaminant that does not pose a significant health risk. This health guideline protects against cancer.
EPA Maximum Contaminant
Level (MCL) 10 ppb
The legal limit for bromate, established in 1998, was based on analytical detection limits at the time that the standard was set. This limit may not fully protect against the risk of cancer due to bromate exposure.
ppb = parts per billion
All test results
| Date | Lab ID | Result |
|---|---|---|
| 2014-04-02 | 9590-007-1000 | ND |
| 2014-06-04 | 9590-007-1115 | 1.000 ppb |
| 2014-07-09 | 9590-005-1145 | ND |
| 2014-07-09 | 9590-006-1245 | ND |
| 2014-07-09 | 9590-007-0925 | ND |
| 2014-10-01 | 9590-007-1010 | ND |
| 2015-01-08 | 9590-007-1000 | ND |
| 2015-04-01 | 9590-007-0950 | 5.50 ppb |
| 2015-07-21 | 9590-007-0940 | 3.80 ppb |
| 2015-07-21 | 9590-005-1120 | ND |
| 2015-07-21 | 9590-006-1415 | ND |
| 2015-10-07 | 9590-007-1110 | 4.50 ppb |
| 2016-01-08 | 9590-007-1210 | 11.0 ppb |
| 2016-05-04 | 9590-007-1025 | 4.40 ppb |
| 2016-07-27 | 9590-006-1545 | ND |
| 2016-07-27 | 9590-007-1245 | 1.80 ppb |
| 2016-07-27 | 9590-006-1245 | 1.90 ppb |
| 2016-10-05 | 9590-007-0900 | 2.70 ppb |
| 2017-01-11 | 9590-007-1040 | 2.20 ppb |
| 2017-02-01 | 9590-007-1050 | ND |
| 2017-07-20 | 9590-007-1050 | ND |
| 2017-07-20 | 9590-006-1330 | ND |
| 2017-09-13 | 9590-005-0840 | ND |
| 2018-06-06 | 9590-007-1040 | ND |
| 2018-07-11 | 9590-007-1200 | 1.10 ppb |
| 2018-07-11 | 9590-006-1015 | ND |
| 2018-10-03 | 9590-007-0945 | 2.10 ppb |
| 2018-12-05 | 9590-007-1030 | 1.50 ppb |
| 2019-07-10 | 1644-007-0830 | ND |
| 2019-07-10 | 1644-007-1200 | ND |
| 2019-10-02 | 1644-007-0840 | ND |