Arsenic
Willow Creek Water Co.
Arsenic is a potent carcinogen and common contaminant in drinking water. Arsenic causes thousands of cases of cancer each year in the U.S. Click here to read more about arsenic.
Samples
Samples exceeding legal limit (MCL)
Samples exceeding
health guidelines
Testing results - average by year
| Year | Average result | Samples taken | Detections | Range of results |
|---|---|---|---|---|
| 2014 | 13.0 ppb | 6 | 4 | ND - 25.1 ppb |
| 2015 | 10.3 ppb | 9 | 6 | ND - 19.0 ppb |
| 2016 | 9.36 ppb | 16 | 14 | ND - 22.2 ppb |
| 2017 | 8.24 ppb | 16 | 16 | 1.10 ppb - 17.2 ppb |
| 2018 | 6.30 ppb | 18 | 11 | ND - 18.2 ppb |
| 2019 | 4.39 ppb | 14 | 11 | ND - 16.9 ppb |
ppb = parts per billion
State and national drinking water standards and health guidelines
EWG Health Guideline 0.004 ppb
The EWG Health Guideline of 0.004 ppb for arsenic 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 arsenic, established in 2001, was based on costs for arsenic removal, as calculated at the time that the standard was set. This limit does not fully protect against the risk of cancer due to arsenic exposure.
ppb = parts per billion
All test results
| Date | Result |
|---|---|
| 2014-04-09 | 18.8 ppb |
| 2014-04-09 | ND |
| 2014-08-29 | 25.1 ppb |
| 2014-09-05 | ND |
| 2014-11-21 | 16.2 ppb |
| 2014-12-15 | 17.9 ppb |
| 2015-05-27 | 14.0 ppb |
| 2015-06-23 | ND |
| 2015-06-23 | 19.0 ppb |
| 2015-07-29 | 16.8 ppb |
| 2015-07-29 | ND |
| 2015-08-28 | 16.9 ppb |
| 2015-10-26 | 7.90 ppb |
| 2015-10-26 | 18.5 ppb |
| 2015-11-30 | ND |
| 2016-01-05 | ND |
| 2016-01-27 | 5.40 ppb |
| 2016-03-24 | 7.00 ppb |
| 2016-03-24 | 13.3 ppb |
| 2016-05-03 | ND |
| 2016-06-09 | 9.50 ppb |
| 2016-06-21 | 22.1 ppb |
| 2016-07-29 | 15.7 ppb |
| 2016-07-29 | 21.2 ppb |
| 2016-08-22 | 22.2 ppb |
| 2016-09-19 | 9.10 ppb |
| 2016-10-17 | 12.3 ppb |
| 2016-10-17 | 5.40 ppb |
| 2016-11-08 | 2.00 ppb |
| 2016-12-28 | 2.30 ppb |
| 2016-12-28 | 2.30 ppb |
| 2017-01-18 | 17.2 ppb |
| 2017-01-18 | 5.90 ppb |
| 2017-02-14 | 5.20 ppb |
| 2017-03-22 | 1.10 ppb |
| 2017-03-22 | 1.10 ppb |
| 2017-04-24 | 6.30 ppb |
| 2017-04-24 | 13.3 ppb |
| 2017-05-02 | 6.70 ppb |
| 2017-07-05 | 6.70 ppb |
| 2017-07-05 | 16.5 ppb |
| 2017-08-09 | 11.9 ppb |
| 2017-09-07 | 10.6 ppb |
| 2017-10-16 | 16.7 ppb |
| 2017-10-16 | 9.50 ppb |
| 2017-11-28 | 1.40 ppb |
| 2017-12-07 | 1.80 ppb |
| 2018-01-15 | ND |
| 2018-02-05 | 12.3 ppb |
| 2018-02-05 | ND |
| 2018-03-05 | ND |
| 2018-04-04 | ND |
| 2018-05-15 | ND |
| 2018-05-15 | 11.6 ppb |
| 2018-06-07 | ND |
| 2018-07-02 | 10.7 ppb |
| 2018-07-12 | 18.2 ppb |
| 2018-08-20 | ND |
| 2018-08-20 | 6.00 ppb |
| 2018-08-20 | 17.6 ppb |
| 2018-09-11 | 9.50 ppb |
| 2018-10-03 | 11.4 ppb |
| 2018-10-03 | 10.9 ppb |
| 2018-11-05 | 4.20 ppb |
| 2018-12-14 | 1.000 ppb |
| 2019-01-02 | ND |
| 2019-01-02 | 1.50 ppb |
| 2019-02-04 | 0.900 ppb |
| 2019-03-25 | 1.30 ppb |
| 2019-04-04 | 0.800 ppb |
| 2019-04-04 | 13.1 ppb |
| 2019-06-14 | ND |
| 2019-07-08 | 10.2 ppb |
| 2019-07-08 | 16.9 ppb |
| 2019-08-09 | 9.60 ppb |
| 2019-09-18 | 2.30 ppb |
| 2019-10-16 | 4.00 ppb |
| 2019-12-17 | 0.800 ppb |
| 2019-12-17 | ND |