Arsenic
Cws-split Mountain Water System
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 |
|---|---|---|---|---|
| 2018 | 4.02 ppb | 26 | 19 | ND - 8.52 ppb |
| 2019 | 4.13 ppb | 27 | 24 | ND - 10.6 ppb |
| 2020 | 2.95 ppb | 27 | 14 | ND - 8.10 ppb |
| 2021 | 3.94 ppb | 29 | 19 | ND - 8.30 ppb |
| 2022 | 3.55 ppb | 26 | 18 | ND - 8.10 ppb |
| 2023 | 3.36 ppb | 27 | 17 | ND - 7.40 ppb |
ppb = parts per billion
State, National, and Health Guidelines for Drinking Water
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 | Lab ID | Result |
|---|---|---|
| 2018-01-09 | CA1500407_005_005-201801091140 | ND |
| 2018-01-09 | CA1500407_006_006-201801091200 | 5.24 ppb |
| 2018-01-23 | CA1500407_005_005-201801231010 | ND |
| 2018-01-23 | CA1500407_006_006-201801230950 | 5.20 ppb |
| 2018-02-07 | CA1500407_006_006-201802071430 | 5.40 ppb |
| 2018-02-07 | CA1500407_005_005-201802071345 | ND |
| 2018-03-14 | CA1500407_005_005-201803141110 | ND |
| 2018-03-14 | CA1500407_006_006-201803141130 | 6.93 ppb |
| 2018-04-04 | CA1500407_006_006-201804041030 | 6.88 ppb |
| 2018-04-04 | CA1500407_005_005-201804040945 | 2.00 ppb |
| 2018-05-02 | CA1500407_006_006-201805020935 | 6.91 ppb |
| 2018-05-02 | CA1500407_005_005-201805020835 | ND |
| 2018-06-12 | CA1500407_006_006-201806120955 | 6.94 ppb |
| 2018-06-12 | CA1500407_005_005-201806120935 | ND |
| 2018-07-17 | CA1500407_006_006-201807171220 | 6.22 ppb |
| 2018-07-17 | CA1500407_005_005-201807171214 | 2.37 ppb |
| 2018-08-14 | CA1500407_006_006-201808141015 | 7.96 ppb |
| 2018-08-14 | CA1500407_005_005-201808141000 | 3.08 ppb |
| 2018-09-18 | CA1500407_006_006-201809181335 | 6.87 ppb |
| 2018-09-18 | CA1500407_005_005-201809181340 | ND |
| 2018-10-03 | CA1500407_005_005-201810031400 | 2.69 ppb |
| 2018-10-03 | CA1500407_006_006-201810031355 | 6.50 ppb |
| 2018-11-13 | CA1500407_005_005-201811131015 | 3.70 ppb |
| 2018-11-13 | CA1500407_006_006-201811131055 | 8.52 ppb |
| 2018-12-10 | CA1500407_006_006-201812101000 | 6.96 ppb |
| 2018-12-10 | CA1500407_005_005-201812100955 | 4.01 ppb |
| 2019-01-15 | CA1500407_005_005-201901151150 | 2.90 ppb |
| 2019-01-15 | CA1500407_005_005-201901151150 | 3.95 ppb |
| 2019-01-15 | CA1500407_006_006-201901151132 | 4.80 ppb |
| 2019-01-15 | CA1500407_006_006-201901151132 | 6.16 ppb |
| 2019-02-06 | CA1500407_005_005-201902061245 | 3.92 ppb |
| 2019-02-06 | CA1500407_006_006-201902061240 | 3.29 ppb |
| 2019-03-12 | CA1500407_006_006-201903121127 | 5.83 ppb |
| 2019-03-12 | CA1500407_005_005-201903121135 | 3.47 ppb |
| 2019-04-10 | CA1500407_005_005-201904100850 | ND |
| 2019-04-10 | CA1500407_006_006-201904101050 | 5.58 ppb |
| 2019-05-08 | CA1500407_005_005-201905081111 | ND |
| 2019-05-08 | CA1500407_006_006-201905081138 | 4.91 ppb |
| 2019-05-13 | CA1500407_002_002-201905130958 | 2.70 ppb |
| 2019-06-05 | CA1500407_006_006-201906051106 | 5.52 ppb |
| 2019-06-05 | CA1500407_005_005-201906051120 | 2.13 ppb |
| 2019-07-22 | CA1500407_005_005-201907220910 | ND |
| 2019-07-22 | CA1500407_006_006-201907220920 | 10.6 ppb |
| 2019-08-19 | CA1500407_005_005-201908190954 | 2.33 ppb |
| 2019-08-19 | CA1500407_006_006-201908191000 | 7.30 ppb |
| 2019-09-04 | CA1500407_005_005-201909041330 | 2.65 ppb |
| 2019-09-04 | CA1500407_006_006-201909041340 | 5.30 ppb |
| 2019-10-09 | CA1500407_006_006-201910090932 | 6.13 ppb |
| 2019-10-09 | CA1500407_005_005-201910090940 | 2.59 ppb |
| 2019-11-13 | CA1500407_005_005-201911131256 | 3.35 ppb |
| 2019-11-13 | CA1500407_006_006-201911131302 | 6.36 ppb |
| 2019-12-04 | CA1500407_005_005-201912041015 | 3.49 ppb |
| 2019-12-04 | CA1500407_006_006-201912041040 | 6.20 ppb |
| 2020-01-22 | CA1500407_005_005-202001221450 | ND |
| 2020-01-22 | CA1500407_006_006-202001221438 | 5.09 ppb |
| 2020-01-22 | CA1500407_006_006-202001221438 | 5.00 ppb |
| 2020-01-22 | CA1500407_005_005-202001221450 | ND |
| 2020-02-11 | CA1500407_007_007-202002111247 | 2.90 ppb |
| 2020-02-24 | CA1500407_005_005-202002241140 | ND |
| 2020-02-24 | CA1500407_006_006-202002241130 | 3.55 ppb |
| 2020-03-17 | CA1500407_006_006-202003171030 | 3.86 ppb |
| 2020-03-17 | CA1500407_005_005-202003171035 | ND |
| 2020-04-01 | CA1500407_005_005-202004011011 | ND |
| 2020-04-01 | CA1500407_006_006-202004011006 | 4.27 ppb |
| 2020-05-06 | CA1500407_005_005-202005061335 | ND |
| 2020-05-06 | CA1500407_006_006-202005061329 | 4.44 ppb |
| 2020-06-09 | CA1500407_006_006-202006090834 | 6.93 ppb |
| 2020-06-09 | CA1500407_005_005-202006090820 | ND |
| 2020-07-06 | CA1500407_005_005-202007061039 | ND |
| 2020-07-06 | CA1500407_006_006-202007060945 | 7.40 ppb |
| 2020-08-05 | CA1500407_005_005-202008051050 | ND |
| 2020-08-05 | CA1500407_006_006-202008051023 | 6.80 ppb |
| 2020-09-15 | CA1500407_005_005-202009150927 | ND |
| 2020-09-15 | CA1500407_006_006-202009151016 | 5.60 ppb |
| 2020-10-21 | CA1500407_005_005-202010211339 | ND |
| 2020-10-21 | CA1500407_006_006-202010211345 | 8.10 ppb |
| 2020-11-19 | CA1500407_006_006-202011191213 | 8.00 ppb |
| 2020-11-19 | CA1500407_005_005-202011191234 | ND |
| 2020-12-16 | CA1500407_005_005-202012160929 | ND |
| 2020-12-17 | CA1500407_006_006-202012171240 | 7.80 ppb |
| 2021-01-12 | CA1500407_005_005-202101121032 | ND |
| 2021-01-12 | CA1500407_006_006-202101121041 | 7.50 ppb |
| 2021-01-26 | CA1500407_005_005-202101261344 | ND |
| 2021-01-26 | CA1500407_006_006-202101261336 | 6.30 ppb |
| 2021-01-26 | CA1500407_006_006-202101261336 | 6.30 ppb |
| 2021-02-04 | CA1500407_005_005-202102041320 | 2.40 ppb |
| 2021-02-04 | CA1500407_006_006-202102041311 | 6.00 ppb |
| 2021-03-09 | CA1500407_005_005-202103090910 | ND |
| 2021-03-09 | CA1500407_006_006-202103090910 | 6.50 ppb |
| 2021-04-06 | CA1500407_005_005-202104060946 | ND |
| 2021-04-06 | CA1500407_006_006-202104060910 | 5.10 ppb |
| 2021-05-06 | CA1500407_005_005-202105061247 | ND |
| 2021-05-06 | CA1500407_006_006-202105061250 | 4.70 ppb |
| 2021-05-25 | CA1500407_005_005-202105251320 | ND |
| 2021-05-25 | CA1500407_006_006-202105251315 | 5.00 ppb |
| 2021-06-24 | CA1500407_006_006-202106241338 | 7.10 ppb |
| 2021-06-24 | CA1500407_005_005-202106241332 | 4.20 ppb |
| 2021-07-27 | CA1500407_006_006-202107270930 | 6.60 ppb |
| 2021-07-27 | CA1500407_005_005-202107270925 | ND |
| 2021-08-31 | CA1500407_005_005-202108310900 | 3.40 ppb |
| 2021-08-31 | CA1500407_006_006-202108310910 | 8.30 ppb |
| 2021-09-09 | CA1500407_005_005-202109090920 | 6.80 ppb |
| 2021-09-09 | CA1500407_006_006-202109090905 | 7.50 ppb |
| 2021-10-28 | CA1500407_005_005-202110281024 | ND |
| 2021-10-28 | CA1500407_006_006-202110281029 | 7.50 ppb |
| 2021-11-03 | CA1500407_005_005-202111030945 | ND |
| 2021-11-03 | CA1500407_006_006-202111030937 | 6.70 ppb |
| 2021-12-15 | CA1500407_005_005-202112151125 | ND |
| 2021-12-15 | CA1500407_006_006-202112151115 | 6.30 ppb |
| 2022-01-18 | CA1500407_005_005-202201181056 | ND |
| 2022-01-18 | CA1500407_005_005-202201181056 | ND |
| 2022-01-18 | CA1500407_006_006-202201181111 | 6.70 ppb |
| 2022-01-18 | CA1500407_006_006-202201181111 | 6.20 ppb |
| 2022-02-10 | CA1500407_005_005-202202101435 | ND |
| 2022-02-10 | CA1500407_006_006-202202101444 | 5.60 ppb |
| 2022-03-15 | CA1500407_005_005-202203151142 | ND |
| 2022-03-15 | CA1500407_006_006-202203151147 | 5.30 ppb |
| 2022-04-07 | CA1500407_005_005-202204071013 | ND |
| 2022-04-07 | CA1500407_006_006-202204071005 | 6.60 ppb |
| 2022-05-03 | CA1500407_005_005-202205031106 | ND |
| 2022-05-03 | CA1500407_006_006-202205031110 | 5.80 ppb |
| 2022-06-15 | CA1500407_006_006-202206151416 | 8.10 ppb |
| 2022-06-15 | CA1500407_005_005-202206151412 | 1.20 ppb |
| 2022-07-13 | CA1500407_006_006-202207130925 | 6.40 ppb |
| 2022-07-13 | CA1500407_005_005-202207130916 | 1.10 ppb |
| 2022-08-11 | CA1500407_005_005-202208110938 | ND |
| 2022-08-11 | CA1500407_006_006-202208110933 | 7.20 ppb |
| 2022-09-14 | CA1500407_006_006-202209141256 | 7.10 ppb |
| 2022-09-14 | CA1500407_005_005-202209141247 | ND |
| 2022-10-06 | CA1500407_006_006-202210060825 | 5.90 ppb |
| 2022-10-06 | CA1500407_005_005-202210060815 | 1.10 ppb |
| 2022-11-15 | CA1500407_006_006-202211151132 | 8.10 ppb |
| 2022-11-15 | CA1500407_005_005-202211151123 | 1.000 ppb |
| 2022-12-15 | CA1500407_006_006-202212151103 | 7.60 ppb |
| 2022-12-15 | CA1500407_005_005-202212151057 | 1.40 ppb |
| 2023-01-12 | CA1500407_006_006-202301121110 | 7.40 ppb |
| 2023-01-12 | CA1500407_005_005-202301121113 | 1.90 ppb |
| 2023-01-26 | CA1500407_005_005-202301260926 | ND |
| 2023-01-26 | CA1500407_006_006-202301260934 | 7.00 ppb |
| 2023-02-07 | CA1500407_005_005-202302071417 | 1.40 ppb |
| 2023-02-07 | CA1500407_006_006-202302071432 | 6.00 ppb |
| 2023-02-23 | CA1500407_007_007-202302231300 | 2.70 ppb |
| 2023-03-13 | CA1500407_005_005-202303131005 | 1.30 ppb |
| 2023-03-13 | CA1500407_006_006-202303130955 | 5.70 ppb |
| 2023-04-12 | CA1500407_006_006-202304121344 | 5.80 ppb |
| 2023-04-12 | CA1500407_005_005-202304121340 | ND |
| 2023-05-18 | CA1500407_006_006-202305180914 | 6.00 ppb |
| 2023-05-18 | CA1500407_005_005-202305180908 | ND |
| 2023-06-08 | CA1500407_006_006-202306081135 | 6.50 ppb |
| 2023-06-08 | CA1500407_005_005-202306081113 | ND |
| 2023-07-12 | CA1500407_006_006-202307120920 | 6.10 ppb |
| 2023-07-12 | CA1500407_005_005-202307120930 | ND |
| 2023-08-15 | CA1500407_005_005-202308151425 | ND |
| 2023-08-15 | CA1500407_006_006-202308151420 | 5.40 ppb |
| 2023-09-06 | CA1500407_005_005-202309060905 | ND |
| 2023-09-06 | CA1500407_006_006-202309060855 | 6.50 ppb |
| 2023-10-10 | CA1500407_005_005-202310101147 | ND |
| 2023-10-10 | CA1500407_006_006-202310101143 | 7.40 ppb |
| 2023-11-15 | CA1500407_005_005-202311150924 | ND |
| 2023-11-15 | CA1500407_006_006-202311150915 | 6.80 ppb |
| 2023-12-14 | CA1500407_005_005-202312140831 | ND |
| 2023-12-14 | CA1500407_006_006-202312140820 | 6.70 ppb |