Arsenic
San Lorenzo Valley Water District
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.
252
Samples
4
Samples exceeding legal limit (MCL)
173
Samples exceeding
health guidelines
Testing results - average by year
| Year | Average result | Samples taken | Detections | Range of results |
|---|---|---|---|---|
| 2014 | 5.67 ppb | 50 | 39 | ND - 18.0 ppb |
| 2015 | 4.33 ppb | 56 | 41 | ND - 11.0 ppb |
| 2016 | 3.40 ppb | 32 | 19 | ND - 10.00 ppb |
| 2017 | 2.14 ppb | 24 | 19 | ND - 3.20 ppb |
| 2018 | 1.84 ppb | 34 | 24 | ND - 3.20 ppb |
| 2019 | 1.28 ppb | 56 | 31 | ND - 4.20 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 | Lab ID | Result |
|---|---|---|
| 2014-01-15 | 9590-023-1415 | 8.00 ppb |
| 2014-01-15 | 9590-024-1420 | ND |
| 2014-01-15 | 9590-034-1450 | 5.90 ppb |
| 2014-02-12 | 9590-023-1405 | 9.40 ppb |
| 2014-02-12 | 9590-024-1415 | ND |
| 2014-02-12 | 9590-034-1350 | 16.0 ppb |
| 2014-03-05 | 9590-023-1220 | 8.20 ppb |
| 2014-03-05 | 9590-024-1230 | ND |
| 2014-03-05 | 9590-034-1300 | 18.0 ppb |
| 2014-03-05 | 9590-035-1235 | 2.20 ppb |
| 2014-04-14 | 9590-023-1045 | 8.00 ppb |
| 2014-04-14 | 9590-024-1050 | ND |
| 2014-04-14 | 9590-034-1545 | 10.00 ppb |
| 2014-04-14 | 9590-035-1545 | 6.30 ppb |
| 2014-05-14 | 9590-023-1150 | 9.10 ppb |
| 2014-05-14 | 9590-024-1200 | ND |
| 2014-05-14 | 9590-034-1205 | 11.0 ppb |
| 2014-05-14 | 9590-035-1205 | 7.20 ppb |
| 2014-05-21 | 9590-034-1530 | 9.80 ppb |
| 2014-05-28 | 9590-034-1350 | 8.60 ppb |
| 2014-06-04 | 9590-034-1200 | 7.40 ppb |
| 2014-06-04 | 9590-035-1200 | 5.60 ppb |
| 2014-06-11 | 9590-023-0950 | 8.50 ppb |
| 2014-06-11 | 9590-024-0955 | ND |
| 2014-06-11 | 9590-034-1050 | 6.80 ppb |
| 2014-06-11 | 9590-035-1000 | 6.80 ppb |
| 2014-07-02 | 9590-034-1415 | 5.30 ppb |
| 2014-07-02 | 9590-035-1415 | 4.60 ppb |
| 2014-07-16 | 9590-023-1400 | 6.80 ppb |
| 2014-07-16 | 9590-024-1340 | 2.20 ppb |
| 2014-07-16 | 9590-034-1325 | 6.10 ppb |
| 2014-07-16 | 9590-035-1325 | 6.00 ppb |
| 2014-08-14 | 9590-023-0920 | 9.20 ppb |
| 2014-08-14 | 9590-034-0925 | 4.80 ppb |
| 2014-09-17 | 9590-023-0920 | 8.90 ppb |
| 2014-09-17 | 9590-024-0915 | ND |
| 2014-09-17 | 9590-034-0940 | 3.80 ppb |
| 2014-09-17 | 9590-035-0940 | 6.50 ppb |
| 2014-10-15 | 9590-023-1455 | 9.40 ppb |
| 2014-10-15 | 9590-024-1500 | ND |
| 2014-10-15 | 9590-034-1515 | ND |
| 2014-10-15 | 9590-035-1505 | 7.40 ppb |
| 2014-11-12 | 9590-023-0955 | 8.70 ppb |
| 2014-11-12 | 9590-024-1005 | ND |
| 2014-11-12 | 9590-034-1010 | 2.60 ppb |
| 2014-11-12 | 9590-035-1010 | 6.50 ppb |
| 2014-12-17 | 9590-023-1225 | 5.90 ppb |
| 2014-12-17 | 9590-024-1205 | ND |
| 2014-12-17 | 9590-034-1155 | 3.50 ppb |
| 2014-12-17 | 9590-035-1155 | 2.60 ppb |
| 2015-01-14 | 9590-023-1050 | 4.80 ppb |
| 2015-01-14 | 9590-024-0950 | ND |
| 2015-01-14 | 9590-034-0940 | 3.10 ppb |
| 2015-01-14 | 9590-035-0940 | 2.50 ppb |
| 2015-02-04 | 9590-034-1016 | 3.30 ppb |
| 2015-02-04 | 9590-035-1016 | 2.70 ppb |
| 2015-02-11 | 9590-023-1130 | 4.70 ppb |
| 2015-02-11 | 9590-024-1100 | ND |
| 2015-02-11 | 9590-034-1050 | 3.20 ppb |
| 2015-02-11 | 9590-035-1050 | 2.60 ppb |
| 2015-03-11 | 9590-023-1335 | 4.50 ppb |
| 2015-03-11 | 9590-024-1245 | ND |
| 2015-03-11 | 9590-034-1235 | 2.70 ppb |
| 2015-03-11 | 9590-035-1235 | 2.40 ppb |
| 2015-04-15 | 9590-023-1130 | 9.40 ppb |
| 2015-04-15 | 9590-024-1135 | ND |
| 2015-04-15 | 9590-035-1140 | 7.70 ppb |
| 2015-04-29 | 9590-023-1110 | 9.90 ppb |
| 2015-04-29 | 9590-035-1115 | 8.10 ppb |
| 2015-05-13 | 9590-023-1210 | 8.00 ppb |
| 2015-05-13 | 9590-024-1215 | ND |
| 2015-05-13 | 9590-035-1220 | 8.00 ppb |
| 2015-06-10 | 9590-023-1445 | 11.0 ppb |
| 2015-06-10 | 9590-024-1450 | ND |
| 2015-06-10 | 9590-035-1455 | 9.20 ppb |
| 2015-07-15 | 9590-023-1335 | 8.50 ppb |
| 2015-07-15 | 9590-024-1340 | ND |
| 2015-07-15 | 9590-034-1345 | 2.90 ppb |
| 2015-07-15 | 9590-035-1345 | 6.00 ppb |
| 2015-08-05 | 9590-023-1430 | 9.70 ppb |
| 2015-08-05 | 9590-024-1500 | ND |
| 2015-08-05 | 9590-034-1445 | 3.40 ppb |
| 2015-08-19 | 9590-010-1400 | ND |
| 2015-08-19 | 9590-022-1415 | ND |
| 2015-08-19 | 9590-025-1445 | ND |
| 2015-08-19 | 9590-026-1500 | 2.80 ppb |
| 2015-08-20 | 9590-023-0830 | 9.30 ppb |
| 2015-08-20 | 9590-024-0835 | ND |
| 2015-08-20 | 9590-034-0845 | 2.80 ppb |
| 2015-08-20 | 9590-035-0845 | 2.90 ppb |
| 2015-09-10 | 9590-023-0950 | 9.10 ppb |
| 2015-09-17 | 9590-023-0910 | 9.70 ppb |
| 2015-09-17 | 9590-024-0915 | 2.50 ppb |
| 2015-09-17 | 9590-034-0920 | 5.10 ppb |
| 2015-09-17 | 9590-035-0920 | 6.90 ppb |
| 2015-10-14 | 9590-023-1150 | 9.80 ppb |
| 2015-10-14 | 9590-024-1155 | ND |
| 2015-10-14 | 9590-034-1200 | 3.90 ppb |
| 2015-11-18 | 9590-023-1120 | 10.00 ppb |
| 2015-11-18 | 9590-024-1125 | ND |
| 2015-11-18 | 9590-034-1130 | 4.00 ppb |
| 2015-11-18 | 9590-035-1130 | 6.60 ppb |
| 2015-12-16 | 9590-023-1045 | 9.20 ppb |
| 2015-12-16 | 9590-024-1050 | ND |
| 2015-12-16 | 9590-034-1055 | 3.40 ppb |
| 2015-12-16 | 9590-035-1055 | 5.90 ppb |
| 2016-01-20 | 9590-023-1225 | 10.00 ppb |
| 2016-01-20 | 9590-024-1235 | ND |
| 2016-01-20 | 9590-034-1230 | 3.50 ppb |
| 2016-01-20 | 9590-035-1230 | 6.50 ppb |
| 2016-02-17 | 9590-024-1410 | ND |
| 2016-03-17 | 9590-023-0830 | 10.00 ppb |
| 2016-03-17 | 9590-024-0840 | ND |
| 2016-03-17 | 9590-034-0835 | 3.20 ppb |
| 2016-03-17 | 9590-035-0835 | 6.40 ppb |
| 2016-04-13 | 9590-023-1435 | 6.80 ppb |
| 2016-04-13 | 9590-024-1445 | ND |
| 2016-04-13 | 9590-034-1450 | 3.40 ppb |
| 2016-04-13 | 9590-035-1450 | 2.30 ppb |
| 2016-05-11 | 9590-023-1150 | 6.40 ppb |
| 2016-05-11 | 9590-024-1210 | ND |
| 2016-05-11 | 9590-034-1200 | ND |
| 2016-05-11 | 9590-035-1200 | ND |
| 2016-06-29 | 9590-023-1030 | 10.00 ppb |
| 2016-06-29 | 9590-024-1035 | ND |
| 2016-06-29 | 9590-035-1040 | 8.50 ppb |
| 2016-07-14 | 9590-023-0930 | 5.80 ppb |
| 2016-07-14 | 9590-024-1130 | ND |
| 2016-07-14 | 9590-034-0940 | 3.00 ppb |
| 2016-07-14 | 9590-035-0940 | 4.10 ppb |
| 2016-08-04 | 9590-023-0840 | 8.00 ppb |
| 2016-08-04 | 9590-024-0850 | ND |
| 2016-08-04 | 9590-034-0845 | 3.20 ppb |
| 2016-08-04 | 9590-035-0845 | 5.10 ppb |
| 2016-10-20 | 9590-034-0955 | 2.60 ppb |
| 2016-10-20 | 9590-035-0955 | ND |
| 2016-11-09 | 9590-034-1230 | ND |
| 2016-11-09 | 9590-035-1230 | ND |
| 2017-01-12 | 9590-034-1445 | 3.10 ppb |
| 2017-01-12 | 9590-035-1445 | 3.20 ppb |
| 2017-02-09 | 9590-034-0830 | 2.70 ppb |
| 2017-02-09 | 9590-035-0830 | 2.50 ppb |
| 2017-03-10 | 9590-034-0930 | ND |
| 2017-03-10 | 9590-035-0930 | ND |
| 2017-03-29 | 9590-034-1140 | ND |
| 2017-03-29 | 9590-035-1140 | ND |
| 2017-04-06 | 9590-034-0850 | 2.50 ppb |
| 2017-04-06 | 9590-035-0850 | 2.50 ppb |
| 2017-05-11 | 9590-034-0935 | 2.60 ppb |
| 2017-05-11 | 9590-035-0935 | 2.70 ppb |
| 2017-07-06 | 9590-034-0845 | 2.70 ppb |
| 2017-07-06 | 9590-035-0845 | 2.60 ppb |
| 2017-08-10 | 9590-034-1230 | 2.40 ppb |
| 2017-08-10 | 9590-035-1230 | 2.30 ppb |
| 2017-09-14 | 9590-034-1017 | 2.50 ppb |
| 2017-09-14 | 9590-035-1010 | ND |
| 2017-10-10 | 9590-034-1230 | 2.90 ppb |
| 2017-10-10 | 9590-035-1230 | 2.80 ppb |
| 2017-11-07 | 9590-034-1005 | 2.80 ppb |
| 2017-11-07 | 9590-035-1005 | 2.80 ppb |
| 2017-12-07 | 9590-034-1155 | 2.90 ppb |
| 2017-12-07 | 9590-035-1155 | 2.90 ppb |
| 2018-01-10 | 9590-034-1400 | 2.90 ppb |
| 2018-01-10 | 9590-035-1400 | 2.80 ppb |
| 2018-02-06 | 9590-034-0920 | 2.60 ppb |
| 2018-02-06 | 9590-035-0920 | 2.60 ppb |
| 2018-03-06 | 9590-034-1345 | 2.60 ppb |
| 2018-03-06 | 9590-035-1345 | 2.80 ppb |
| 2018-04-09 | 9590-034-1420 | 2.00 ppb |
| 2018-04-09 | 9590-035-1420 | ND |
| 2018-05-16 | 9590-034-0930 | 2.60 ppb |
| 2018-05-16 | 9590-035-0930 | 2.70 ppb |
| 2018-06-07 | 9590-034-0800 | 2.60 ppb |
| 2018-06-07 | 9590-035-0800 | 2.50 ppb |
| 2018-07-05 | 9590-025-1030 | ND |
| 2018-07-05 | 9590-026-1000 | 3.20 ppb |
| 2018-07-05 | 9590-034-0915 | 2.70 ppb |
| 2018-07-12 | 9590-034-1245 | 2.60 ppb |
| 2018-07-12 | 9590-035-1245 | 2.70 ppb |
| 2018-07-18 | 9590-010-1030 | ND |
| 2018-07-18 | 9590-022-1045 | ND |
| 2018-08-09 | 9590-034-0755 | 2.90 ppb |
| 2018-08-09 | 9590-035-0755 | 2.60 ppb |
| 2018-08-14 | 9590-024-0830 | 2.00 ppb |
| 2018-09-12 | 9590-024-1050 | ND |
| 2018-09-12 | 9590-034-1055 | 2.50 ppb |
| 2018-09-12 | 9590-035-1055 | 2.40 ppb |
| 2018-10-08 | 9590-024-0845 | ND |
| 2018-10-08 | 9590-034-0855 | 2.80 ppb |
| 2018-10-08 | 9590-035-0855 | 2.50 ppb |
| 2018-11-02 | 9590-024-0915 | ND |
| 2018-11-02 | 9590-034-0900 | 2.50 ppb |
| 2018-11-15 | 9590-035-0915 | 2.60 ppb |
| 2018-12-05 | 9590-024-1200 | ND |
| 2018-12-05 | 9590-034-1215 | ND |
| 2018-12-05 | 9590-035-1225 | ND |
| 2019-01-08 | 9590-024-1345 | ND |
| 2019-01-08 | 9590-035-1400 | ND |
| 2019-02-04 | 9590-024-1015 | 2.80 ppb |
| 2019-02-04 | 9590-035-1000 | ND |
| 2019-03-04 | 9590-024-0920 | ND |
| 2019-03-04 | 9590-035-0930 | ND |
| 2019-04-04 | 9590-024-1345 | ND |
| 2019-04-04 | 9590-034-1355 | 2.10 ppb |
| 2019-04-04 | 9590-035-1400 | ND |
| 2019-04-23 | 9590-024-0940 | ND |
| 2019-04-23 | 9590-034-1000 | ND |
| 2019-04-23 | 9590-035-1005 | ND |
| 2019-05-02 | 9590-024-1020 | ND |
| 2019-05-02 | 9590-034-1010 | 2.30 ppb |
| 2019-05-02 | 9590-035-1015 | 2.20 ppb |
| 2019-06-11 | 9590-024-0830 | ND |
| 2019-06-11 | 9590-034-0840 | 2.00 ppb |
| 2019-06-11 | 9590-035-0845 | ND |
| 2019-06-21 | 9590-024-0835 | ND |
| 2019-06-21 | 9590-034-0820 | 2.30 ppb |
| 2019-06-21 | 9590-035-0825 | 2.00 ppb |
| 2019-06-28 | 9590-024-0815 | ND |
| 2019-06-28 | 9590-034-0825 | 2.10 ppb |
| 2019-06-28 | 9590-035-0820 | 2.10 ppb |
| 2019-07-12 | 9590-024-0800 | ND |
| 2019-07-12 | 9590-034-0815 | 2.40 ppb |
| 2019-07-12 | 9590-035-0825 | 2.10 ppb |
| 2019-07-24 | 9590-024-1415 | ND |
| 2019-07-24 | 9590-034-1455 | 2.20 ppb |
| 2019-07-24 | 9590-035-1500 | 2.10 ppb |
| 2019-08-02 | 9590-024-0820 | ND |
| 2019-08-02 | 9590-034-0805 | 2.30 ppb |
| 2019-08-02 | 9590-035-0810 | 2.30 ppb |
| 2019-08-09 | 9590-024-0820 | ND |
| 2019-08-09 | 9590-034-0800 | 2.50 ppb |
| 2019-08-09 | 9590-035-0805 | 2.10 ppb |
| 2019-09-13 | 9590-024-0855 | ND |
| 2019-09-13 | 9590-034-0900 | 2.40 ppb |
| 2019-09-13 | 9590-035-0905 | 2.10 ppb |
| 2019-09-26 | 9590-024-0945 | ND |
| 2019-09-26 | 9590-034-1000 | 2.90 ppb |
| 2019-09-26 | 9590-035-0955 | 2.00 ppb |
| 2019-10-23 | 9590-024-0813 | ND |
| 2019-10-23 | 9590-034-0825 | 2.20 ppb |
| 2019-10-23 | 9590-035-0835 | 2.50 ppb |
| 2019-11-04 | 9590-024-1450 | ND |
| 2019-11-04 | 9590-034-1455 | 2.20 ppb |
| 2019-11-04 | 9590-035-1500 | 2.10 ppb |
| 2019-11-20 | 9590-024-1240 | ND |
| 2019-11-20 | 9590-034-1250 | 2.30 ppb |
| 2019-11-20 | 9590-035-1255 | 2.20 ppb |
| 2019-12-13 | 9590-034-1500 | 2.40 ppb |
| 2019-12-13 | 9590-035-1510 | 2.30 ppb |
| 2019-12-20 | 9590-024-1100 | ND |
| 2019-12-20 | 9590-034-1135 | 2.00 ppb |
| 2019-12-20 | 9590-035-1140 | 4.20 ppb |