What Arsenic is, and why it's regulated
What the EPA limit means
10 µg/L
Maximum Contaminant Level — the enforceable ceiling a supplier must stay under.
0.0 µg/L
Health goal (MCLG) — the level with no known health effect. It is a goal, not a legal limit, and is often zero for carcinogens.
SYR4
Where these measurements come from. Hover the tag for the EPA programme and years.
Where Arsenic was found
The water suppliers reporting the highest levels, worst first. For lead and copper that is the 90th-percentile result the action level is written against; for Six-Year Review data, the 95th percentile of each system's samples.
| Supplier | City | State | Level vs EPA limit |
|---|---|---|---|
| Ridgewood Estates | Bigfork - Lake Co | MT | 580 µg/L 5800% of the EPA limit, at the 95th percentile of samples — 10 µg/L |
| Hidden Lake Colony | Cut Bank | MT | 393.4 µg/L 3934% of the EPA limit, at the 95th percentile of samples — 10 µg/L |
| Carlsbad Desalination Plant | Carlsbad | CA | 332.624 µg/L 3326% of the EPA limit, at the 95th percentile of samples — 10 µg/L |
| Foxglove Apartments | Harvard | NH | 241.8 µg/L 2418% of the EPA limit, at the 95th percentile of samples — 10 µg/L |
| Dexter Oaks Co-Op | Dexter | OR | 236.515 µg/L 2365% of the EPA limit, at the 95th percentile of samples — 10 µg/L |
| Whispering Pines Inn | Hollister | CA | 181.3 µg/L 1813% of the EPA limit, at the 95th percentile of samples — 10 µg/L |
| Topaz Lake Water Co Inc | Topaz | NV | 168 µg/L 1680% of the EPA limit, at the 95th percentile of samples — 10 µg/L |
| Grizzly Ranch Csd | Portola | CA | 165.1 µg/L 1651% of the EPA limit, at the 95th percentile of samples — 10 µg/L |
| Paxton Water Corporation | Paxton | IN | 133 µg/L 1330% of the EPA limit, at the 95th percentile of samples — 10 µg/L |
| Colonial Meadows Water Company | Bloomington | IL | 123.2 µg/L 1232% of the EPA limit, at the 95th percentile of samples — 10 µg/L |
| Sierra East Hoa | Coleville | CA | 122.2 µg/L 1222% of the EPA limit, at the 95th percentile of samples — 10 µg/L |
| Csa 70 w-4 Pioneertown | San Bernardino | CA | 120 µg/L 1200% of the EPA limit, at the 95th percentile of samples — 10 µg/L |
| Calistoga Farm Worker Center | Napa | CA | 120 µg/L 1200% of the EPA limit, at the 95th percentile of samples — 10 µg/L |
| Rim Rock Water Company | Grover Beach | CA | 110.5 µg/L 1105% of the EPA limit, at the 95th percentile of samples — 10 µg/L |
| 15th Avenue | — | CA | 107 µg/L 1070% of the EPA limit, at the 95th percentile of samples — 10 µg/L |
| Charles Brown Water Company | Shoshone | CA | 104.85 µg/L 1049% of the EPA limit, at the 95th percentile of samples — 10 µg/L |
| Keeler Community Service District | Bakerfield | CA | 104 µg/L 1040% of the EPA limit, at the 95th percentile of samples — 10 µg/L |
| Bruni Rural Wsc | Bruni | TX | 100.2 µg/L 1002% of the EPA limit, at the 95th percentile of samples — 10 µg/L |
| Igiugig Water System | Igiugig | AK | 97.46 µg/L 975% of the EPA limit, at the 95th percentile of samples — 10 µg/L |
| Oasis Mobile Home Park | Thermal | CA | 94.15 µg/L 942% of the EPA limit, at the 95th percentile of samples — 10 µg/L |
| Qvwd-West & East Combined Water System | Tehachapi | CA | 94.1 µg/L 941% of the EPA limit, at the 95th percentile of samples — 10 µg/L |
| Loma Linda Water Corp | Fruitland | ID | 93.5 µg/L 935% of the EPA limit, at the 95th percentile of samples — 10 µg/L |
| Hungry Gulch Mwc | Lake Isabella | CA | 90.15 µg/L 902% of the EPA limit, at the 95th percentile of samples — 10 µg/L |
| U.S.N., San Nicolas Island | Point Mugu | CA | 86 µg/L 860% of the EPA limit, at the 95th percentile of samples — 10 µg/L |
| Sunset Colony | Britton | SD | 85.9 µg/L 859% of the EPA limit, at the 95th percentile of samples — 10 µg/L |
Frequently asked questions about Arsenic
What is Arsenic in drinking water?
Arsenic occurs naturally in rock and groundwater; long-term exposure is linked to skin, bladder and lung cancer.
What is the EPA limit for Arsenic?
The EPA's Maximum Contaminant Level for Arsenic is 10 µg/L, and its health goal (MCLG) is 0.0 µg/L. A result above the limit means the supplier must act; the goal is the level at which no health effects are expected.
How common is Arsenic in US tap water?
Of the 33,988 water suppliers with results on file, 15,303 detected Arsenic — 45% of those tested.