What was found in Los Osos's water
The level at the city's main supplier, the highest level anywhere in the city, the EPA limit for each, and where every figure comes from.
| Contaminant | Level vs EPA limit | Suppliers | Source |
|---|---|---|---|
| Nitrate-Nitrite | 521250 µg/L 5213% of the EPA limit, at the 95th percentile of samples — 10000 µg/L Main supplier: LOS OSOS COMMUNITY SERVICES DISTRICT · 7,086 people · 2017 | 2/2 | SYR4 |
| Nitrate | 14300 µg/L 143% of the EPA limit, at the 95th percentile of samples — 10000 µg/L Main supplier: LOS OSOS COMMUNITY SERVICES DISTRICT · 7,086 people · 2019
Highest in the city: 18000 µg/L — S & T MUTUAL WATER COMPANY · 591 people · 2019 | 2/2 | SYR4 |
| Fluoride | 213.5 µg/L 5.3% of the EPA limit 4000 µg/L Main supplier: LOS OSOS COMMUNITY SERVICES DISTRICT · 7,086 people · 2019 | 1/2 | SYR4 |
| Barium | 185 µg/L 9.3% of the EPA limit 2000 µg/L Main supplier: LOS OSOS COMMUNITY SERVICES DISTRICT · 7,086 people · 2019 | 1/2 | SYR4 |
| Copper | 41 µg/L 3.2% of the EPA limit 1300 µg/L Main supplier: LOS OSOS COMMUNITY SERVICES DISTRICT · 7,086 people · 2019
Highest in the city: 58 µg/L — S & T MUTUAL WATER COMPANY · 591 people · 2019 | 2/2 | SYR4 |
| Chromium | 33.31 µg/L 33% of the EPA limit 100 µg/L Main supplier: LOS OSOS COMMUNITY SERVICES DISTRICT · 7,086 people · 2019 | 1/2 | SYR4 |
| Lithium | 16.1 µg/L No EPA limit set Main supplier: LOS OSOS COMMUNITY SERVICES DISTRICT · 7,086 people · 2024 | 1/2 | UCMR-5 |
| TTHM | 7.6 µg/L 9.5% of the EPA limit 80 µg/L Main supplier: LOS OSOS COMMUNITY SERVICES DISTRICT · 7,086 people · 2019 | 1/2 | SYR4 |
| Lead | 6.4 µg/L 43% of the EPA limit 15 µg/L Main supplier: LOS OSOS COMMUNITY SERVICES DISTRICT · 7,086 people · 2019 | 1/2 | SYR4 |
| Bromoform | 5.66 µg/L No EPA limit set Main supplier: LOS OSOS COMMUNITY SERVICES DISTRICT · 7,086 people · 2019 | 1/2 | SYR4 |
| Dibromochloromethane | 2.475 µg/L No EPA limit set Main supplier: LOS OSOS COMMUNITY SERVICES DISTRICT · 7,086 people · 2019 | 1/2 | SYR4 |
| Dibromoacetic Acid | 1.77 µg/L No EPA limit set Main supplier: LOS OSOS COMMUNITY SERVICES DISTRICT · 7,086 people · 2019 | 1/2 | SYR4 |
| Total Haloacetic Acids (HAA5) | 1.77 µg/L 3% of the EPA limit 60 µg/L Main supplier: LOS OSOS COMMUNITY SERVICES DISTRICT · 7,086 people · 2019 | 1/2 | SYR4 |
| PFBS | 0.0180 µg/L No EPA limit set Main supplier: LOS OSOS COMMUNITY SERVICES DISTRICT · 7,086 people · 2024 | 1/2 | UCMR-5 |
| Pfpea | 0.0168 µg/L No EPA limit set Main supplier: LOS OSOS COMMUNITY SERVICES DISTRICT · 7,086 people · 2024 | 1/2 | UCMR-5 |
| Pfhxa | 0.0166 µg/L No EPA limit set Main supplier: LOS OSOS COMMUNITY SERVICES DISTRICT · 7,086 people · 2024 | 1/2 | UCMR-5 |
| PFOA | 0.0147 µg/L No EPA limit set Main supplier: LOS OSOS COMMUNITY SERVICES DISTRICT · 7,086 people · 2024 | 1/2 | UCMR-5 |
| PFOS | 0.0117 µg/L No EPA limit set Main supplier: LOS OSOS COMMUNITY SERVICES DISTRICT · 7,086 people · 2024 | 1/2 | UCMR-5 |
| PFHXS | 0.0084 µg/L No EPA limit set Main supplier: LOS OSOS COMMUNITY SERVICES DISTRICT · 7,086 people · 2024 | 1/2 | UCMR-5 |
| Pfba | 0.0060 µg/L No EPA limit set Main supplier: LOS OSOS COMMUNITY SERVICES DISTRICT · 7,086 people · 2024 | 1/2 | UCMR-5 |
| Pfhpa | 0.0054 µg/L No EPA limit set Main supplier: LOS OSOS COMMUNITY SERVICES DISTRICT · 7,086 people · 2024 | 1/2 | UCMR-5 |
| Lead | 0.0011 mg/L 7.3% of the EPA limit 0.0150 mg/L Main supplier: LOS OSOS COMMUNITY SERVICES DISTRICT · 7,086 people · 2026 | 2/2 | LCR |
Each bar shows the measured level as a share of the EPA limit: green is
well under, amber is close to it, red is over. For lead and copper the
limit applies to exactly the 90th-percentile figure shown, so red there
means a real exceedance. For everything else the limit applies to a
running annual average while the figure is the 95th percentile of the
system's samples — over 100% is worth reading, but is not by itself a
violation.
Formal violations are listed separately.
These are the utilities' own EPA-reported results, not a city-wide
average. A detection means the lab measured the
substance — it isn't the same as exceeding a legal limit. Hover a source
tag to see the EPA program and years behind each figure.
Water suppliers serving Los Osos
| Supplier | Population served |
|---|---|
| LOS OSOS COMMUNITY SERVICES DISTRICT | 7,086 |
| S & T MUTUAL WATER COMPANY | 591 |
Frequently asked questions about Los Osos tap water
Is Los Osos tap water safe to drink?
EPA testing detected 22 contaminants in the water serving Los Osos. A detection isn't the same as a violation — most detected levels are within federal limits. Check the level and source for each contaminant above, and your utility's annual Consumer Confidence Report for the official compliance status.
How many water suppliers serve Los Osos?
2 public water suppliers report drinking-water monitoring for Los Osos, California to the EPA. Each is listed above with its population served.
What contaminants are in Los Osos's water?
The contaminants EPA monitoring detected in Los Osos include Nitrate-Nitrite, Nitrate, Fluoride, Barium, Copper. The full list, with the level at the main supplier and the data source, is in the table above.
Where does this data come from?
Every figure is official EPA drinking-water monitoring — the Lead & Copper Rule, the UCMR-5 nationwide testing program, and the EPA Six-Year Review — not our own testing. Each number is labelled with its source and period.