# San Luis Obispo Water Department — San Luis Obispo, Ca, CA — Drinking Water Quality (2023)

> Contaminant levels for the San Luis Obispo Water Department — San Luis Obispo, Ca, CA public water system from its 2023 Consumer Confidence Report, compared to federal limits.

- Page: https://www.thewatermap.com/water/ca/san-luis-obispo-water-department-san-luis-obispo-ca/2023
- JSON API: https://www.thewatermap.com/api/water/ca/san-luis-obispo-water-department-san-luis-obispo-ca/2023
- Source: the utility's annual Consumer Confidence Report (CCR)
- Verification: transcribed by a model, cross-checked by a second model, approved before publishing
- Reporting year: 2023
- Contaminants measured: 15
- Contaminants with a federal limit: 3
- Contaminants at or above the federal limit: 0
- Part of The Water Map — https://www.thewatermap.com

## Contaminants measured

| Contaminant | Category | Measured level | Sampling context | Federal limit | Status |
|---|---|---|---|---|---|
| Chlorine | Disinfectants | 0.09–1.9 mg/L (Range) | System-wide | No federal limit | Within the limit |
| HAA5 | Disinfection byproducts | 21–49 ug/L (Range) | System-wide | No federal limit | Approaching the limit |
| TTHM | Disinfection byproducts | 27–75 ug/L (Range) | System-wide | No federal limit | Approaching the limit |
| Fluoride | Inorganic chemicals | 0–0.9 mg/L (Range) | System-wide | 4 mg/L (MCL) | Within the limit |
| Aluminum | Metals | 0.05–0.15 mg/L (Range) | System-wide | No federal limit | Detected — no federal limit |
| Arsenic | Metals | 2–2 ug/L (Range) | System-wide | No federal limit | Within the limit |
| Chromium, Total | Metals | 24–24 ug/L (Range) | System-wide | No federal limit | Within the limit |
| Copper | Metals | 0.15 mg/L (90th percentile) | At the tap | 1.3 mg/L (Action level) | Within the limit |
| Lithium | Metals | 10–10 ug/L (Range) | System-wide | No federal limit | Detected — no federal limit |
| Selenium | Metals | 6 ug/L (Reported level) | System-wide | No federal limit | Within the limit |
| Sodium | Metals | 32 mg/L (Reported level) | System-wide | No federal limit | Detected — no federal limit |
| Hardness | Physical & aggregate | 126–317 mg/L (Range) | System-wide | No federal limit | Detected — no federal limit |
| TOC | Physical & aggregate | 26–43 (Range) | System-wide | No federal limit | Detected — no federal limit |
| Turbidity | Physical & aggregate | 100 (Reported level) | System-wide | No federal limit | Detected — no federal limit |
| Gross Alpha | Radionuclides | 0.735–0.735 pCi/L (Range) | System-wide | 15 pCi/L (MCL) | Within the limit |

## What these contaminants are

- **Chlorine** — A disinfectant added to drinking water to kill bacteria and viruses. Effective and necessary, but high residual levels can cause taste and odor issues; the EPA caps the residual disinfectant level.
- **HAA5** — Haloacetic acids — a group of five disinfection byproducts formed when disinfectants react with organic matter. Long-term exposure above the federal limit is associated with an increased cancer risk.
- **TTHM** — Total trihalomethanes — a group of four chemicals (including chloroform) formed when chlorine reacts with natural organic matter. Long-term exposure above the federal limit is linked to liver, kidney, and central-nervous-system effects and increased cancer risk.
- **Fluoride** — A mineral often added to drinking water to help prevent tooth decay. Beneficial at low levels, but long-term exposure above the federal limit can cause bone disease and tooth mottling.
- **Aluminum** — A common element sometimes used as a treatment coagulant. Regulated only as a secondary (cosmetic) standard; high levels can discolor water.
- **Arsenic** — A naturally occurring element that also enters water from industry and agriculture. A known human carcinogen; long-term exposure is linked to skin, bladder, and lung cancer.
- **Chromium, Total** — Total chromium — the sum of all chromium forms, from natural deposits and industrial discharge. Long-term exposure above the federal limit can cause allergic dermatitis; includes hexavalent chromium.
- **Copper** — A metal that enters water from corroding household plumbing. Short-term exposure causes stomach distress; long-term exposure can damage the liver and kidneys.
- **Lithium** — A naturally occurring element found in some groundwater. No enforceable federal limit; on the EPA contaminant candidate list for further study.
- **Selenium** — A trace element from natural deposits and industrial discharge. Essential in tiny amounts, but long-term exposure above the federal limit can cause hair and fingernail loss and circulatory problems.
- **Sodium** — A naturally occurring salt component. Not federally regulated for health; relevant for people on sodium-restricted diets.
- **Hardness** — A measure of dissolved calcium and magnesium minerals. Not federally regulated for health; affects scaling, soap use, and taste.
- **TOC** — Total organic carbon — a measure of organic material dissolved in the water. Not harmful itself, but it is the raw material that forms disinfection byproducts; removal is a treatment requirement.
- **Turbidity** — A measure of cloudiness from suspended particles in the water. High turbidity can shelter microbes from disinfection; the EPA enforces it through a treatment-technique standard.
- **Gross Alpha** — Gross alpha particle activity — a combined measure of alpha-emitting radioactive substances. Long-term exposure above the federal limit increases cancer risk.

## How to read this

- A water-quality report covers an entire service area, not a single address.
- 'Federal limit' is the EPA standard (MCL, action level, treatment technique, etc.) that the measured level is compared against.
- 'At or above the federal limit' means the utility's own reported figure met or exceeded that standard.

_Figures are the utility's own published numbers. Generated 2026-06-04 from thewatermap.com._