# City of Millbrae — Millbrae, Ca, CA — Drinking Water Quality (2021)

> Contaminant levels for the City of Millbrae — Millbrae, Ca, CA public water system from its 2021 Consumer Confidence Report, compared to federal limits.

- Page: https://www.thewatermap.com/water/ca/millbrae-millbrae-ca/2021
- JSON API: https://www.thewatermap.com/api/water/ca/millbrae-millbrae-ca/2021
- 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: 2021
- Contaminants measured: 16
- Contaminants with a federal limit: 5
- Contaminants at or above the federal limit: 1
- Part of The Water Map — https://www.thewatermap.com

## Contaminants measured

| Contaminant | Category | Measured level | Sampling context | Federal limit | Status |
|---|---|---|---|---|---|
| Chlorine | Disinfectants | 3 mg/L (Average) | System-wide | 4 mg/L (MCL) | Within the limit |
| Bromate | Disinfection byproducts | 1.3 ug/L (Average) | System-wide | No federal limit | Within the limit |
| HAA5 | Disinfection byproducts | 23 ug/L (Average) | System-wide | No federal limit | Within the limit |
| Perchlorate | Disinfection byproducts | Not detected ug/L (Average) | System-wide | No federal limit | Detected — no federal limit |
| Fluoride | Inorganic chemicals | 0.3 mg/L (Average) | System-wide | 4 mg/L (MCL) | Within the limit |
| Nitrate | Inorganic chemicals | 12 mg/L (Average) | System-wide | 10 mg/L (MCL) | At or above the limit |
| Copper | Metals | 145 ug/L (90th percentile) | At the tap | No federal limit | Within the limit |
| Lead | Metals | 11 ug/L (90th percentile) | At the tap | No federal limit | Within the limit |
| Manganese | Metals | 5.5 ug/L (Average) | System-wide | No federal limit | Detected — no federal limit |
| Nickel | Metals | Not detected ug/L (Average) | System-wide | No federal limit | Detected — no federal limit |
| Escherichia coli (E. coli) | Microbial | 0 (Average) | System-wide | No federal limit | None detected |
| Giardia lamblia | Microbial | 0.01 (Average) | System-wide | No federal limit | Detected — no federal limit |
| Total Coliform | Microbial | 0 (Average) | System-wide | No federal limit | None detected |
| Chromium | Other | 21 ug/L (Average) | System-wide | 0.02 ug/L (Public health goal) | Within the limit |
| TOC | Physical & aggregate | 2.3 mg/L (Average) | System-wide | No federal limit | Detected — no federal limit |
| Uranium | Radionuclides | Not detected pCi/L (Average) | System-wide | 20 pCi/L (MCL) | Detected — no federal 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.
- **Bromate** — A disinfection byproduct formed when bromide-containing water is treated with ozone. Classified as a probable human carcinogen; the EPA sets a strict maximum contaminant 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.
- **Perchlorate** — A chemical used in rocket fuel and fireworks that can also form during disinfection. Can interfere with thyroid hormone production; has no national enforceable limit but is regulated in some states.
- **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.
- **Nitrate** — A compound from fertilizer runoff, septic systems, and erosion of natural deposits. Levels above the federal limit can cause 'blue baby syndrome,' a serious oxygen-transport condition in infants.
- **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.
- **Lead** — A toxic metal that leaches into water from old service lines, solder, and plumbing fixtures. There is no safe level of lead; it harms brain development in children and raises blood pressure in adults. The EPA sets an action level, not a health goal above zero.
- **Manganese** — A naturally occurring metal from soil and rock. No enforceable federal limit; high levels stain fixtures and laundry and can affect taste, with a health advisory for infants.
- **Nickel** — A metal from natural deposits and industrial discharge. Long-term exposure can cause skin and other effects; monitored under EPA rules.
- **Escherichia coli (E. coli)** — Escherichia coli — bacteria found in the gut of humans and animals. Its presence in drinking water indicates fecal contamination and a real risk of waterborne illness.
- **Total Coliform** — A group of bacteria used as an indicator of overall water-system sanitation. Coliforms themselves are usually harmless, but their presence signals that disease-causing organisms could enter the system.
- **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.
- **Uranium** — A naturally occurring radioactive metal from erosion of natural deposits. Long-term exposure above the federal limit can damage the kidneys and increase 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._