# Modesto, City of — Modesto, Ca, CA — Drinking Water Quality (2023)

> Contaminant levels for the Modesto, City of — Modesto, Ca, CA public water system from its 2023 Consumer Confidence Report, compared to federal limits.

- Page: https://www.thewatermap.com/water/ca/modesto-modesto-ca/2023
- JSON API: https://www.thewatermap.com/api/water/ca/modesto-modesto-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: 18
- Contaminants with a federal limit: 10
- 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 | 0.85 mg/L (Average) | System-wide | 4 mg/L (MCL) | Within the limit |
| HAA5 | Disinfection byproducts | 17.8 ug/L (Running annual avg) | System-wide | No federal limit | Within the limit |
| Perchlorate | Disinfection byproducts | 0.2 ug/L (Average) | System-wide | No federal limit | Detected — no federal limit |
| Fluoride | Inorganic chemicals | 0.01 mg/L (Average) | System-wide | 4 mg/L (MCL) | Within the limit |
| Nitrate | Inorganic chemicals | 4.1 mg/L (Average) | System-wide | 10 mg/L (MCL) | Within the limit |
| Arsenic | Metals | 4.3 ug/L (Average) | System-wide | No federal limit | Within the limit |
| Barium | Metals | 0.11 mg/L (Average) | System-wide | 2 mg/L (MCL) | Within the limit |
| Copper | Metals | 0.056 mg/L (90th percentile) | At the tap | 1.3 mg/L (Action level) | Within the limit |
| Lead | Metals | Not detected ug/L (90th percentile) | At the tap | No federal limit | None detected |
| Lithium | Metals | 2.11 ug/L (Average) | System-wide | No federal limit | Detected — no federal limit |
| Total Coliform | Microbial | 1.6 (Maximum) | Month | 0 (Public health goal) | Detected — no federal limit |
| Pce | Other | 0.06 ug/L (Average) | System-wide | No federal limit | Within the limit |
| Tce | Other | 0.09 ug/L (Average) | System-wide | No federal limit | Within the limit |
| PFOA | PFAS ("forever chemicals") | 0.55 ng/L (Average) | System-wide | 4 ng/L (MCL) | Within the limit |
| Gross Alpha | Radionuclides | 2.11 pCi/L (Average) | System-wide | 15 pCi/L (MCL) | Within the limit |
| Uranium | Radionuclides | 8.19 pCi/L (Average) | System-wide | 20 pCi/L (MCL) | Detected — no federal limit |
| DBCP | VOCs & pesticides | 3.4 ng/L (Average) | System-wide | No federal limit | Within the limit |
| Dichlorodifluoromethane | VOCs & pesticides | 0.000003 mg/L (Average) | System-wide | 1 mg/L (NL) | 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.
- **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.
- **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.
- **Barium** — A metal from erosion of natural deposits and industrial discharge. Long-term exposure above the federal limit can raise blood pressure.
- **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.
- **Lithium** — A naturally occurring element found in some groundwater. No enforceable federal limit; on the EPA contaminant candidate list for further study.
- **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.
- **PFOA** — Perfluorooctanoic acid, a PFAS 'forever chemical' once used in nonstick and stain-resistant products. Linked to cancer, liver damage, and immune effects; the EPA set an enforceable limit of 4 parts per trillion.
- **Gross Alpha** — Gross alpha particle activity — a combined measure of alpha-emitting radioactive substances. Long-term exposure above the federal limit increases cancer risk.
- **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.
- **DBCP** — 1,2-dibromo-3-chloropropane — a banned soil fumigant pesticide. A probable human carcinogen; long-term exposure above the federal limit can cause reproductive harm.

## 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._