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Not health advice. Contact your local water utility for concerns.
Data from EPA Water Quality Reports. For official information, contact your water utility or health department.
Real EPA measurements of nitrates for California water systems — Six-Year Review compliance samples 2012–2019 (historical). Methodology
These cities have nitrates levels above 50% of the EPA limit but within compliance
| City | Level | % of Limit | Population |
|---|---|---|---|
| Hemet | 9.94 mg/L | 99.4% | 33,828 |
| El Monte | 6.38 mg/L | 63.8% | 248,000 |
| Burbank | 6.31 mg/L | 63.1% | 105,603 |
| Fresno | 6.09 mg/L | 60.9% | 545,716 |
| Chino Hills | 6.08 mg/L | 60.8% | 76,414 |
| Upland | 5.71 mg/L | 57.1% | 78,376 |
| Colton | 5.70 mg/L | 57.0% | 46,525 |
| Riverside | 5.68 mg/L | 56.8% | 298,398 |
| Livermore | 5.24 mg/L | 52.4% | 60,414 |
| Pasadena | 5.22 mg/L | 52.2% | 164,344 |
Showing 10 of 12 cities with elevated levels
Every California system with a nitrates result in EPA's data, sorted by level. Averages of 2012–2019 finished-water samples, non-detects counted as zero — historical, not today's tap.
| City | Level | Period | EPA Limit | % of Limit | Status |
|---|---|---|---|---|---|
| HemetGrade B | 9.94 mg/LAverage of 2 samples | 2012–2019 | 10.00 mg/L | 99.4% | Warning |
| El MonteGrade A | 6.38 mg/LAverage of 3117 samples | 2012–2019 | 10.00 mg/L | 63.8% | Warning |
| BurbankGrade A | 6.31 mg/LAverage of 909 samples | 2012–2019 | 10.00 mg/L | 63.1% | Warning |
| FresnoGrade C | 6.09 mg/LAverage of 6619 samples | 2012–2019 | 10.00 mg/L | 60.9% | Warning |
| Chino HillsGrade A | 6.08 mg/LAverage of 180 samples | 2012–2019 | 10.00 mg/L | 60.8% | Warning |
| UplandGrade A | 5.71 mg/LAverage of 18 samples | 2012–2019 | 10.00 mg/L | 57.1% | Warning |
| ColtonGrade C | 5.70 mg/LAverage of 16 samples | 2012–2019 | 10.00 mg/L | 57.0% | Warning |
| RiversideGrade B | 5.68 mg/LAverage of 2334 samples | 2012–2019 | 10.00 mg/L | 56.8% | Warning |
| LivermoreGrade D | 5.24 mg/LAverage of 1063 samples | 2012–2019 | 10.00 mg/L | 52.4% | Warning |
| PasadenaGrade A | 5.22 mg/LAverage of 1836 samples | 2012–2019 | 10.00 mg/L | 52.2% | Warning |
| Apple ValleyGrade B | 5.17 mg/LAverage of 27 samples | 2012–2019 | 10.00 mg/L | 51.7% | Warning |
| SalinasGrade A | 5.07 mg/LAverage of 2340 samples | 2012–2019 | 10.00 mg/L | 50.7% | Warning |
| MantecaGrade B | 5.00 mg/LAverage of 1136 samples | 2012–2019 | 10.00 mg/L | 50.0% | Warning |
| Jurupa ValleyGrade A | 4.96 mg/LAverage of 2121 samples | 2012–2019 | 10.00 mg/L | 49.6% | Safe |
| OntarioGrade D | 4.84 mg/LAverage of 392 samples | 2012–2019 | 10.00 mg/L | 48.4% | Safe |
| TustinGrade B | 4.82 mg/LAverage of 201 samples | 2012–2019 | 10.00 mg/L | 48.2% | Safe |
| ModestoGrade D | 4.75 mg/LAverage of 3999 samples | 2012–2019 | 10.00 mg/L | 47.5% | Safe |
| ClovisGrade C | 4.60 mg/LAverage of 690 samples | 2012–2019 | 10.00 mg/L | 46.0% | Safe |
| Monterey ParkGrade D | 4.59 mg/LAverage of 2600 samples | 2012–2019 | 10.00 mg/L | 45.9% | Safe |
| San BernardinoGrade A | 4.56 mg/LAverage of 2638 samples | 2012–2019 | 10.00 mg/L | 45.6% | Safe |
| DelanoGrade A | 4.45 mg/LAverage of 127 samples | 2012–2019 | 10.00 mg/L | 44.5% | Safe |
| FontanaGrade A | 4.24 mg/LAverage of 993 samples | 2012–2019 | 10.00 mg/L | 42.4% | Safe |
| BrentwoodGrade A | 4.17 mg/LAverage of 5 samples | 2012–2019 | 10.00 mg/L | 41.7% | Safe |
| LodiGrade C | 4.07 mg/LAverage of 207 samples | 2012–2019 | 10.00 mg/L | 40.7% | Safe |
| PomonaGrade C | 4.00 mg/LAverage of 2851 samples | 2012–2019 | 10.00 mg/L | 40.0% | Safe |
Showing 25 of 95 cities. View individual city pages for detailed reports.
Nitrates pose the greatest risk to infants under six months of age. High nitrate levels can cause methemoglobinemia, also known as "blue baby syndrome," which reduces the blood's oxygen-carrying capacity. Pregnant women are also at risk as nitrate exposure has been linked to neural tube defects, preterm birth, and low birth weight. IMPORTANT: Boiling water does NOT remove nitrates - it concentrates them.
Runoff from fertilizer use; leaching from septic tanks; erosion of natural deposits; agricultural runoff
Based on our analysis of EPA Safe Drinking Water Information System (SDWIS) data and local water utility reports,nitrates has been detected in 95 California water systems. The average level across all tested cities is 22% of the EPA Maximum Contaminant Level (MCL), with the highest detection at 99.4% of the limit.
The EPA MCL for nitrate is 10 mg/L measured as nitrogen. The EPA MCL for nitrates is 10 mg/L. This limit is set to protect public health based on available scientific evidence about the contaminant's health effects.
95 California cities have nitrates detected in their water supply. All tested cities are within EPA safety limits.
Blue baby syndrome in infants, pregnancy complications, potential cancer risk. The most vulnerable groups include infants under 6 months and pregnant women.
The most effective methods for removing nitrates include Reverse Osmosis, Ion Exchange, Distillation. Look for filters certified by NSF/ANSI for nitrates reduction.
The EPA Maximum Contaminant Level (MCL) for nitrates is 10 mg/L.The EPA MCL for nitrate is 10 mg/L measured as nitrogen.
This page shows what California utilities reported for nitrates. It cannot tell you what is coming out of your own tap: utility samples are taken across a whole system and averaged, levels vary by address and season, and anything picked up after the water leaves the main never appears in their report.
Home water test kitscheck your own tap before buying any filterRecommended filtration methods for nitrates removal:
Removes 83-92% of nitrates
Specifically designed for nitrate removal
Effective but energy-intensive
Paid links. We earn a commission if you buy, at no extra cost to you. Filters are matched to the removal methods listed above for nitrates.