Arsenic vs Nitrates
EPA limits, health effects, treatment options, and affected U.S. utilities — compared
Quick Answer
Both Arsenic and Nitrates share the same risk classification (moderate). Arsenic affects 190 utilities in our database vs. 2,174 for Nitrates.
Heavy Metals
Arsenic is a naturally occurring metalloid found in geological deposits across the western United States, New England, and the Midwest.
Agricultural Chemicals
Nitrates are colorless, odorless compounds that occur naturally in soil but reach dangerous levels in water primarily from agricultural fertilizer runoff and septic system leakage.
Head-to-Head Comparison
| Metric | Arsenic | Nitrates |
|---|---|---|
| Category | Heavy Metals | Agricultural Chemicals |
| Risk Classification | moderate | moderate |
| EPA MCL | 10 ppb | 10 mg/L |
| Utilities in Violation | 190 | 2,174 |
| Well Water Risk | Yes — test recommended | Yes — test recommended |
| Primary Sources |
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| Recommended Treatments |
Health Effects Compared
Arsenic Health Effects
- Bladder, lung, and skin cancer — the most well-established associations
- Skin thickening (keratosis) and dark spots with chronic high exposure
- Peripheral neuropathy and cardiovascular disease
- Type 2 diabetes association at elevated levels
- Developmental and cognitive effects in children
- Immune system disruption
Who is affected: Rural residents relying on private wells in the western U.S., New England, and parts of the Midwest face the highest risk. Populations in areas with natural arsenic-rich geology (volcanic rock, marine sedimentary deposits) are disproportionately affected.
Nitrates Health Effects
- Methemoglobinemia ('blue baby syndrome') in infants under 6 months — potentially fatal without emergency treatment
- Reduced blood oxygen-carrying capacity — causes bluish skin discoloration, rapid heart rate, and in severe cases death
- Colorectal cancer: a 2021 epidemiological study found 17% higher risk at 5–9.9 mg/L nitrate exposure
- Bladder and kidney cancer association with long-term exposure above 5 mg/L (IARC Group 2A)
- Adverse birth outcomes: preterm birth and neural tube defects associated with elevated exposure during pregnancy
- Thyroid disruption: nitrate competes with iodide uptake, potentially impairing thyroid function with chronic exposure
Who is affected: Infants under 6 months face the most acute risk — their digestive systems have higher bacterial activity that converts more nitrate to nitrite, and fetal hemoglobin is more susceptible to methemoglobin formation. Pregnant women are advised to limit exposure because nitrate may affect fetal oxygenation and is associated with adverse birth outcomes at higher levels. People with hereditary methemoglobin reductase deficiency cannot reduce methemoglobin effectively. Rural residents relying on private wells in the Midwest Corn Belt (Iowa, Nebraska, Kansas, Indiana, Illinois), California's Central Valley (Tulare, Fresno, Merced counties), and the Mid-Atlantic are at the highest risk of exceeding the EPA limit.
Filters That Remove Both
These treatment methods are effective against both Arsenic and Nitrates: