Arsenic in Drinking Water
Inorganic Chemical · MCL: 10 ppb · 1 systems exceeding limit
Overview
Arsenic is a naturally occurring element that can contaminate drinking water, particularly in groundwater sources. The EPA lowered the arsenic MCL from 50 ppb to 10 ppb in 2006. Many small water systems in the western US still struggle to meet this standard due to high natural arsenic levels in groundwater. The EPA Safe Drinking Water program sets and enforces the maximum contaminant levels shown here.
Health Effects
Long-term exposure to arsenic in drinking water increases the risk of skin, bladder, lung, kidney, and liver cancer. It can also cause cardiovascular disease, diabetes, and neurological effects. Children exposed to arsenic may experience cognitive development issues.
Sources of Contamination
Arsenic occurs naturally in rocks and soil and can dissolve into groundwater. It is more common in the western and southwestern United States. Industrial activities such as mining, smelting, and pesticide application can also contribute to arsenic contamination.
Treatment & Removal
Reverse osmosis, activated alumina, and iron-based adsorptive media can effectively remove arsenic from drinking water. Point-of-use reverse osmosis systems are the most effective home treatment option. Water systems use oxidation/filtration, coagulation/filtration, or ion exchange to treat arsenic.
How to Remove Arsenic From Water
These filtration methods are effective for reducing Arsenic in drinking water:
| Filter Method | Effectiveness | Cost Range | Certification |
|---|---|---|---|
| Reverse Osmosis (RO) | 95-99% removal | $200-500 (under-sink) | NSF/ANSI 58 |
| Adsorptive Media (iron-based) | 95-99% removal | $200-600 (point-of-use) | NSF/ANSI 53 |
| Distillation | 99%+ removal | $100-400 (countertop) | NSF/ANSI 62 |
Reverse Osmosis (RO) — details
Effective for both arsenic III and arsenic V after oxidation.
Adsorptive Media (iron-based) — details
Specialized iron oxide media designed for arsenic. Very effective for arsenic V.
Distillation — details
Highly effective but slow and energy intensive.
Water Systems with Arsenic Detected
Aqua Pa Main System
Bryn Mawr, Pennsylvania
Phoenix City Of
Phoenix, Arizona
Tucson City Of
Tucson, Arizona
Gilbert, Town Of
Gilbert, Arizona
Chandler City Of
Chandler, Arizona
Provo City
Provo, Utah
St George City Water System
St George City, Utah
Aquarion-Eastern Fairfield County
Shelton, Connecticut