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
Phoenix City Of
Phoenix, Arizona
Aqua Pa Main System
Bryn Mawr, Pennsylvania
Tucson City Of
Tucson, Arizona
Aquarion-Eastern Fairfield County
Shelton, Connecticut
Gilbert, Town Of
Gilbert, Arizona
Chandler City Of
Chandler, Arizona
Provo City
Provo, Utah
St George City Water System
St George City, Utah
Frequently Asked Questions
Arsenic has been detected in 1 water systems that exceed the EPA maximum contaminant level (MCL) of 10 ppb, affecting approximately 1,600,000 people. Check your local water system's annual Consumer Confidence Report or search by ZIP code on this site.
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.
Effective filtration methods for Arsenic include Reverse Osmosis (RO), Adsorptive Media (iron-based), Distillation. Look for filters certified to NSF/ANSI standards for Arsenic removal. See the detailed comparison table above for effectiveness ratings and cost ranges.
The EPA Maximum Contaminant Level (MCL) for Arsenic is 10 ppb. The MCL Goal (MCLG), the level with no known health risk, is 0 ppb. Water systems must test regularly and notify customers if levels exceed the MCL.