Arsenic in Drinking Water: Arsenic is one of the most serious naturally occurring contaminants that can be found in drinking water. It has no taste, smell, or color, making it impossible to detect without testing. Long-term exposure to elevated arsenic levels has been linked to an increased risk of several cancers and other health problems, which is why the U.S. Environmental Protection Agency (EPA) strictly regulates arsenic in public drinking water.
While most public water systems meet federal standards, arsenic can still be a concern in certain regions—especially for homeowners who rely on private wells. Fortunately, effective treatment technologies are available.
This guide explains what arsenic is, where it comes from, the health risks associated with exposure, current EPA regulations, how to test your water, and the best filtration methods for reducing arsenic.
Want to learn about other contaminants commonly found in drinking water?
➡️ Drinking Water Contaminants Explained
What Is Arsenic?
Arsenic is a naturally occurring element found in rocks, soil, and groundwater. It can dissolve into water supplies as groundwater moves through mineral deposits. In some areas, arsenic contamination may also result from mining, industrial activities, or historical agricultural practices, although natural geological sources are the most common cause in the United States.
Because arsenic is invisible, odorless, and tasteless, laboratory testing is the only reliable way to determine whether it is present in your drinking water.
How Does Arsenic Get Into Drinking Water?
Arsenic enters drinking water through several pathways:
- Natural weathering of arsenic-containing rocks and minerals
- Groundwater flowing through arsenic-rich geologic formations
- Mining and smelting activities
- Certain industrial processes
- Historical use of arsenic-containing pesticides and wood preservatives
Private wells are generally at greater risk because they are not regulated under the Safe Drinking Water Act.
Health Risks of Arsenic Exposure
Most health concerns are associated with long-term exposure to elevated levels of inorganic arsenic.
Potential health effects include:
Increased Cancer Risk
Long-term ingestion of arsenic has been linked to increased risks of:
- Bladder cancer
- Lung cancer
- Skin cancer
- Kidney cancer
- Liver cancer
- Prostate cancer
Skin Changes
Early signs of chronic arsenic exposure may include:
- Darkened skin patches
- Thickened skin on the palms or soles
- Skin lesions
Other Health Effects
Research has associated prolonged arsenic exposure with:
- Cardiovascular disease
- Neurological effects
- Immune system impacts
- Endocrine effects, including diabetes
- Pulmonary effects
These effects are primarily associated with long-term exposure to concentrations above regulatory standards.
EPA Guidelines for Arsenic
The EPA regulates arsenic under the Safe Drinking Water Act.
Current standards are:
- Maximum Contaminant Level Goal (MCLG): 0 µg/L (zero) — a non-enforceable public health goal.
- Maximum Contaminant Level (MCL): 10 µg/L (10 parts per billion or 0.010 mg/L) — the enforceable legal limit for public drinking water systems.
Public water systems are required to monitor arsenic and comply with this standard. Private well owners are responsible for testing and treating their own water.
How to Test for Arsenic
Because arsenic cannot be detected by taste, smell, or appearance, testing is essential.
Check Your Consumer Confidence Report
If you receive municipal water, your annual Consumer Confidence Report (CCR) lists regulated contaminants, including arsenic if it is detected.
Laboratory Testing
Certified drinking water laboratories can accurately measure arsenic concentrations and are the preferred option for homeowners and well owners.
Private Wells
If your home uses a private well, test for arsenic:
- When purchasing a home
- After drilling a new well
- Every few years, or more frequently if local conditions warrant
- Whenever you notice changes in water quality or receive updated local guidance
Best Filtration Methods for Arsenic
Not every household water filter removes arsenic effectively.
1. Reverse Osmosis (Best Overall)
Reverse osmosis is one of the most effective residential technologies for reducing arsenic.
Benefits include:
- Excellent arsenic reduction
- Removes lead, fluoride, PFAS, nitrates, chromium, and many dissolved solids
- Improves taste and odor
- Ideal for drinking and cooking water
Reverse osmosis is the solution most homeowners choose when they want broad contaminant reduction rather than treatment for a single contaminant.
2. Adsorptive Media (Activated Alumina or Iron-Based Media)
Specialized treatment systems using activated alumina or iron-based media can effectively reduce arsenic and are often used for point-of-entry or whole-house treatment, particularly in homes with private wells.
3. Distillation
Distillation can also reduce arsenic but is generally slower and less practical than reverse osmosis for everyday household use.
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Can Boiling Water Remove Arsenic?
No.
Boiling water does not remove arsenic. Because water evaporates during boiling while arsenic remains behind, boiling can actually increase the concentration of arsenic in the remaining water.
If arsenic is present, an appropriately certified filtration system is the recommended solution.
How to Reduce Arsenic Exposure
If arsenic is detected in your water:
- Confirm the concentration through certified laboratory testing.
- Install a treatment system certified for arsenic reduction.
- Replace filters and membranes according to the manufacturer’s schedule.
- Retest your water periodically to verify continued performance.
If you rely on a private well, regular monitoring is particularly important because water quality can change over time.
Frequently Asked Questions
Is arsenic naturally found in drinking water?
Yes. In many regions, arsenic enters groundwater naturally as water passes through arsenic-containing rocks and soils.
Does reverse osmosis remove arsenic?
Yes. Properly maintained reverse osmosis systems are among the most effective residential technologies for reducing arsenic in drinking water.
Is arsenic more common in well water?
It can be. Because private wells draw directly from groundwater and are not regulated like public water systems, naturally occurring arsenic may be more common in some well-water supplies.
Should I test my well for arsenic?
Yes. If your home uses a private well, periodic testing for arsenic is strongly recommended, especially in areas where naturally elevated arsenic levels are known to occur.
Final Thoughts
Arsenic is a naturally occurring contaminant that poses a significant health concern when present in drinking water above recommended limits over many years. Because it has no taste, odor, or color, testing is the only way to know whether your water contains elevated levels.
If testing reveals arsenic above the EPA’s drinking water standard—or if you simply want greater peace of mind—a certified reverse osmosis system is one of the most effective and practical solutions for reducing arsenic while also addressing many other common drinking water contaminants.
To learn more about arsenic and other contaminants that may affect your home’s water quality, visit our complete contaminant resource:
