How does arsenic get into drinking water?

Arsenic enters drinking water primarily through natural geological processes — it dissolves from rock formations into groundwater as water percolates through arsenic-bearing minerals. This is why arsenic is most common in groundwater-dependent regions like the Southwest. It can also enter water from industrial contamination, mining operations, and agricultural chemical runoff.

Does a Brita filter remove arsenic?

No. Standard Brita and most basic carbon pitcher filters are NOT effective at removing arsenic. You need a reverse osmosis system, distillation unit, or a filter with iron-based adsorptive media specifically designed for arsenic. Always check for NSF certification specific to arsenic removal.

Is arsenic in well water dangerous?

Yes — arsenic in well water can be very dangerous because private wells are not regulated by the EPA and may never be tested. If you're on a private well in the Southwest, New England, or Upper Midwest, testing for arsenic should be a priority. The EPA MCL is 10 ppb, but health effects have been documented at lower levels. Reverse osmosis or iron-based adsorptive media are the recommended treatment options.

heavy metal

Arsenic in Drinking Water

Updated: 2026-05-16Written by: TapWaterGuide Editorial Team

What is Arsenic and is it dangerous in tap water? Arsenic is a heavy metal contaminant found in drinking water. The EPA maximum contaminant level (MCL) is 10 ppb. The stricter EWG health guideline is 0.004 ppb. Health effects include cancer — bladder, lung, skin, kidney, and liver cancer with chronic exposure and cardiovascular disease including heart disease and stroke. The most effective removal methods are Reverse Osmosis, Distillation, Adsorptive Media.

Last updated: 2026-05-16 · Source: EPA, WHO, EWG

Regulatory Limits

EPA MCL

10 ppb

Lowered from 50 ppb to 10 ppb in 2006. Many health advocates consider this still too high.

EWG Guideline

0.004 ppb

2,500x stricter than EPA MCL. Based on cancer risk from lifetime exposure.

MCLG (Goal)

0 ppb

The level at which no known health effects occur

Health Effects

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Cancer — bladder, lung, skin, kidney, and liver cancer with chronic exposure

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Cardiovascular disease including heart disease and stroke

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Type 2 diabetes — linked to arsenic exposure even at levels below the EPA MCL

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Skin lesions and changes in pigmentation

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Neurodevelopmental effects in children, including reduced IQ

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Reproductive harm including miscarriage and low birth weight

Especially vulnerable: Infants and children, Pregnant women, People with diabetes or cardiovascular disease, Private well users in affected regions

How to Remove Arsenic from Water

Technology	Effectiveness	Notes
Reverse Osmosis	high	Removes 95-99% of arsenic (both arsenate and arsenite with pre-oxidation).
Distillation	high	Highly effective but impractical for large volumes.
Adsorptive Media	high	Iron-based adsorptive media (like Bayoxide E33) is highly effective and used in POE systems.
Ion Exchange	moderate	Effective for arsenate (As V) but not arsenite (As III). Pre-oxidation may be needed.
Activated Carbon	low	Standard carbon filters are NOT effective for arsenic removal.
Water Softener	none	Water softeners do NOT remove arsenic.

Where Arsenic Is Most Common

Southwest US — Arizona, Nevada, New Mexico, parts of California and Texas

New England — Maine, New Hampshire, parts of Vermont and Massachusetts

Upper Midwest — Michigan, Minnesota, Wisconsin

Parts of the Great Plains — Oklahoma, Nebraska, South Dakota

An estimated 2.1 million Americans are served by water systems with arsenic above 10 ppb

Common sources include: Natural geological deposits — arsenic occurs naturally in rock formations, especially in the Southwest, New England, and Upper Midwest, Mining and smelting operations — legacy contamination from historical mining, Agricultural chemicals — some older pesticides contained arsenic compounds, Pressure-treated wood — CCA (chromated copper arsenate) treated lumber leaches arsenic, Well water in affected geological regions — private wells are not regulated by EPA.

Best Filters for Arsenic Removal

We've tested and compared the top water filters that are NSF-certified to remove Arsenic. Each recommendation is matched to specific contaminant removal performance, not just marketing claims.

View our top arsenic filter picks →