Arsenic in Drinking Water in Maine
What residents of Maine need to know about arsenic in drinking water — including natural geological sources, private well risk, which utilities have documented violations, and how to remove arsenic from tap water.
Source: EPA SDWIS, Maine Division of Environmental Health, USGS · Last reviewed: 2025-01-01
Quick Answer
Is arsenic in drinking water a concern in Maine?
Yes — Maine is one of the most arsenic-affected states in the country for private well users. The state's granite and metamorphic bedrock geology is naturally rich in arsenic-bearing minerals, and a very high proportion of Maine residents — approximately 45% — use private wells drilled into this bedrock. Maine has documented some of the highest arsenic detection rates in private wells of any state in the Northeast.
Where does arsenic come from in Maine's water?
Granite, schist, and metamorphic bedrock is the overwhelmingly dominant arsenic source in Maine. Private wells drilled into bedrock fractures — the standard residential well type in Maine — are the primary exposure pathway. Arsenic leaches from arsenic-bearing minerals in the rock into groundwater over geological time. Maine's long bedrock contact times and old geological formations create conditions for elevated arsenic.
What should Maine residents know?
Maine residents on private wells should test for arsenic — it is one of the most important water quality tests for Maine well owners, alongside radon and nitrate. Maine DHHS actively encourages and subsidizes private well testing. Standard pitcher and refrigerator filters do not remove arsenic. Reverse osmosis or activated alumina is required for treatment. Maine's DHHS provides a list of certified laboratories for testing.
Key Facts
| EPA MCL | 10 µg/L (10 ppb) |
| MCLG | Zero |
| Primary source | Granite and metamorphic bedrock — arsenic-bearing New England crystalline geology |
| Private well rate | ~45% of Maine residents on private wells — very high bedrock arsenic occurrence rate |
| Maine testing rate | Estimated 10–15%+ of Maine bedrock wells exceed 10 ppb MCL |
| State program | Subsidized testing available; testing required at real estate transfer for bedrock wells |
| State regulator | Maine Division of Environmental Health |
| Health effects | Bladder, lung, skin cancer; cardiovascular; diabetes risk |
| Effective treatment | Reverse osmosis or activated alumina — pitcher filters do NOT remove arsenic |
Why Arsenic Matters in Maine
Maine's arsenic problem is among the most significant of any eastern state. The combination of arsenic-bearing granite and metamorphic bedrock, widespread private well use (~45% of residents), and old geological formations creates a high arsenic occurrence rate in residential wells. Studies have found that 10–15% or more of Maine bedrock wells may exceed the 10 ppb MCL, and even more may exceed health-based goals at lower thresholds. Maine DHHS has been proactive — the state requires testing of bedrock wells at real estate transfer and provides subsidized testing for low-income residents.
Maine Arsenic Program
Maine DHHS has documented widespread arsenic in private wells — Maine has one of the highest private well arsenic rates in the nation due to its crystalline granite bedrock. Approximately 10% of Maine private wells tested exceed 10 ppb arsenic, and some exceed 100 ppb. Maine offers free private well testing and has guidance for arsenic treatment specifically tailored to Maine's well water conditions.
Largest Maine Water Utilities
No arsenic violations on record in EPA SDWIS for Maine utilities in our database. Browse the largest utilities to review their full water quality record.
How Does Arsenic Get Into Drinking Water?
Arsenic in drinking water is almost always naturally occurring — it leaches from arsenic-bearing rocks and minerals into groundwater over time. New England granite, Southwest volcanic geology, and Upper Midwest glacial aquifers are the primary high-risk formations. It has no taste, odor, or color.
Full arsenic overview — geology maps, health effects, all 50 statesWho Should Pay Closest Attention
Private well owners throughout Maine face arsenic risk from bedrock geology. Oxford, Franklin, Somerset, and Kennebec counties have among the highest documented occurrence rates, but arsenic can occur in any Maine county where bedrock wells are used. Maine's rural character means the majority of well owners in inland communities may be affected.
Private well owners near mining districts or agricultural areas
Residents in states with documented volcanic or geothermal geology
Long-term consumers of water from small groundwater systems
Households in homes built before 1960 with older well casings
Residents whose well water has never been tested for arsenic
Anyone living in a state where bedrock wells are common
How to Check Your Situation in Maine
- 1
Identify your water source. If you use a public utility, use the ZIP lookup on this page to find your system and check its compliance record.
- 2
If on public water, review your utility's most recent Consumer Confidence Report (CCR) for arsenic monitoring data. The MCL is 10 ppb — your report should show recent test results.
- 3
If on a private well, order an arsenic test from a Maine Division of Environmental Health-certified laboratory. A basic arsenic test costs $15–$40. The state agency website maintains a certified lab list.
- 4
Test your well at the tap — not just at the wellhead. The entire water distribution system within your home can affect water quality.
- 5
If your test shows arsenic above 5 ppb, install certified treatment immediately. If above 10 ppb, do not use the water for drinking or cooking until treatment is installed.
- 6
Retest after installing treatment to confirm it is working as certified. Replace filter media on the manufacturer's schedule — an exhausted filter may not perform as rated.
Treatment Options for Arsenic
Boiling does not remove arsenic — it concentrates it. Standard activated carbon filters (Brita, etc.) do not effectively remove arsenic. Certified treatment is required.
NSF/ANSI Standard 58 — Reverse Osmosis
RO systems certified to NSF/ANSI 58 remove 85–95% of arsenic. Under-sink installation. Most effective for removing multiple contaminants simultaneously. Replace membranes and pre-filters on schedule.
Activated Alumina Filters
Activated alumina is specifically designed for arsenic and fluoride removal. Point-of-use or whole-house options available. Must be certified by NSF International or WQA for arsenic reduction. Requires periodic media regeneration or replacement.
Iron/Manganese Oxidation Filters
Effective for arsenic in iron-rich well water, which is common in the Midwest and New England. Oxidation converts dissolved iron and arsenic to a form that can be filtered out. Best when arsenic is co-occurring with high iron levels.
What does NOT work for arsenic
Standard activated carbon filters (Brita, refrigerator filters, most pitcher filters) do NOT effectively remove arsenic. Boiling concentrates arsenic. Water softeners do not remove arsenic. Only use products with NSF certification specifically for arsenic reduction.
Take Action Now
If you use a private well in Maine, test for arsenic — especially if you are in a region with granite, volcanic, or sedimentary geology. A basic arsenic test costs $15–$40 at a state-certified lab.
Public water users: check your utility's Consumer Confidence Report (CCR) for arsenic results. The EPA MCL is 10 ppb — any detection warrants attention.
If arsenic is detected above 10 ppb (or even below it, given MCLG is zero), install an NSF/ANSI 58-certified reverse osmosis system for drinking and cooking water.
Standard carbon filters do NOT remove arsenic — do not rely on a Brita or refrigerator filter for arsenic protection.
Frequently Asked Questions
Related Pages
Arsenic — National Overview
All U.S. utilities with arsenic records
Maine State Overview
All utilities and water quality data
Maine Well Water Guide
Testing, risks & certified labs for private wells
Reverse Osmosis Guide
Removes 85–95% of arsenic
Best Arsenic Filter Guide
What actually works (carbon doesn't)
PFAS in Drinking Water
The 'forever chemical' contamination overview
All Contaminants
Complete reference library
Data Sources & Provenance
All data on this page is sourced from official U.S. government or public datasets.
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Maine Division of Environmental Health ↗