Arsenic in Drinking Water in Massachusetts
What residents of Massachusetts 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, Massachusetts Environmental Protection / Drinking Water Program, USGS · Last reviewed: 2025-01-01
Quick Answer
Is arsenic in drinking water a concern in Massachusetts?
Yes — Massachusetts has significant arsenic concerns for private well users due to New England's arsenic-bearing granite and metamorphic bedrock. Approximately 20% of Massachusetts residents use private wells, and studies have found that a substantial fraction of bedrock wells in the state exceed the 10 ppb MCL. Worcester County, north-central Massachusetts, and the Pioneer Valley have particularly high documented occurrence rates.
Where does arsenic come from in Massachusetts's water?
Granite, schist, and gneiss bedrock is the primary arsenic source throughout Massachusetts. Private wells drilled into this crystalline bedrock — standard practice in rural Massachusetts — are the primary exposure pathway. Arsenic occurs naturally in arsenic-bearing minerals in the rock and leaches slowly into fracture water over geological time. No contamination event is required — the arsenic is inherent in the geology.
What should Massachusetts residents know?
Massachusetts private well owners should test for arsenic every few years. Massachusetts DPH provides guidance and a list of certified labs. The state has set health-based guidelines that recommend action at levels below the federal MCL. Standard pitcher and refrigerator filters do not remove arsenic. Reverse osmosis or NSF-certified activated alumina treatment is required.
Key Facts
| EPA MCL | 10 µg/L (10 ppb) |
| MCLG | Zero |
| Primary source | Granite and metamorphic bedrock statewide — arsenic in natural mineral form |
| Highest occurrence | Worcester County, Franklin County, Hampshire County — above-average bedrock arsenic rates |
| State recommendation | MassDEP recommends testing at every real estate transfer and every few years for existing wells |
| State regulator | Massachusetts Drinking Water Program (MassDEP) |
| 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 Massachusetts
Massachusetts's arsenic problem in private well water is well-documented. The state's granite and metamorphic bedrock — which extends across the Piedmont and New England Upland — is naturally arsenic-bearing. Studies by USGS and MassDEP have found elevated arsenic in a significant percentage of private bedrock wells statewide, with Worcester County and north-central Massachusetts showing particularly high rates. Massachusetts has taken a proactive approach — publishing arsenic occurrence data by town, providing guidance documents, and recommending testing at every real estate transfer.
Massachusetts Arsenic Program
Massachusetts MassDEP has documented significant arsenic in private wells across the state, particularly in the crystalline rock regions of central and western Massachusetts and the South Shore. Massachusetts conducted a statewide private well survey finding elevated arsenic in areas of Worcester, Middlesex, Plymouth, and Bristol counties. The state recommends arsenic testing for all new private wells.
Massachusetts Utilities With Arsenic Violation Records
The utilities listed below have at least one arsenic violation on record in EPA's SDWIS database. Violations may be open or resolved — see individual utility pages for current status and risk level.
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 Massachusetts face risk from bedrock geology. Worcester County, Franklin County, Hampshire County (Pioneer Valley), and rural areas of Plymouth and Middlesex counties have high documented occurrence rates. No part of Massachusetts with bedrock wells is entirely free of arsenic risk.
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 Massachusetts
- 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 Massachusetts Environmental Protection / Drinking Water Program-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 Massachusetts, 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
Massachusetts State Overview
All utilities and water quality data
Massachusetts 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.