Arsenic in Drinking Water in Hawaii
What residents of Hawaii 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, Hawaii Department of Health, USGS · Last reviewed: 2025-01-01
Quick Answer
Is arsenic in drinking water a concern in Hawaii?
Arsenic is a lower concern in Hawaii compared to most states due to the relatively young volcanic basalt geology of the Hawaiian Islands. Basaltic rock generally has lower arsenic content than older granitic or sedimentary formations. However, some geothermal areas on the Big Island and areas with volcanic ash deposits can have localized elevated arsenic. Public water systems in Hawaii are generally in compliance with the MCL.
Where does arsenic come from in Hawaii's water?
The primary arsenic pathway in Hawaii, where it occurs, is from natural volcanic geology — particularly in geothermal zones on the Big Island and from volcanic ash or hydrothermal mineral deposits. Hawaii's basal aquifer systems generally show low arsenic, but localized hotspots can occur near geothermal activity and in some areas of older volcanic formations.
What should Hawaii residents know?
Hawaii residents generally face lower arsenic risk than most mainland states. Public water systems are monitored and generally compliant. Private well users on the Big Island near geothermal zones (Puna district) should test as a precautionary measure. Hawaii DOH maintains monitoring data for public systems.
Key Facts
| EPA MCL | 10 µg/L (10 ppb) |
| MCLG | Zero |
| Primary source | Geothermal/volcanic geology — relatively lower arsenic risk than mainland states due to young basaltic geology |
| Highest risk area | Big Island East Rift Zone/Puna district — geothermal activity |
| State regulator | Hawaii Department of Health — Water Supply Division |
| Health effects | Bladder, lung, skin cancer at elevated concentrations |
| Effective treatment | Reverse osmosis or activated alumina — if elevated arsenic is detected |
Why Arsenic Matters in Hawaii
Hawaii's young basaltic geology generally provides lower arsenic groundwater compared to older continental geological formations. However, geothermal activity on the Big Island — particularly in the East Rift Zone near Kilauea — can create localized elevated arsenic in groundwater and surface water. The 2018 Kilauea eruption and associated lava flows disrupted groundwater systems in the Puna district. Hawaii DOH monitors public water systems and maintains data on arsenic occurrence.
Hawaii Arsenic Program
Hawaii DOH monitors arsenic under federal SDWIS. Hawaii's volcanic geology can produce locally elevated arsenic in some groundwater, though this is less widespread than on the mainland. Newer volcanic lava flows generally have lower arsenic; older, weathered volcanic soils may have higher concentrations. Private well owners should test as a baseline.
Largest Hawaii Water Utilities
No arsenic violations on record in EPA SDWIS for Hawaii 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
Puna district residents on the Big Island near active geothermal zones, and private well users in areas with volcanic ash or hydrothermal deposits, should test for arsenic as a precautionary measure. Maui residents in areas with older volcanic geology should also consider testing.
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 Hawaii
- 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 Hawaii Department of 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 Hawaii, 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
Hawaii State Overview
All utilities and water quality data
Hawaii 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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Hawaii Department of Health ↗