Arsenic contamination is one of the most significant water quality concerns for New Hampshire private well owners. Unlike contaminants that affect taste or smell and announce their presence, arsenic is colorless, odorless, and tasteless. You cannot detect it without testing, and its health effects from long-term low-level exposure are serious.
New Hampshire has some of the highest rates of naturally occurring arsenic in drinking water in the United States. The geologic conditions that make the state beautiful — its granite bedrock and metamorphic rock formations — release arsenic into groundwater at concentrations that frequently exceed the EPA’s maximum contaminant level of 10 micrograms per liter (10 ppb). A significant percentage of New Hampshire private wells test above this threshold.
Understanding the Health Risk
Arsenic’s health effects from chronic exposure are well-documented. Long-term ingestion of water with elevated arsenic has been associated with increased risk of bladder, lung, kidney, and skin cancers, as well as cardiovascular disease and diabetes. The risk increases with the level of exposure and the duration of that exposure — which is why addressing arsenic in drinking water is a legitimate health priority, not a bureaucratic nicety.
The EPA standard of 10 ppb reflects a compromise between health protection and the practical feasibility of treatment. Some health researchers argue that the standard should be lower. For context, the World Health Organization’s guideline is also 10 ppb, and some European countries have set more stringent standards.
For expert advice on arsenic in well water, the starting point is always a water test from a certified laboratory. If you haven’t tested your well for arsenic — particularly if your home draws water from bedrock — testing should be a priority.
How Arsenic Gets Into Well Water
Arsenic in New Hampshire groundwater is predominantly naturally occurring. It’s found in certain rock types that are common in the state’s geological formation, particularly in the southern and central parts of the state. As groundwater moves through rock, it dissolves arsenic that would otherwise remain locked in the mineral structure.
This is distinct from arsenic contamination that results from human activity — pesticide use, industrial discharge, mining — though anthropogenic arsenic contamination does exist in some parts of the country. In most New Hampshire situations, elevated arsenic is a natural geology issue, not a consequence of local industry or agriculture.
The depth of your well can influence arsenic levels. Deeper wells drilled into bedrock are more likely to encounter arsenic-bearing rock formations than shallow dug wells, though there are exceptions. Arsenic levels can also vary seasonally and can change over time, which is why periodic retesting (every 3-5 years is commonly recommended) is important even if your initial test came back below the action level.
Treatment Options: Proven Technologies for Arsenic Removal
Once arsenic is confirmed in your well water above levels you’re comfortable with — whether at or above the EPA standard or simply at concentrations you want to eliminate as a precaution — several effective treatment technologies are available.
Reverse osmosis (RO) is one of the most effective and widely used treatment methods for arsenic removal. RO systems force water through a semipermeable membrane that blocks most dissolved solids, including arsenic. Point-of-use RO systems installed at the kitchen sink produce water with arsenic removal rates typically above 95% and often above 99%. The tradeoff is that RO systems produce a waste water stream (the water that doesn’t pass through the membrane) and require membrane replacement on a regular schedule.
If you’re looking to improve tap water with reverse osmosis, a point-of-use system at the kitchen sink addresses your primary exposure pathway — drinking water and cooking water — at a manageable cost. For whole-house arsenic treatment, point-of-entry RO systems exist but are significantly more expensive and produce substantial waste water volumes.
Adsorptive media filtration uses media designed to bind arsenic — typically iron-based or activated alumina media. Whole-house adsorptive media systems treat all water entering the home, addressing exposure pathways beyond drinking and cooking (though drinking water is the dominant exposure route). These systems require periodic media replacement and more frequent monitoring to confirm treatment effectiveness.
Ion exchange using anion exchange resins removes arsenic effectively and is used in both point-of-use and whole-house configurations. Like adsorptive media, the resin requires periodic regeneration or replacement.
The Importance of Treatment System Sizing and Maintenance
Arsenic removal systems don’t work correctly in all water conditions without proper sizing. Competing ions in the water — particularly phosphate, silicate, and other negatively charged species — can reduce the effectiveness of adsorptive and ion exchange systems. High iron concentrations can foul membranes and media prematurely.
This is why comprehensive water testing before selecting and sizing a treatment system matters. An arsenic removal system New Hampshire professional should review your complete water chemistry before specifying equipment, not just your arsenic level in isolation. A system specified without that full picture may underperform or fail prematurely.
Maintenance is equally important. RO membranes have a service life that varies based on water chemistry and usage, and operating a membrane beyond its service life reduces removal efficiency. Adsorptive media has a capacity limit — once it’s saturated with arsenic, it stops removing arsenic from the water. Testing the treated water periodically (not just the untreated well water) confirms that the treatment system is performing as intended.
Practical Steps for New Hampshire Homeowners
If you’re a private well owner and haven’t tested for arsenic recently:
- Test your water. Use a certified laboratory for accurate results. The NH Department of Environmental Services provides a list of certified labs, and many water treatment companies offer testing as part of a consultation.
- Understand your results. Know what the EPA standard is, what your levels are, and what exposure that implies. A professional can help put test results in context.
- Consider your exposure pathways. Drinking and cooking water are the primary routes for arsenic ingestion. A point-of-use system at the kitchen sink addresses these directly and cost-effectively. If you have concerns about bathing water (less significant for arsenic than for some other contaminants), discuss whole-house options.
- Install the right system. Sized and specified correctly for your water chemistry, an arsenic removal system delivers reliable protection for years. Get it right the first time by working with professionals who know New Hampshire’s water quality issues.
- Verify and maintain. Test treated water periodically to confirm the system is working. Follow the manufacturer’s maintenance schedule for filter or membrane replacement.
Arsenic in well water is a real health concern in New Hampshire, but it’s a solvable one. The technology exists, it’s reliable, and local professionals who specialize in this issue are available throughout the state. The most important step is simply knowing what’s in your water — and then acting on that knowledge.
