Arsenic is the quietest contaminant in this series. It has no taste, no smell, and no color — your senses give you zero warning. The only way to know it’s in your water is a lab test. That’s the first thing to understand, because everything else follows from it.
This isn’t a factory-spill story. Most arsenic in drinking water is natural — it dissolves out of bedrock into groundwater. If you’re on a private well, that’s the pathway. The hotspots in the U.S. are bedrock wells in New England, the Southwest, the Great Lakes region, and the upper Midwest — and yes, New Jersey has its own piece of this: arsenic is the second most common contaminant to exceed drinking-water standards in NJ private wells, with the Piedmont region carrying the highest risk. (Some arsenic does come from people — old arsenical pesticides, mining and smelting waste — but geology is the main source.)
The health picture, honestly
Arsenic is an IARC Group 1 carcinogen. As the series rule goes: Group 1 is a hazard classification — it means arsenic can cause cancer, not that any dose will. The cancer evidence comes from people who drank high-arsenic water for years, mostly in studies from Taiwan, Chile, and Bangladesh.
Here’s what long-term exposure to elevated inorganic arsenic actually does. The most characteristic effect is a pattern of skin changes: patches of darkened or lightened skin, and thickening — small “corns” or warts — on the palms, soles, and torso. These can show up after years of exposure and can precede non-melanoma skin cancer. The cancer picture from the research: increased risk of skin, lung, and bladder cancer, with liver, kidney, and prostate cancers also implicated. Studies also link chronic exposure to cardiovascular disease, nerve damage (a “pins and needles” numbness in hands and feet), and type 2 diabetes.
The honest framing: this is about years of drinking water over the limit, not a glass from the tap. EPA’s federal limit is 10 parts per billion (micrograms per liter) — and its health goal is zero, meaning there’s no level considered risk-free. New Jersey doesn’t wait for Washington here: our state standard is 5 ppb, half the federal limit, and it’s held that number since 2006. If your water is at or under 5, you’re in good shape.
How to test
No dip strip, no home kit for real answers — arsenic needs a certified lab. If you’re on city water, your utility tests it and reports it on your annual water-quality report. If you’re on a private well, that test is on you: use a state-certified drinking-water lab. Test before you treat, test again after you install anything, and retest yearly. Arsenic levels in a well can shift, and filters wear out.
One more NJ note: if you’ve bought or sold a house here, arsenic is part of the Private Well Testing Act — it gets tested at real estate transactions. Check the paperwork.
What actually removes it
Several proven methods — but with one catch that matters, so read this section twice. Arsenic comes in two forms: As(III) and As(V). Some treatment only handles one of them.
- Reverse osmosis. The workhorse. An under-sink RO handles both arsenic forms, and EPA’s own testing program found RO knocking out roughly 99% of total arsenic. This is the default recommendation for drinking and cooking water.
- Anion exchange. Effective — but only against As(V). If your well water has a big share of As(III), the water needs an oxidation pre-treatment step to convert it to As(V) first. This is why you need a full lab analysis before buying a system, not just a number.
- Adsorptive media (activated alumina and iron-based). Solid whole-house options — iron-oxide media in particular can handle As(III) too, which makes it a good fit for some well chemistries.
- Distillation. Works — boils the water, leaves the arsenic behind. Slow and energy-hungry for whole-house use, but legitimate.
Whatever you choose, look for NSF/ANSI certification with arsenic listed on it. Uncertified claims are just marketing.
What does NOT remove it:
- Carbon filters — your pitcher, faucet, or fridge filter. Carbon-based pitcher filters do not remove arsenic, period. (A rare few pitchers are NSF-certified for arsenic — unless the box says exactly that, assume it isn’t.)
- A water softener. It swaps hardness minerals; arsenic sails through.
- Boiling. Makes it worse — water evaporates, arsenic stays, concentration goes up.
- UV, chlorine, and sediment/particle filters. They disinfect or clarify; arsenic is neither.
One thing you can relax about: arsenic is barely absorbed through skin. Showering, bathing, washing clothes — fine. Protect the water you drink and cook with, and you’ve handled the exposure.
What I’d buy
Treatment type: an under-sink reverse osmosis system, NSF/ANSI 58 certified, with arsenic on the certification sheet — it handles both arsenic forms, no pre-treatment chemistry to fuss over, and it knocks out plenty of other things in the same pass. For a well with mostly As(III) and a whole-house approach, an iron-oxide adsorptive media system, sized to your water test, is the other legitimate play. Either way: test first, install second, retest after.
The bottom line
Arsenic is the argument for testing your well even when everything seems fine — because with this one, fine is exactly what dangerous looks like. New Jersey’s 5 ppb bar is stricter than the federal one, so check your number against that. If you’re over, the fix is real and proven: RO for the kitchen, adsorptive media for the whole house, nothing else sold as a shortcut.
Start here: What’s In Your Water? — learn how to read your water report and test your own tap.
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