Arsenic
A naturally occurring carcinogen with no taste, no smell and no colour. Wells are where it shows up.
- Safe range
- 0 – 0.01 mg/L (US EPA primary standard, which is enforceable and health-based; the health goal beneath it is zero, because no safe level of arsenic has been established.)
- Ideal range
- 0 mg/L
- Measured in
- mg/L
What it is
Arsenic dissolves into groundwater out of the rock it sits in. It is not a pollution story in most places — it is geology, and some aquifers simply have it. It gives water no taste, no odour and no appearance, so there is no way to suspect it without testing.
Why it matters
Arsenic is a known human carcinogen, and the harm comes from drinking it for years rather than from any one glass. EPA lowered the enforceable limit substantially in the early 2000s and sets the health goal at zero, which is why this platform reads any detection as worth attention even when the water is legally compliant. If you are on a private well and have never tested, this is one of the two or three things most worth doing.
How to measure it
A laboratory, and there is no substitute. Arsenic matters at concentrations far below anything a colour chart resolves, and it gives you no sensory clue to prompt the test.
Certified laboratory, mail-in kit
- How trustworthy
- Reference grade
- Cost
- Most expensive
- Effort
- Careful sampling, then days or weeks of waiting
You are posted bottles and instructions, you fill them exactly as told, and you post them back. Weeks later a report arrives with figures nobody has to interpret by eye. This is what a result you intend to act on should be built from.
Ask for arsenic by name, or buy a well panel that lists it. A basic bacteria-and-nitrate test does not include it, which is how people conclude their well is fine.
Watch out: Ask for speciation if the result comes back elevated. Knowing whether it is arsenic III or V is what decides which treatment works, and running the test again later costs another sample.
Where to find it: State-certified drinking water laboratories; your state's certification officer keeps the list, and many public health departments will point you at one.
Test strips
- How trustworthy
- Ballpark
- Cost
- Low cost
- Effort
- Under a minute, wherever you drew the sample
A plastic strip with reagent pads on it. Dip it, hold it level, and match each pad against the chart on the bottle at the time the label tells you to. Most strips read several parameters at once.
Arsenic strips exist and are a screen rather than a measurement. A positive is a reason to send a sample; a negative is not proof of absence at the levels that matter.
Where to find it: Pool shops, hardware stores, supermarkets and online, sold both per parameter and as multi-packs. Buy strips made for your kind of water: pool strips and drinking water strips read very different scales for the same chemistry.
Your utility's annual water quality report
- How trustworthy
- Reference grade
- Cost
- Free
- Effort
- A few minutes of reading
Every community water system in the US has to publish one each year, free, listing what it found and what the limits are. It is real laboratory data about the water leaving the plant and travelling the mains. What it cannot describe is your own plumbing.
Public systems test for arsenic and publish it. If you are on mains water, last year's report already answers this.
Where to find it: Your water bill, your supplier's website, or the EPA's index of reports. It is also called a Consumer Confidence Report or CCR.
Taking the sample
For several of these the sample is where the error is, and no instrument recovers from a bad one.
- • Take the sample from a tap you actually drink from, after running it briefly. Unlike lead, arsenic comes from the source rather than the plumbing, so a first-draw sample is not required.
Further reading: US EPA: National Primary Drinking Water Regulations, the enforceable health-based limits; US EPA: certified drinking water laboratories, by state; US EPA: private drinking water wells, including what to test for and when
If it is too low
No detectable arsenic. This is the result you want.
- • Nothing. Retest every few years if you are on a well.
If it is too high
Long-term exposure raises cancer risk, and the water should not be used for drinking or cooking until it is treated. Bathing in it is not the concern; ingestion is.
- • Stop drinking and cooking with it while you arrange treatment. Boiling does not help and concentrates it.
- • Reverse osmosis at the kitchen tap is the usual point-of-use answer; specialised adsorptive media treat the whole house.
- • Ask the laboratory which form was found. Arsenic III and arsenic V are removed differently, and a treatment system sized for the wrong one underperforms quietly.
Common questions
Can I taste or smell arsenic in water?
No. It is completely undetectable by taste, smell or appearance at every concentration that matters. This is the single most important thing to know about it: water with a dangerous level of arsenic looks and tastes exactly like water without any.
Does boiling remove arsenic?
It does the opposite. Boiling evaporates water and leaves the arsenic behind, so the concentration goes up. Boiling is for microbiological problems; it makes every dissolved chemical worse.
WiseWaterGauge helps you record and understand your own readings. It is not a substitute for a certified laboratory test, and nothing here is medical or regulatory advice. If a health parameter is out of range, confirm it with an accredited lab and speak to your water provider.