Arsenic cannot be detected without testing, and a state-certified lab water test for arsenic is the recommended route. A state-certified lab should do the test before any filter purchase, because the lab report guides the treatment choice. The Environmental Protection Agency (EPA) caps arsenic in public drinking water at 10 parts per billion (ppb).
Arsenic occurs naturally in some rock and soil and can dissolve into groundwater, according to the Agency for Toxic Substances and Disease Registry (ATSDR). Industrial and agricultural sources can add more. The Centers for Disease Control and Prevention (CDC) notes that arsenic in water has no color, taste or odor, so a clear glass that tastes fine proves nothing.
The EPA's private wells guidance tells well owners to test at least once a year for total coliform bacteria, nitrates, total dissolved solids and pH. Arsenic is not on that yearly list. A well owner orders it separately, when there is a specific reason for concern.
Arsenic in Water Cannot Be Detected Without Testing
Arsenic in drinking water cannot be detected without testing, because the CDC and ATSDR both state that it has no color, taste or odor, and a state-certified lab is the recommended route. The EPA sets 10 ppb, or 0.010 milligrams per liter (mg/L), as the maximum for public drinking water. Private wells sit outside that rule, so a well owner who wants an answer has to order the test.
ATSDR links long-term exposure to arsenic in drinking water with skin changes and a higher risk of certain cancers. We do not diagnose. A lab number cannot tell you what caused a symptom in your home, so bring any health question, along with the lab report, to a clinician.
Boiling does not remove arsenic (CDC). Boiling kills microbes but leaves dissolved substances such as arsenic in the pot, according to the CDC, and evaporation can concentrate what stays behind.
Private Well Owners Decide When to Test for Arsenic
Private well owners decide whether and when to test for arsenic, because the EPA does not regulate private wells. The EPA places both testing and treatment on the well owner.
The EPA recommends that well owners test at least once a year for total coliform bacteria, nitrates, total dissolved solids and pH. For other contaminants, arsenic among them, it recommends testing when there is a specific concern. Our well water testing guide covers the yearly panel, our coliform bacteria test page covers the bacteria check, and what to test first helps you put the list in order.
Add arsenic to the lab order when you have reason to think any of those affect the water under a well. The EPA private wells page sets no fixed retest interval for arsenic, so the specific-concern rule governs timing.
A Certified Lab Water Test for Arsenic Beats a Home Kit
A state-certified lab gives a result you can base a treatment decision on, while a home kit result needs a lab behind it before you spend money. The EPA directs private well owners to state-certified laboratories for testing. Home test kits exist; check the kit maker's documentation for accuracy at 10 ppb.
The decision line for arsenic sits at the EPA's 10 ppb public-water limit. A kit has to read accurately near that number to help you decide anything. Any accuracy claim for a kit comes from its maker, and our rule on this site is that a positive or borderline kit result goes to a certified lab before anyone buys treatment.
Choose a kit when you want a first look before ordering a lab test. Choose the lab when the result will decide a filter purchase, a retest or a switch to another water source. Our water test kit guide covers home kits in more detail.
| Factor | State-certified lab | Home test kit |
|---|---|---|
| Who stands behind it | A lab certified by your state, per EPA guidance | The kit maker |
| Role in a decision | Basis for retest, treatment or a new water source | First look only; a positive or borderline result goes to a lab |
| Verdict | Use for any decision that costs money | Use for screening, then send results to a lab |
Collecting the Sample Follows the Lab's Own Instructions
Sample collection for arsenic follows the certified lab's written instructions, using the containers the lab supplies. Your state or local health department can give you a list of certified labs and sampling instructions, according to the EPA. Use only the lab's containers.
Each lab writes its own sampling steps. Follow the lab's sheet exactly, step by step.
When you order, ask whether the report can show the form of arsenic in the water. Treatment guidance ties the right device to that form. That one detail on the report shapes the fix later.
- Ask your state or local health department for its list of state-certified labs.
- Order an arsenic test from a lab on that list and request its sample containers.
- Read the lab's sampling instructions in full before you open a container.
- Collect the water exactly as the instructions describe.
- Return the sample by the method and deadline the lab sets.
- Keep the paperwork so you can match the report to the date and tap you sampled.
Reading a Water Test for Arsenic in Parts per Billion
Find the arsenic line on the lab report and compare its number with the EPA's 10 ppb limit for public drinking water. If the report uses mg/L instead of ppb, multiply by 1,000. The arithmetic follows from the EPA's own figures, since 0.010 mg/L times 1,000 equals its 10 ppb limit.
A result at or below the EPA's 10 ppb meets the number public water systems must meet. A result above it exceeds that federal standard, even though the rule does not bind a private well. For a private well, the owner decides what to do with the number.
Our guide to reading a water report walks through the rest of a lab report line by line.
| Report value (mg/L) | Same value (ppb) | Against the EPA's 10 ppb limit |
|---|---|---|
| 0.005 | 5 | Below the limit |
| 0.010 | 10 | At the limit |
| 0.015 | 15 | Above the limit |
| 0.050 | 50 | Five times the limit |
Who This Arsenic Testing Advice Does Not Serve
Arsenic testing advice written for private wells does not fit every reader. Three groups need a different next step.
Three results would change the advice on this page. A lab result above the EPA's 10 ppb limit moves you to the decision below. A borderline home-kit reading means sending a sample to a certified lab, and a new specific concern, such as a nearby industrial or agricultural source, is a reason to test again after an earlier clean result.
- Public water customers: the EPA's 10 ppb standard already applies to your water system. You can still order a personal test from a certified lab.
- Anyone with symptoms they connect to their water: a lab number is no diagnosis. Take the report to a clinician.
- Anyone counting on boiling or an uncertified filter: boiling does not remove arsenic, according to the CDC, and a filter without an arsenic reduction certification gives you no documented arsenic reduction.
Retest, Treat or Switch Sources After a High Arsenic Result
When a certified lab reports arsenic above the EPA's 10 ppb limit, retest first, then pick between certified treatment and another water source. Treatment devices for arsenic should carry an NSF/ANSI certification that names arsenic reduction, according to NSF International. Reverse osmosis systems fall under NSF/ANSI 58.
Whether a given device fits depends on the form of arsenic in the water, according to treatment guidance. Let the lab report steer the choice. Our well water filter guide, reverse osmosis system guide and page on what reverse osmosis removes cover the device types.
Start today by asking your state or local health department for its certified lab list and ordering a water test for arsenic.
- Retest with a state-certified lab before you buy anything, so one sample does not decide the purchase.
- Stop boiling as a fix, because boiling does not remove arsenic and can concentrate it, according to the CDC.
- Use another water source for drinking while you decide on treatment.
- Buy only a device whose NSF/ANSI certification names arsenic reduction.
Common questions
What level of arsenic in water is dangerous?
The EPA sets 10 ppb as the maximum arsenic level for public drinking water, and that is the line to read a lab result against. The EPA sets no separate number for private wells, because it does not regulate them. ATSDR links long-term exposure to skin changes and a higher risk of certain cancers, so take health questions to a clinician.
Can I taste arsenic in water?
No. Arsenic in water has no color, taste or odor, according to the CDC. It cannot be detected without testing, and a state-certified lab is the recommended route.
Does boiling remove arsenic?
No. Boiling kills microbes but leaves dissolved substances such as arsenic behind, according to the CDC. Evaporation can concentrate what remains.
How often should I test a well for arsenic?
The EPA sets no fixed arsenic interval for private wells. Its yearly list covers total coliform bacteria, nitrates, total dissolved solids and pH, and it advises testing for other contaminants when there is a specific concern.
Do home arsenic test kits work?
Check the kit maker's documentation for accuracy at 10 ppb. A kit can give a first look. Send a positive or borderline kit result to a state-certified lab before you buy treatment.
Does a pitcher or carbon filter remove arsenic?
Look for an NSF/ANSI certification that names arsenic reduction, according to NSF International. A filter without that listing gives you no documented arsenic reduction. Match any device to the lab report, because the form of arsenic affects which treatment fits.
Where do I find a certified lab for an arsenic test?
Your state or local health department can supply a list of certified labs and sampling instructions, according to the EPA. Use the lab's own containers. Follow its instructions exactly.