Arsenic Water Test

Who should test for arsenic

Arsenic has no color, smell or taste, so you won't notice it in your glass. A lab test is the only way to know how much is there.

Most arsenic in well water comes from the ground itself. EPA lists the main source of arsenic in drinking water as erosion of natural deposits, along with runoff from orchards and from glass and electronics production wastes. The Ohio Department of Health puts it simply: arsenic occurs naturally in rocks and soil, and it enters drinking water supplies from natural deposits in the earth or from agricultural and industrial practices. That means a well can pick up arsenic even when nothing nearby looks like a pollution source.

Private wells are not regulated like public water. EPA says the quality of water from private domestic wells is not regulated by the federal government under the Safe Drinking Water Act, nor by most state governments. Around 15 percent^[4] of the U.S. population relies on private wells, and nobody tests those wells unless the owner does. If your water comes from a public system, your utility is responsible for meeting the federal arsenic limit, so the case for your own arsenic test is strongest on a well.

Arsenic is one of the contaminants most often found above health benchmarks in wells. The U.S. Geological Survey studied about 2,100^[2] domestic wells sampled in 1991–2004^[2]. It found that more than one in five (23 percent)^[2] of those wells had at least one contaminant at a concentration greater than a human-health benchmark. The contaminants most often over a benchmark were inorganic chemicals, and all of them except nitrate came mainly from natural sources. Arsenic was among the most frequent: it was above the EPA maximum contaminant level in 6.8 percent^[3] of wells nationwide, and in more than 10 percent^[3] of wells in several aquifer types, such as crystalline-rock aquifers in New England and basin-fill aquifers in California, Nevada, Arizona, New Mexico, Texas and Nebraska.

Some health departments name arsenic in their routine well checks. The Ohio Department of Health recommends that private water system owners test a few parameters on a regular basis, including total coliform bacteria, E. coli, nitrates and arsenic. The goal is to keep a record of your water quality and spot changes over time.

You have the most reason to test for arsenic if:

• Your home is on a private well and you have never had it tested for arsenic, or you don't have the results.
• You are buying a home with a well. A first test gives you a baseline before you rely on the water.
• Your well was recently drilled, deepened or repaired. Test the new setup rather than relying on old results.
• A neighbor's well tested high. A neighbor's result is a reason to test your own well, not a substitute for it.
• Someone in the home is pregnant or a young child drinks the water and you want a reliable baseline.

If you are on a well and want to see arsenic alongside the other tests that fit your situation, you can build a test plan in a few questions. Our well water testing guide covers the tests to run on a well every year.

Certified lab or home kit

There are two ways to check water for arsenic: send a sample to a state-certified laboratory, or use a test kit you read at home. Only a certified lab gives you a measured concentration you can compare with the federal limit.

A certified lab gives you a number. A state-certified drinking water lab measures how much arsenic is in your sample and reports it as a concentration, using approved methods such as the ones in the Lab methods list at the end of this section. You can compare that number with the EPA maximum contaminant level and with your own earlier results. If you later add treatment, a lab retest shows whether the level dropped. For a private well, a state-certified lab is the usual route, because there is no utility that tests the well for you. Our directory of certified water testing labs lists state-certified labs in the states we cover, and our guide to well water testing cost shows verified lab prices.

A home strip kit gives you a rough read. Home kits you read yourself, often by matching a test strip's color to a chart, can be a quick first look. But a color match is not a measured concentration from a certified lab, and you can't compare it with a regulatory benchmark the same way. A strip that shows nothing does not prove your water is below the federal limit.

When to choose a lab:

• You want a number to compare with the EPA maximum contaminant level.
• You are deciding whether to spend money on treatment, or checking whether treatment works.
• You are buying or selling a home with a well and need a result you can show someone else.
• A home kit showed anything at all, and you want to confirm it.

Use a home kit as a screening step if you like, and confirm anything that matters with a certified lab.

Lab methods

• EPA 200.8 (ICP-mass spectrometry)
• EPA 200.9 (atomic absorption; platform)
• SM 3113 B (atomic absorption; furnace)
• SM 3114 B (hydride atomic absorption)

Source: ecfr.gov (source for lab methods) (opens in a new tab)

How to collect an arsenic sample

An arsenic sample is simpler to take than a lead sample. Arsenic usually comes from the well water itself rather than from your plumbing, so you are not trying to catch water that has been sitting in the pipes overnight. Always follow the instructions that come with your lab's kit, since they are written for the bottle and method that lab uses.

The quick guide near the top of this page lists the sample bottle and the acid preservative that the federal method calls for. Many labs send bottles with the preservative already inside, so the steps below include how to handle it.

1. Pick the right tap. Use a cold-water tap you drink or cook from, usually the kitchen sink. If you have any treatment device, ask the lab whether to sample before it, after it, or both. Sampling before treatment tells you about the well; sampling after it tells you what you are drinking.
2. Remove anything on the faucet that could add debris. Take off a hose or attachment, but leave the faucet itself as it is unless your kit says otherwise.
3. Run the cold water for a short time. Let it run until it is steady and cool so the sample represents the water coming from the well, not water that sat in a warm pipe. Your lab's instructions give the exact time.
4. Fill the bottle without rinsing it. If the bottle contains a preservative, don't rinse it out or let it overflow. Fill to the line, then cap it tightly. Avoid touching the inside of the cap or bottle.
5. Label and record. Write the date, time, tap and whether the sample was taken before or after any treatment.
6. Return it on time. Ship or drop off the sample within the time your lab gives you, along with any form it asks you to complete.

Common mistakes to avoid

• Rinsing out a bottle that came with preservative inside.
• Sampling only after a filter or softener when you wanted to know about the well itself.
• Mixing up labels when you send more than one bottle.
• Holding the sample past the return date your lab gives you.

What your arsenic level means

Your lab report gives a number. Here is how to read it against the federal benchmarks.

The EPA maximum contaminant level (MCL) for arsenic is 0.010 mg/L^[1]. It is the legal limit for public water systems, and it has been in force since January 23, 2006^[1]. Private wells don't have to meet it, but it is the federal benchmark you can compare a well result with.

The health goal is zero. EPA's maximum contaminant level goal for arsenic is 0 mg/L^[1]. The goal is a health target, not a legal limit. It means that a result below the MCL is under the legal limit for public water, not that the water has no arsenic at all.

Why the limit matters. EPA lists the possible effects of long-term exposure above the MCL as skin damage or problems with circulatory systems, and a possible increased risk of getting cancer. A water test can't diagnose anything; if you have health concerns, talk to a health professional and bring your lab report. Our guide to arsenic in water covers the health effects, where arsenic comes from and what to do after a confirmed result.

Putting your result in context

• No arsenic detected. No treatment needed based on this result. Keep the report as a baseline and retest periodically, or after work on the well.
• Arsenic detected, below the MCL. No treatment needed based on the federal limit. Because the health goal is zero, some households choose to retest to confirm the level and track it over time.
• At or above the MCL. Retest with a certified lab to confirm before you make any decision. Then compare approaches based on the confirmed number and the rest of your water chemistry, and retest after any change.

Don't decide on treatment from a single home-kit reading. Any treatment choice should start from a confirmed certified-lab result. Our guide on how to lower arsenic in your water explains whether arsenic can be removed from a well, the treatment options after a confirmed result, and when no treatment is needed.