The short answer
Arsenic is a natural element that can contaminate drinking water. Long-term exposure through drinking water is linked to bladder and skin cancer. A safe water supply is the most important way to prevent exposure, and private well owners are responsible for testing their own water.
Arsenic is classified as a known human carcinogen (IARC Group 1).
People can be exposed by drinking contaminated water, tobacco smoke, or food from plants irrigated with contaminated water.
NCI links long-term arsenic in drinking water to bladder and skin cancer, and says lung and other cancers have also been linked.
A carcinogen classification describes hazard — whether something can cause cancer — not your personal risk at a given exposure.
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This page is for anyone wondering about arsenic in water, food, or the workplace. It explains how people are exposed, the link to cancer, and how to lower exposure.
The simple version
Arsenic is a natural element in the environment. It can get into drinking water. Long-term exposure through drinking water is linked to cancer. A safe water supply is the most important way to protect yourself.
What arsenic is
Arsenic occurs naturally in the environment. Inorganic arsenic compounds were widely used as pesticides until the mid-1900s and were found in some medicines until the 1970s.
How people are exposed
Common ways people come into contact with it:
- Drinking water that is contaminated with arsenic.
- Smoking tobacco, or being around tobacco smoke.
- Eating food from plants watered with contaminated water.
NCI says arsenic in contaminated drinking water is generally thought to be more harmful than arsenic in contaminated food.
The cancer connection
NCI says drinking arsenic-containing water for a long time is associated with an increased risk of bladder cancer and skin cancer. Cancers of the lung, digestive tract, liver, kidney, and the lymphatic and blood-forming systems have also been linked to arsenic exposure.
The International Agency for Research on Cancer (IARC) studies the causes of cancer on behalf of the World Health Organization. It places arsenic and inorganic arsenic compounds in Group 1, carcinogenic to humans. That is the strongest evidence category.
Hazard is not the same as risk
Hazard and risk are not the same thing. Calling arsenic a carcinogen is a claim about hazard. It means arsenic can cause cancer under some conditions. Your own risk is a separate question. It depends on the dose you take in, how long you take it in, and other factors. Two agents in one group can carry very different real-world risks. A listing answers "can it cause cancer?" It leaves "how likely is it for me?" open.
How to lower your exposure
NCI says access to a safe water supply for drinking, food preparation, and irrigating food crops is the most important way to prevent arsenic exposure.
- EPA's drinking water standard for arsenic is 10 parts per billion for public water systems. EPA says private wells are not regulated by the federal government, so owners are responsible for checking their own water. Ask your state or local health department how to get a well tested.
- If a test shows high levels, ask the testing lab or your health department about treating the water or switching to a safer source.
- Do not smoke, and stay away from secondhand smoke.
Any one exposure is easier to judge in context. Our overview of cancer prevention and what raises cancer risk give you that context.
The bottom line
Arsenic is a known human carcinogen (IARC Group 1). Your water supply is the piece you can most easily check. If you use a private well, get it tested. A single label is not worth losing sleep over.
Common questions
Does arsenic cause cancer?
Yes. Arsenic is classified as a known human carcinogen, which means there is strong evidence it can cause cancer in people. How much any one person's risk rises depends on how much they are exposed to and for how long.
How are people exposed to arsenic?
NCI lists drinking contaminated water, smoking tobacco or being around tobacco smoke, and eating food from plants irrigated with contaminated water.
Which cancers are linked to arsenic?
NCI says drinking water with arsenic over a long time is associated with bladder and skin cancer. Lung, digestive tract, liver, kidney, and blood and lymph system cancers have also been linked to arsenic.
How can I reduce my exposure to arsenic?
NCI says a safe water supply is the most important step. EPA says private well owners are responsible for testing their own water.
Does a carcinogen label mean I will get cancer?
No. A classification is about hazard — whether arsenic can cause cancer under some conditions — not a prediction that any one exposed person will develop cancer. Your actual risk depends on the amount and length of exposure and other factors.
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Last updated: 2026-10-16Next planned review: 2028-07-05
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Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes, and this is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Source checked — This page was written with AI assistance and then compared with the sources listed on it, looking for statements those sources do not back up. That check is not a sentence-by-sentence record and can miss errors. It is not a medical review, and it does not confirm the page is complete or right for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
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