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Arsenic is a naturally occurring element found in rocks and soil, and it can dissolve into groundwater that supplies wells and public tap water systems. It can also be released into the environment through industrial activities like mining and manufacturing.
Arsenic comes in two main forms: inorganic arsenic, which is the most toxic and commonly found in contaminated drinking water. It is classified as a human carcinogen. Organic arsenic, which is found in seafood, is generally much less toxic.
Why tap water is a concern: In many regions, the main source of significant arsenic exposure is drinking water drawn from contaminated groundwater.
Main exposure routes from tap water
1. Drinking and eating (ingestion)
This is by far the most important route for arsenic from tap water.
• Direct drinking: Every glass of contaminated water adds to your daily arsenic dose.
• Cooking and food preparation: Using contaminated water to cook rice, pasta, soups, or infant formula can significantly increase total intake, because some foods (like rice) can absorb and retain arsenic from the cooking water.
• Chronic exposure: Health risks are driven mainly by long-term, low-to-moderate ingestion over years, not just one or two exposures.
2. Skin contact (dermal absorption)
• Showers, baths, handwashing: Arsenic in water can contact the skin, and human skin is a relatively poor barrier for inorganic arsenic.
• When it matters more: High concentrations, prolonged immersion, or damaged skin could increase absorption
3. Inhalation from water use
• Showering, humidifiers, sprays: Arsenic is not volatile, so it does not readily evaporate into the air like some chemicals.
• Aerosols: Tiny droplets (e.g., from high-pressure showers or misters) can be inhaled
When a person ingests inorganic arsenic—usually through contaminated water or food—it can harm nearly every organ system in the body. Short‑term exposure to high levels may cause nausea, vomiting, abdominal pain, and diarrhea. Long‑term exposure is even more dangerous: it can lead to skin changes, nerve problems, and serious diseases such as skin, lung, and bladder cancers. Chronic exposure has also been linked not only to cancer, but cardiovascular disease, diabetes, and developmental problems in children.
Who is more vulnerable?
For these groups, prioritizing low-arsenic water for drinking and cooking is especially important.
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Infants and young children: Higher intake per body weight and developing organs make them more sensitive to toxic effects.
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Pregnant people and fetuses: In utero exposure is associated with adverse developmental and long-term health outcomes.
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People with pre-existing cardiovascular, kidney, or metabolic conditions: Chronic arsenic exposure may add extra stress to already vulnerable systems.
Practical safety guidance for households
1. Testing your water
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If you use a private well:
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Periodic testing for arsenic is strongly recommended, especially in regions known for elevated groundwater arsenic.
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If you are on public water
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Your water utility is required to monitor arsenic and report results, but you can request the latest water utility report or have your own test done if you want extra reassurance.
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2. Reducing ingestion exposure
If arsenic is elevated:
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Use safe water for all ingestion-related uses:
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Drinking, cooking, making coffee/tea, mixing infant formula, and washing produce.
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Point-of-use treatment:
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Technologies such as ion exchange, reverse osmosis, distillation, or specific adsorptive media can effectively reduce arsenic at the tap when properly designed and maintained.
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Bottled water:
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Can be a temporary option while you address arsenic treatment, especially for infants, pregnant people, or if levels are significantly above guidelines...however, bottled water comes with other health concerns that should not be ignored.
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Key takeaways in plain language
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The biggest risk from arsenic in tap water is from drinking it and using it in food and beverages. Secondarily, absorption through skin during bathing/showering has increased risk. Your skin is your largest organ!
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Long-term, low-level exposure can increase the risk of cancer, heart disease, diabetes, and skin problems, even if you don’t feel sick right away.
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Testing and, if needed, treating your water are the most effective ways to protect yourself and your family.