UK legal limit: 10 µg/L. Find out what arsenic is, its health effects, and how to check and reduce it in your tap water.
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Arsenic is a naturally occurring metalloid found in the Earth's crust. It dissolves into groundwater as water passes through arsenic-bearing rock formations, including some shales, sandstones, and minerals common in the UK's geology. In the UK, arsenic concentrations in tap water are tightly regulated and generally very low — but some groundwater-sourced zones, particularly in parts of Cornwall, Devon, Scotland, and areas with historic mining activity, can have naturally elevated arsenic levels in source water.
The UK legal limit for arsenic in drinking water is 10 µg/L (micrograms per litre), in line with the WHO guideline value and stricter than earlier limits. UK water companies routinely test for arsenic and treat source water to bring arsenic levels well below the legal limit before distribution. Compliance rates are high — over 99.9% of UK samples pass the arsenic standard.
Arsenic is classified by the International Agency for Research on Cancer (IARC) as a Group 1 carcinogen — known to cause cancer in humans at high doses. Long-term exposure to drinking water containing arsenic above 50 µg/L (five times the current UK limit) is associated with increased risk of skin, lung, bladder, and kidney cancers. It is also associated with skin thickening (hyperkeratosis) and peripheral neuropathy.
Critically, these health effects are primarily documented in countries where arsenic in groundwater naturally occurs at hundreds or thousands of µg/L — Bangladesh and West Bengal are the most extreme cases. At UK tap water concentrations (typically 1–5 µg/L, well below the 10 µg/L limit), no health effects have been demonstrated.
The highest natural arsenic concentrations in UK groundwater tend to occur in: Cornwall and Devon (historic tin and copper mining, arsenic-bearing rock), parts of Scotland (arsenic-bearing metamorphic rocks), some areas of Wales, and a few zones served by Devon and Cornwall groundwater abstraction. Water treatment effectively reduces arsenic in all these areas to below the 10 µg/L limit.
Reverse osmosis (RO) is the most effective consumer technology for arsenic removal — an NSF/ANSI 58 certified RO system removes 90–99% of arsenic from drinking water. Activated alumina and iron oxide media are also used specifically for arsenic adsorption in treatment works and some point-of-use filters. Standard activated carbon (jug filters) does not effectively remove arsenic.
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Arsenic is naturally present at very low levels in some UK groundwater. UK water companies test and treat water to ensure arsenic stays below the legal limit of 10 µg/L. Compliance rates are over 99.9%. Most UK tap water contains less than 1–3 µg/L arsenic.
At UK tap water concentrations (typically below 5 µg/L), arsenic is not associated with health risks. Health concerns from arsenic relate to sustained exposure at levels far above the UK limit — as seen in countries with naturally contaminated groundwater at 50–1,000+ µg/L.
The UK legal limit for arsenic in drinking water is 10 µg/L, in line with the WHO guideline. This is five times stricter than limits in many countries.
Areas with historic mining (Cornwall, Devon), parts of Scotland, and some Welsh groundwater zones can have higher natural arsenic in source water — but all are treated before supply to meet the 10 µg/L limit.
Yes. Reverse osmosis (RO) filters certified to NSF/ANSI 58 remove 90–99% of arsenic. Standard jug filters (activated carbon) do not effectively remove arsenic.
If you live in an area with historic mining or you're on a private well, testing is worthwhile. For mains tap water, water companies test routinely. Enter your postcode to check your zone's compliance data.