Arsenic
Cities measured
87
Detected in
87 / 87
EU limit
10 μg/L
Highest
5.8 μg/L — Hanoi
Overview
Arsenic leaches into groundwater from arsenic-bearing minerals in volcanic and sedimentary rocks. Surface water sources like Lake Mälaren (Stockholm) generally have lower arsenic than groundwater. Industrial contamination — mining, smelting, pesticide use — can also elevate arsenic.
Health Relevance
Chronic arsenic exposure via drinking water is a major global public health problem, causing skin lesions, peripheral neuropathy, and significantly elevated risk of bladder, lung, kidney, liver, and skin cancers. Arsenic is the most important chemical cause of cancer from drinking water globally.
Regulatory Limits
Drinking Water Directive 2020/2184
10 μg/L (WHO also 10 μg/L — acknowledged as a provisional guideline due to feasibility constraints).
Controversy & Contested Science
The WHO acknowledges its 10 μg/L limit carries a lifetime cancer risk of approximately 6 per 10,000 — far above the standard 1-in-10,000 target for carcinogens. The limit was set at 10 μg/L primarily due to analytical detection limits in 2001, not because 10 μg/L is safe. An estimated 140 million people globally drink water with > 10 μg/L arsenic. Bangladesh and West Bengal host the world's worst arsenic groundwater crisis — affecting 50+ million people — as an unforeseen consequence of well-drilling programs intended to avoid contaminated surface water.