Mercury
Cities measured
87
Detected in
87 / 87
EU limit
1 μg/L
Highest
1.2 μg/L — Karachi
Overview
Mercury in drinking water exists primarily as inorganic Hg²⁺. Sources include geological weathering, coal combustion deposition, industrial discharge, and historically from chlor-alkali plants. Methylmercury — the organic and far more toxic form — biomagnifies through the food chain, particularly in fish.
Health Relevance
Inorganic mercury targets the kidneys at elevated exposures. Methylmercury is a potent neurotoxin that crosses the blood-brain and placental barriers, causing severe developmental neurological damage. Drinking water is a minor mercury exposure route; fish consumption is the dominant pathway.
Regulatory Limits
Drinking Water Directive 2020/2184
1 μg/L.
Controversy & Contested Science
The Minamata disease tragedy (Japan, 1956–1960s) — Chisso Corporation releasing methylmercury wastewater into Minamata Bay, bioaccumulating in fish — caused 2,000+ deaths and 10,000+ neurological injuries. Chisso suppressed internal research findings for years while residents continued eating contaminated fish. Minamata disease is still being diagnosed. The global Minamata Convention (2013) — named for the disaster — regulates mercury use and emissions internationally, but enforcement in signatory nations varies widely.