Contaminant
Mercury
A persistent toxic metal whose principal water concern is not drinking water concentration but bioaccumulation as methylmercury in fish.
Key facts
- Contaminant group
- Metal
- World Health Organization — guideline
- 6 µg/lFor inorganic mercury in drinking water.
- European Union — legal limit
- 1 µg/l
- United Kingdom — legal limit
- 1 µg/l
- United States — legal limit
- 2 µg/l
Where it comes from
- Coal combustion and atmospheric deposition
- Artisanal and small-scale gold mining
- Chlor-alkali and other industrial discharge
- Natural mineralisation
How it behaves in water
Inorganic mercury entering water bodies is methylated by bacteria, particularly in anoxic sediments and wetlands. Methylmercury biomagnifies up the food chain, reaching concentrations in predatory fish millions of times those in the surrounding water.
How it is measured
Measured in micrograms per litre in water, and in milligrams per kilogram in fish tissue, which is generally the more relevant exposure route.
Regulatory position
| Jurisdiction | Value | Status | Notes |
|---|---|---|---|
| World Health Organization | 6 µg/l | guideline | For inorganic mercury in drinking water. |
| European Union | 1 µg/l | legal limit | — |
| United Kingdom | 1 µg/l | legal limit | — |
| United States | 2 µg/l | legal limit | — |
Table sources
- World Health Organization — Guidelines for Drinking-water Quality. Public but restricted · CC BY-NC-SA 3.0 IGO
- European Commission — Drinking Water Directive (EU) 2020/2184 and reporting. Open — attribution required · European Commission reuse policy (Decision 2011/833/EU)
- Drinking Water Inspectorate — Drinking water quality in England and Wales. Open — attribution required · Open Government Licence v3.0
- United States Environmental Protection Agency — Safe Drinking Water Information System. Open · US Government work — public domain
Health context
Methylmercury is a developmental neurotoxicant; the Minamata disease outbreak in Japan established its effects definitively. Drinking water is rarely the significant exposure route in populations with mercury exposure.
What removes it
| Row | Effective | Not reliably effective |
|---|---|---|
| 1 | Coagulation and filtration | Boiling |
| 2 | Granular activated carbon | Sediment filtration alone |
| 3 | Reverse osmosis | — |
| 4 | Ion exchange | — |
Relationships
Related intelligence
Sources
- World Health Organization — Guidelines for Drinking-water Quality. Public but restricted · CC BY-NC-SA 3.0 IGO
- Peer-reviewed scientific literature — Open-access hydrology, water chemistry and water use research. Public but restricted · Publisher terms — public access, reuse not clearly granted