Cadmium
A cumulative kidney toxin with a biological half-life of decades. Its principal exposure route is food rather than water, but contaminated irrigation water is how it gets into food.
Key facts
- Contaminant group
- Metal
- World Health Organization — guideline
- 3 µg/l
- European Union — legal limit
- 5 µg/l
- United Kingdom — legal limit
- 5 µg/l
- United States — legal limit
- 5 µg/l
Where it comes from
- Zinc smelting and refining, where cadmium occurs as a co-contaminant
- Nickel-cadmium battery manufacture and disposal
- Phosphate fertilisers, which carry trace cadmium from the rock phosphate
- Corrosion of galvanised pipework and some solders
How it behaves in water
Mobile in acidic and low-organic-matter conditions and strongly retained in neutral to alkaline soils. Taken up readily by crops — rice and leafy vegetables in particular — which is why irrigation water quality matters more for cadmium than drinking water does.
How it is measured
Measured in micrograms per litre by ICP-MS. Contamination during sampling is a genuine risk given the low concentrations involved.
Regulatory position
| Jurisdiction | Value | Status | Notes |
|---|---|---|---|
| World Health Organization | 3 µg/l | guideline | — |
| European Union | 5 µg/l | legal limit | — |
| United Kingdom | 5 µg/l | legal limit | — |
| United States | 5 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
Accumulates in the kidney over a lifetime, with a biological half-life measured in decades. Chronic exposure causes renal tubular damage and contributes to bone demineralisation — the itai-itai disease outbreak in Japan, caused by cadmium-contaminated irrigation water, established the mechanism.
What removes it
| Row | Effective | Not reliably effective |
|---|---|---|
| 1 | Coagulation and filtration at appropriate pH | Boiling, which concentrates it |
| 2 | Ion exchange | Activated carbon alone |
| 3 | Reverse osmosis | Sediment filtration |
| 4 | Lime softening | — |
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