Hydrocarbons and fuel
Petrol, diesel and heating oil reaching groundwater from leaking tanks and spills. Detectable by taste and smell at concentrations far below health limits, which makes them unusually self-announcing.
Key facts
- Contaminant group
- Industrial
- World Health Organization — guideline
- 10 µg/l for benzene
- European Union — legal limit
- 1 µg/l for benzene
- United Kingdom — legal limit
- 1 µg/l for benzene
- United States — legal limit
- 5 µg/l for benzene
Where it comes from
- Leaking underground storage tanks at filling stations
- Domestic heating oil tank failures — a common cause of private supply contamination
- Road runoff
- Industrial spills and pipeline leaks
How it behaves in water
Most hydrocarbons are less dense than water and float on the water table as a separate phase, which is why they are called light non-aqueous phase liquids. Soluble fractions — benzene, toluene, ethylbenzene, xylenes — dissolve and form a plume. Benzene is the compound of most concern and among the most mobile.
How it is measured
Micrograms per litre by GC-MS. Taste and odour thresholds for petroleum products are typically well below health-based limits, so a supply that smells of fuel is usually detectable long before it is unsafe.
Regulatory position
| Jurisdiction | Value | Status | Notes |
|---|---|---|---|
| World Health Organization | 10 µg/l for benzene | guideline | — |
| European Union | 1 µg/l for benzene | legal limit | — |
| United Kingdom | 1 µg/l for benzene | legal limit | — |
| United States | 5 µg/l for benzene | 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
Benzene is an established human carcinogen, classified by IARC in Group 1, and causes leukaemia at occupational exposure levels. Other petroleum components are of lower concern.
What removes it
| Row | Effective | Not reliably effective |
|---|---|---|
| 1 | Air stripping, since the compounds of concern are volatile | Boiling in an enclosed space, which transfers the compounds to the air you breathe |
| 2 | Granular activated carbon | Sediment filtration |
| 3 | Removing the source — the tank or spill — which is the only durable fix | Water softening |
| 4 | Aeration | — |
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