Land that is contaminated contains substances in or under the land that are actually or potentially hazardous to health or the environment. Areas with a long history of industrial production will have many sites which may be affected by their former uses such as mining, industry, chemical and oil spills and waste disposal. These sites are known as Brownfield Land

Brownfield land

Brownfield sites are abandoned or underused industrial and commercial facilities available for re-use. Expansion or redevelopment of such a facility may be complicated by real or perceived environmental contaminations. Cf. Waste...

Contamination can also occur naturally as a result of the geology of the area, or through agricultural use.

United Kingdom (excluding Northern Ireland)

There is currently no specific legislation in Northern Ireland covering contaminated Land.
A Requirement was placed on all local Authorities in England, Wales and Scotland to investigated potentially contaminated sites and, where necessary, ensure they are remediated by Part IIA of the Environmental Protection Act 1990

Legal Definition of "Contaminated Land"

Section 78A(2) of the Environmental Protection Act 1990 defines "Contaminated Land" as:

“Contaminated land” is any land which appears to the local authority in whose area it is situated to be in such a condition, by reason of substances in, on or under the land, that—

(a) significant harm is being caused or there is a significant possibility of such harm being caused; or

(b) pollution of controlled waters is being, or is likely to be, caused;