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Land contamination can give rise to volatile contaminants which can pose a risk of harm to human health by asphyxiation or illness if inhaled. Vapours and gases such as methane may also pose a risk of fire or explosion.



Chartered Institute of Environmental Health

  • The Local Authority Guide to Ground Gas. Wilson, S., Card, G. and Haines, S.: Chartered Institute of Environmental Health, London, 2008. - Out of Print



Environment Agency




United States Environmental Protection Agency


Land contamination can affect the health of people living, working, visiting or otherwise present on a site. The risk assessment process is used to establish whether there is an unacceptable risk to humans.

Contaminated Land Exposure Assessment (CLEA)

CLEA Software and Handbook

Toxicological Reports (TOX) (INFO-RA2-2d)

Soil Guideline Values (SGVs) (INFO-RA2-2e)

Category 4 Screening Levels (C4SL)

Generic Screening Values (GAC)


General Information 

 TPH Working Group Series (TPHCWG)

Contaminated Land Reports (CLR) - All withdrawn

      • CLR7 Overview of the Development of Guideline Values and Related Research, DEFRA/EA, 2002. (INFO-RA2-2a) CLR7 has been withdrawn.
      • CLR9 Contaminants in Soils: Collation of Toxicological Data and Intake Values for Humans. Consolidated Main Report, CLR 9 DEFRA/EA, 2002. (INFO-RA2-2b). The Environment Agency completely re-wrote the old CLR9 report (now called the Human health toxicological assessment of contaminants in soil (Science Report Final SC050021/SR2)) to take account of Defra's ‘Way Forward’ exercise on Soil Guideline Values and other changes to the underlying science.
      • CLR 10 The Contaminated Land Exposure Assessment Model (CLEA): Technical Basis and Algorithms. DEFRA/EA, 2002. (INFO-RA2-2c). This has been withdrawn and rewritten as CLEA.

A number of regulatory regimes now require an ecological risk assessment (ERA) to be carried out. All these regimes are concerned, in one way or another, with assessing the risk of significant harm to an organism, an animal or a whole ecosystem. To ensure consistency in ERA, Defra and the EA have developed an ERA framework for use in land quality assessments.

ERA framework

The framework offers a series of tiered activities, decisions and actions that provide a practical match between available resources and the severity of a land contamination problem. It allows decisions to be made rationally, consistently and transparently and forms the basis for discussions between the relevant parties (these may include: site owners, regulatory authorities and the local community).

ERA guidance


Land contamination can affect groundwater, freshwater and coastal waters. Groundwater is particularly vulnerable to contamination as it underlies many sites and is difficult to clean up once polluted.




Department of the Environment

Environment Agency