Contaminated Land Exposure Assessment - CLEA 2002

Note The CLEA 2002 model was withdrawn in October 2006. It is recommended that CLEA UK be used instead.

The UK Department for Environment, Food and Rural Affairs (DEFRA), previously the Department for the Environment, Transport and the Regions (DETR) have released the first of a new set of guideline values, calculated using the Contaminated Land Exposure Assessment (CLEA) model.

The CLEA 2002 model was (finally) released in March 2002. This is an evolution of the CLEA 1997 model originally developed by the late Professor Colin Ferguson at Nottingham Trent University, and later at Nottingham University (after the entire Land Management Team were headhunted by the latter institution).

In common with other UK strategies, this approaches the problem of contaminated land with the idea of fitness for a particular purpose. It is based on human toxicological data and uses Monte Carlo simulations to model the potential pathways for human exposure, taking into account the intrinsic uncertainties.

Guideline values produced by the model indicate a level below which the site is considered safe. Above the guideline value, further investigation is required. Thus the CLEA guidelines provide an objective basis for decision-making, based on an assessment of risk to human health.

Soil Guideline Values as a Function of Land Use

These are the values published in the SGV series of documents, and are based on the sandy soil described in >CLR 10. They will vary according to soil type. It is very important that you refer to the original source documents for full guidance on how to apply these values.

All values in mg/kg dry weight soil


plant uptake [A]

plant uptake [B]

Allotments [C]

industrial [D]

Arsenic (As) 20 20 20 500
Cadmium (Cd) 1 (pH 6)
2 (pH 7)
8 (pH 8)
30 1 (pH 6)
2 (pH 7)
8 (pH 8)
Chromium (Cr) 130 200 130 5000
Mercury ( inorganic Hg) 8 15 8 480
Nickel (Ni) 50 75 50 5000
Lead (Pb) 450 450 450 750
Selenium (Se) 35 260 35 8000

[A] House with a garden and therefore the possibility of ingestion of home-grown vegetables
[B] House or apartment with no private garden area
[C] Open space, often made available by the local authority, for people to grow fruit and vegetables for their own consumption
[D] Assumes that work takes place in a single-storey building, factory or warehouse where employees spend most time indoors involved in office-based or light physical work. Does not apply to sites with 100% hard cover, such as car parks

CLEA publications

These are the documents originally released. All were available as free downloads from the DEFRA website. The CLEA 2002 modeling software is also available as freeware from the same source.

Overview Documents (CLR Series)

CLR 7 Assessment of Risks to Human Health from Land Contamination: An overview of the development of Soil Guideline Values and Related Research
CLR 8 Potential Contaminants for the Assessment of Land
CLR 9 Contaminants in soil: Collation of Toxicological Data and Intake Values for Humans
CLR 10 The Contaminated Land Exposure Assessment (CLEA) Model: Technical Basis and Algorithms 

Contaminants in soil: Collation of Toxicological Data and Intake Values for Humans (TOX Series)

TOX 1  Arsenic 
TOX 3 Cadmium 
TOX 4  Chromium
TOX 6  Lead 
TOX 7  Mercury 
TOX 8   Nickel
TOX 10  Selenium
TOX 12 Dioxins, Furans and Dioxin-like PCBs

Guideline Values for Contamination in Soil (SGV Series)

SGV 1  Arsenic
SGV 3  Cadmium
SGV 4  Chromium
SGV 5  Mercury
SGV 7  Nickel
SGV 9  Selenium
SGV 10  Lead

§ Source: CLR, TOX and SGV documents, in PDF format, and the CLEA 2002 software model may be downloaded  from the Environment Agency archive.