Legislative issues

In March 2002, the Department for Environment Food and Rural Affairs and the Environment Agency published a comprehensive package of technical guidance relevant to the assessment of human health risks arising from long-term exposure to contaminants in the soil. The government's view was that this package should supersede, in respect of human health, the ICRCL (Inter Departmental Committee on the Redevelopment of Contaminated Land) Guidance Note 59/83 (2nd edition).

The package, titled the Contaminated Land Exposure Assessment Model (CLEA), comprises the Contaminated Land Reports, software and, importantly, soil guideline values for individual substances. These are the key instruments for generic assessment of the health risks from land contamination and represent a cross-government consensus on the technical approach to undertaking such assessments.

The CLEA package deals with the direct assessment of risks to human health from soil contamination and is based on:

• toxicological criteria that establish a level of unacceptable human intake of a contaminant derived from soil;
• estimates of human exposure to soil contamination based on generic land use, which take into account the characteristics of animals and children, their activity patterns and the fate and transport of the contaminants in the soil.

Soil guideline values for individual substances provide generic assessment criteria. They are indicators for 'intervention' either in the form of further detailed risk assessment or remediation. The approach taken is in line with current policy objectives and guidance and closely relates to the requirements in the statutory guidance for Part IIA of the Environmental Protection Act 1990.

Soil guideline values are intended to be just that, the guidelines for consideration early and often in the process of risk-based management of sites. They serve a useful purpose in encouraging a transparent and consistent approach and can also be helpful in focusing resources on situations that require more detailed assessment. However, a soil guideline value should only be used after the assessor is satisfied that all the conditions assumed are appropriate for the site. The CLEA tool software can be used by specialists to:

• derive generic soil assessment criteria using generic assumptions about the characteristics of contaminants and people likely to be present on a site;
• derive site-specific soil assessment criteria by entering data on the characteristics of contaminants and people likely to be present on site or using a non-generic approach;
• assess whether a measured concentration in soil (and where available, measured site concentrations for contaminants within soil air, ambient and indoor air, and fruits and vegetables) would present a potential risk to human health for a particular set of circumstances

It is regularly updated, as recently as September 2015, to reflect current research including that developing low risk category 4 screening levels for assessment of land affected by contamination.