December 15, 2011 by Ed Stutt


The discipline of chemical risk assessment for contaminated land continues to be in a state of flux. Revised Statutory Guidance from Defra for the Contaminated Land Regime is due to go through Parliament in the coming months and this will contain new initiatives such as the “traffic light system” for assessment of Part 2A sites and incorporate the consideration of existing background concentrations (both rural and urban) for contaminants in soil.

Prior to these developments the Environment Agency published revised technical guidance and updated versions of the CLEA model in 2008 and 2009 but funding issues and re-organisations within the Agency left the job finished as updated guidance was not issued for some of the commonly occurring and ‘difficult’ contaminants. New Soil Guideline Value (SGV) reports were not produced for lead, polycyclic aromatic hydrocarbons (PAHs) and cyanides and recent developments in the toxicological understanding of these compounds mean that the TOX reports published in 2002 are now reasonably considered to be out of date. This leaves regulators and practitioners in a difficult position due to the absence of suitable technical guidance.

Assessments of lead toxicology by the European Food Standards Agency (EFSA) and Joint FAO/WHO Expert Committee on Food Additives (JECFA) have indicated that there are likely to be effects on the cognitive development of children (measured by loss of IQ) at much lower levels than previously thought. If used in CLEA to generate generic assessment criteria, the health criteria value derived by EFSA for dietary risk assessment of lead would result in the derivation of generic assessment criteria lower than the average value for lead in UK rural soils.

At the Society of Brownfield Risk Assessment (SoBRA) 2011 summer workshop on lead risk assessment for contaminated land I co-hosted a very lively debate on the toxicology of lead and attempts to select a health criteria value for use in human health risk assessment. The outcome of these disucssions will be contained in a SoBRA technical paper to assist practitioners in the risk assessment of this contaminant.