April 10, 2014 by Ed Stutt


27th March 2014 saw Defra publish the eagerly awaited output from the research project to develop Category 4 Screening Levels (C4SLs) for assessment of land affected by contamination. C4SLs are intended for use in determining whether land is ‘clearly not contaminated’ as defined by the revised Part 2A Statutory Guidance, i.e. Category 4 is where there is no risk or the level of risk to human health is acceptably low. The framework developed presents a departure from the conventional approach of defining ‘minimal risk’ and the derivation of C4SLs has involved the development of a new toxicological criterion, the ‘low level of toxicological concern’ (LLTC), alongside modifications to the exposure modelling previously used to determine soil guideline values (SGVs) and similar generic assessment criteria.

I was part of the project team that undertook this challenging research project, alongside other exposure modellers, toxicologists and risk analysts. The output published by Defra includes the main report detailing the development of a framework to derive C4SLs and the proposed screening levels for some of the most important and commonly encountered contaminants in the assessment of contaminated land. The accompanying policy document from Defra details the recommended C4SLs for arsenic, benzo(a)pyrene, lead, cadmium, benzene and hexavalent chromium.

Ed Stutt is a Principal Consultant at wca with 18 years experience as an environmental scientist working in academia and consultancy. His areas of expertise include the fate and transport of chemicals in the environment, contaminated land exposure and human health risk assessment. Prior to joining wca Ed spent four years at SLR Consulting where he was engaged in contaminated land risk assessment, working on both Part 2A sites and private developments. In addition to contributing to the development of C4SLs Ed was a co-author on the dioxins SGV report & several CLEA TOX reports, as well being the project manager for the initial work to develop soil screening values (SSVs) for ecological risk assessment of contaminated land.

Ed has recently been joined at wca by George Kowalczyk. George is an internationally recognised toxicologist who joins wca from Public Health England (previously Health Protection Agency and Department of Health) where he has had strategic roles in national chemicals policy and guidance, particularly for contaminated land.