Limitations of the CLEA model when assessing human health risks from dioxins and furans in soil at an allotments site in Rochdale, NW England

Many allotments in the UK today are situated on urban brownfield areas which creates a potential human health risk from soil borne contamination. This paper looks specifically at the risks to allotment users at a site in Rochdale, UK, from polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD and PCDF). A contaminated land investigation was undertaken involving the collection and analysis of 24 soil samples from the top 0.0-0.3 m of the soil profile. Homogenised egg samples were also collected and analysed from plots where poultry were kept. The concentration of PCDD and PCDF in soil at the site varied from 0.69 to 13.62 mu g kg(-1); two plots out of a total of eight exceeded the soil guideline value (SGV) of 8 mu g kg(-1), however all plots fell below the site specific assessment criteria (SSAC) of 15.9 mu g kg(-1). Human health risks were assessed using the Environment Agency's contaminated land exposure assessment (CLEA) model. The assessment using CLEA alone did not provide enough evidence to indicate significant possibility of significant harm (SPOSH) across the entire allotment site. However, when the likely exposure from the soil was combined with potential exposure from consumption of site laid eggs, the results indicated that the potential risks could constitute SPOSH. This paper gives evidence to support the bioconcentration of PCDD and PCDF in eggs and highlights the importance of considering pollutant linkages outside the generic CLEA model.