Your head on a block-Part 2A decisions Dr Naomi Earl Associate Director Head of Human Health Risk Assessment Land Quality Atkins Limited

23 September 2009Your head on a block-Part 2A decisions The Part 2A decision Is the condition for “significant possibility of significant harm” to human health being met on site by one or more pollutant linkages “If the amount of the pollutant in the pollutant linkage in question…which a human being might take in….would represent an unacceptable intake…assessed on the basis of relevant information on the toxicological properties of that pollutant” (Table B, Chapter A Annex 3)

23 September 2009Your head on a block-Part 2A decisions What does “unacceptable” mean? In the absence of overarching national guidance, depends on local authority opinion  Contaminated land officer/Environmental health officer?  CLO/EHO’s line manager?  Councillors?  Lawyers?  All of the above? All of these groups comprise individuals with different levels of knowledge and attitudes to risk

23 September 2009Your head on a block-Part 2A decisions Risks of getting it “wrong” Too precautionary Sets local precedent which may result in high proportion of local area being “contaminated” Potential for blight Out of step with neighbouring authorities Potential for legal challenge ?Site may not be priority for funding? Insufficiently precautionary –harder to prove but Out of step with neighbouring authorities Local pressure groups (Risk of significant harm?)

23 September 2009Your head on a block-Part 2A decisions Some key aspects to consider Evidence for level of intake Toxicology Scope for refining Conceptual Site Model May help to consider what approach you might take to some of these in advance of any site investigation

23 September 2009Your head on a block-Part 2A decisions Evidence for level of intake “Lies, damned lies and statistics” New CIEH guidance-make sure you use the correct test!  Upper confidence level-”How confident can I be that a representative site concentration lies below assessment criterion?”  Lower confidence level “How confident can I be that representative site concentration lies above assessment criterion” Does exotic distribution derived from statistical tool mask two different populations? Care how you “mix and match” targeted and non-targeted results

23 September 2009Your head on a block-Part 2A decisions Evidence for level of intake –statistics don’t tell the whole story No substitute for “eyeballing” data up front Do there appear to be two populations visually, even if statistics say not? e.g. when a “zone” covers a large area, with more than one property lying within a hotspot May “dilute” genuine hotspot Hotspot may raise mean of whole zone so more properties considered than should be May need to be prepared to reconsider initial zoning depending on results of investigation

23 September 2009Your head on a block-Part 2A decisions Evidence for level of intake – how certain do you want/need to be? Unexplained solitary high concentrations Initial Scenario Confidence in laboratory data and precise recording of visual and olfactory indicators critical

23 September 2009Your head on a block-Part 2A decisions Is it like this one?…. …or like this one? Consider further SI to answer… Consider including contingency to go back to certain percentage properties?

23 September 2009Your head on a block-Part 2A decisions Toxicology-the underlying basis Complex and province of experts but some basic questions to consider: What is effect that Health Criteria Value based on? Would it meet criteria for “significant harm”? Is there a consensus between various expert organisations? Do you understand uncertainty factors used-(what for, how many) ?

23 September 2009Your head on a block-Part 2A decisions Toxicology-mean daily intakes Calculated or 50% rule? Dietary intake based on: mean estimates in food or upper bound estimates? mean consumption rates or higher level consumers? Water intake based on: mean drinking water levels? maximum measured drinking water levels? drinking water standards? Air intake based on: national data? urban data? mean estimates or upper estimates? old dataset, recent dataset or combined dataset?

23 September 2009Your head on a block-Part 2A decisions Is there scope to refine the CSM? Which pathways driving risks for contaminants of concern? What are key uncertainties in these pathways? Can these uncertainties be reduced by collection of more data Vapour sampling if vapour pathway risk driver? Bioaccessibility data if soil ingestion risk driver? Site specific plant uptake factor? Further information about form contaminant is in?

23 September 2009Your head on a block-Part 2A decisions Other Factors What would you personally consider a significant margin of exceedance of your SSAC and does it depend on the substance (and do your colleagues agree)? What decisions have been made by the local contaminated land group? Do you want to take background concentrations of local soils into account? Comparison of local air quality to estimated air concentrations from soil contamination?