ASSESSING THE ENVIRONMENTAL CONSEQUENCE OF POTENTIAL MAJOR ACCIDENTS Andrew Hitchings, Policy Advisor, UK Environment Agency Briefly revisit presentation given by the UK CA at Implementing Seveso II conference in London Nov 2000.

WHY? Seveso II, Annex III: “Systematic identification of major hazards …. and assessment of their likelihood and severity” Why ? Seveso II, Annex III "Systematic identification of major hazards... and assessment of their likelihood and severity" Seveso II requires a risk based approach and extends to consideration of health and safety of people but also broader environment.

dose-response / surrogate standards distribution modelling HOW ? Release Exposure Harm fault-tree and event -tree analysis dose-response / surrogate standards distribution modelling source pathway receptor source pathway receptor source pathway receptor All risks can be assessed by looking at three key components: source, pathway and receptor (sometimes called a target). Particularly valuable when looking for blockages in the source- pathway-receptor which prevent a MA and can powerful in screening. Screening - scale of release & frequency.

ENVIRONMENTAL RISK ASSESSMENT Conceptual models and source-pathway receptor analysis; risk screening and prioritisation Identify hazard substances dangerous to the environment used at site and describe all aspects of the site and the surrounding environment HAZOP / Fault and event tree analysis Identify initial events that may result in a major accident Fault and event tree analysis Reference to relevant environmental criteria Estimate the frequency/ probability of initial release event occurring Quantify the potential environmental impact following a release Source-pathway receptor analysis Generic / tailored risk assessment with fault and event tree analysis and/or distribution modelling Identify on-site exposure routes following initial release Estimate the likelihood of such environmental impacts occurring Generic model for COMAH ERA from UK CA. Point of slide show that risk assessment process for the wider environment is same as for direct protection of human health which for UK focus of Seveso I implementation. Same tools are valid and applicable such as HAZOP, Fault and Event tree analysis, atmospheric or water bourne dispersion models. This area where the problems for ERA as applicable to COMAH come. Lack of relevant environmental criteria. Fault and event tree analysis Criteria Description of environmental risk acceptance criteria for a Major Accident To The Environment Identify all risk management measures to manage unacceptable MATTE risks Assess the acceptability/ tolerability of the risks Reference to relevant environmental criteria

CHALLENGES (1) Environment more complicated Many more receptors flora, fauna, built environment More pathways ground water, surface water, air, land Different media water, air, land, soil Where I talk about environment I mean excluding human health. UK The HSE concerned with protection of human health and Environment agencies SEPA & EA with wider environment.

CHALLENGES (2) Lack of Dose-Response Data species level toxicity data at inappropriate end points either NOEC or LC50 population level standards (Environmental Quality standards) at inappropriate end point for many dangerous substance/receptor combinations basic lack of data NOEC - no observed effect concentration LC 50 - lethal to 50%

SOLUTION 1 Major Accidents to the Environment (MATTE) defined in impact terms “the more extensive the areas and quantities of natural & semi-natural resource damaged, the longer the effects are likely to last, and the more intensive or severe these effects … the more likely event will be regarded as a MATTE” (NNRs, SSSI, MNRs) >0.5ha (or 10%) adversely affected, >10% of habitat or population adversely affected (SAC, SPA, Ramsar) >0.5ha (or 5%) adversely affected, >5% of habitat or population adversely affected UK Government published thresholds for damage across various receptors that would indicate a MATTE. Very helpful after the event but again have problems in predictive risk assessment stage.

SOLUTION 2 Media specific dose-response surrogates environmental harm doses for dangerous substances to complement human health precautionary principle Proportionate Environmental Risk Assessment focus on technical measures not environmental risk assessment assumptions/methods Develop media specific dose response surrogates which try and agree with industry. Simplification & consistency. Found some difficulties in UK with desire to get into regulator/regulated arguments about whether x concentration kills 4 or 5% and that counter-productive and should be putting effort into the technical & other preventative measures in place.

SOLUTION (?) 3 Increasing chemical concentration LC/EC50 for most sensitive species* LC/EC50 values for other, less sensitive species* EQS or EAL COMAH threshold should lie in this range EQS adding another level COMAH thresholds. Figure shows where it should lie but methodology and testing with various dangerous substances. Chemical impacts rather than thermal or explosion impacts.

WHO? UK Environment Agencies EU Challenge research into developing environmental doses EU Challenge scope for collaboration between member states industry and competent authorities UK will be happy to publish our research and collaborative ventures.