1. 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.

2. 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.

3. 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.

4. 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

5. 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.

6. 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%

7. 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.

8. 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.

9. 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.

10. 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.