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An index of environmental harm

Compared to human health and technological risk assessment, environmental and ecological risk assessment is a relatively new scientific endeavour. In 1995, ASK and Hungarian consultancy AGEL-CBI joined a research consortium carrying out early work in this field in applying and testing a concept called the environmental harm index (EHI).

The case:
The operator of a hazardous installation governed by Seveso Directive is legally obliged to consider potential major accidents to the environment in the same way as major accidents affecting the safety of the public, in a degree of detail proportionate to the risk. But damage to an ecosystem is difficult to assess qualitatively, let alone quantitatively, even in principle, and the difficulty is compounded by the dearth of relevant data. Nevertheless, when ASK joined the team, researchers from the UK and Netherlands had already published preliminary work on the EHI. At this stage, it was a purely theoretical concept developed to assess the severity of a potential accident - such as a spill of a toxic substance - in an aquatic ecosystem.

ASK’s involvement:
ASK was brought in to carry out a critical review of the work and assist in extending its use to real ecosystems, paying special attention to lakes. Working together with AGEL-CBI, ASK advised on how the EHI might need to be adapted to lakes, which differ in several important ways from other aquatic ecosystems. For instance, lakes tend to retain pollutants far longer than rivers or estuaries and therefore accumulation of doses needs to be taken into account.

The result:
Having tested the EHI against a number of reference incidents, the team confirmed that its predictions were reasonable. Based on these results, it was possible to create a scheme for assessing risk based on combined values of EHI and frequency of potential accidents, analogous to the familiar schemes for assessing societal risk.

A summary of this work appears in Major Accidents to the Environment by ASK’s Ivan Vince.

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