Appendix 9

European Environmental Quality Standard values relative to copper

The release of certain substances like heavy metals may lead to adverse effects on aquatic plants and animals. When substances are measured in the aqueous environment, it is usual to quote them as a concentration in the receiving medium of water. The initial unit of measurement is micrograms of substance per litre of water (µg/l).

Aquatic releases of ecotoxic substances can be compared on the basis of how much dilution in receiving waters is required before the concentration reaches a recognised quality standard. Many substances are toxic to some degree, but the more toxic substances may be especially identified by having specific concentration standards set in receiving waters. In Europe, these standards are known as Environment Quality Standards (EQS). Where there is no formal EQS, we have used figures that have been proposed by the regulatory authorities. In the absence of either of these sources of data, figures derived by Zeneca's Brixham Environmental Laboratory, based upon known toxicological information have been used ¹. The potency factor for this category is derived from the EQS, expressed as µg/1. EQS values in seawater conditions have been used.

We use the reciprocal of the EQS as our potency factor so that we always multiply the emission by the potency factor. The reciprocal factor is then divided by the factor for copper so that the aquatic ecotoxic releases are compared to category standards.

The potential impact for a metal is defined as tonne/year released, multiplied by the factor relative to copper. The units of this parameter are tonne/year copper equivalent.

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1. Brixham Environmental Laboratory; Implementation of controls on the discharge of dangerous substances to water in the UK, Zeneca Internal Report (unpublished).