160
A.R.D. Stebbing . R.I. Willows
In relating toxicological to an economic analysis of environmental contamination, it is clear that an economic optimum level of contamination (where MAC and
MDC intersect) would permit higher levels of inputs than would be desirable on
ecological grounds alone. It is evident that, near threshold concentrations, disproportionately large effects may result from small changes in concentration. Since
many environmental factors influence the precise threshold, a safety margin is essential. That the utilisation of assimilative capacity then becomes less economically efficient indicates the cost of precaution and the reduction of risk.
8.4
Chemical Versus Biological Monitoring of Assimilative Capacity
Enyironmentallegislation is both enabled and constrained by the monitoring techniques necessary to implement it. Progress in adopting more effective legislation is
constrained by advances in research and monitoring techniques. Often the adoption
of such techniques by a regulator may also depend on simplicity of application and
cost-effectiveness, as well as efficacy.
Chemical analysis presently provides the most important means by which regulators monitor the effectiveness of environmental legislation. The EQS itself is expected
to provide the link between chemical contamination and its biological rele-vance, since
it is based on laboratory toxicity data, as already discussed (see Section 8.3.3). However, it is significant, when considering the role of particles and sediments as binding
sites for many contaminants, that there are no EQS for them in the particulate phase.
We ask whether it is better to monitor "targets" or "factors" (Holdgate 1979), the chemical causes of pollution or their biological effects, or some integration of the two approaches.
To present the arguments clearly, we consider first the advantages and disadvantages
of an approach that depends on analytical chemistry (Section 8.4.1), before considering one that relies on biological techniques (Section 8.4.2). However, it is evident that
monitoring of chemical contaminants that does not relate to their biological consequences or effects is of little benefit in determining the use of assimilative capacity.
For those that do, it is only necessary to control contaminants that have biologically harmful consequences. It is essential to establish causality rigorously, to provide an adequate
body of evidence to impose regulation and control with the minimum of delay and
without excessive cost. Thus after considering the arguments for chemical and biological approaches alone, we go on to advocate an integrated approach (Section 8.4.3), as
we will demonstrate that while chemical analyses do not adequately indicate toxic
impacts, biological techniques do not adequately identify their chemical causes.
8.4.1
Chemical Monitoring
A chemical approach to the control of pollution was appropriate for an era when contamination of the water system was principally by point source inputs of effluents with relatively few chemical constituents of concern entering rivers; essentially one dimensional
systems with unidirectional flow. Contamination of the water course is now more complex because of the numbers of chemicals released into the environment, the many and
diffuse routes that they may take, and that our qmcerns have now extended from rivers
A.R.D. Stebbing . R.I. Willows
In relating toxicological to an economic analysis of environmental contamination, it is clear that an economic optimum level of contamination (where MAC and
MDC intersect) would permit higher levels of inputs than would be desirable on
ecological grounds alone. It is evident that, near threshold concentrations, disproportionately large effects may result from small changes in concentration. Since
many environmental factors influence the precise threshold, a safety margin is essential. That the utilisation of assimilative capacity then becomes less economically efficient indicates the cost of precaution and the reduction of risk.
8.4
Chemical Versus Biological Monitoring of Assimilative Capacity
Enyironmentallegislation is both enabled and constrained by the monitoring techniques necessary to implement it. Progress in adopting more effective legislation is
constrained by advances in research and monitoring techniques. Often the adoption
of such techniques by a regulator may also depend on simplicity of application and
cost-effectiveness, as well as efficacy.
Chemical analysis presently provides the most important means by which regulators monitor the effectiveness of environmental legislation. The EQS itself is expected
to provide the link between chemical contamination and its biological rele-vance, since
it is based on laboratory toxicity data, as already discussed (see Section 8.3.3). However, it is significant, when considering the role of particles and sediments as binding
sites for many contaminants, that there are no EQS for them in the particulate phase.
We ask whether it is better to monitor "targets" or "factors" (Holdgate 1979), the chemical causes of pollution or their biological effects, or some integration of the two approaches.
To present the arguments clearly, we consider first the advantages and disadvantages
of an approach that depends on analytical chemistry (Section 8.4.1), before considering one that relies on biological techniques (Section 8.4.2). However, it is evident that
monitoring of chemical contaminants that does not relate to their biological consequences or effects is of little benefit in determining the use of assimilative capacity.
For those that do, it is only necessary to control contaminants that have biologically harmful consequences. It is essential to establish causality rigorously, to provide an adequate
body of evidence to impose regulation and control with the minimum of delay and
without excessive cost. Thus after considering the arguments for chemical and biological approaches alone, we go on to advocate an integrated approach (Section 8.4.3), as
we will demonstrate that while chemical analyses do not adequately indicate toxic
impacts, biological techniques do not adequately identify their chemical causes.
8.4.1
Chemical Monitoring
A chemical approach to the control of pollution was appropriate for an era when contamination of the water system was principally by point source inputs of effluents with relatively few chemical constituents of concern entering rivers; essentially one dimensional
systems with unidirectional flow. Contamination of the water course is now more complex because of the numbers of chemicals released into the environment, the many and
diffuse routes that they may take, and that our qmcerns have now extended from rivers