Can cost-effectiveness analysis of control measures for persistent chemicals be improved? A critical evaluation of approaches for assessing "effectiveness"

Persistence, that is the ability of a chemical to accumulate in the environment over time, is a core concern triggering regulatory action under the European chemicals legislation REACH. Due to lacking quantitative information about environmental impacts and damage costs, cost-effectiveness analysis (CEA) has been applied for evaluating the performance of regulatory control measures. Different indicators for assessing the effectiveness of a control measure have been used, (i) the expected aggregate emission reduction, (ii) the change of the environmental mass at steady-state, and (iii) the change of the cumulative environmental stock. This paper examines the conceptual characteristics of these indicators when being used in CEA. The analysis elaborates on an illustrative example of three persistent chemicals with different intrinsic properties. We find that estimates of aggregate emission reduction and of the change of steady-state mass misrepresent the environmental pollution burden of persistent chemicals because they ignore the time path of pollution in the environment. This can induce misleading conclusions on the relative cost-effectiveness of control measures and can lead to an erroneous prioritization of measures. Cumulative stock estimates, while not being equivalent to quantitative risk or impact assessment, capture the time path of pollution in environmental media and, therefore, provide an approximation of the environmental impact potential of persistent chemicals. This is a prerequisite for a concern-driven evaluation of risk-management measures for persistent chemicals.