Animal Waste, Water Quality and Human Health

434Animal Waste, Water Quality and Human Healthfor a fixed amount of funding that has been allocated to achieve a policy objective.The drawback of cost-effectiveness analysis is that it does not identify the benefitsof actions or the willingness of society to pay for improvements. For these reasons,CBA is, if practicable, the evaluation approach of choice.The various steps distinguished in a CEA are described below:Step 1: Define the objective involved.Step 2: Determine the extent to which the objective is met.Step 3: Identify sources of pollution and impacts now and in the future over theappropriate time horizon.Step 4: Identify measures to bridge the gap between the reference (baseline) andtarget situation.Step 5: Assess the effectiveness of these measures in reaching the objective.Step 6: Assess the costs of these measures.Step 7: Rank measures in terms of increasing unit costs.Step 8: Assess the least cost way to reach the objective.Once again, carrying out a CEA is a multi-disciplinary exercise. A number ofapproaches are used in practice at varying levels of complexity, scale,comprehensiveness and completeness for carrying out a CEA. These arediscussed, for example, in Zhang & Folmer (1998). A distinction is madebetween bottom-up and top-down approaches. The bottom-up approach focuseson technological details of measures and their impact on individual enterprises(micro level), whereas top-down approaches usually consider the widereconomic impacts of pollution abatement measures and strategies, often withoutdetailed technical specification of the proposed measures (macro level).Economic evaluation using CBA or CEA involves multiple assumptions andoften produces uncertain results. Estimates of the costs and benefits associatedwith alternative interventions rely on data to the extent that they are available,relevant, and accurate, but also rely on judgments, values, assumptions, andextrapolations. When undertaking economic evaluation, the sources ofuncertainty should be identified, characterized, and communicated clearly, forexample by conducting a sensitivity analysis. In this respect, reporting on theuncertainties and conducting sensitivity analyses are important components ofany evaluation and the presentation of benefits and costs of an interventionshould not be expressed as though they are precise measures of actual economiccosts and benefits.It may also be necessary to consider intervention options that differ in thetemporal pattern of benefits and costs, or that differ in their duration. It is then