Better accounting for long-term health effects in economic assessments: an illustration for air pollution in the Canton of Geneva

Objectives: We propose a general framework for estimating long-term health and economic effects that takes into account four time-related aspects.We apply it to a reduction in exposure to air pollution in the Canton of Geneva. Study design: Methodological developments on the evaluation of long-term economic and health benefits, with an empirical illustration. Methods: We propose a unified frameworkdthe comprehensive impact assessment (CIA)dto assess the long-term effects of morbidity and mortality in health and economic terms. This framework takes full account of four time-related issues: cessation lag, policy/technical implementation timeframe, discounting and time horizon. We compare its results with those obtained from standard quantitative health impact assessment (QHIA) in an empirical illustration involving air pollution reduction in the canton of Geneva. Results: We find that by neglecting time issues, the QHIA estimates greater health and economic benefits than the CIA. The overestimation is about 50% under reasonable assumptions and increases ceteris paribus with the magnitude of the cessation lag and the discount factor. It decreases both with the time horizon and with the implementation timeframe. Conclusion: A proper evaluation of long-term health and economic effects is an important issue when they are to be used in cost-benefit analyses, particularly for mortality, which often represents the largest fraction. We recommend using the CIA to calculate more accurate values.