Expressing air pollution-induced health-related externalities in physical terms with the help of DALYs

The unintended impacts of industrial activity on human health and the environment have regularly been assessed and monetised (referred to as "external costs"). External costs are, however, a rather abstract aggregate so that decision makers cannot easily relate them to tangible impacts. At the same time, physical health impact indicators have different units that cannot readily be compared and communicated in a joint way. To support better informed decisions at policy or company level, we propose and demonstrate a way to facilitate communication on non-monetized, that is, physical health indicators quantified in studies. The concept Disability-Adjusted Life Year (DALY) is chosen as metric due to its widespread use. We establish a comprehensive and consistent set of six health endpoints caused by particles and ozone, and derive related up-to-date DALYs. Further we apply the DALY values to a French smart grid demonstration project. Owing to its size, the gains in terms of reduced DALYs are however small. In contrast to external cost assessments, in the frame of which morbidity endpoints usually contribute to around 10-15%, they are found to be insubstantial in the overall DALY score (i.e. below 1%). This is because DALYs only consider time losses weighted by severity while external costs also factor in further welfare effects, i.e. combining resource, disutility and opportunity costs of illness. As a result, methodological limitations, mainly existing for the morbidity-related DALY values, appear to be less of concern. Overall, using the DALYs with and without morbidity impacts is justifiable. Either choice in the communication of health-related physical externalities induces the need to explain the limitations in terms of the treatment of morbidity endpoints (notably their definition and the disability weights used) or their complete disregard.