Official websites use. Share sensitive information only on official, secure websites. Address correspondence to James K. Recent literature reveals misunderstanding about these concepts. Total life years lost in a population due to exposure can be estimated but cannot be disaggregated by age or cause of death.
When individuals facing larger or smaller changes in mortality risk cannot be identified, the mean change in population hazard is sufficient for valuation; otherwise, the economic value can depend on the distribution of risk reductions.
Health effects of environmental exposures are quantified for use in impact studies and environmental burden of disease EBD studies. EBD studies evaluate the harms to health from exposure compared with some counterfactual situation, to provide perspective on the importance of different exposures and the possible benefits of reducing them.
The problem is that etiologic deaths are not statistically identified: the time at which an exposed individual dies can be observed, but the time at which she would have died had she not been exposed is counterfactual and cannot be observed.
From mortality data alone, one cannot distinguish between situations in which a few people die much earlier than they would have if unexposed and situations in which many people die a little earlier than they would have if unexposed. The fraction of deaths in an exposed population that are etiologic can be bounded but the bounds are much farther apart than the ends of typical confidence or uncertainty intervals presented in the literature. The total number of life years lost due to exposure is statistically identified but cannot be disaggregated into life years lost conditional on death at specified ages or from specified diseases, as these quantities are not statistically identified.
