Third, the economic valuation estimates used in this ExternE analysis are from recent stated preference studies conducted in France, Italy, and United Kingdom (Alberini et al., 2006b). Their selected central estimate of EUR 50,000 per life year was derived from the median WTP value for the 5 in 1,000 mortality risk change over 10 years (median VSL was about EUR1.1 million). The ExternE authors converted this 10-year mortality risk change to its equivalent in increased life expectancy for each age/gender cohort and calculated the VSLY implicit in the WTP responses.
As this overview has suggested, there is a broad and deep literature documenting a range of health effects from exposure to ozone, and this has had an important role in the setting and implementation of NAAQS for ozone for over 35 years. In considering whether and how the recent studies of ozone and mortality should be incorporated in estimating benefits going forward, the Committee focused on two primary areas of questions:
The Robustness of the Ozone Mortality Studies. The estimation from epidemiologic evidence of health impacts, and the economic value of those impacts, requires confidence, as noted above, that ozone exposures can adequately be separated from other exposures in the epidemiology studies and that the epidemiology has adequately controlled for possible confounding factors. Although a number of others in Europe and California have made the judgment that these studies are adequate, the Committee was charged to make an independent determination on these questions. These questions are addressed in detail by the Committee in Chapters 3 and 4.
The Appropriate Methods for Estimating the Value of Potential Ozone Mortality Benefits. If the epidemiology studies provide adequate evidence for the estimation of mortality impacts, there are important questions about the appropriate methods for estimating the value of such impacts that are described initially above, and are addressed in detail in Chapter 5.