Making up for air pollution related mortality and accounting for the number of deaths has become an important environmental indicator in its own right, but differences across the Atlantic over how to account for these are making it difficult to find common ground in climate policy appraisals, where co-benefits from reducing air pollution of fossil fuels is to be factored in. This article revisits established quantification methodologies for air pollution related mortality applied by government agencies in USA and EU. Demographic lifetables are applied to explore uncertainties over latency periods and the number of affected victims. These lifetable simulations are based on WHO consensus estimates for the mortality risk ratio related to long-term exposures and suggest an average loss of life expectancy of 9–11 years for an annual air pollution exposure increase of 10 ugPM 2.5 /m3. With a common OECD base value approach the air pollution costs related to fossil fuels are found to be about 3 times lower with EU versus US methodology.