By contrast with directly countable events, which can
be listed in national health statistics (eg, deaths or
injuries due to traffic accidents), it is not possible todirectly identify the victims of complex substances and
mixtures with cumulative toxicity, such as smoking or air
pollutants. Neither are the health-relevant characteristics
of the exposure unanimously defined, nor are the health
outcomes specifically linked to air pollution only.
Therefore, uncertainty remains an inherent
characteristic of any attempt to derive attributable cases.
We prudently dealt with uncertainty, deriving the
number of cases “at least” attributable to air pollution.
We did not include all health outcomes associated with
ambient air. For mortality, we ignored potential effects
on newborn babies or infants.18 Although infant
mortality is low in the countries considered, and thus the
number of attributable cases is small, the impact on
years of life lost, and therefore the economic valuation,
could be considerable.