Air Quality Guidelines Global Update 2005 - World Health ...

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AIR QUALITY GUIDELINES
in 12 European countries (11). Applying dose−response information, primarily
from industrialized countries, the World Bank estimated the benefits of air pollution
control in Mexico City (12). Recently, Hubbell et al. (13) estimated both
the health and economic effects associated with exposure to current levels of
ground-level ozone in the United States, while USEPA (14,15) estimated the effects
associated with meeting alternative ambient standards for fine PM. An assessment
was conducted on the health impacts of air pollution and the potential
benefits of current and future control strategies in Europe under the Clean Air
for Europe (CAFE) programme (16,17). Additional methodological guidance for
estimating the health effects of air pollution is provided by Ostro (18) as part
of WHO’s Environmental Burden of Disease project, the USEPA Clean Air Act
Compliance Council (an independent scientific review panel for USEPA) (19),
the US National Research Council (20), the World Health Organization (21) and
from Europe, ExternE (22) and Sanderson & Hurley (23).
Finally, statistical software to calculate HIA is available (e.g. BenMAP from
USEPA and AirQ 2.2.3 from the WHO Regional Office for Europe), although decisions
on which epidemiological studies to use and how to apply them are left to
the software user. All of these efforts use CR functions culled from the epidemiological
literature, relating changes in air pollution measured at fixed site monitors
to increases in mortality and morbidity.
Inputs for the analysis
For a given city, country or region, quantitative assessment of the health impact
of outdoor air pollution is based on four components: (a) pre- and post-air-pollution
concentrations and exposure assessment; (b) size and composition of population
groups exposed to current levels of air pollution; (c) background incidence
of mortality and morbidity; and (d) CR functions (Fig 1).
Pre- and post-air-pollution concentrations
Analysts need to determine the current exposure of the population to ambient
pollution, based either on existing fixed-site monitors or on model-based estimates.
Ideally, these concentrations are based on several recent years of complete
data (to reduce the influence of an atypical year or season) from monitors that
are reasonably representative of population exposure. The monitors should not
be unduly influenced by local sources such as a nearby highway, factory or power
plant but should rather reflect exposures over a wide area. Typically, fixed-site,
population-oriented monitors have been averaged across a metropolitan area
to characterize air quality in epidemiological studies. Therefore, a similar metric
should be used in HIA. As an alternative to measured pollution concentrations,
the global burden of disease project relied on economic models to estimate
pollution concentrations for cities throughout the world (2). Besides the
current concentration, the analyst needs to determine a counterfactual such as