BACKGROUND : The systematic evaluation of the results of time-series studies of air pollution is challenged
by differences in model specification and publication bias.
METHODS : We evaluated the associations of inhalable particulate matter (PM) with an aerodynamic
diameter of 10 μm or less (PM10) and fine PM with an aerodynamic diameter of 2.5 μm
or less (PM2.5) with daily all-cause, cardiovascular, and respiratory mortality across multiple
countries or regions. Daily data on mortality and air pollution were collected from 652
cities in 24 countries or regions. We used overdispersed generalized additive models with
random-effects meta-analysis to investigate the associations. Two-pollutant models were
fitted to test the robustness of the associations. Concentration–response curves from each
city were pooled to allow global estimates to be derived.
RESULTS : On average, an increase of 10 μg per cubic meter in the 2-day moving average of PM10
concentration, which represents the average over the current and previous day, was associated
with increases of 0.44% (95% confidence interval [CI], 0.39 to 0.50) in daily all-cause
mortality, 0.36% (95% CI, 0.30 to 0.43) in daily cardiovascular mortality, and 0.47% (95%
CI, 0.35 to 0.58) in daily respiratory mortality. The corresponding increases in daily mortality
for the same change in PM2.5 concentration were 0.68% (95% CI, 0.59 to 0.77), 0.55%
(95% CI, 0.45 to 0.66), and 0.74% (95% CI, 0.53 to 0.95). These associations remained
significant after adjustment for gaseous pollutants. Associations were stronger in locations
with lower annual mean PM concentrations and higher annual mean temperatures. The
pooled concentration–response curves showed a consistent increase in daily mortality with
increasing PM concentration, with steeper slopes at lower PM concentrations.
CONCLUSIONS : Our data show independent associations between short-term exposure to PM10 and PM2.5
and daily all-cause, cardiovascular, and respiratory mortality in more than 600 cities across
the globe. These data reinforce the evidence of a link between mortality and PM concentration
established in regional and local studies.