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. 2019 Aug 22;381(8):705-715.
doi: 10.1056/NEJMoa1817364.

Ambient Particulate Air Pollution and Daily Mortality in 652 Cities

Affiliations

Ambient Particulate Air Pollution and Daily Mortality in 652 Cities

Cong Liu et al. N Engl J Med. .

Abstract

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. (Funded by the National Natural Science Foundation of China and others.).

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Conflict of interest statement

No potential conflict of interest relevant to this article was reported.

Figures

Figure 1.
Figure 1.. Distribution of the Cities with Data on PM10.
Shown is the geographic distribution of the 598 cities in the 24 countries and regions that had available data on particulate matter with an aerodynamic diameter of 10 μm or less (PM10) and were included in the analysis. Also shown are the annual mean PM10 concentrations. See the interactive map, available at NEJM.org.
Figure 2.
Figure 2.. Distribution of Cities with Data on PM2.5.
Shown is the geographic distribution of the 499 cities in the 16 countries and regions that had data on particulate matter with an aerodynamic diameter of 2.5 μm or less (PM2.5) and were included in the analysis. Also shown are the annual mean PM2.5 concentrations. See the interactive map, available at NEJM.org.
Figure 3.
Figure 3.. Pooled Concentration–Response Curves.
Shown are the pooled concentration–response curves for the associations of 2-day moving average concentrations of PM10 (Panel A) and PM2.5 (Panel B) with daily all-cause mortality. The y axis represents the percentage difference from the pooled mean effect (as derived from the entire range of PM concentrations at each location) on mortality. Zero on the y axis represents the pooled mean effect, and the portion of the curve below zero denotes a smaller estimate than the mean effect. The dashed lines represent the air-quality guidelines or standards for 24-hour average concentrations of PM10 or PM2.5 according to the World Health Organization Air Quality Guidelines (WHO AQG), WHO Interim Target 1 (IT-1), WHO Interim Target 2 (IT-2), WHO Interim Target 3 (IT-3), European Union Air Quality Directive (EU AQD), U.S. National Ambient Air Quality Standard (NAAQS), and China Air Quality Standard (AQS).

Comment in

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