Short-Term Exposure to Fine Particulate Matter and Nitrogen Dioxide and Mortality in 4 Countries

Ma Y, Nobile F, Marb A, Dubrow R, Stafoggia M, Breitner S, Kinney PL, Chen K.  JAMA Netw Open. 2024 Mar 4;7(3):e2354607. doi: 10.1001/jamanetworkopen.2023.54607. PMID: 38427355.

Key Points

Question  What are the associations between short-term changes in fine particulate matter (PM_2.5) and nitrogen dioxide (NO₂) concentrations and changes in daily all-cause mortality rates?

Findings  This cross-sectional study of more than 8.9 million deaths found that a 10-μg/m³ increase in daily PM_2.5 concentrations was associated with increases in daily all-cause deaths per 100 000 people of 0.01 in Jiangsu, China, 0.03 in California, 0.10 in central-southern Italy, and 0.04 in Germany; corresponding increases in mortality rates for the same increase in NO₂ concentrations were 0.04, 0.03, 0.10, and 0.05, respectively.

Meaning  The findings of this study add to the growing evidence that increases in short-term exposures to PM_2.5 and NO₂ may be associated with increases in mortality rates.

Abstract

Importance  The association between short-term exposure to air pollution and mortality has been widely documented worldwide; however, few studies have applied causal modeling approaches to account for unmeasured confounders that vary across time and space.

Objective  To estimate the association between short-term changes in fine particulate matter (PM_2.5) and nitrogen dioxide (NO₂) concentrations and changes in daily all-cause mortality rates using a causal modeling approach.

Design, Setting, and Participants  This cross-sectional study used air pollution and mortality data from Jiangsu, China; California; central-southern Italy; and Germany with interactive fixed-effects models to control for both measured and unmeasured spatiotemporal confounders. A total of 8 963 352 deaths in these 4 regions from January 1, 2015, to December 31, 2019, were included in the study. Data were analyzed from June 1, 2021, to October 30, 2023.

Exposure  Day-to-day changes in county- or municipality-level mean PM_2.5 and NO₂ concentrations.

Main Outcomes and Measures  Day-to-day changes in county- or municipality-level all-cause mortality rates.

Daily Mean Fine Particulate Matter (PM_2.5) and Nitrogen Dioxide (NO₂)
Concentrations in Each Spatial Unit in All Study Regions

Results  Among the 8 963 352 deaths in the 4 study regions, a 10-μg/m³ increase in daily PM_2.5 concentration was associated with an increase in daily all-cause deaths per 100 000 people of 0.01 (95% CI, 0.001-0.01) in Jiangsu, 0.03 (95% CI, 0.004-0.05) in California, 0.10 (95% CI, 0.07-0.14) in central-southern Italy, and 0.04 (95% CI, 0.02- 0.05) in Germany. The corresponding increases in mortality rates for a 10-μg/m³ increase in NO₂ concentration were 0.04 (95% CI, 0.03-0.05) in Jiangsu, 0.03 (95% CI, 0.01-0.04) in California, 0.10 (95% CI, 0.05-0.15) in central-southern Italy, and 0.05 (95% CI, 0.04-0.06) in Germany. Significant effect modifications by age were observed in all regions, by sex in Germany (eg, 0.05 [95% CI, 0.03-0.06] for females in the single-pollutant model of PM_2.5), and by urbanicity in Jiangsu (0.07 [95% CI, 0.04-0.10] for rural counties in the 2-pollutant model of NO₂).

Conclusions and Relevance  The findings of this cross-sectional study contribute to the growing body of evidence that increases in short-term exposures to PM_2.5 and NO₂ may be associated with increases in all-cause mortality rates. The interactive fixed-effects model, which controls for unmeasured spatial and temporal confounders, including unmeasured time-varying confounders in different spatial units, can be used to estimate associations between changes in short-term exposure to air pollution and changes in health outcomes.

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