Prolonged short-term exposure to a high concentration of ambient fine particulate matter and effect modification on daily mortality

Lim, Hyungryul; Bae, Sanghyuk; Choi, Jonghyuk; Choi, Kyung-Hwa; Bae, Hyun-Joo; Kim, Soontae; Ha, Mina; Kwon, Ho-Jang

doi:2022.0.0.e2022052

Original article

Epidemiology and Health 2022;e2022052.
DOI: https://doi.org/10.4178/epih.e2022052 [Accepted] Published online Jun 9, 2022.

Prolonged short-term exposure to a high concentration of ambient fine particulate matter and effect modification on daily mortality

¹Department of Preventive Medicine, College of Medicine, Dankook University, Cheonan, Republic of Korea, Cheonan, Korea
²Department of Preventive Medicine, College of Medicine, The Catholic University of Korea, Seoul, Republic of Korea, Seoul, Korea
³Korea Environment Institute, Sejong, Republic of Korea, Sejong, Korea
⁴Department of Environmental and Safety Engineering, Ajou University, Suwon, Republic of Korea, Suwon, Korea

Correspondence Ho-Jang Kwon ,Email: hojangkwon@gmail.com

Received: Feb 18, 2022 Accepted after revision: Jun 9, 2022

Abstract

Objectives:
Although evidence for the short-term effect of fine particulate matter (PM_2.5) on daily mortality is very high, epidemiologic studies on the effect of prolonged continuous exposure to high concentrations are rare. This study aimed to investigate how the size of the mortality effect of PM_2.5 would be modified when a high concentration period persisted.
Method:
We used daily mortality counts, simulated levels of daily PM_2.5, measured daily mean temperatures, and relative humidity data from seven metropolitan cities from 2006 to 2019. Generalized additive models (GAMs) with quasi-Poisson distribution in seven cities and random-effects meta-analyses were used to pool city-specific effects. To investigate effect modification by continuous exposure to prolonged high concentrations, we applied categorical consecutive day variables to the GAMs as effect modification terms for PM_2.5.
Results:
The mortality risk was increased by 0.33% (95% CI, 0.16–0.50), 0.47% (95% CI, -0.09–1.04), and 0.26% (95% CI, -0.08–0.60) for all-cause, respiratory, and cardiovascular diseases, respectively with increase of 10 μg/m³ of PM_2.5 concentration. The risk for all-cause mortality per 10 μg/m³ increase in PM_2.5 on the first and fourth consecutive days was significantly increased by 0.63% (95% CI, 0.20–1.06) and 0.36% (95% CI, 0.01–0.70), respectively.
Conclusions:
We found a significantly increased risk of all-cause, respiratory, and cardiovascular mortality for daily PM2.5, when the day of high concentration began and the days lasted for more than four days with a high concentration ≥35 μg/m³. The elderly showed a stronger effect of persistently high PM_2.5.

Keywords: Air pollution; Fine particulate matter; PM2.5; Short-term exposure; Mortality; Prolonged exposure