Acute effects of air pollution on all-cause mortality: a natural experiment from haze control measures in Chiang Mai Province, Thailand

Nitaya Vajanapoom; Patcharee Kooncumchoo; Thuan-Quoc Thach

doi:10.7717/peerj.9207

Acute effects of air pollution on all-cause mortality: a natural experiment from haze control measures in Chiang Mai Province, Thailand

PeerJ. 2020 May 27:8:e9207. doi: 10.7717/peerj.9207. eCollection 2020.

Authors

Nitaya Vajanapoom¹, Patcharee Kooncumchoo², Thuan-Quoc Thach³

Affiliations

¹ Center of Excellence in Global Health, Faculty of Public Health, Thammasat University, Pathumtani, Thailand.
² Faculty of Allied Health Sciences, Thammasat University, Pathumtani, Thailand.
³ School of Public Health, The University of Hong Kong, Hong Kong, China.

Abstract

Background: Serious haze episodes have been a seasonal event in Chiang Mai province for more than a decade. In 2008, local government agencies introduced comprehensive measures to control haze and limit its impacts on public health. This study assessed the acute effects of ambient air pollutants on all-cause mortality before and after the introduction of those haze control measures.

Methods: We obtained daily mortality counts and data on mass concentrations of particulate matter <10 micron in aerodynamic diameter (PM₁₀), gaseous pollutants (SO₂, NO₂, O₃, and CO), and meteorology in Chiang Mai Province between January 2002 and December 2016. We analyzed the data using a case-crossover approach adjusting for temperature, relative humidity, seasonality, and day-of-week. We assessed change in the excess risks of all-cause mortality associated with an increase in interquartile range (IQR) of pollutant concentration before and after control measures came into force.

Results: We found decreased PM₁₀ levels and markedly reduced excess risks of daily mortality associated with an IQR increase in PM₁₀ concentrations in the years after haze-control measures were implemented (2009-2016). We found mixed results for gaseous pollutants: SO₂ showed no significant change in excess risk of daily mortality throughout the study period, while NO₂ and CO showed significant excess risks only in the period 2012-2016, and 8-h maximum O₃ showed a decrease in excess risk despite an increase in its atmospheric levels after the introduction of haze control measures in 2008.

Conclusions: The findings indicate that the government haze control measures first introduced in Chiang Mai province in 2008 have successfully reduced episodic PM₁₀ concentrations, which has led to a decrease in short-term all-cause mortality.

Keywords: Air pollution; Biomass burning; Haze control; Haze smoke; Health effects; Mortality; Particulate matter.

Grants and funding

This work was supported by the National Research Council of Thailand and Thailand Research University Network. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.