Air quality management policy and reduced mortality rates in Seoul Metropolitan Area: A quasi-experimental study

Background: The air quality management policy was introduced in Seoul and Incheon metropolitan cities in the Republic of Korea, from 2005 to 2014. Despite particulate matter concentrations decreasing after policy implementation, the consequent health benefits have not been evaluated. Therefore, we evaluated the effects of the air quality management policy on cause-specific mortality rates in Seoul and Incheon. Methods: Using interrupted time series analysis with a generalized Poisson regression model, we compared daily average mortality rates before (baseline, 2004–2005) and after (2006–2007, 2008–2009, 2010–2011, 2012–2013) the policy implementation. To account for the long term mortality trends, we weighted daily mortality rate of Seoul and Incheon with daily mortality rate of Daejeon (another metropolitan city with no air quality management policy implemented during the same period). Results: Decline in the particulate matter concentration was greater in Seoul and Incheon than in Daejeon. After adjusting for potential confounders, there were 8% decrease in cardiovascular disease mortality rates and 10% decrease in cerebrovascular disease mortality rates in Seoul in 2012–2013 compared to the baseline period. In Incheon, an 8% reduction in cerebrovascular disease mortality rates in 2012–2013 was calculated. There was no change in mortality rates due to external causes or respiratory disease after policy implementation. Conclusions: Our study suggests that the air quality management policy was effective in reducing cardiovascular and cerebrovascular mortality rates in Seoul and cerebrovascular mortality rates in Incheon.