Health effects of PM10 on mortality have been studies worldwide. However, not many studies have questioned possibility that short-term effects of PM10 can be changed over time. Identifying temporal variability of the effects would be of help to getting more valid PM10 effect estimates which are a major basis for public health policies. In this study, temporal variability of short-term effects of PM10 for mortality was investigated from 2001 to 2015 in Seoul, Korea. A time series analysis was used to estimate the effects of PM10 on all-cause, circulatory, and respiratory mortality. Study period was divided into five years of moving time window, and relative risks and its 95% confidence intervals were estimated using distributed lag model for each time window. The annual average of PM10 in Seoul decreased from 52.6 μg/m3 in 2001 to 40.5 μg/m3 in 2015. There were significant temporal trends in PM10 effects regarding each mortality. The effects of PM10 tend to slightly increase in early of the study period and then dropped in recent years. An increase of 2 days of cumulative exposure of PM10 was associated with 0.31% (95% confidence interval: 0.15, 0.46) increase in all-cause mortality for 2001-2005 period, 0.61% (95% confidence interval: 0.34, 0.89) increase in 2005-2009 period, and -0.06% (95% confidence interval: -0.38, 0.25) increase in 2011-2015 period. We found evidence that short-term effects of PM10 on mortality have been changed over time in Seoul, Korea. The observed temporal trend might attributable from two factors which are change of PM10 compositions and population vulnerability. If effects of PM10 vary over time, considering its change would be necessary not only in the estimation of the PM10 effect but also its application for a variety of public health policies.
Keywords: Air pollution; Effect modification; Particulate matter; Time variability.
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