Characterization of fine particulate matter and associations between particulate chemical constituents and mortality in Seoul, Korea

Background: Numerous studies have linked fine particles [≤ 2.5 µm in aerodynamic diameter (PM_2.5)] and health. Most studies focused on the total mass of the particles, although the chemical composition of the particles varies substantially. Which chemical components of fine particles that are the most harmful is not well understood, and research on the chemical composition of PM_2.5 and the components that are the most harmful is particularly limited in Asia.Objectives: We characterized PM_2.5 chemical composition and estimated the effects of cause-specific mortality of PM_2.5 mass and constituents in Seoul, Korea. We compared the chemical composition of particles to those of the eastern and western United States.Methods: We examined temporal variability of PM_2.5 mass and its composition using hourly data. We applied an overdispersed Poisson generalized linear model, adjusting for time, day of week, temperature, and relative humidity to investigate the association between risk of mortality and PM_2.5 mass and its constituents in Seoul, Korea, for August 2008 through October 2009.Results: PM_2.5 and chemical components exhibited temporal patterns by time of day and season. The chemical characteristics of Seoul’s PM_2.5 were more similar to PM_2.5 found in the western United States than in the eastern United States. Seoul’s PM_2.5 had lower sulfate (SO₄) contributions and higher nitrate (NO₃) contributions than that of the eastern United States, although overall PM_2.5 levels in Seoul were higher than in the United States. An interquartile range (IQR) increase in magnesium (Mg) (0.05 μg/m³) was associated with a 1.4% increase (95% confidence interval: 0.2%, 2.6%) in total mortality on the following day. Several components that were among the largest contributors to PM_2.5 total mass—NO₃, SO₄, and ammonium (NH₄)—were moderately associated with same-day cardiovascular mortality at the p < 0.10 level. Other components with smaller mass contributions [Mg and chlorine (Cl)] exhibited moderate associations with respiratory mortality on the following day (p < 0.10).Conclusions: Our findings link PM_2.5 constituents with mortality and have implications for policy making on sources of PM_2.5 and on the relevance of PM_2.5 health studies from other areas to this region.