Background: Research on how individual chemical components of PM affect human health has been focusing on fine particles (i.e., PM2.5). PM composition differs by size, with more crustal materials in coarser PM and more combustion-related components in finer PM, and thus their associated health risks could differ. Evidence regarding the health impacts on PM10 chemical composition is scarce.Aims: We examined the short-term association between PM10 composition and daily emergency hospital admissions in Hong Kong.Methods: Twenty-four hour concentrations of PM10 mass and eighteen components from six general air monitoring stations, daily cardiovascular (CVD) and respiratory (RESP) hospital admission data and meteorological measurements were obtained. Generalized additive models were used for the analysis.Results: Between 2001-2007, daily average concentration of PM10 mass in Hong Kong was 54.3 μg/m3. Major contributors to PM10 included organic matter (OM), sulfate, elemental carbon (EC), nitrate, and ammonium. After adjusting for weather, seasonal/time trends, day-of-week and influenza epidemic, an inter-quartile range increment in nitrate (3.4 μg/m3) was associated with 1.8% (95% CI: 1.1-2.5 at lag 0 day) and 1.6% (95% CI: 1.0-2.3 at lag 3 day) increase in CVD and RESP hospital admissions respectively. Similar associations with OM were also found. EC, trace metals (iron, nickel, vanadium) and water-soluble ions (ammonium, sodium, potassium, chlorine ion) were linked with increased hospital admissions, particularly in the cool season. Stronger effects were observed for admissions among elderly (065 years) and RESP admissions among men.Conclusions: Ambient levels of secondary particles (nitrate) and OM that is primarily from combustion were associated with the largest risks of hospital admissions across the PM10 components in Hong Kong. Potential seasonal influence and effect modifiers for PM10 composition-related health effects warrant further investigation.
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