Background: Despite decades of evidence linking PM pollution with adverse health effects, significant knowledge gap remains regarding the health impacts of PM sources. Like size and chemical composition, PM sources appear to determine PM's toxicological characteristics. Aims: We examined the short-term impacts of source-specific PM10 mass and daily emergency hospital admissions in Hong Kong. Methods: Concentrations of 18 PM10 chemical components measured between 2001 and 2007 were analyzed via positive matrix factorization source apportionment. Generalized additive models were used to estimate source-specific excess risks at lags 0-3 days for cardiovascular (CVD) and respiratory (RESP) hospital admissions, adjusting for weather, seasonal/temporal trends, day-of-week and influenza epidemic. Results: Eight PM10 sources were identified: vehicle exhaust, soil/road dust, regional combustion, residual oil, fresh and aged sea salt, secondary sulfate and secondary nitrate. Secondary sulfate, vehicle exhaust and regional combustion contributed over half of the PM10 mass. An inter-quartile range increment in secondary nitrate (7.4 μg/m3) was associated with the largest percent increase of hospital admissions (1.8%; 95% CI: 1.2-2.5 at lag 0 for CVD; 1.4%; 95% CI: 0.8-2.0 at lag 3 for RESP), followed by vehicle exhaust and aged sea salt. Different sources were found to be variably associated with different outcomes: vehicle showed stronger associations with RESP, regional combustion and residual oil with CVD. Associations with PM10 from soil/road dust, secondary sulfate and fresh sea salt were mostly insignificant. Conclusions: Findings suggest that secondary nitrate from mobile sources and other fuel combustion, and vehicle exhaust are major contributors to the increased hospital admissions linked to PM10. Aged sea salt from regional transport of sea salt that passed through other polluted air is also an important risk factor for adverse health effects in coastal cities.
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