Respirable Particulate Constituents and Risk of Cause-Specific Mortality in the Hong Kong Population

Emerging studies examined the associations of particulate matter constituents with nonaccidental and cardiorespiratory diseases, but few have investigated more specific causes of cardiorespiratory diseases or other system diseases, especially in Asia. We estimated the association between respirable particulate matter (PM10) constituents and a spectrum of deaths using a quasi-Poisson time-series model in Hong Kong. Positive associations were identified between cause specific deaths and elemental carbon, organic carbon (OC), nitrate, and potassium ion (K+), but only the associations for OC and K+ were robust in the two-constituent models adjusting for other constituents. The estimated effects of OC were strongest on mortality from the respiratory system with cumulative percent excess risk (ER%) of 3.82% (95% CI: 0.96%, 6.92%) per interquartile range (6.7 mu g/m(3)) increase over 7 days prior to death (lag(0-7)), especially for pneumonia (ER%: 4.32%; 95% CI: 0.70%, 8.26%). The digestive system was most sensitive to with cumulative ER% of 6.74% (95% CI: 0.37%, 14.01%) per interquartile range (0.6 mu g/m(3)) increase. This study indicates that PM10 constituents from biomass burning (OC and K+) were more toxic than other constituents for deaths in Hong Kong, especially for mortalities from respiratory and digestive systems. These findings should have potential biological and pollution control implications.