Background: Epidemiological research on the effects of coarse particles (PMc, particulate matter between 2.5 and 10 μm in aerodynamic diameter) on respiratory morbidity is sparse and inconclusive. Pneumonia is an inflammatory condition of lung caused by infections, which may be triggered and exacerbated by PMcexposure. Aim: To estimate the effect of PMcon emergency hospital admissions for pneumonia after controlling for PM2.5and gaseous pollutants. Method: PMcconcentrations were estimated by subtracting PM2.5from PM10measurements in each of the 10 air monitoring stations from January 2011 to December 2012 in Hong Kong and then citywide daily average concentrations of PMcwere computed from the 10 stations. Generalised additive Poisson models were used to examine the relationship between PMcand daily emergency hospital admissions for pneumonia, adjusting for PM2.5and gaseous pollutants (NO2, SO2and O3). Subgroup analyses by gender and age were also performed to identify the most susceptible subpopulations. Results: PMcand PM2.5were significantly associated with emergency pneumonia hospitalisations. Every 10 μg/m3increment of PMcin the past 4 days (lag0-lag3) was associated with a 3.33% (95% CI 1.54% to 5.15%) increase in emergency hospitalisations for pneumonia. The effect estimates of PMcwere robust to the adjustment of PM2.5, NO2or SO2, but attenuated on the inclusion of O3in the model. Women, children and older people might be more vulnerable to PMcexposure. Conclusions: Short-term PMcexposure is associated with emergency hospitalisations for pneumonia in Hong Kong. Air quality regulation specifically for PMcmight be considered.
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