Association of daily cause-specific mortality with ambient particle air pollution in Wuhan, China

In Asia, limited literature has been published on the association between daily mortality and ambient air pollution. We examined the associations of daily cause-specific mortality with daily mean concentrations of particulate matter (PM) with a mass median aerodynamic diameter less than 10 μm (PM₁₀) in Wuhan, China using 4 years of data (2001-2004). There are approximately 4.5 million residents in Wuhan who live in the city core area of 201 km² where air pollution levels are higher and pollution ranges are wider than the majority of cities in the published literature. We use quasi-likelihood estimation within the context of the generalized additive models (GAMs) (natural spline (NS) models in R) to model the natural logarithm of the expected daily death counts as a function of the predictor variables. We found consistent PM₁₀ effects on mortality with the strongest effects on lag 0 day. Every 10 μg/m³ increase in PM₁₀ daily concentration at lag 0 day was significantly associated with an increase in non-accidental (0.36%; 95% CI 0.19-0.53%), cardiovascular (0.51%; 95% CI 0.28-0.75%), stroke (0.44%; 95% CI 0.16-0.72%), cardiac (0.49%; 95% CI 0.08-0.89%), respiratory (0.71%; 95% CI 0.20-1.23%), and cardiopulmonary (0.46%; 95% CI 0.23-0.69%). In general, these effects were stronger among the elderly (≥65 years or ≥45 years) than among the young. The exploration of exposure-response relationships between PM₁₀ and cause-specific mortality suggests the appropriateness of assuming linear relationships, where the PM₁₀ concentration in Wuhan ranged from 24.8 to 477.8 μg/m³. We conclude that there is consistent evidence of acute effects of PM₁₀ on cardiopulmonary mortality. A linear no threshold exposure-response relationship is suggested between PM₁₀ and the studied cause-specific mortality.