Background

Scarce evidence is available on the health effects of various chemical constituents of PM_2.5 on hospital visits in China.

Objectives

To examine the short-term associations between a wide range of PM_2.5 constituents and hospital outpatient and emergency room visits in Shanghai.

Methods

We obtained daily concentrations of PM_2.5 total mass, organic carbon (OC), elemental carbon (EC), eight water-soluble ions and thirteen elemental constituents between January 1, 2014 and December 31, 2015. We analyzed the data using over dispersed generalized additive models with Poisson regression. Single-constituent, PM_2.5-adjusted and constituent-residual models were built respectively to assess the associations. Exposure-response curves for the PM_2.5 constituents with robust effects were graphed.

Results

The average daily mean PM_2.5 concentration was 63.3 μg/m³ in Shanghai during the study period. An interquartile range (IQR) increase in PM_2.5 was associated with a 2.57% (95% confidence interval [CI]: 1.28%, 3.87%) increase in outpatient visits, and a 3.60% (95% CI: 2.16%, 5.03%) increase in emergency room visits. We observed robust and positive associations between Mg²⁺, Ca²⁺, six elemental components (Ca, Mn, Fe, Zn, Ga and Se) and outpatient visits. OC, EC, Cl⁻, Mg²⁺, Ca²⁺ and ten elemental components (Ca, Cr, Mn, Fe, Zn, Ga, As, Se, Pb, and Ni) were significantly and positively associated with emergency room visits. The exposure-response relationships were positive and generally linear for the above constituents.

Conclusions

This time-series study in Shanghai demonstrated significant associations between various carbonaceous, water-soluble and elemental constituents of PM_2.5 and hospital visits, providing evidence for source-specific control of particulate air pollution.