Ambient particulate matter, landscape fire smoke, and emergency ambulance dispatches in Sydney, Australia

Background: Emergency ambulance dispatches (EAD) are a novel outcome for evaluating the public health impacts of air pollution. We assessed the relationships between ambient particulate matter (PM) from all sources, PM from landscape fire smoke (LFS), and EADs likely to be associated with cardiorespiratory problems in the Sydney greater metropolitan region for an 11-year period from 2004 to 2015.

Methods: EAD codes are assigned at the time of the call to emergency services using standard computer assisted algorithms. We assessed EADs coded as: breathing problems, chest pain, stroke or cerebrovascular accident (stroke), cardiac or respiratory arrest and death (arrest), and heart or defibrillator problems (other heart problems). Using a daily times series study design with a generalized linear Poisson regression model we quantified the association between EAD and daily PM_2.5 from all sources (PM_2.5,all) and PM_2.5 primarily due to LFS (PM_2.5,LFS).

Results: Increases of 10μg·m^-3 in PM_2.5,all were positively associated with same day EAD for breathing problems (RR=1.03, 95% CI 1.02 to 1.04), arrest (RR = 1.03, 95% CI 1.00 to 1.06), and chest pain (RR = 1.01 CI 1.00 to 1.02) but not with other outcomes. Increases of 10μg·m^-3 PM_2.5,LFS were also positively associated with breathing problems on the same day (RR = 1.04, 95% CI 1.02 to 1.05) and other heart problems at lag of two days (RR = 1.05, 95% CI 1.01 to 1.09).

Conclusions: Emergency dispatches for breathing problems are associated with PM_2.5,all and PM_2.5,LFS and provide a sensitive end point for continued research and surveillance activities investigating the impacts of daily fluctuations in ambient PM_2.5.