Ambient particulate matter, landscape fire smoke, and emergency ambulance dispatches in Sydney, Australia
Introduction
The association between ambient particulate matter (PM) and adverse health outcomes has been clearly established, yet evidence gaps remain. For example, the relative impacts of particles from different sources are still under active investigation, and some health outcomes have not been well characterised because relevant datasets are not readily available to researchers (Englert, 2004, Davidson et al., 2005, Pope and Dockery, 2006).
Sources of PM include traffic, industrial emissions, re-suspension of dust, sea salt, atmospheric formation of secondary particles, and biomass burning. The contribution of each source to the total PM concentration varies both spatially and temporally (Belis et al., 2013). Landscape fire smoke (LFS) is a major source of PM2.5 (PM less than 2.5 μm in aerodynamic diameter) in many areas, with a global estimate of 340,000 premature deaths attributable to LFS each year (Johnston et al., 2012). However, studying the population health impacts of LFS is challenging for many reasons: (1) episodes of LFS are typically unpredictable and short-lived; (2) the spatial and temporal distributions of smoke impacts are much different from those of PM from other, well-monitored sources; (3) the exposure affects densely populated urban areas and sparsely populated rural areas; and (4) severe smoke events can cause much higher peak concentration than PM from other sources.
Many studies of LFS exposure have examined its association with emergency room visits, hospital admissions, or mortality. However, these data are not ideal for capturing the spatial and temporal variations in health status that might be associated with LFS, because the exposure location is not accurately geolocated and/or time-stamped. Furthermore, these data are typically not available in near-real-time, which limits their utility for public health surveillance of air quality events. Emergency ambulance dispatches (EAD) are systematically collected, centrally logged, geolocated, and time-stamped, making them potentially useful for both retrospective research and prospective surveillance related to LFS exposures. However, the utility of these data has been relatively unexplored with respect to air pollution, while they have been used in research and surveillance related to injuries and outbreak of infectious disease (Mostashari et al., 2003, Schuurman et al., 2008).
A limited number of studies published to date suggest that data collected by ambulance services, including EAD codes, paramedic assessment codes, and specific clinical data could be endpoints sensitive to ambient air quality. For example, Michikawa et al. (2014) and Zauli Sajani et al. (2014) observed a positive association between increased PM and EAD for non-traumatic causes, especially for respiratory causes. Youngquist et al. (2016) found associations between ambient PM2.5 and diabetic symptoms and fainting. More specifically, Dennekamp et al. (2015), Haikerwal et al. (2015) examined data from the cardiac arrest registry of the Victorian Ambulance Service and identified clear positive associations between LFS, PM2.5 and out-of-hospital cardiac arrests. In this study we aimed to (1) evaluate the sensitivity of different EAD codes to ambient PM2.5 from all sources (PM2.5,all) and ambient PM2.5 predominantly derived from LFS (PM2.5,LFS) and (2) quantify the association between PM2.5,all and PM2.5,LFS with dispatch codes most likely to be associated with cardiovascular or respiratory problems.
Section snippets
Study population and outcome data
Sydney, the capital of the state of New South Wales (NSW), is the largest city in Australia with a population of approximately 4.9 million in the greater Sydney metropolitan region. We received EAD data from the Ambulance Service of NSW for 1 January 2004 through 31 December 2014. Information extracted from the EAD included the date and time of the call, geographical coordinates of the event, and the reason for the call. Calls were recorded following the Medical Priority Dispatch System (MPDS),
Results
A total of 86 LFS days were detected during the whole study period, with about 70% occurring from September through to December. On average, LFS events occurred on days with relatively higher temperatures and lower RH. The average daily PM2.5 concentrations on LFS and non-LFS days were 16.4 μg·m− 3 and 6.8 μg·m− 3, respectively (Table 1).
Breathing problems and chest pain were the most common reasons for ambulance dispatches codes evaluated, with averages of approximately 100 and 70 dispatches per
Discussion
We found that PM2.5,all and PM2.5,LFS were associated with EAD for breathing problems on the same and following day, and with other heart problems at a lag of two days. PM2.5,all was also associated with same day arrest and chest pain. Results for PM2.5 related to LFS were generally similar to those for PM2.5 from all sources. The confidence intervals associated with the PM2.5,LFS were wider, especially for the less frequent EAD codes of stroke, other heart problems, and arrest. These
Conclusions
In this work EAD data were analysed in a time series study design to assess the effects of PM2.5 from all sources and PM2.5 primarily due to LFS on human health. We have shown that emergency dispatches for breathing problems, other heart problems, chest pain and cardiac arrest may be sensitive end points for continued research and surveillance activities investigating the impacts of ambient PM2.5.
Acknowledgments
This work was supported by the Australian Research Council (ARC) through project grants LP130100146 and DE130100924. We would also like to thank Ambulance Service of NSW, NSW Office of Environment and Heritage and NSW Environment Protection Authority (EPA) for providing us with EAD, air quality and meteorological data.
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