Effects of bushfire smoke on daily mortality and hospital admissions in Sydney, Australia

Particulate air pollution and cardiorespiratory hospital admissions in a temperate Australian city: A case-crossover analysis

BACKGROUND

Although ambient air pollution exposure has been linked with poor health in many parts of the world, no previous study has investigated the effect on morbidity in the city of Adelaide, South Australia.

OBJECTIVE

To explore the association between particulate matter (PM) and hospitalisations, including respiratory and cardiovascular admissions in Adelaide, South Australia.

METHODS

For the study period September 2001 to October 2007, daily counts of all-cause, cardiovascular and respiratory hospital admissions were collected, as well as daily air quality data including concentrations of particulates, ozone and nitrogen dioxide. Visibility codes for present weather conditions identified days when airborne dust or smoke was observed. The associations between PM and hospitalisations were estimated using time-stratified case-crossover analyses controlling for covariates including temperature, relative humidity, other pollutants, day of the week and public holidays.

RESULTS

Mean PM(10) concentrations were higher in the warm season, whereas PM(2.5) concentrations were higher in the cool season. Hospital admissions were associated with PM(10) in the cool season and with PM(2.5) in both seasons. No significant effect of PM on all-age respiratory admissions was detected, however cardiovascular admissions were associated with both PM(2.5) and PM(10) in the cool season with the highest effects for PM(2.5) (4.48%, 95% CI: 0.74%, 8.36% increase per 10μg/m(3) increase in PM(2.5)).

CONCLUSION

These findings suggest that despite the city's relatively low levels of air pollution, PM concentrations are associated with increases in morbidity in Adelaide. Further studies are needed to investigate the sources of PM which may be contributing to the higher cool season effects.

Extreme air pollution events from bushfires and dust storms and their association with mortality in Sydney, Australia 1994-2007

INTRODUCTION

Extreme air pollution events due to bushfire smoke and dust storms are expected to increase as a consequence of climate change, yet little has been published about their population health impacts. We examined the association between air pollution events and mortality in Sydney from 1997 to 2004.

METHODS

Events were defined as days for which the 24h city-wide concentration of PM(10) exceeded the 99th percentile. All events were researched and categorised as being caused by either smoke or dust. We used a time-stratified case-crossover design with conditional logistic regression modelling adjusted for influenza epidemics, same day and lagged temperature and humidity. Reported odds ratios (OR) and 95% confidence intervals are for mortality on event days compared with non-event days. The contribution of elevated average temperatures to mortality during smoke events was explored.

RESULTS

There were 52 event days, 48 attributable to bushfire smoke, six to dust and two affected by both. Smoke events were associated with a 5% increase in non-accidental mortality at a lag of 1 day OR (95% confidence interval (CI)) 1.05 (95%CI: 1.00-1.10). When same day temperature was removed from the model, additional same day associations were observed with non-accidental mortality OR 1.05 (95%CI: 1.00-1.09), and with cardiovascular mortality OR (95%CI) 1.10 (95%CI: 1.00-1.20). Dust events were associated with a 15% increase in non-accidental mortality at a lag of 3 days, OR (95%CI) 1.16 (95%CI: 1.03-1.30).

CONCLUSIONS

The magnitude and temporal patterns of association with mortality were different for smoke and dust events. Public health advisories during bushfire smoke pollution episodes should include advice about hot weather in addition to air pollution.

Homicide by Asthma

Asthma may be the cause of death in some homicides. Bronchial asthma is a common disease, and the National Institutes of Health have estimated that 10.5% (30.2 million) of the United States population have been diagnosed with asthma. Acute exacerbations of bronchial asthma may be rapidly fatal, and medical examiner/coroner offices commonly encounter such deaths. Though asthma is a natural disease, acute exacerbations may be triggered by outside stressors, including harmful or criminal activities such as assaults. In these instances, the manner of death is appropriately certified as homicide. We describe three homicides in which asthma was deemed to be the proximate cause of death. In each of these fatalities, the decedent was subjected to physical and/or emotional stress of a harmful or criminal nature that resulted in an acute exacerbation of asthma that resulted in their death. Medical examiners/coroners must consider the decedent's history of disease; the circumstances surrounding the death; and the autopsy, histologic, and toxicologic findings in order to properly certify the cause and manner of death. A fatality with a natural proximate cause of death still may be certified as a homicide.

The effects of bushfire smoke on respiratory health

Bushfire smoke has the potential to affect millions of people and is therefore a major public health problem. The air pollutant that increases most significantly as a result of bushfire smoke is particulate matter (PM). During bushfire smoke episodes, PM concentrations are usually much higher than urban background concentrations, at which effects on respiratory health have been observed. The smoke can cover large areas including major cities and even small increases in the risk of respiratory health effects can cause large public health problems. The association between respiratory morbidity and exposure to bushfire smoke is consistent with the associations found with urban air pollution. Although using different methods, all studies looking at Emergency Department presentations in relation to a bushfire smoke event have found associations and most studies have also found an association with hospital admissions. However, only a few studies have distinguished between the effects of bushfire PM(10) (particles with a median aerodynamic diameter less than 10 µm) and background PM(10). These studies suggest that PM(10) from bushfire smoke is at least as toxic as urban PM(10), but more research is needed.

Creating an integrated historical record of extreme particulate air pollution events in Australian cities from 1994 to 2007

Epidemiological studies of exposure to vegetation fire smoke are often limited by the availability of accurate exposure data. This paper describes a systematic framework for retrospectively identifying the cause of air pollution events to facilitate a long, multicenter analysis of the public health effects of vegetation fire smoke pollution in Australia. Pollution events were statistically defined as any day at or above the 95th percentile of the 24-hr average concentration of particulate matter (PM). These were identified for six cities from three distinct ecoclimatic regions of Australia. The dates of each event were then crosschecked against a range of information sources, including online newspaper archives, government and research agency records, satellite imagery, and aerosol optical thickness measures to identify the cause for the excess particulate pollution. Pollution events occurred most frequently during summer for cities in subtropical and arid regions and during winter for cities in temperate regions. A cause for high PM on 67% of days examined in the city of Sydney was found, and 94% of these could be attributed to landscape fire smoke. Results were similar for cities in other subtropical and arid locations. Identification of the cause of pollution events was much lower in colder temperate regions where fire activity is less frequent. Bushfires were the most frequent cause of extreme pollution events in cities located in subtropical and arid regions of Australia. Although identification of pollution episodes was greatly improved by the use of multiple sources of information, satellite imagery was the most useful tool for identifying bushfire smoke pollution events.

Assessing the vulnerability of eco-environmental health to climate change

There is an urgent need to assess the vulnerability of eco-environmental health to climate change. This paper aims to provide an overview of current research, to identify knowledge gaps, and to propose future research needs in this challenging area. Evidence shows that climate change is affecting and will, in the future, have more (mostly adverse) impacts on ecosystems. Ecosystem degradation, particularly the decline of the life support systems, will undoubtedly affect human health and wellbeing. Therefore, it is important to develop a framework to assess the vulnerability of eco-environmental health to climate change, and to identify appropriate adaptation strategies to minimize the impact of climate change.