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The purpose of this presentation will be to analyse the impact of  bushfires in Australia since 2019 and evaluate  backburning strategies to alleviate this issue. 

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The purpose of this presentation will be to analyse the impact of  bushfires in Australia since 2019 and evaluate  backburning strategies to alleviate this issue. 

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The impact of climate change on tourism in Australia : a case study relating to bushfires in Australia in 2019/2020

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CHRS Shute Lane, Bruton, UK

Copyright © 2020 by author(s) and Scientific Research Publishing Inc.

This work is licensed under the Creative Commons Attribution International License (CC BY 4.0).
http://creativecommons.org/licenses/by/4.0/
Received: July 23, 2020; Accepted: August 28, 2020; Published: August 31, 2020

ABSTRACT
Keywords:
The 2019-2020 bushfires in Australia caused the loss of 34 lives and an estimated 100 bn AU$ damage. This has sharpened the apparent division between Australians who believe that the increasing number of bushfires is due to climate change, and those who suggest that fuel loads must be managed more carefully. Bushfires whose area equals or exceeds 1 mHa have been analysed in this paper. The results show that the number, duration, and size have increased over the period 1850-2020, but that since 1953, there has been a downward trend in the number of big bushfires. There is a range of temperatures of about 20˚C that are associated with the fires, with a modal temperature of 30˚C - 32.5˚C. Using an analysis of the maximum temperatures for the period 1970-2020 as a standard for comparison with bushfires for the period 1850-2020, shows that during bushfire events the standardised temperatures have a downward trend. This is most clearly shown by the application of the Fisher Exact Test. This suggests that the fuel load in forests is a key factor for bushfires. The role of pre-bushfire rainfall shows a rapid rise in the area burnt when the rainfall exceeds 150 mm month −1 which would lead to more plant growth and hence fuel load. The role of traditional burning over the whole of Australia is described based on documentary evidence. A tentative cost benefit analysis has shown that a comprehensive program of wildfire management is cost effective. The recommendations of previous research, National Inquiries and more recent management practices, have all failed to prevent the 2019-20 fire disaster in .

Bushfires, Standardised Temperatures, Fishers Exact Test, Native Burning

1. Introduction: A Dilemma for Australia

When the first English and Dutch explorers reached Australia in the late 17 th and 18 th century they were struck by the openness of the landscape, consistently describing it as a gentleman's park ( Gammage, 2011). But the appearance of the "gentlemen" who created the attractive areas of grassland with open woodland parks gave the explorers a shock, and for over 200 years the first Australians were regarded as savage and ignorant: how could they have created such a beautiful landscape whilst having a primitive way of life as judged by European standards? Some early settlers did however appreciate their skilled use of fire ( Bunbury & Morrell, 1930), but with the imposition of a European style of farming the role of fire in the national ecology and conservation was largely forgotten. Within a few decades large uncontrolled fires took place ( Pyne, 1991), some of which resulted in vast destruction of property and the loss of about 800 lives over the next 150 years ( Ellis, Kanowske, & Whelan, 2004). During the latter part of the 20 th century concern had been widely raised about rising temperatures and the prediction of higher temperatures in the future. The result is that climate change is considered to be the main cause of bushfires in and elsewhere ( Bradstock et al., 2009; Lucas et al., 2007; Lucas, 2010; Climate Council, 2017, 2019; Keeley & Syphard, 2016; Harris et al., 2020). These studies fail to consider the whole record of serious bushfires with an area in excess of 1 M Ha, and the rainfall leading up to and during the events. Foresters take a more pragmatic view especially following the 1939 fire in Victoria ( Ellis, Kanowski, & Whelan, 2004; Morgan et al., 2020). The latter authors highlight that since 1939 there have been over 50 public inquiries and reports yet devastating fires still take place. With the rise of environmentalism a negative perception of fire management has arisen with the view that "nature knows best" ( Attiwill & Adams, 2013). This ignores over 30,000 years of landscape management that so impressed the first explorers ( Gammage, 2011).

This paper seeks to resolve the dilemma by first describing the fire regime and history of big bushfires in since 1850, including their number, duration and size. Second, an analysis is made of the temperatures during the bushfire events in order to detect the likely effect of climate change. Third the influence of pre-bushfire rainfall is analysed. Fourth, the qualitative evidence from early paintings and descriptions of the landscape are considered, especially in the light of a growing acceptance that some burning may be of benefit to the ecology and public safety. Fifth, a tentative cost benefit analysis is presented which may help to guide future policy. Finally, the discussion will acknowledge that conservation and preservation are mutually exclusive in a continent that has been described as Fire's lucky country ( Pyne, 1991).

2. Data Sources

The main source of bushfire history is the Report of the Inquiry into the 2004 bushfires ( Ellis, Kannowski, & Whelan, 2004). The bushfire of 2007 is fully described by Smith (2007) while details of the fire of 2019-2020 were obtained from press reports. The Australian Bureau of Meteorology (BoM) provided temperature and rainfall data which can be downloaded from their website www.Bom.gov.au. Further data for the 1851 event were obtained from Ashcroft et al. (2014). All of this data has undergone quality control. However, very few sites have long term records that go back before 1950. Figure 1 shows the location of the sites used in this study and their location is given in Table 1.

. Location of the climate stations used in this study.

3. Bushfire Regime and History

Bushfires are an integral part of the Australian environment ( Cheney, 1995) and ecology ( Russell-Smith, Whitehead, & Cooke, 2009). Australia is located over nearly 30˚ of latitude from 11˚S - 39˚S excluding Tasmania. Generally speaking the fire season starts during the late autumn to winter in the north and spreads southwards to affectQueensland in the spring and summer and then the south and west of in the summer and autumn. A large number of causes have been put forward ( Linacre & Hobbs, 1977), the chief ones being high temperatures, illegal burning of unwanted vegetation, deliberate action, lightning, and careless action of campers and others. These causes tend to lead to moderate sized fires, whereas this paper has its focus on those 1 MHa and above. This is because they can cause the most damage and have a reasonable chance of being associated with the major and therefore most important causes. However, there is a growing body of knowledge that places more importance on the fuel load of forests which has increased since the early European settlers went to Australia ( Abbott & Burrows, 2003; Burrows & McCaw, 2013; Lullfitz et al., 2017; Morgan et al., 2020).

A total of 29 separate events since 1850 have been identified Table 2. Those of 1974, 2002, 2003, and 2020 are multiple events and so have been analysed either as a combined event taking into account their temporal dependency, or as spatially independent events.

4. Changes in Bushfire Number, Size, and Duration

Figure 2 shows the changes in bushfire number the data for which has been binned into 10 groups of 17 years, since in many years there are no big bushfires. This gives fewer degrees of freedom but is more robust because of the use of binned data ( Hoaglin, Mosteller, & Tukey, 1983). For the whole period there is a significant upward trend. Before 1939 there were only two big bushfires. After 1953 there is a significant downward trend in the number of fires.

Figure 3 shows the changes in the area burnt from 1851-2020. The large number of relatively small fires is dwarfed by those in 1969, 1974 and 2002, so a trend analysis of both binned and discrete data show an excessively steep trend: Y = 0.4062T − 765.9055 sig. 5%; Y = 0.3471T − 647.3829 not sig. 5% respectively.

The changes in the duration of the fires is shown in Figure 4 where the data for 19 independent events are shown, the median duration being used for 1974 and 2020 and the average duration for 2002 and 2003. There is an increase of duration from about 50 days in the first half of the 20 th century to more than 100 days in the 21 st century.

5. The Influence of Temperature and Rainfall

The fact that fires take place at different times of the year across Australia means that identifying the effect of temperature is not straightforward. The frequency distribution of the mean maximum temperature during the bushfires is shown in Figure 5.

. Bushfires 1 MHa or greater 1851-2020.

NB. For 2002 and 2003 the median temperature and Z score are equal to the average.

There is a range of nearly 20˚C in temperature that is associated with big bushfires. The modal value is 30˚C - 32.5˚C, above which the frequency declines rapidly. The likely effect of temperature on the area burnt is shown in Figure 6 where the envelope curve is well described by a logistic fit to the data.

The biggest three events took place in the Northern Territory and which also has the highest mean maximum temperatures. The group of events which have high temperatures but are well below the envelope curve took place in the other five States.

Since there is a wide variety of temperature associated with bushfires, in order to compare any changes in temperature that may have affected their occurrence it is necessary to standardise the temperature during each event. This is achieved by calculating Z scores for each event. This will be based on stations which are in the same area as the fire, where the standardised temperature:

where σ = standard deviation. If this process is not carried out then any trend in temperature could be strongly affected by the temporal distribution of the events. For example a small cluster of fires in the Northern Territories will have higher temperatures than a fire taking place in Western or Southern Australia . This would lead to the spurious conclusion that temperatures are getting hotter or cooler if they took place near the end or start of the study period. A further point is that the period of record for calculating average temperature may need to be longer than the standard WMO (2007) 30 year time period when the events under study are themselves rare, such as in an analysis of severe hailstorms ( Clark, 2020). In the present study the period used to calculate the average temperatures at each site was 1970-2020. There are 19 independent events. Figure 7 shows that there is a significant downward trend in the standardised

mean maximum temperature for the bushfires over the whole study period. Using the actual temperatures, the result not shown here, shows no correlation.

The downward trend in Z scores is further investigated in this case using the Fisher Exact Test. This uses the frequency of occurrence of two independent samples that fall into one of two mutually exclusive classes ( Siegel, 1956), and has been in use in a wide variety of situations from medicine ( Riffenburgh, 2005), biology ( van Nood et al., 2013) and geology ( Butler et al., 2010). The method calculates the probability that the two samples are different, in this case a decline in the Z value. This means the null hypothesis is in one direction and is therefore a one tailed test. The sample of bushfires is divided into the periods 1850-1970 and 1971-2020. The frequencies of Z scores of +0.8 or less than 0.8 is determined directly from the data. The null hypothesis is that there is no significant difference between the Z scores of the first and second time periods. The Fisher exact Test is calculated:

For all fire events:

Z > 0.8 <0.8 Total

1850-1970 9 1 10

1971-2020 6 13 19

Total 15 14 29 (Grand total)

F = (10! 19! 15! 14!)/(9! 1! 6! 13! 29!)

F = 0.00349

The probability of a more extreme situation is calculated viz:

Z >0.8 <0.8 Total

1950-1970 10 0 10

1971-2020 5 14 19

Total 15 14 29

F = (10! 19! 15! 14!)/(10! 0! 5! 14! 29!)

F = 0.000149

The total probability = 0.00349 + 0.000149 = 0.0036

The null hypothesis is rejected at the 0.4% level.

The test was performed again under different criteria:

Z Threshold

0.8 0.7

Spatially independent fires n = 25 0.016 0.007

Spatially and temporally independent events n = 19 0.009 0.017

All these results are significant well below the 5% probability level. This shows even more clearly that the Z scores in the first time period are different (higher) than in the second time period.

Rainfall preceding a fire may have a significant effect on the size and duration of a fire. This was noted by Pyne (1991) for the 1974 bushfires in Northern Territory, following considerable rainfall during late winter and spring. A total of 24 spatially independent events were assessed for their antecedent rainfall. This rainfall took place over different time periods so the average rainfall per month was chosen as the explanatory variable and then related to the area burnt. Figure 8 shows the result wherein a logistic curve best describes the data shown.

A maximum burnt area of 50 MHa was assumed in the analysis. For events that have rainfall less than 125 mm per month the area burnt is restricted to less than 10 MHa.

6. Fuel Load and Big Bushfires

The importance of reducing the quantity of combustible material to help prevent fires is no where better stated than by the Health and Safety Executive in the UK: www.hse.gov.uk/construction/safetytopics/processfire.htm

"the quantity of combustible materials on site should be kept to the minimum and all such materials safely stored and used"

Given that big bushfires have caused so much death and destruction in modern day it is legitimate to ask the question how the oldest civilisation in the world ( Malaspinas et al., 2016) managed the problem of fire in the biggest single nation island in the world? Although the native population of has probably been there for at least 40,000 years, no written records have so far been found that describe the bushfire situation before the arrival of Europeans in the 18 th century. After arrival in eastern , Captain Cook on 1 st May 1770 wrote in his journal:

"we made an Excursion into the Country, which we found diversified with Woods, Lawns, and Marsh. The woods are free from underwood of every kind, and the trees are at such a distance from one another that the whole Country, or at least greater part of it, might be Cultivated without being obliged to cut down a single tree."

Time and again the journals of Dawson (1830), Haydon (1846), Mossman & Bannister (1853), and others wrote of the "park like" scenery, "truly beautiful: studded with single trees, as if planted for ornament" ( Dawson, 1830).

Even more telling are the observations made by Henry Bunbury. The manuscript extract shown in Figure 9 speaks for itself.

If these writings were not enough evidence of the way in which the native people managed the land, the paintings of 13 independent artists between 1770 and 1872 and reproduced in Gammage (2011) confirm the park like appearance and the way in which the natural resources of the land are being harvested for food. Perhaps the best known of these is the painting by Joseph Lycett, an artist turned forger and then on parole as an official artist. This is reproduced here as Figure 10.

It shows the presence of open grassland as a result of clearing part of the forest; the use of fire to move kangaroos out of hiding, and the natives hunting them for food. Since the civilisation has lasted over 30,000 years it is very unlikely that they have over exploited the land.

More recently considerable interest has been taken in native fire activity ( Jones, 1969; Kimber, 1983; Preece, 2002; Abbott, 2003; McCaw et al., 2005; Burrows et al., 2006; Bird et al., 2009; Boer et al., 2009; Gammage, 2011; Burrows & McCaw, 2013; Lullifitz et al., 2017). In particular to use indigenous knowledge for better management ( Ansell et al., 2020). There is now greater recognition that this knowledge, which had been gathered over many thousands of years, is invaluable for the reduction in wildfires, and could also be used to enhance landscape value and ecology ( Russell-Smith et al., 2009, 2020).

7. Cost Benefit Analysis for Big Bushfires

Although cost benefit analysis has a long history when it comes to the assessment of bushfires there is still much disagreement about methodology ( Ladds et al., 2017), and with the effects on ecosystems and tourism not included in the thesis by Florec (2016), there is considerable scope for improvement. In 2018 tourism was valued at just under 150 bn AU$ ( Tourism Research Australia, 2019), and following the 2019-2020 bushfires the Government has pledged 4.5 bn AU$ to help the industry by the end of 2020 https://www.abc.net.au/news/2020-01-19/federal-government-announces-bushfire-recovery-tourism-package. After the 2009 bushfire tourism declined by about 12% based on long term arrivals into the country. One of the chief effects of bushfires is that of smoke inhalation (Johnston et al., 2002; Yu et al., 2020). The same concerns relate to prescribed burning ( Ravi et al., 2019). The present study has not included the smaller bushfires, some of which like the Black Friday 2009 event caused losses estimated at 11.8 bn AU$ ( Ladds et al., 2017). This estimate did not include loss of ecosystem value or long term health effects.

The 2019-2020 bushfires in Australia are the most serious in recent decades and the estimated costs, both tangible and intangible may be around 100bn AU$ https://theconversation.com/with-costs-approaching-100-billion-the-fires-are-australias-costliest-national-disaster although no detailed analysis has yet been published.

In a national assessment of the cost and benefits of fires in Australia, Ashe et al. (2010) estimated, at 2005 prices that the total cost of fire fighting was 11,990 MAU$, with losses totalling 1755 M AU$. In view of this unfavourable result a brief estimate of the cost of reducing the fuel load is now presented.

Table 2 shows that there have been 27 big bushfires in about 80 years. Thus the annual frequency is 0.33 fires per year. If the true cost of the damage during one of these fires is 100 bn AU$ then the annual cost is 0.33 × 100 = 33 bnAU$. Allowing for some overestimate this could be reduced to 30 bnAU$. If a forest worker has a 35 hour week and is paid 15 AU$ per hour then the annual cost in wages alone for a two man team would be 35 × 52 × 15 × 2 = 54,600 AU$. With a potential benefit of 30 bnAU$ per year a cost of 54,600 AU$ would pay for 549,000 two men teams. If on average they were able to clear 1Ha per week then in a year about 27.4 MHa would be maintained. If a firebreak 200 m wide and 1 km long for each km ² were produced by clearing and later maintained by controlled burning, then in a year an area of 0.686 Mkm ² would be covered. If continued for 11 years this would result in the whole of mainland being treated. However, the area covered by all forests and woodlands is about 4.16 Mkm ² (Department of Environment and water resources, 2007) thereby reducing the time to just over six years. If the cost of damage was reduced to 20 bn AU$ year −1 the completion time would increase to nine years. The position of new firebreaks could be carried out by experiment, with due regard to topographic, hydrological and edaphic factors taken into account with the aim of producing the kind of mosaic of habitats that was described by Bowman (2003). The felled timber could be sold for a variety of purposes ( FAO, 2009) and not necessarily burnt on site.

This analysis does not take into account the damage caused by smaller fires. The most tragic was Black Saturday in in 2009 when 173 people were killed. A more comprehensive study is called for, which will include the cost of the potential rise in prevalence of chronic diseases due to air, land and water pollution, leading to increased mortality ( Yu et al., 2020).

8. Discussion

The historic record of big bushfires shows that during the 19 th century only one was recorded. It is unlikely that others have been missed. During the 20 th century the number and size of bushfires increased and it has been logical to suggest that rising temperatures have been the cause ( Climate Council, 2019; Keeley & Syphard, 2016), and by Dutta et al. (2014) where the data set used is only seven years long. But temperatures in excess of 40˚C have occurred many times in the past, while the range of bushfire temperatures is considerable as shown in Figure 5. What has prevented a clearer understanding of the role of maximum temperatures on big bushfires is to neglect an analysis of the temperatures during the events. This leads to a dilemma regarding cause and effect, and fails to address the problem of fuel load since the decline of the practice of native burning. In Europe fire was seen as a menace, but in Australia many plant species depend upon fire for habitat, germination and distribution ( Bowman, 1998; Bird et al., 2009). Furthermore, some struggle with the idea that humans are part of the natural environment and disagree about whether humans or the environment are at risk, and why, ( Altangerel & Kull, 2013), or as Attiwill & Adams (2013) summed up the politics of bushfires, even in the presence of evidence to the contrary many still believe that "nature knows best". But the nature they refer to excludes traditional burning which produced the landscape so admired by the early settlers.

This paper has shown that although big bushfires have increased in size, number and duration the deviation of temperature from the mean, expressed in units of standard deviation or Z scores, has declined over the past 170 years. Furthermore, that extra rainfall when it occurs before the bushfire season, can lead to bigger bushfires. Although factors such as the deliberate starting of fires plays a part, the main reason for the changes in their frequency, size and duration has been the great increase in the fuel load in most parts of Australia. The temporal distribution of rainfall complicates the picture in that it promotes plant growth and available material for burning. When followed by a prolonged period of hot weather conditions are ripe for extensive fires. When placed in a global context ( Meyn et al., 2007; Bowman et al., 2014) the climate of Northern Territory, with a mean annual rainfall of around 1000 mm can be expected to have the most extensive fires, which is apparent from Figure 8 of this paper. The continued use of fire by Aboriginal Natives was, by all accounts, so well informed that their language developed words to describe the fire situation, conditions, and purpose of the fire.

The year 2020 witnessed one of the worst fires in many parts of . It is hard to understand that with the longest experience of fires in the whole world the traditional knowledge and practice of fire management, hunting, and landscape creation and maintenance has been largely ignored, with the proliferation of studies designed to find out what has been known for thousands of years. The implications of this and other studies should be quite clear: manage the land as it was for millennia or face more destructive fires in the future. In the words of Bill Gammage (2011): "If we are to survive, let alone feel at home, we must begin to understand our country. If we succeed, one day we might become Australian".

Conflicts of Interest

The author declares no conflicts of interest regarding the publication of this paper.

Cite this paper

Clark, C. (2020). Causes of Big Bushfires in Australia: Higher Temperatures and Rainfall or More Fuel? Journal of Geoscience and Environment Pro- tection, 8, 79-94. https://doi.org/10.4236/gep.2020.88007

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References

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Causes of Big Bushfires in Australia: Higher Temperatures and Rainfall or More Fuel?

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The 2019-2020 bushfires in Australia caused the loss of 34 lives and an estimated 100 bn AU$ damage. This has sharpened the apparent division between Australians who believe that the increasing number of bushfires is due to climate change, and those who suggest that fuel loads must be managed more carefully.

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Abstract

Smoke from bushfires (also known as wildfires or forest fires) has blanketed large regions of Australia during the southern hemisphere summer of 2019/2020, potentially endangering residents who breathe the polluted air. While such air pollution is known to cause respiratory irritation and damage, its effect on the is not well described. In this review, we aim to outline the potentially damaging effects of bushfire smoke on brain health. We also describe the composition of air pollution, including ambient (PM) and bushfire PM, before covering the general health effects of each. The investigated entry routes for ambient PM and postulated entry routes for bushfire PM are discussed, along with epidemiological and experimental evidence of the effect of both PMs in the brain. It appears that bushfire PM may be more toxic than ambient PM, and that it may enter the brain through extrapulmonary or olfactory routes to cause inflammation and brain particulate matter oxidative stress. Ultimately, this review highlights the desperate requirement of greater research into the effects of bushfire PM on brain health.

Introduction

Australia has experienced what is arguably its most destructive bushfire (wildfire or forest fire) season in history (southern hemisphere summer of 2019/2020). Fire-fighting teams, residents and the native wildlife have all been negatively impacted. Importantly, general population health is at risk, as the recent bushfires/wildfires have covered much of Eastern Australia and even New Zealand in thick smoke (Nolan et al., 2020) dramatically decreasing the air quality. In fact, the air has been reported to be, for a time, of equal quality to some of the most highly populated and polluted cities in the world (Nogrady, 2019). Unfortunately, due to the rising threat of climate change, it is expected that the bushfire season will increase in frequency and severity (Steffin, 2013). It is now more important than ever to understand the population health effects of prolonged exposure to bushfire-derived pollution.

The negative effect of air pollution, primarily ambient air pollution from vehicles or industrial coal burning, in the respiratory system has been well established and informs air quality regulations in Australia (Spickett et al., 2011). The respiratory effect of bushfire smoke has also been investigated, and bushfire smoke has been postulated to be equally, if not more damaging to respiratory cells than ambient air pollution (Franzi et al., 2011). Studies have also demonstrated that ambient air pollution can enter the brain and cause oxidative stress and inflammation, though there has been little focus on the effects of bushfire smoke in brain health. As fires are predicted to become an increasingly frequent event in Australia and worldwide due to climate change, it is important to understand the possible effects of bushfire smoke on the brain. This review summarises the general health effects, brain routes of entry and neurological effects of ambient air pollution and bushfire smoke and concludes that bushfire smoke is a potential threat to brain health.

Section snippets

Air pollution composition

Air pollution is a heterogenous mixture of gases, metals and particulate matter (PM; Fig. 1) (Vallero, 2014). PM is regarded as a biologically important component of air pollution (Moller et al., 2010; Morakinyo et al., 2016), and sources can include vehicle emissions, brake-pad dust, industry pollution, solid fuel combustion in domestic heating, or bushfire smoke. The PM level and impact can depend on altitude, location and climate events. This review will refer to ambient PM, meaning

Ambient PM

It has been repeatedly reported that poor air quality impacts human health. Multiple studies have confirmed associations between non-accidental hospitalisation and periods of increased ambient air pollution (Ab Manan et al., 2018). The majority of studies have investigated respiratory effects, with a meta-analysis finding vehicle emissions to significantly increase the risk of developing asthma in childhood (Khreis et al., 2017), and researchers reporting that PM is particularly hazardous to

Extrapulmonary entry route

While bushfire smoke has not currently been demonstrated to enter the brain, multiple brain entry routes for ambient PM, particularly for PM 2.5 and UFP, have been described. It has been reported that UFP can undergo extrapulmonary travel after inhalation and alveolar deposition (Kreyling et al., 2002; Nemmar et al., 2002; Oberdorster et al., 2002), and that pulmonary inflammation caused by PM 2.5 may increase the permeability of vascular endothelium in the lungs, leading to systemic circulation

Ambient PM: in vitro and in vivo studies

Once in the brain, PM is postulated to cause oxidative toxicity and inflammation by interacting with neurons and supporting cells (Table 2). PM 2.5 was shown to cause oxidative toxicity in rats when up to 10 μg/mL of PM 2.5 was incubated on homogenised olfactory bulb, cerebral cortex, striatum, hippocampus and cerebellum (Fagundes et al., 2015). All studied concentrations led to severe oxidative stress and lipid peroxidation in the cerebellum and hippocampus, whilst other brain regions appeared

Taking action

Bushfire smoke is postulated to have significant effects on brain health, and if this problem is not promptly addressed, we may see the long-term effects of bushfire smoke earlier than we imagined. Hence, further research into the effects of bushfire smoke on brain health and disease will be instrumental in preventing population-wide health effects. Importantly, increasing the understanding of these effects will allow the translation to legislative changes and public health campaigns. For now,

Funding

A.R.W is a recipient of an NHMRC Senior Research Fellowship (APP1118452).

Congressional Research Service
Wildfire statistics

Risk of respiratory and cardiovascular hospitalisation with exposure to bushfire particulates: new evidence from Darwin, Australia

European Forest Fire Information System
Forest fires in europe, Middle East and North africa 2018

PM₁₀, and children's respiratory symptoms and lung function in the PATY study

2022, Environmental Research

The fine particles arising from the wildfire smoke travelled in the atmosphere, reaching out to the South Pacific Ocean and South America, significantly affecting aerosol optical depth (Li et al., 2021). This has become a concern in multiple communities, especially in Australia and North American, as well as European countries affected in the summer of 2021 (Dennekamp and Abramson, 2011; Jones et al., 2020; Milton and White, 2020; Nguyen et al., 2021; Osborne et al., 2020; Walter et al., 2020; Wettstein et al., 2018). There have been a number of large wildfires in North America, such as the latest ones in California, which may last until Christmas 2021.

Airborne particulate matter (PM) comprises both solid and liquid particles, including carbon, sulphates, nitrate, and toxic heavy metals, which can induce oxidative stress and inflammation after inhalation. These changes occur both in the lung and systemically, due to the ability of the small-sized PM (i.e. diameters ≤2.5 μm, PM 2.5) to enter and circulate in the bloodstream. As such, in 2016, airborne PM caused ∼4.2 million premature deaths worldwide. Acute exposure to high levels of airborne PM (eg. during wildfires) can exacerbate pre-existing illnesses leading to hospitalisation, such as in those with asthma and coronary heart disease. Prolonged exposure to PM can increase the risk of non-communicable chronic diseases affecting the brain, lung, heart, liver, and kidney, although the latter is less well studied. Given the breadth of potential disease, it is critical to understand the mechanisms underlying airborne PM exposure-induced disorders. Establishing aetiology in humans is difficult, therefore, in-vitro and in-vivo studies can provide mechanistic insights. We describe acute health effects (e.g. exacerbations of asthma) and long term health effects such as the induction of chronic inflammatory lung disease, and effects outside the lung (e.g. liver and renal change). We will focus on oxidative stress and inflammation as this is the common mechanism of PM-induced disease, which may be used to develop effective treatments to mitigate the adverse health effect of PM exposure.

2022, Environment International

The smoke containing the high concentration of PM2.5 can indirectly have irreversible impact on fire fighters' health when they are exposed in fire environment for long time. The impact on physical health includes not only short-term effects (Karanasiou et al., 2021), but also long-term effects on the fighters' heart, lung and even brain (Milton and White, 2020; Ontawong et al., 2020). Many studies have been conducted on how the factors such as fuel loading, fuel moisture content, meteorological condition, and spatial distribution of fuel affect forest fire characteristics, and on how the exposure of PM2.5 affects fire fighters' health and safety in the process of forest fire fighting.

PM 2.5 is one of major pollutants emitted from forest fires. High PM 2.5 concentration not only affects short-term human respiration health, but also poses a long-term threat to human cardiopulmonary functionality. Therefore, it is of great importance to quantitatively assess the PM 2.5 released by forest combustion in forest fire studies. In this study we examine relationships between the PM 2.5 concentration and environment and fuel characteristics laboratory experiments. In the experiments, fuel beds with controlled moisture contents and loads were first built; then 144 ignition experiments were conducted for various combinations of wind speeds using a wind tunnel device. Fire behavior characteristics and PM 2.5 concentrations released from fuel combustion were measured and analyzed. The experimental results show that the relationship between fire characteristics, fire intensity and the influencing factors of wind speed, fuel moisture content, and fuel load can be explained by the fundamental theory of forest combustion. Although PM 2.5 concentration rises with the increase of wind speed, the decrease of fuel moisture content, and the increase of fuel load, there appears to be a fuel load threshold for a given combination of wind speed and fuel moisture content that the increase of PM 2.5 concentration decelerates quickly after the load passes the threshold value. After screening fire behavior characteristics that affect PM 2.5 concentration, we found that fire line intensity and flame width are the ones with the strongest association with the concentration. With flame width as independent variable, we have built two regression models to predict PM 2.5 and fire line intensity which are treated as dependent variable; the models have high accuracy with R ² = 0.92 for predicting PM 2.5 and R ² = 0.97 for predicting fire line intensity. Study results can be used as reference to protect the health of forest fire fighters, and can be helpful for forest fire smoke management.

2021, Journal of Hazardous Materials

Long-term exposures to PM2.5 are associated with an increased incidence of stroke (Jiang et al., 2020), impaired cognitive function (McGuinn et al., 2020; Cserbik et al., 2020), changes in cerebral hemodynamics (Younan et al., 2020), and decreased hippocampal volume and cortical thickness (Hedges et al., 2019). The toxicity of PM2.5 on the central nervous system has been speculated to be a direct consequence interactions between PM2.5 and the brain (Guarneros et al., 2020; Milton and White, 2020). PM2.5 particles have been known to cause brain tissue damages (Lee et al., 2020), behavior disorders (Chu et al., 2019) and early symptoms of neurological diseases (Wang et al., 2018) through inductions of oxidative stress (Lakroun et al., 2015), myelin sheaths destruction (Wei et al., 2017), DNA hydroxymethylation (Zhang et al., 2018), and neurotransmitter disorders.

Neurodegenerative diseases may be caused by air pollution, such as PM 2.5. However, particles still need to be elucidated the mechanism of synergistic neurotoxicity induced by pollutant-loading PM 2.5. In this study, we used a reductionist approach to study leading role of lead (Pb) in PM 2.5-induced hippocampal neuronal apoptosis and synaptic damage both in vivo and in vitro. Pb in PM 2.5 caused neurotoxicity: 1) by increasing ROS levels and thus causing apoptosis in neuronal cells and 2) by decreasing the expression of PSD95 via interfering with the calcium signaling pathway through cAMP/CREB/pCREB/BDNF/PSD95 pathway and reducing the synapse length by 50%. This study clarifies a key factor in PM 2.5-induced neurotoxicity and provides the experimental basis for reducing PM 2.5-induced neurotoxicity.

2021, The Impacts of Climate Change: A Comprehensive Study of Physical, Biophysical, Social, and Political Issues

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The potential impact of bushfire smoke on brain health

# data[].attributes.attachment_link.description
Smoke from bushfires (also known as wildfires or forest fires) has blanketed large regions of Australia during the southern hemisphere summer of 2019/...