Figure 2 . Firefighting . |
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( PM 10
). 91 PM is quantified in μg / m 3 .
Predominant sources of fine PM are fossil fuel and biomass combustion , industry , agriculture , and windblown dust . 92 In Australian summers , bushfire smoke and dust storms are the main sources of PM 10
, and in winter , wood heaters are an important source . 93
PM 10 can penetrate and lodge
deep inside the lungs , while PM 2 . 5 penetrates the alveolar barrier and enters the blood stream . PM 2 . 5 is the principal air pollutant posing the greatest health threat . 94 The elderly , children , and those with pre-existing CV or respiratory disease are at increased risk . 95
More than 90 % of the global population is exposed to air pollution levels that exceed the WHO air quality guidelines ( AQG ) of PM 2 . 5 less than 10μg / m 3 annual mean , less than 25μg / m 3 24-hour mean , PM 10 less than 20μg / m 3 annual mean and less than 50μg / m 3 24-hour mean . Ambient air pollution ( particularly PM 2 . 5
) is a global mortality risk factor , estimated to cause millions of premature deaths and disability adjusted life years , with CVD ( IHD and stroke ) accounting for 60-80 % of these . 7 , 96-99
Long-term low-level air pollution is associated with increased mortality worldwide , including in Australia , despite air pollution concentrations being below the WHO AQG . 96 , 100 , 101 It is estimated to shorten life expectancy by 8.6 months in Europe . 101
PM 2 . 5 air pollution has been
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nearly 5 % of MIs worldwide . 116
Longer-term exposure ( several years ) amplifies these risks . 117 The risk is increased even when pollutant concentrations are below WHO standards . 118 Living in an area with chronically elevated PM 2 . 5 leads to an increase in CV mortality and all-cause mortality . 119
Possible mechanisms include inflammation induced by PM 2 . 5
, oxidative stress and vascular / endothelial dysfunction , which can facilitate the development of hypertension , diabetes and atherosclerosis . 120-126
The toxicity of PM 2 . 5 can vary , depending on its composition and source . PM 2 . 5 from coal combustion is associated with higher IHD mortality risk than PM 2 . 5 from other common sources ( soil and biomass combustion ), as is PM 2 . 5 from diesel traffic . 127 Traffic exhaust increases MI , and is considered the single most preventable acute trigger for MI . 128 , 129 Combustion is also a leading source of NO 2 which is associated with increased CV mortality . 130 During extreme ambient air pollution episodes , PM 2 . 5 can exceed 500-1000μg / m 3 , levels on par with active smoking . 131
Pathophysiology
The mechanisms linking air pollution and cardiometabolic disease are complex . 204 Air pollution , particularly
PM 2 . 5
, induces oxidative stress and inflammation , resulting in acute , subacute and chronic responses promoting atherosclerosis and CV events . 205-6
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exposure demonstrate rapid effects in reducing BP . 211-214
Temperature and air pollution : a two-way effect
High temperatures , particularly heatwaves , modify air pollution effects on mortality and CV outcomes , and high air pollution enhances temperature effects . The joint effect of temperature and air pollution is thought to be greater than the individual impacts . 215
High temperatures enhance the total and CVD mortality risk associated with air pollution , and on days of high air pollution , both heatand cold-related mortality risks increase . 216 Studies have generally found stronger associations with high temperatures and air pollution on allcause / CVD mortality , compared with low temperatures . 217-224
A US study found higher seasonal and annual temperatures increased CVD and IHD mortality risks associated with PM 2 . 5
. 225 A greater increase
in all-cause and CVD deaths , with increases in temperature in the warm season , was found for high-ozone days ( these occur when air pollutants chemically react in the presence
can be exacerbated by increased body temperature . 232 The elderly are more susceptible to the interactive effects of high temperatures or heatwaves and PM 10 on CV mortality , as well as
225 , 233-235 to the adverse effects of PM . This is because of a decreased capacity to effectively thermoregulate , with reduced sweat gland output , blood flow to the skin and cardiac output . 236
Wildfire smoke exposure
Climate change contributes to increasing wildfire frequency , longer fire seasons and larger areas burned . 7 , 237-239 Wildfire smoke contains multiple air pollutants . 240 Bushfires and hazard reduction burns expose Australians to
PM 2 . 5
, which penetrates the respiratory and circulatory systems , causing oxidative stress and inflammation .
241 , 242
The 2019 / 20 summer bushfires were unprecedented , with smoke affecting approximately 11 million people in NSW , Queensland , ACT and Victoria . 243 The bushfire smoke caused
More than 90 % of the global population is exposed to air pollution levels that exceed the WHO air quality guidelines .
air quality to be many times the hazardous levels set by the WHO , and the 24-hour mean PM 2 . 5 concentration exceeded the 95th percentile of
244 , 245 historical values on most days .
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during heatwaves , with an increased effect on mortality . 253
The studies assessing CV morbidity and wildfire smoke are inconsistent , finding some or no association . Rates of OHCA and MI hospitalisations were associated with wildfire-related PM 2 . 5 in Australia . 254 , 255 ED visits and hospitalisations for CHF were associated with wildfire smoke exposure in some studies , but not in others . 256-258 ED visits for IHD were higher on smoke-affected days in one Sydney study , but no associations for IHD hospital admissions were reported in other studies . 257-260 While there is insufficient evidence to determine whether wildfire smoke exposure is associated with specific CV outcomes , there is evidence that ambient PM 2 . 5 exposure ( the predominant air pollutant in wildfire smoke ) is associated with increased CV morbidity . 261
Firefighting and CVD
Hotter temperatures and increased extreme weather events place outdoor and manual labourers at increased risk of heat-related illnesses , occupational risks and death . This is particularly true for emergency service workers ( see figure 2 ). 262
The leading cause of fire dutyrelated deaths is a sudden cardiovascular event ( CVE ), including sudden cardiac arrest ( SCA ) and MI . 263 Sudden cardiac death ( SCD ) causes 45-50 % of firefighter duty-related fatalities ; 90 % of these are caused by CHD . 263
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described as “ the most important environmental risk factor contributing to global CV mortality and disability ”. 102 There is evidence of a causal relationship between short- and longterm exposure to air pollution ( particularly PM 2 . 5
) and CV mortality and morbidity , including MI , stroke and heart failure . 103-111
Short-term exposure to PM 2 . 5
( few hours to days ) increases the relative risk ( RR ) of acute CVEs , MI , hospitalisation or death from heart failure , stroke and arrhythmia . 112-115 Similar risks are reported for short-term exposures to gaseous pollutants such as
NO 2
, CO and CO 2
. 112-115 Short-term air pollution exposure is an important trigger for MI globally , accounting for
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PM 2 . 5 inhalation causes vascular dysfunction , altered haemodynamics , augmented thrombosis , heightened arrhythmia potential and proatherosclerotic changes .
Activation of the sympathetic nervous system , endothelial dysfunction , systemic and tissue inflammation , and oxidative stress , altered adipocyte expression , hypothalamic activation , impaired renal function , obesity and weight gain , and direct effects of inhaled nanoparticles are proposed mechanisms by which PM 2 . 5 increases BP and diabetes risk . 208-210
Short-term inhalation of air particles has been shown to elevate BP and / or alter vascular indices , and personal strategies to lower pollution
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of sunlight , producing high levels of ozone close to the ground ), but not during the cold period . 226 The heatwave effect on total and CV mortality is larger during high-ozone or
high-PM 10 days . 227 A recent Australian study found stronger heatwave effects on high-level ( compared with low-level ) PM 10 days for emergency hospital admissions for cardiac arrest , conduction disorders and hypertensive disease . 228 The lag to the effects of high temperature and PM 10 on CV morbidity and mortality is short .
164 , 229 , 230
Heat stress activates the thermoregulatory system , which may increase systemic absorption of toxins and air pollutants . 231 The biological strength of a chemical or toxin
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The bushfire pollution is estimated to have caused 417 excess CVD-related deaths , 1124 CVD and 2027 respiratory hospitalisations , and 1305 ED presentations for asthma . 245
Wildfire smoke exposure is associated with increased all-cause and CV mortality . 246-251 PM 10 and PM 2 . 5 are hazardous components of wildfire smoke , short-term exposure to which increases all-cause and CVD mortality . 134 The increase in daily PM 2 . 5 concentration during December 2019 in Australia was estimated to induce an increase of greater than 5.6 % in daily all-cause mortality and 4.5 % in CV mortality . 252 The risks of air pollution and wildfires are amplified when combined with high temperatures
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More than 30 % of SCDs occur during or shortly after firefighting activity ; more than 60 % of firefighter SCDs occur during other duties including the alarm response , training drills and simulated fires . 263-265 There are 17-25 duty-related nonfatal CVE ( MI and
266 , 267 strokes ) for every fatal event .
The strenuous physical activity ( often with PPE ), emotional stress , sympathetic nervous system activation and environmental conditions ( heat and pollutants in fire smoke ) encountered while firefighting place strain on the CV system . These exposures alone or in concert increase the risk of CVE among susceptible individuals , such as those with CHD or underlying structural CVD . 268 , 269 The vascular , cardiac
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