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Acute cardiovascular effects of biofuel exhaust exposure
Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Pulmonary Medicine.
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Background

Anthropogenic air pollution is a global health problem estimated to contribute to millions of premature deaths. Exposure to biomass smoke is common due to varying sources, such as wildfires, indoor cooking over open fires, and residential heating from wood stoves. In urban environments transportation and industry rely heavily on the combustion of fossil fuels yet environmental policies increasingly support a shift to renewable fuels such as biodiesel. It has not been investigated how either wood smoke or biodiesel exhaust affect human health in general or the cardiovascular system in particular. We hypothesized that wood smoke exposure would induce acute cardiovascular impairment via similar underlying mechanisms as have been established for petrodiesel exhaust exposure. We also hypothesized that replacing petrodiesel with biodiesel, as a blend or pure biodiesel, would generate an exhaust profile with a less harmful effect on the cardiovascular system than petrodiesel exhaust.

Methods

In four separate studies healthy non-smoking subjects were exposed to different air pollutants in controlled exposure chambers followed by clinical investigations of the cardiovascular system. All studies were performed as randomized controlled trials in a crossover fashion with each individual acting as her own control. In study I healthy volunteers were exposed to wood smoke at a target concentration of particulate matter (PM) 300 µg/mfor three hours followed by measures of blood pressure, heart rate variability and central arterial stiffness. In study II subjects were exposed to wood smoke at a target concentration of PM 1000 µg/mfor one hour followed by measures of thrombus formation using the Badimon technique and vasomotor function using forearm venous occlusion plethysmography. In study III subjects were exposed to petrodiesel exhaust and a 30% rapeseed methyl ester (RME30) biodiesel blend for one hour at a target concentration of PM 300 µg/m3. Following exposure, thrombus formation and vasomotor function were assessed as in study II. In study IV subjects were exposed to petrodiesel exhaust at a target concentration of PM 300 μg/m3for one hour and pure rapeseed methyl ester (RME100) exhaust generated at identical running conditions of the engine. Following exposure, thrombus formation and vasomotor function were assessed as in study II and III.

Results

In study I fourteen subjects (8 males) were exposed to wood smoke at P M 294±36 μg/m3. Compared to filtered air exposure, measures of central arterial stiffness were increased and heart rate variability was decreased following wood smoke exposure. No effect was seen on blood pressure. In study II sixteen males were exposed to wood smoke at PM 899±100 μg/m3. We found no evidence of increased thrombus formation or impaired vasomotor function following wood smoke exposure. In study III sixteen subjects (14 males) were exposed to petrodiesel exhaust (PM 314±27 µg/m3) and RME30 exhaust (PM 309±30 µg/m3). Thrombus formation and vasomotor function were equal following either exposure. In study IV nineteen males were exposed to petrodiesel exhaust (PM 310±34 µg/m3, 1.7±0.3 x105 particles/cm3) and RME100 exhaust (PM 165±16 µg/m3, 2.2±0.1 x10particles/cm3). As in study III, thrombus formation and vasomotor function were identical following both exposures.

Conclusions

We have for the first time demonstrated that wood smoke exposure can increase central arterial stiffness and decrease heart rate variability in healthy subjects. We did not, however find evidence of increased thrombus formation and impaired vasomotor function following wood smoke exposure at a higher concentration for a shorter time period. We have, for the first time, demonstrated that exhaust from RME biodiesel induced acute adverse cardiovascular effects of increased thrombus formation and impaired vasomotor function in man. These effects are on par with those seen following exposure to petrodiesel exhaust, despite marked physicochemical differences of the exhaust characteristics.

Place, publisher, year, edition, pages
Umeå: Umeå Universitet , 2014. , 96 p.
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1690
Keyword [en]
Cardiovascular, air pollution, endothelial dyssfunction, arterial stiffness, wood smoke, woodsmoke, biodiesel, RME, biofuel, diesel exhaust
National Category
Cardiac and Cardiovascular Systems
Identifiers
URN: urn:nbn:se:umu:diva-96449ISBN: 978-91-7601-175-1 (print)OAI: oai:DiVA.org:umu-96449DiVA: diva2:764764
Public defence
2014-12-12, Sal D, 9 trappor, byggnad 1D, Norrlands Universitetssjukhus, Universitetssjukhuset, Umeå, 12:56 (English)
Opponent
Supervisors
Funder
Swedish Heart Lung FoundationAFA Insurance
Available from: 2014-11-21 Created: 2014-11-20 Last updated: 2014-12-17Bibliographically approved
List of papers
1. Exposure to wood smoke increases arterial stiffness and decreases heart rate variability in humans
Open this publication in new window or tab >>Exposure to wood smoke increases arterial stiffness and decreases heart rate variability in humans
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2013 (English)In: Particle and Fibre Toxicology, ISSN 1743-8977, E-ISSN 1743-8977, Vol. 10, 20- p.Article in journal (Refereed) Published
Abstract [en]

Background: Emissions from biomass combustion are a major source of indoor and outdoor air pollution, and are estimated to cause millions of premature deaths worldwide annually. Whilst adverse respiratory health effects of biomass exposure are well established, less is known about its effects on the cardiovascular system. In this study we assessed the effect of exposure to wood smoke on heart rate, blood pressure, central arterial stiffness and heart rate variability in otherwise healthy persons. Methods: Fourteen healthy non-smoking subjects participated in a randomized, double-blind crossover study. Subjects were exposed to dilute wood smoke (mean particle concentration of 314 +/- 38 mu g/m(3)) or filtered air for three hours during intermittent exercise. Heart rate, blood pressure, central arterial stiffness and heart rate variability were measured at baseline and for one hour post-exposure. Results: Central arterial stiffness, measured as augmentation index, augmentation pressure and pulse wave velocity, was higher after wood smoke exposure as compared to filtered air (p < 0.01 for all), and heart rate was increased (p < 0.01) although there was no effect on blood pressure. Heart rate variability (SDNN, RMSSD and pNN50; p = 0.003, p < 0.001 and p < 0.001 respectively) was decreased one hour following exposure to wood smoke compared to filtered air. Conclusions: Acute exposure to wood smoke as a model of exposure to biomass combustion is associated with an immediate increase in central arterial stiffness and a simultaneous reduction in heart rate variability. As biomass is used for cooking and heating by a large fraction of the global population and is currently advocated as a sustainable alternative energy source, further studies are required to establish its likely impact on cardiovascular disease.

Place, publisher, year, edition, pages
London, England: BioMed Central, 2013
Keyword
Biomass, Air pollution, Arterial stiffness, Blood pressure, Heart rate variability, Cardiovascular
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:umu:diva-80767 (URN)10.1186/1743-8977-10-20 (DOI)000323545200001 ()
Available from: 2013-09-25 Created: 2013-09-25 Last updated: 2017-12-06Bibliographically approved
2. Effect of wood smoke exposure on vascular function and thrombus formation in healthy fire fighters
Open this publication in new window or tab >>Effect of wood smoke exposure on vascular function and thrombus formation in healthy fire fighters
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2014 (English)In: Particle and Fibre Toxicology, ISSN 1743-8977, E-ISSN 1743-8977, Vol. 11, 62Article in journal (Refereed) Published
Abstract [en]

Background: Myocardial infarction is the leading cause of death in fire fighters and has been linked with exposure to air pollution and fire suppression duties. We therefore investigated the effects of wood smoke exposure on vascular vasomotor and fibrinolytic function, and thrombus formation in healthy fire fighters. Methods: In a double-blind randomized cross-over study, 16 healthy male fire fighters were exposed to wood smoke (~1 mg/m3 particulate matter concentration) or filtered air for one hour during intermittent exercise. Arterial pressure and stiffness were measured before and immediately after exposure, and forearm blood flow was measured during intra-brachial infusion of endothelium-dependent and -independent vasodilators 4–6 hours after exposure. Thrombus formation was assessed using the ex vivo Badimon chamber at 2 hours, and platelet activation was measured using flow cytometry for up to 24 hours after the exposure. Results: Compared to filtered air, exposure to wood smoke increased blood carboxyhaemoglobin concentrations (1.3% versus 0.8%; P < 0.001), but had no effect on arterial pressure, augmentation index or pulse wave velocity (P > 0.05 for all). Whilst there was a dose-dependent increase in forearm blood flow with each vasodilator (P < 0.01 for all), there were no differences in blood flow responses to acetylcholine, sodium nitroprusside or verapamil between exposures (P > 0.05 for all). Following exposure to wood smoke, vasodilatation to bradykinin increased (P = 0.003), but there was no effect on bradykinin-induced tissue-plasminogen activator release, thrombus area or markers of platelet activation (P > 0.05 for all). Conclusions: Wood smoke exposure does not impair vascular vasomotor or fibrinolytic function, or increase thrombus formation in fire fighters. Acute cardiovascular events following fire suppression may be precipitated by exposure to other air pollutants or through other mechanisms, such as strenuous physical exertion and dehydration.

Place, publisher, year, edition, pages
BioMed Central, 2014
Keyword
Wood smoke, Air pollution, Fire-fighters, Vascular function, Thrombosis
National Category
Cardiac and Cardiovascular Systems Pharmacology and Toxicology
Identifiers
urn:nbn:se:umu:diva-96446 (URN)10.1186/s12989-014-0062-4 (DOI)000209599200001 ()25487196 (PubMedID)
Note

First published in thesis in manuscript form.

Available from: 2014-11-20 Created: 2014-11-20 Last updated: 2017-12-05Bibliographically approved
3. Rapeseed Methyl Ester Biodiesel Exhaust Exposure Causes Vascular Dysfunction in Man
Open this publication in new window or tab >>Rapeseed Methyl Ester Biodiesel Exhaust Exposure Causes Vascular Dysfunction in Man
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(English)Manuscript (preprint) (Other academic)
National Category
Cardiac and Cardiovascular Systems
Identifiers
urn:nbn:se:umu:diva-96448 (URN)
Available from: 2014-11-20 Created: 2014-11-20 Last updated: 2015-04-17

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