Oxidative Stress and the Effects of Air Pollution
Air pollution, especially airborne particulate matter (PM), is associated with an increase in both morbidity and mortality from cardiovascular disease, although the underlying mechanisms remain incompletely established. The one consistent observation that links the pulmonary and cardiovascular effects of inhaled PM is oxidative stress. This article examines the evidence for the role of oxidative stress in the cardiovascular effects of air pollution, beginning with observations from epidemiological and controlled exposure studies and then exploring potential mechanistic pathways involving free radical generation from PM itself, to effects of PM on cell cultures, isolated organs, healthy animals and animal models of disease. Particular emphasis is placed on the vascular and atherosclerotic effects of urban air pollution and diesel exhaust emissions as rich sources of environmental ultrafine particles.
The WHO recently issued a statement estimating that over 1 million deaths worldwide can be attributed to the effects of air pollution, (over and above that accounted for by conventional risk factors; see ). The magnitude of these effects may be staggering; however, air pollution has long been recognized as being detrimental to health. Episodes of air pollution, such as the 'great smog of London' in 1952, result in large numbers of deaths from cardiorespiratory diseases, leading the scientific community, politicians and the general public to consider the need to improve air quality. Until two decades ago, however, attention largely focused on the respiratory effects of air pollution, where there is a clear link between episodes of high air pollution and a worsening of allergic and inflammatory conditions of the lung, such as asthma and chronic obstructive pulmonary disease. More recent evidence demonstrates clear associations between air pollution and cardiovascular disease, and due to the high prevalence of cardiovascular disease in the western world, the cardiovascular effects of air pollution are arguably greater than those attributed to pulmonary consequences.
There is now a wealth of evidence linking exposure to urban air pollution, especially airborne particulate matter (PM), to adverse effects on the cardiovascular system, yet the mechanisms underlying these effects remain incompletely explained. Local and systemic oxidative stress has emerged as the likely common link between pulmonary exposure and systemic effects, including the cardiovascular system. This article has been structured to introduce the subject of the cardiovascular effects of air pollution through an overview of the epidemiological studies, followed by a summary of controlled exposure studies, which highlight the wide-ranging effects of air pollution. The article describe the evidence for the role of oxidative stress in the cardiovascular effects of air pollution, beginning with clinical observations and then taking a step-wise approach to explore potential mechanistic pathways involving free-radical generation from PM itself, to effects of PM on cell cultures, isolated organs, healthy animals and models of disease. The article focuses on the action of (outdoor) urban air pollution and vehicle exhaust emissions, placing particular emphasis on the vascular and atherosclerotic effects of the particulate components of these common pollutants.
Abstract and Introduction
Abstract
Air pollution, especially airborne particulate matter (PM), is associated with an increase in both morbidity and mortality from cardiovascular disease, although the underlying mechanisms remain incompletely established. The one consistent observation that links the pulmonary and cardiovascular effects of inhaled PM is oxidative stress. This article examines the evidence for the role of oxidative stress in the cardiovascular effects of air pollution, beginning with observations from epidemiological and controlled exposure studies and then exploring potential mechanistic pathways involving free radical generation from PM itself, to effects of PM on cell cultures, isolated organs, healthy animals and animal models of disease. Particular emphasis is placed on the vascular and atherosclerotic effects of urban air pollution and diesel exhaust emissions as rich sources of environmental ultrafine particles.
Introduction
The WHO recently issued a statement estimating that over 1 million deaths worldwide can be attributed to the effects of air pollution, (over and above that accounted for by conventional risk factors; see ). The magnitude of these effects may be staggering; however, air pollution has long been recognized as being detrimental to health. Episodes of air pollution, such as the 'great smog of London' in 1952, result in large numbers of deaths from cardiorespiratory diseases, leading the scientific community, politicians and the general public to consider the need to improve air quality. Until two decades ago, however, attention largely focused on the respiratory effects of air pollution, where there is a clear link between episodes of high air pollution and a worsening of allergic and inflammatory conditions of the lung, such as asthma and chronic obstructive pulmonary disease. More recent evidence demonstrates clear associations between air pollution and cardiovascular disease, and due to the high prevalence of cardiovascular disease in the western world, the cardiovascular effects of air pollution are arguably greater than those attributed to pulmonary consequences.
There is now a wealth of evidence linking exposure to urban air pollution, especially airborne particulate matter (PM), to adverse effects on the cardiovascular system, yet the mechanisms underlying these effects remain incompletely explained. Local and systemic oxidative stress has emerged as the likely common link between pulmonary exposure and systemic effects, including the cardiovascular system. This article has been structured to introduce the subject of the cardiovascular effects of air pollution through an overview of the epidemiological studies, followed by a summary of controlled exposure studies, which highlight the wide-ranging effects of air pollution. The article describe the evidence for the role of oxidative stress in the cardiovascular effects of air pollution, beginning with clinical observations and then taking a step-wise approach to explore potential mechanistic pathways involving free-radical generation from PM itself, to effects of PM on cell cultures, isolated organs, healthy animals and models of disease. The article focuses on the action of (outdoor) urban air pollution and vehicle exhaust emissions, placing particular emphasis on the vascular and atherosclerotic effects of the particulate components of these common pollutants.
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