查看更多>>摘要：Exposure to airborne particulate matter results in various adverse health effects. Unlike other pollutants, such as ozone, sulfur dioxide, carbon monoxide, and oxides of nitrogen, for which there is significant exposure, particulate matter exposure is much more complex because it is not a single chemical species or even a limited number of chemical species. Particulate matter includes various chemical species in particles having a wide range of diameters and shapes that have widely varying toxicities. People are exposed to particles in the ambient environment, in indoor spaces, and in the occupational environment. This article reviews the information available on the concentrations of particulate matter and its composition in these general environmental categories.
查看更多>>摘要：The concept of dose is fundamental to the discipline of toxicology. For inhaled particles, dose considerations include the sequential processes of inhalation, particle deposition, and particle clearance. Several important parameters modify each of these processes, including environmental, anatomic, and physiologic factors. When such factors are considered, it is possible to identify subpopulations and individuals who are likely to receive particle doses that greatly exceed those for the average population. Higher than average doses can be expected for people who are young, have certain acute or chronic lung diseases, are engaged in exercise, or are exposed in close proximity to sources of air pollutants. Although considerable research has improved the understanding of inhaled particle doses, much is still to be learned before high-risk groups and individuals can be protected properly.
查看更多>>摘要：Ultrafine, or nano-, particles (< 100 nm) have been associated in epidemiological, human clinical, and animal studies with adverse cardiopulmonary outcomes. Deposition of inhaled ultrafine particles in the respiratory tract is mainly governed by diffusion and is most efficient for alveolar regions of the lung, although deposition occurs in other regions, too. The nose is also a very efficient filter for smaller ultrafine (< 5 nm, diffusion) particles. Solid poorly-soluble ultrafine particles are not efficiently cleared via mucociliary or macrophage-mediated mechanisms and are, thus, likely to be taken up by epithelial cells and translocate to extrapulmonary sites (interstitium, lymph and blood circulation, neurons). These translocation processes are explored here as well potential consequences that result from exposure of extrapulmonary organs to inhaled ultrafine particles.
查看更多>>摘要：Inflammation provides a potential mechanistic link between inhalation of particles and the diverse health effects found in epidemiologic studies. Considerable uncertainty remains as to the importance of the inflammation in mediating these effects and where that inflammation is occurring: lung, vascular endothelium, or distant organs, including the heart. This article briefly reviews the role of inflammation in pulmonary and cardiovascular disease and explores the evidence that the health effects of PM exposure are mediated, at least in part, by inflammation.
查看更多>>摘要：Numerous reports link oxidative stress to particulate matter (PM)-induced adverse health effects. Increasing evidence is being collected that reactive oxygen species and oxidative stress are involved in PM-mediated injury. The physical characteristics and the chemical composition of PM play a key role in reactive oxygen species generation in vitro and in vivo. According to the hierarchical oxidative stress hypothesis, antioxidant phase II enzymes protect against PM-induced inflammation and cytotoxicity. This concept is useful in understanding PM-induced disease models, susceptibility, and biomaker development to access exposures outcomes and is useful for developing therapeutic intervention in PM-induced adverse health effects.
查看更多>>摘要：Considerable work has been done to elucidate the effects of polluted air, most of which has studied acute effects of particles. Studies suggest that the effects of longer term exposures are more than just the daily sum of the acute effects. Because most of the studies of acute effects have examined changes in health status occurring within days of the exposure, this article takes a broad definition of long-term exposure to include averaging times of months to years. It concludes that health effects increase as length of exposure increases, but much of that increase occurs within the first year.
查看更多>>摘要：This article focuses on responses to ambient particles by the heart. Available data from human studies and animal studies are reviewed in an attempt to find a common understanding in the findings. The pathophysiologic mechanisms responsible for these health effects are likely to be complex, and it is highly probable that several different mechanisms work in concert. Current evidence suggests that inhaled particles exert their effects on the heart via the autonomic nervous system and via the coronary vasculature. Direct effects on the myocardium by inhaled ambient particles or their constituents require more research.
查看更多>>摘要：Exposure to particulate air pollution is associated with acute and chronic cardiovascular morbidity and mortality. The mechanisms involved in these effects are not fully elucidated. Research has proved that fine particles, principally the ultrafine fraction, which are predominantly derived from combustion of fossil fuel, are the most toxic. Recent clinical and experimental studies have reported mechanistic observations linking fine and ultrafine particles to the coagulation cascade, platelet function, and subsequent development of atherosclerosis and thrombosis. These effects have been explained either by release of soluble mediators by the lungs, which affect blood coagulation parameters, or by the direct translocation of ultrafine particles into the systemic circulation or the alteration of autonomic cardiac control. Despite recent advances, additional studies are needed to investigate the pathophysiologic mechanisms linking particulate air pollution and hemostasis.
查看更多>>摘要：The demonstrated effects of lower levels of ambient particles on cardiovascular and respiratory system morbidity and mortality were initially surprising in light of current concepts of occupational particle exposure and acute and chronic cardiopulmonary effects. Specifically, the exposure levels, as defined by the weight of the particles per liter of breathing air, at which recognized disease occurs under workplace conditions are considerably higher than the observed levels of ambient particles associated with serious adverse health effects. The possible reasons for this difference have not been adequately addressed. To further address this question, a re-examination of workplace exposure-response relationships is needed, which may include emphasis on measuring exposures to fine and ultrafine particles rather than to total particle mass concentration alone.
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