Showing papers in "Air Pollution and Health in 1999"
TL;DR: The pattern of cardiopulmonary health effects associated with particulate air pollution, which has been observed by epidemiological studies, is the strongest evidence of the health effects of this pollution.
Abstract: Publisher Summary This chapter discusses the adverse effects of particulate air pollution on health The overall epidemiologic evidence is consistent with the premise that particulate air pollution common to many urban and industrial environments is an important risk factor for cardiopulmonary disease and mortality Although the biological linkages remain poorly understood, the results of the acute and chronic exposure studies are complementary Much of the recent epidemiological effort has focused on the effects of acute exposure, primarily because of the relative availability of relevant time-series data sets However, the effects of chronic exposure may be more important in terms of overall public health relevance Long-term, repeated exposure increases the risk of chronic respiratory disease and the risk of cardiorespiratory mortality Short-term exposures can exacerbate existing cardiovascular and pulmonary disease and increase the number of persons in a population who become symptomatic, require medical attention, or die The pattern of cardiopulmonary health effects associated with particulate air pollution, which has been observed by epidemiological studies, is the strongest evidence of the health effects of this pollution
373 citations
TL;DR: The anatomy and physiology of respiratory surfaces, which constitute the interface between inhaled air and the organism, are discussed, which are characterized by so-called tight junctions near the apical margin of adjoining cells.
Abstract: Publisher Summary This chapter discusses the anatomy and physiology of respiratory surfaces, which constitute the interface between inhaled air and the organism. Throughout the airspaces, the respiratory epithelium is characterized by so-called tight junctions near the apical margin of adjoining cells. These structures, whose molecular anatomy is beginning to yield its secrets, impose a significant barrier to solute movement between the surface liquid and the intercellular space, which communicates with the submucosa across a relatively porous basement membrane. In addition, the tight junctional apparatus effectively separates the apical and basolateral membranes of each epithelial cell, thus allowing for selective insertion of various receptors and channels, which confer the polarity underlying vectorial transcellular transport, and selective secretion of epithelial cell products to one or the other face of the epithelium. The apical surfaces of the epithelial cells, which line the lumen of the airways, and air spaces are covered by a continuous layer of extracellular airways surface liquid (ASL) that contains about 93% water. In the cartilaginous airways, the ASL consists of a periciliary “sol” layer and a more lumenally located mucus “gel” layer. The thickness of the sol layer is appropriate to the height of the cilia so that during their power stroke, the cilia contacts the undersurface of the gel layer. Mucin is produced and stored in condensed form as membrane-enclosed granules in the apical portion of specialized secretory cells in bronchial epithelia and in the mucous glands.
221 citations
TL;DR: In this paper, an important defense mechanism in the airways against inhaled particles is the mucociliary escalator, which trap deposited particles. But the mechanisms of these effects are not well understood.
Abstract: Publisher Summary This chapter addresses issues in relation to the adverse health effects of PM 10 ( mass of particulate air pollution). Epidemiological studies have demonstrated a clear relationship between the levels of PM 10 and exacerbations of asthma and chronic obstructive pulmonary disease. Deaths, not only from respiratory causes, but also from vascular causes, that is, myocardial infarction and cerebrovascular accidents, are also related to levels of PM 10 . The mechanisms of these effects are not well understood. The ability of the lung to protect itself against inhaled particles, and the susceptibility of individuals to the effects of particles, will determine the outcome in terms of the adverse effects of environmental particles. An important defense mechanism in the airways against inhaled particles is the mucociliary escalator. In the large proximal airways, goblet cells secrete mucus, which trap deposited particles. Mucus has a major role in protecting the airways, particularly as it is a rich source of antioxidants.
120 citations
TL;DR: In this article, the main source of air pollution is the burning of fossil fuels, particularly in power stations and motor vehicles, and emissions from both these sources have begun to decline in recent years owing to the introduction of efficient abatement measures.
Abstract: Publisher Summary National anthropogenic annual emission inventories can, on their own, give a misleading picture regarding the appropriate sources to control. What is important for most pollutants are those sources that make major contributions to elevated concentrations during pollution episodes. As most people live in cities, urban inventories are important for identifying these sources. The main source of air pollution is the burning of fossil fuels, particularly in power stations and motor vehicles. Emissions from both these sources have begun to decline in recent years owing to the introduction of efficient abatement measures. In most urban areas, road transport is the dominant source of pollution as measures to reduce wintertime smogs in earlier decades lead to the re-location of many large stationary sources to rural or semi-rural sites. Road transport is the single most important source of most of the classical air pollutants. The exceptions are sulfur dioxide and volatile organic compounds. To develop effective control strategies for reducing urban emissions, it is important to know which type of vehicles are contributing most to the total road traffic emissions. It is not possible to measure emissions from every single one. Instead, emissions are generally calculated from a measure of activity relating to the emissions, such as fuel consumption for stationary sources and distance traveled for mobile sources. Emission factors, derived from measurements of individual or representative sources, are then multiplied by the appropriate statistic to give the emission rate.
82 citations
TL;DR: It is suggested that O 3 air pollution is associated with a substantial portion of all respiratory hospital visits and admissions in the summer, and the absolute size of the effect varies somewhat across localities and statistical approaches.
Abstract: Publisher Summary Aggregate population time-series epidemiology studies examining the acute effects of ambient O 3 have yielded significant associations with a wide range of adverse health outcomes, including lung function decrements, the aggravation of pre-existing respiratory disease, increases in daily hospital admissions, and premature mortality. Individual-level camp studies clearly indicate that increases in the number of asthma exacerbations and their effects also are associated with increases in O 3 concentration, which corroborates the reported aggregate-level associations. In addition, less severe acute effects, such as increased number of restricted activity days, decreased lung function, and diminished athletic performance, can occur even in healthy individuals. This indicates that the adverse effects of O 3 exposures are not limited to especially susceptible subpopulations, but that O 3 exposures can also adversely affect a large percentage of general population. The emergency room visit and hospital admission studies collectively indicate that, when the major confounders are addressed, consistent associations are seen between acute occurrences of respiratory morbidity and O 3 exposures. The evidence is especially strong for hospital admissions as this association has been seen by numerous researchers at a variety of localities using a wide range of appropriate statistical approaches. Although the absolute size of the effect varies somewhat across localities and statistical approaches, these analyses collectively suggest that O 3 air pollution is associated with a substantial portion of all respiratory hospital visits and admissions in the summer.
79 citations
TL;DR: In this paper, the effect of metals on health was discussed, and it was shown that exposure to air pollution particles corresponds to the concentrations of metals present in the particles and can be reproduced by instillation of individual metals.
Abstract: Publisher Summary This chapter discusses the effect of metals on health. The atmosphere constitutes a prime vehicle for the movement and redistribution of metals. Human activities have had a major impact on both the global and regional cycles of metals. As a result, there has been a significant contamination of air and water resources, and an accumulation of metals in food chains. Metal cations are a constituent of both emission source and ambient air pollution particles. These metals have been shown to present an oxidative stress both in vitro and in vivo . Lung injury after exposure to air pollution particles corresponds to the concentrations of metals present in the particles and, in an animal model, can be reproduced by instillation of individual metals. The adverse health effects attributed to suspended sulfates have also been demonstrated to be significantly associated with atmospheric concentrations of transition metals capable of complexing with the oxidized sulfur groups. Similarly, the correlations between in vivo tissue damage and particle size may reflect the increased concentrations of catalytically active metals present in smaller particles.
50 citations
TL;DR: In this paper, the authors provide estimates of the risk of lung cancer associated with occupational exposure to diesel exhaust, which cannot be readily attributed to known sources of bias or confounding, however, no study provides quantitative estimates of past exposure of study subjects to any constituent of diesel exhaust; therefore, the doseresponse relation cannot be estimated with great accuracy from available epidemiologic data.
Abstract: Publisher Summary Over 40 studies provide estimates of the risk of lung cancer associated with occupational exposure to diesel exhaust. The studies of occupational exposure to diesel exhaust and lung cancer have consistently observed elevated lung cancer rates among exposed workers, which cannot be readily attributed to known sources of bias or confounding. Unfortunately, however, no study provides quantitative estimates of the past exposure of study subjects to any constituent of diesel exhaust; therefore, the dose-response relation cannot be estimated with great accuracy from the available epidemiologic data. The most frequently studied occupational groups have been railroad workers and truck drivers. The studies of truck drivers show a 20–50% excess incidence and/or mortality from lung cancer, which persists when cigarette smoking is accounted for in data analysis. Some studies included only small numbers of subjects, and therefore, they offer imprecise estimates of the relative risk as indicated by the width of the 95% confidence intervals. However, the upper bounds of the 95% confidence intervals indicate that few of the results are consistent with more than a tripling of risk and the larger studies are consistent with less than a doubling.
48 citations
TL;DR: The results from controlled human exposure studies and from retrospective epidemiology studies of air pollution events, strongly suggest that the young and aged are most at risk and that asthma and other manifestations of hypersensitivity, as well as an increased incidence of upper respiratory infections are the predominant symptoms.
Abstract: Publisher Summary It is clear that inhaled air pollutants modulate immune responses in the lungs. The results from more than 30 years of research under controlled laboratory conditions have categorically demonstrated that exposure of laboratory animals to the most common types of air pollutants result in an increased risk for pulmonary infections. The best understood consequence of this modulation is an increased susceptibility to infectious bacterial agents in laboratory rodents. The role that pollutant exposure may have in infectious viral disease is much less clear, and the effects of air pollutants on viral replication and viral-associated immune responses have rarely been demonstrated. Differences in sensitivity among animal species and among exposure conditions make extrapolation from animal to human difficult. As a result, the overall risk factors for respiratory infections in humans still remain difficult to assess. For example, while associations between acute health effects and particulate air pollution have been commonly reported, it has also been shown that these effects can just be likely because of meteorological conditions. Regardless of these potential confounding factors, the results from controlled human exposure studies and from retrospective epidemiology studies of air pollution events, strongly suggest that the young and aged are most at risk and that asthma and other manifestations of hypersensitivity, as well as an increased incidence of upper respiratory infections are the predominant symptoms.
48 citations
TL;DR: In this paper, the authors focus on the historical development of environmental contamination in the United Kingdom, and show that indoor air pollution has a history much longer than documentary records, and that it was widely experienced in the distant past Mummified lung tissue provides the most useful source of information on prehistoric exposure to particulate materials.
Abstract: Publisher Summary This chapter focuses on the historical developments of environmental contamination in the United Kingdom It is likely that indoor air pollution has a history much longer than documentary records Archaeological evidence suggests that it was widely experienced in the distant past Mummified lung tissue provides the most useful source of information on prehistoric exposure to particulate materials, but this can be found only where it has been preserved by tanning, freezing, or desiccation Outdoor pollution becomes significant with the development of populous cities, or large industrial activities In the past, cities were often small in terms of population, but the inhabitants lived at a high density, which could easily lead to pollutants becoming concentrated Additionally, while some industrial processes took place in forests, or near mining operations, where fuel was abundant, small-scale air pollution sources were also found scattered within cities The cities of antiquity used wood as a fuel, and it was not until the thirteenth century, when the depletion of forests caused wood shortage, that London became the first city to use large quantities of coal As the fuel became increasingly used in London for the production of mortar and some metal working, the smoke problem became severe enough, and by the 1280s, it needed regulation Accounts like these show the readiness of medieval administrators to link health with air pollution Smoke itself may not have been regarded as a serious threat to health because some writers argued that wood smoke indoors contributed to a healthy family
46 citations
TL;DR: The epidemiological principles of investigating air pollution episodes are straightforward, but in practice, there are many difficulties and assumptions that make comparison of different studies or meta-analysis very difficult.
Abstract: Publisher Summary In extreme situations, air pollution episodes cause widespread public apprehension and are associated with measurable effects on health. Air pollution is usually the direct or indirect consequence of burning fuel for transport, industry, or domestic use, but may also come from other sources such as forest fires or volcanic eruptions. Episodes of pollution from the burning of fuel tend to occur not because of an increase in emissions, but because stagnant weather conditions impair their dispersal. In the developed world, episodes that occurred in the postwar decades are unlikely to be repeated, but there remains the risk of less severe episodes and of other disasters such as forest fires and volcanic eruption. Episodes give information about the effects of pollution mixtures in different contexts. Unfortunately, this heterogeneity has not been successfully exploited for identifying the most harmful constituents of pollution or for investigating exposure-response relationships. The epidemiological principles of investigating episodes are straightforward, but in practice, there are many difficulties and assumptions that make comparison of different studies or meta-analysis very difficult.
40 citations
TL;DR: The purpose of measuring biomarkers of xenobiotic exposure is ultimately to provide a better linkage between the exposure with biological effects and/or clinical disease, and to provide information regarding the mechanism(s) leading to a biological effect.
Abstract: Publisher Summary A biomarker of exposure can be defined as the degree of individual exposure to xenobiotics in a given environment by providing a measurement of internal dose. A relatively narrow definition of an exposure biomarker would be the level of the parent compound or secondary products, such as metabolites, and/or reaction products in biological fluid, cells, or subcellular component, for example, DNA and protein adducts. Ideally, the purpose of measuring biomarkers of xenobiotic exposure is ultimately to provide a better linkage between the exposure with biological effects and/or clinical disease. Thus, biomarkers represent a spectrum between health and disease. Biomarkers of exposure may become critical in the prevention or treatment of a disease. It may also provide information regarding the mechanism(s) leading to a biological effect, and to determine if similar processes are occurring across species. An important attribute of exposure biomarkers is that it takes into account individual determinants of the dosimetry and metabolism of the absorbed pollutant. The factors that affect these rest mainly with individual susceptibility and can include avoidance behavior, personal protective equipment, physiological and psychological adaptations, physical activity, metabolic factors, and organ transport rates. Thus, measurement of the external exposure may not adequately correlate with the target tissue dose or internal dose because of these factors.
TL;DR: In this article, the gravimetric measurement of the PM10 (mass of particulate air pollution) fraction of airborne particulate matter has been studied, where the authors focus on the particle size in the innermost regions of the lungs.
Abstract: Publisher Summary This chapter focuses on the gravimetric measurement of the PM10 (mass of particulate air pollution) fraction of airborne particulate matter The term PM10 stands for a fraction of airborne matter that contains particles with an aerodynamic diameter of less than 10 μm Technically speaking, the PM10 fraction of an airborne dust consists of particles that pass through a size-selective inlet with a 50% efficiency cutoff at 10 μm aerodynamic diameter An interest in the fraction called PM25 (its definition is analogous to PM10) also needs special consideration as this fine fraction is suspected to be the major contributor to health effects because it can penetrate easily to the innermost regions of the lungs In industrialized countries, the daily deposition of PM10 particles in the lungs is roughly around 250 μg/day, which represents a small dose, in terms of traditional toxicology studies Studies of PM10 have considered this total material, but have not asked how much its chemical or physical characteristics contribute to its total toxicity Airborne PM10 matter may not only be dangerous because of its inorganic chemistry, but also because of the complex organic materials it contains These include benzene, 1–3 butadiene, polychlorinated biphenyls, and polynuclear aromatic hydrocarbons Many of these are known to be highly suspected potential carcinogens
TL;DR: In the power generation sector, in most countries and in Europe at least, there has been a shift from uncontrolled coal and oil-fired generation to a position where a much higher proportion of the output comes from cleaner fuels such as gas or nuclear power as mentioned in this paper.
Abstract: Publisher Summary Trends in emission patterns have displayed similar characteristics in many developed countries. This has been most clearly demonstrated in the power generation and domestic sectors, and in transport. In the power generation sector, in most countries and in Europe at least, there has been a shift from uncontrolled coal and oil-fired generation to a position where a much higher proportion of the output comes from cleaner fuels such as gas or nuclear power. Where coal and oil are still used, then they are often used in conjunction with some form of abatement technology such as flue gas desulphurization. The net result of these changing patterns is that for most industrial sectors, emissions of pollutants, such as SO2, have become decoupled from measures of economic output of the sector. The domestic sector has also seen major changes in fuel use, and hence, emissions have increased. In most countries in North West Europe, and elsewhere, coal was at one time the predominant fuel. The changing patterns of emissions have had significant implications on urban air quality. The movement away from coal in the domestic, commercial, and smaller industrial sectors has in itself resulted in significant decreases in concentrations of pollutants such as SO2 and particles. This trend has been enhanced in many countries by the shifts in emission patterns from electricity generation, not only in moving to cleaner fuels and technologies, but also by moving to larger power plants in rural areas away from towns.
TL;DR: In this article, the authors provide an overview of air quality in cities of developing countries from Africa, Asia, and America in the 1990s, and identify other approaches that merge economic development, and protect both health and the environment.
Abstract: Publisher Summary This chapter provides an overview of air quality in cities of developing countries from Africa, Asia, and America in the 1990s. Levels of air pollutants, and especially of particulate matter, are a serious problem in many cities of developing countries and should be a matter of serious concern to public health authorities. Comprehensive, long-term air quality management programs are needed in these cities to ensure tolerable levels of pollution are not exceeded and that the population exposure is reduced to acceptable levels. Such a program involves a wide range of local authorities, industry, transport, and local communities. Efforts must not be limited to combating only outdoor pollution. Improvement of cooking and heating facilities can greatly reduce exposures occurring indoors and, through improvement of fuel use efficiency, can also benefit ambient levels of pollution. Growing numbers of motor vehicles, often old and ill-maintained, and using poor quality fuel, will pose an increasing risk to health through emissions of large quantities of fine particles. These emissions increase the population exposure to lead, affecting neurological development of children. This emerging risk, possibly replacing or adding to the impacts, should be avoided through programs that promote the use of cleaner vehicles, and by identifying other approaches that merge economic development, and protect both health and the environment.
TL;DR: Exposure to high levels of SO 2 are needed before there are significant changes in pulmonary defenses, but exposure to lower levels of acidic sulfates will alter mucociliary transport, alveolar clearance of particles, and airway reactivity, even in normal individuals.
Abstract: Publisher Summary This chapter describes the effect of sulfur dioxide (SO 2 ) on health. The toxicologically significant sulfur oxides are the gaseous SO 2 , produced primarily from combustion sources, and sulfuric acid and ammonium bisulfate, the secondarily derived particulate strongly acidic sulfates. Controlled clinical studies strongly suggest that asthmatics are more sensitive to SO 2 , responding with bronchoconstriction at much lower exposure levels than do normal individuals. Toxicologically, exposure to high levels of SO 2 are needed before there are significant changes in pulmonary defenses, but exposure to lower levels of acidic sulfates will alter mucociliary transport, alveolar clearance of particles, and airway reactivity, even in normal individuals. While the exact mechanisms underlying the toxicity of sulfur oxides are not known with certainty, the main response to SO 2, that is, bronchoconstriction, is because of contraction of airway smooth muscle via the parasympathetic reflex and/or following release of humoral mediators. This is probably due most directly to the bisulfite ion produced upon dissolution of SO 2 in airway fluids. On the other hand, the toxicity of acid sulfates is most likely because of the deposition of H + on airway surfaces, and it appears that a threshold exists for both the number of deposited acid particles as well as the mass concentration needed to produce any biological response.
TL;DR: This chapter discusses epidemiologic approach for investigating the health effects of outdoor air pollution and the scientific methods used to study disease occurrence in human populations, including description of the occurrence of disease and identification of the causes of disease.
Abstract: Publisher Summary Epidemiology will remain an important research method for addressing the health effects of air pollution. It provides evidence directly from human population that is complementary to the findings of toxicologic studies. This chapter discusses epidemiologic approach for investigating the health effects of outdoor air pollution. Epidemiology comprises the scientific methods used to study disease occurrence in human populations, including description of the occurrence of disease and identification of the causes of disease. Epidemiologic studies address the effects of inhaled pollutants as exposure occurs in the community. Their results can document the occurrence of adverse effects of air pollution and describe the relationship between exposure and response, and characterize effects on susceptible groups within the population, for example, persons with asthma. In general, epidemiologic studies are carried out with several objectives: to determine if air pollution or a source of air pollution poses a hazard to human health; to characterize the relationship between the level of exposure and the response; and to examine responses of potentially susceptible populations to pollutant exposures. Although epidemiologic studies are subject to potentially limiting methodologic problems, new approaches for assessing exposure to pollutants and health outcomes should strengthen the epidemiologic approach for investigating the health effects of air pollution.
TL;DR: There is still not enough evidence from epidemiological studies alone to establish whether health effects are causally related to NO2, but it seems reasonable to assume that NO2 is at least partially responsible for the observed health effects of urban pollution mixtures.
Abstract: Publisher Summary There is still not enough evidence from epidemiological studies alone to establish whether health effects are causally related to NO2. From the overall evidence, including findings from toxicological studies, it seems reasonable to assume that NO2 is at least partially responsible for the observed health effects of urban pollution mixtures. The World Health Organization Centre for Europe recommends in the revised Air Quality Guidelines for Europe as a long-term guideline for NO2 an annual value of 40 μg/m3 (21 ppb) and, based on clinical data, a 1-h guideline of 200 μg/m3 (100 ppb). The directive of the Economic Commission for Europe proposes the same values as limit values to protect human health. The short-term value of 200 μg/m3 averaged over 1h must not be exceeded during more than 8 out of 8760 hours per calendar year; the long-term limit value will be 40 μg/m3 averaged over a calendar year.
TL;DR: A limited number of studies indicate that the cells completing the repair phase within the first week following a single injury do not develop resistance to injury when re-exposed, and are apparently as susceptible as an initially exposed population.
Abstract: Publisher Summary A large number of experimental studies have been directed at defining the risk, significant biological effects, and doses relevant to decrements in health following ozone exposure. The patterns that cellular compartments, metabolic processes, and physiological events follow after exposure are reasonably well understood. It is clear from animal studies that exposure history has a major impact on the nature of the biological response. The effect of fluctuating and episodic environmental patterns of air pollution has also been examined via animal studies, but demands further study, particularly in higher primates. Cells that repopulate target areas following acute initial injury appear to be relatively resistant to further injury during the very earliest portions of the repair phase. However, continual exposure during repair alters the repair process, increasing the level of resistance of the cell population in target zones. The inflammatory response progresses through a series of different stages, extended and modified only to a limited extent by continual exposure. A limited number of studies indicate that the cells completing the repair phase within the first week following a single injury do not develop resistance to injury when re-exposed. They are apparently as susceptible as an initially exposed population.
TL;DR: In this article, the authors highlight some of the organic air pollutants to which humans are exposed and highlight the adverse health effects of exposure to toluene, which may enhance or reduce any adverse effect.
Abstract: Publisher Summary This chapter highlights some of the organic air pollutants to which humans are exposed. The general population is exposed to benzene in the outdoor environment mainly through inhalation of polluted air from vehicles, and to a lesser extent, from industrial sources. In the indoor environment, tobacco smoke is the main source of benzene. To put the contribution of ambient air to total benzene exposure into context, it is important to consider microenvironments in which the potential for exposure may be high. Benzene has been associated with a number of adverse health effects over a range of exposure levels. Acute toxic effects on the central nervous system are experienced at high levels of exposure, usually as a result of accident or abuse. Toluene is another most widespread hydrocarbon in the environment. Although it occurs naturally in crude oil, natural gas deposits, and in emissions from volcanoes and forest fires, its presence is largely because of its high volume of production and extensive use. Dysfunction of the central nervous system (CNS) is the adverse health effect of primary concern with exposure to toluene. Acute and subchronic inhalation of toluene in several animal species has been shown to produce CNS depression, disturbance of the circadian rhythm, and behavioral effects. Most of the effects in humans are the result of exposure to toluene in association with other organic solvents, such as benzene, which may enhance or reduce any adverse effect.
TL;DR: In this article, the authors proposed a monitoring-based air quality management strategy that uses monitoring to provide information on the present levels of air pollution and involves the use of air quality standards to provide a benchmark of acceptable air quality.
Abstract: Publisher Summary Measurements of air pollutant concentrations are normally carried out at fixed site monitoring stations. An alternative for some pollutants is to attach personal monitors to volunteers to measure personal exposure directly. Such measurements can differ greatly from fixed site measurements of concentration as the population spend majority of their time indoors, where concentrations can differ appreciably from those out-of-doors. Measurements of air pollutant concentrations are best considered in the context of the entire air quality management process. In general, the purpose of local air quality management is to safeguard human health, and hence an understanding of the overall process is valuable. The strategy uses monitoring to provide information on the present levels of air pollution and involves the use of air quality standards to provide a benchmark of acceptable air quality. If measured concentrations are comfortably within health-based air quality standards, then little action may be required. However, in urban areas throughout the world, concentrations of some air pollutants are liable to exceed air quality standards and development of control strategies is essential. Such control strategies entail reduction of emissions from one or more categories of source, and before embarking on such a policy, the regulatory authority will wish to have quantitative knowledge of the likely benefits of the strategy, and probably have conducted a cost/benefit appraisal in which the cost-effectiveness of different control strategies can be compared.
TL;DR: In this article, the effect of air pollutants on the airway inflammation was investigated in a controlled exposure study of asthmatics with mild and significant disease, and it was shown that subjects with mild disease are more likely to have less inflammation than those with more significant disease.
Abstract: Publisher Summary In general, controlled exposure studies of airborne pollutants are performed in a facility with an exposure chamber in which not only the level of the pollutant of interest is controlled, but also other factors, including temperature, relative humidity, light, and sound levels. The actual dose of the pollutant depends on the concentration of the pollutant, the duration of exposure, and the ventilation rate of the subject, which is usually manipulated by exercise. Exercise also is important in determining whether nasal or oronasal breathing occurs. An important criticism of most controlled exposure studies is that the level of the pollutant employed to show an effect is often much higher than that which is actually encountered with ambient pollution. However, it should be noted that, for ethical and practical reasons, most controlled exposure studies of asthmatics only include subjects with mild disease. Subjects with mild disease are likely to have less airway inflammation than those with more significant disease. If the effect of air pollutants is because of an ability to alter airway inflammation, then subjects with more significant disease are likely to respond to lower levels of pollutants. Likewise, the interaction of pollutants with allergen also is important and the level of pollutant needed to alter allergen-induced responses may be less than that required to have a more overt effect on the airway itself.
TL;DR: In bronchitis and chronic obstructive lung disease, abnormalities in the short-term phase of particle clearance are present in peripheral and central airways respectively.
Abstract: Publisher Summary Inertial impaction, sedimentation, and diffusion are the primary mechanisms that govern particle deposition in the human lung. During particle exposures, ventilatory parameters known to affect regional lung deposition include: the depth of the tidal volume, which determines particle penetration into small airways; mean inspiratory airflow, which is an index of forces governing aerosol impaction onto airway walls; and the duration of the breath cycle, which determines respiratory residence time and influences sedimentation and diffusion of particles. In healthy subjects, exposure to ozone acutely enhances the lung deposition of fine particles. The presence of obstructive lung disease centralizes deposition of inhaled particulate and enhances the deposition of fine and ultrafine particles. Clearance of particles from the lower respiratory tract is dependent upon the location and solubility of the particle. For insoluble particles, removal is a dynamic process involving two phases: a short-term airway phase and a long-term alveolar component. Neither phase is a complete or perfect defense against deposited particulate. In bronchitis and chronic obstructive lung disease, abnormalities in the short-term phase of particle clearance are present in peripheral and central airways respectively.
TL;DR: Self and passive exposure to tobacco smoke, and atmospheric and occupational pollution, all interact and may, in a susceptible group, overcome the authors' normal defenses to initiate and perpetuate chronic inflammation, and the development of several lung conditions, all of which have a major impact on world health.
Abstract: Publisher Summary The associations among smoking, atmospheric and occupational pollution, and lung inflammation and disease are strong. The associations become even more convincing when one examines the improvement of life expectancy and its quality by giving up the smoking habit and improving the air they breathe. Considering lung function and cellular responses, there are acute effects on airway dynamics, mucociliary clearance, epithelial and vascular permeability, and immune function. Cells known to be affected include especially airway lining epithelial cells, while there are different affects on lymphocyte subsets, alveolar macrophages, neutrophils, mast cells, fibroblasts, and platelets. Molecular and biochemical effects include: metabolism of a variety of exogenous chemicals by microsomal mixed function oxidases and altered binding of metabolized products to DNA, alterations of DNA, stimulation of lipolysis, arachidonic acid metabolism, increased production of intracellular messengers, transcription factors, and increased release of proinflammatory cytokines. Self and passive exposure to tobacco smoke, and atmospheric and occupational pollution, all interact and may, in a susceptible group, overcome our normal defenses to initiate and perpetuate chronic inflammation, and the development of several lung conditions, all of which have a major impact on world health.
TL;DR: In this article, the authors studied the effect of wind speed and direction on the formation of atmospheric turbulence in the form of turbulent eddies and found that inversions in general act as a physical barrier to the vertical mixing of pollutants.
Abstract: Publisher Summary
Weather and its longer term counterpart climate play a key role in the relationship between air pollution and health. The dispersion and diffusion of air pollution is heavily dependent on the three-dimensional physical and dynamical properties of the atmosphere. Atmospheric stability, which refers to the thermal structure of the atmosphere, controls the extent to which pollutants may be dispersed and diffused vertically. Of the various stability states, absolute stability poses the greatest potential for the accumulation of pollutants in the boundary layer owing to the presence of inversions. Although there are a variety of inversion types, inversions in general act as a physical barrier to the vertical mixing of pollutants. Wind generally serves to transport and disperse pollutants. However, high-frequency variations of wind speed and direction generate atmospheric turbulence in the form of turbulent eddies. Diffusion of pollutants occurs when the size of the turbulent eddies is smaller than the pollution plume, whereas transport of pollution occurs if the eddies are larger than the plume. Increases in temperatures related to climate change may enhance the rate of formation of secondary pollutants such as ozone, especially during summer in the megacities of the future. Climate change can therefore bring about an increased frequency of extreme weather events and high-pollution concentrations.
TL;DR: In this paper, the authors provide suggestions on informing the public about air pollution, including providing accurate, accessible, and understandable information in a form that is easily understood, and providing the public with information about levels of air pollution.
Abstract: Publisher Summary This chapter provides suggestions on informing the public about air pollution. Providing the public with information about levels of air pollution should be an integral part of any air quality strategy. Such information should be accurate, accessible, and provided in a form that is easily understood. Air pollution information can be provided in a number of tiers of increasing complexity and detail. This should both enable the lay public to take on board relevant air pollution information, and at the same time give air pollution specialists access to increasingly disaggregated data sets, including raw data sets for those interested to use in their own data analysis. In addition, air pollution information can be provided in different formats and over different time frames ranging from real-time data via the electronic media to publications in the form of periodic or annual reports, or occasional publicity material such as leaflets. Such information should be up to date and should include forecasts for the following day or days so that individuals can take steps: to avoid the effects of pollution and to reduce activities that lead to raised levels of pollution. Many countries provide such advice.
TL;DR: This chapter focuses on the effects of exposure to ambient concentrations of carbon monoxide, and there is some dispute over whether more subtle effects on the CNS may occur as a result of repeated low-level exposures.
Abstract: Publisher Summary
This chapter focuses on the effects of exposure to ambient concentrations of carbon monoxide. Severe poisoning by carbon monoxide often results in lasting damage to the central nervous system (CNS). This may be delayed, progressive, irreversible, and lethal. Though anoxia is undoubtedly important, autoimmune processes leading to a spongiform degeneration or leukoencephalopathy have been suggested. Leukoencephalopathy is not seen following acute exposure to low concentrations of carbon monoxide, but there is some dispute over whether more subtle effects on the CNS may occur as a result of repeated low-level exposures. Carbon monoxide exerts its toxic effects by reducing the capacity of hemoglobin to transport oxygen and by interfering with the release of such oxygen as is carried. The hypoxia produced is particularly dangerous in that the partial pressure of oxygen is maintained despite a fall in the amount of oxygen per unit volume of blood. Thus, early stimulation of the respiratory centre is delayed. Moreover, exposure to carbon monoxide is much more likely to lead to fainting on exertion than exposure to low concentrations of oxygen.
TL;DR: This chapter emphasizes the use of animal models that can be rendered more susceptible to air pollution health effects, and how closely the model mimics the human in terms of its biological handling of the pollutant.
Abstract: Publisher Summary This chapter emphasizes the use of animal models that can be rendered more susceptible to air pollution health effects. Much of the understanding of the toxicity of major air pollutants, such as tropospheric ozone, sulfur dioxide, nitrogen dioxide, particulate matter, carbon monoxide, and other “air toxic” pollutants (for example, phosgene and metal/acid aerosols) has been derived from studies using laboratory animal models. Although a variety of inbred or outbred strains of mice, rats, hamsters, guinea pigs, rabbits, dogs, and primates have been used in inhalation toxicology studies, most studies have employed healthy animals to examine the basic mechanisms underlying pollutant-induced injury. It has been recognized that human susceptibilities to air pollution effects vary dramatically depending on the pre-existent conditions of the host, such as diseases, nutritional deficiencies. Pulmonary structure and pattern of air flow vary widely between animals and human, and therefore, it is critical that the animal model is chosen wisely. Selection of the appropriate model depends upon the condition being modeled and how closely the model mimics the human in terms of its biological handling of the pollutant.
TL;DR: In this article, the authors define an air quality standard as "a description of a level of air quality or air pollution", which is adopted by a regulatory authority as enforceable.
Abstract: Publisher Summary Air quality guidelines and standards have an important role to play in the management of air quality. Such standards are generally established and enforced by regulatory agencies in national governments. It is generally accepted that an air quality standard is a description of a level of air quality or air pollution, which is adopted by a regulatory authority as enforceable. At its simplest, an air quality standard should be defined in terms of one or more concentrations and associated averaging times. In addition, information on the form of exposure and monitoring, which are relevant in assessing compliance with the standard, methods of data analysis and quality assurance and quality control requirements, should be added. Air quality standards are also important in informing the public about air quality. Used in this way they are a double-edged weapon as the public may assume that once a standard is exceeded, adverse effects on health will occur. This may not be the case. If standards are set at levels below the guidelines, then it is even less likely that adverse effects will follow small exceedances.
TL;DR: In this article, the authors focus on estimating the health benefits by quantifying the number of specific health effects expected to be reduced and their associated monetary value as a result of the Title IV-related reductions in ambient sulfate aerosols.
Abstract: Publisher Summary This chapter focuses on estimating the health benefits by quantifying the number of specific health effects expected to be reduced and their associated monetary value as a result of the Title IV-related reductions in ambient sulfate aerosols. It is estimated that the annual health benefits of Title IV required reductions in SO 2 in 2010 in the eastern United States are likely to fall between 17 billion dollars and 70 billion dollars, with an estimated mean value of 40 billion dollars. There is reason to expect some possible upward bias at the higher end of this range, and the results of the sensitivity analyses suggest that the benefits in 2010 fall between 16 billion dollars and 40 billion dollars. The health benefits alone compare favorably with Title IV's estimated annualized cost of SO 2 emission controls: 1.3 billion dollars for 1997 and between 2.2 billion dollars (U.S. General Accounting Office, 1994) and 2.5 billion dollars (U.S. Environmental Protection Agency, 1995b) for 2010.
TL;DR: In this article, risk assessment is used to estimate the effect of a point source of pollution on the surrounding population or to assess the impact of air pollution or on an air pollutant in general.
Abstract: Publisher Summary This chapter provides an introduction to risk assessment and illustrates its application to outdoor air pollution. Risk assessment may be used to estimate the effect of a point source of pollution on the surrounding population or to assess the effect of air pollution or on an air pollutant in general. It has also been used by advocacy organizations to motivate more stringent control measures on the basis of estimated public health burden. In spite of relatively limited use to date in the context of outdoor air pollution, risk assessment can inform decision makers about the management of risks of air pollution, providing an estimate of the attributable burden of disease and of the potential consequences of alternative control strategies. In managing environmental pollutants, including air pollution, risk assessment plays an increasing role. It can inform policy decisions and characterize the anticipated benefits of control measures. It can be used to rank environmental problems and assign priorities to various public health threats, including air pollution. Expanding use worldwide, building from the development of risk assessment in the United States and other countries, can be anticipated.