Particulate matter (PM) is a complex, heterogeneous mixture that changes in time and space. It encompasses many different chemical components and physical characteristics, many of which have been ...cited as potential contributors to toxicity. Each component has multiple sources, and each source generates multiple components. Identifying and quantifying the influences of specific components or source-related mixtures on measures of health-related impacts, especially when particles interact with other co-pollutants, therefore represents one of the most challenging areas of environmental health research. Current knowledge does not allow precise quantification or definitive ranking of the health effects of PM emissions from different sources or of individual PM components and indeed, associations may be the result of multiple components acting on different physiological mechanisms. Some results do suggest a degree of differential toxicity, namely more consistent associations with traffic-related PM emissions, fine and ultrafine particles, specific metals and elemental carbon and a range of serious health effects, including increased morbidity and mortality from cardiovascular and respiratory conditions. A carefully targeted programme of contemporary toxicological and epidemiological research, incorporating more refined approaches (e.g. greater speciation data, more refined modelling techniques, accurate exposure assessment and better definition of individual susceptibility) and optimal collaboration amongst multidisciplinary teams, is now needed to advance our understanding of the relative toxicity of particles from various sources, especially the components and reactions products of traffic. This will facilitate targeted abatement policies, more effective pollution control measures and ultimately, a reduction in the burden of disease attributable to ambient PM pollution.
► Identifying toxic component(s) of particulate matter is a major challenge. ► Evidence suggesting differential toxicity of components and sources are discussed. ► Targeted and contemporary studies are needed to further understand relative toxicity of particles. ► Goals of refined research are abatement policies, pollution control measures and improved health.
Despite past improvements in air quality, very large parts of the population in urban areas breathe air that does not meet European standards let alone the health-based World Health Organisation Air ...Quality Guidelines. Over the last 10 years, there has been a substantial increase in findings that particulate matter (PM) air pollution is not only exerting a greater impact on established health endpoints, but is also associated with a broader number of disease outcomes. Data strongly suggest that effects have no threshold within the studied range of ambient concentrations, can occur at levels close to PM₂.₅ background concentrations and that they follow a mostly linear concentration–response function. Having firmly established this significant public health problem, there has been an enormous effort to identify what it is in ambient PM that affects health and to understand the underlying biological basis of toxicity by identifying mechanistic pathways—information that in turn will inform policy makers how best to legislate for cleaner air. Another intervention in moving towards a healthier environment depends upon the achieving the right public attitude and behaviour by the use of optimal air pollution monitoring, forecasting and reporting that exploits increasingly sophisticated information systems. Improving air quality is a considerable but not an intractable challenge. Translating the correct scientific evidence into bold, realistic and effective policies undisputedly has the potential to reduce air pollution so that it no longer poses a damaging and costly toll on public health.
•52 studies investigating mechanisms behind impacts of desert dust on health are reviewed.•Desert dust may be a risk factor for inflammatory and allergic lung diseases.•Adhered chemicals, biological ...and mineralogical components are candidate activators.•Desert dust surface reactions may enhance toxicity of aerosols in urban environments.
Desertification and climate change indicate a future expansion of the global area of dry land and an increase in the risk of drought. Humans may therefore be at an ever-increasing risk of frequent exposure to, and resultant adverse health effects of desert sand dust. This review appraises a total of 52 experimental studies that have sought to identify mechanisms and intermediate endpoints underlying epidemiological evidence of an impact of desert dust on cardiovascular and respiratory health. Toxicological studies, in main using doses that reflect or at least approach real world exposures during a dust event, have demonstrated that virgin sand dust particles and dust storm particles sampled at remote locations away from the source induce inflammatory lung injury and aggravate allergen-induced nasal and pulmonary eosinophilia. Effects are orchestrated by cytokines, chemokines and antigen-specific immunoglobulin potentially via toll-like receptor/myeloid differentiation factor signaling pathways. Findings suggest that in addition to involvement of adhered chemical and biological pollutants, mineralogical components may also be implicated in the pathogenesis of human respiratory disorders during a dust event. Whilst comparisons with urban particulate matter less than 2.5 μm in diameter (PM2.5) suggest that allergic inflammatory responses are greater for microbial element-rich dust- PM2.5, aerosols generated during dust events appear to have a lower oxidative potential compared to combustion-generated PM2.5 sampled during non-dust periods. In vitro findings suggest that the significant amounts of suspended desert dust during storm periods may provide a platform to intermix with chemicals on its surfaces, thereby increasing the bioreactivity of PM2.5 during dust storm episodes, and that mineral dust surface reactions are an unrecognized source of toxic organic chemicals in the atmosphere, enhancing toxicity of aerosols in urban environments. In summary, the experimental research on desert dust on respiratory endpoints go some way in clarifying the mechanistic effects of atmospheric desert dust on the upper and lower human respiratory system. In doing so, they provide support for biological plausibility of epidemiological associations between this particulate air pollutant and events including exacerbation of asthma, hospitalization for respiratory infections and seasonal allergic rhinitis.
Exposure to ambient air pollution is associated with adverse cardiovascular outcomes. These are manifested through several, likely overlapping, pathways including at the functional level, endothelial ...dysfunction, atherosclerosis, pro-coagulation and alterations in autonomic nervous system balance and blood pressure. At numerous points within each of these pathways, there is potential for cellular oxidative imbalances to occur. The current review examines epidemiological, occupational and controlled exposure studies and research employing healthy and diseased animal models, isolated organs and cell cultures in assessing the importance of the pro-oxidant potential of air pollution in the development of cardiovascular disease outcomes. The collective body of data provides evidence that oxidative stress (OS) is not only central to eliciting specific cardiac endpoints, but is also implicated in modulating the risk of succumbing to cardiovascular disease, sensitivity to ischemia/reperfusion injury and the onset and progression of metabolic disease following ambient pollution exposure. To add to this large research effort conducted to date, further work is required to provide greater insight into areas such as (a) whether an oxidative imbalance triggers and/or worsens the effect and/or is representative of the consequence of disease progression, (b) OS pathways and cardiac outcomes caused by individual pollutants within air pollution mixtures, or as a consequence of inter-pollutant interactions and (c) potential protection provided by nutritional supplements and/or pharmacological agents with antioxidant properties, in susceptible populations residing in polluted urban cities.
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•Oxidative imbalance can occur at each potential juncture at which inhaled air pollutants affect the cardiovascular system.•Evidence supports a role for oxidative stress in specific cardiac endpoints and onset/progression of metabolic conditions.•Evidence of an oxidative pathway is particularly robust for traffic-related pollution.•Studies are needed to determine if nutritional/pharmacological agents offer protection to people residing in polluted cities.
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•Epidemiological evidence links exposure to poor air quality to lentigines and wrinkles.•Experimental studies provide mechanistic explanations involving oxidative stress.•Polluted air ...may hasten skin ageing through indirect systemic effects via the lung and/or direct effects on cutaneous tissue.•Prevention measures would need to combine strategies that target both ‘routes’.•Air pollution is one of several environmental stressors that combined, may have additive/synergistic effects on the skin.
Implementation of regulatory standards has reduced exhaust emissions of particulate matter from road traffic substantially in the developed world. However, nonexhaust particle emissions arising from ...the wear of brakes, tires, and the road surface, together with the resuspension of road dust, are unregulated and exceed exhaust emissions in many jurisdictions. While knowledge of the sources of nonexhaust particles is fairly good, source-specific measurements of airborne concentrations are few, and studies of the toxicology and epidemiology do not give a clear picture of the health risk posed. This paper reviews the current state of knowledge, with a strong focus on health-related research, highlighting areas where further research is an essential prerequisite for developing focused policy responses to nonexhaust particles.
Exposure to combustion‐related particulate matter (PM), at concentrations experienced by populations throughout the world, contributes to pulmonary and cardiac disease through multiple mechanistic ...pathways that are complex and interdependent. Current evidence supports an interactive chain of events linking pollution‐induced pulmonary and systemic oxidative stress, inflammatory events, and translocation of particle constituents with an associated risk of vascular dysfunction, atherosclerosis, altered cardiac autonomic function, and ischemic cardiovascular and obstructive pulmonary diseases. Because oxidative stress is believed to play such an instrumental role in these pathways, the capacity of particulate pollution to cause damaging oxidative reactions (the oxidative potential) has been used as an effective exposure metric, identifying toxic components and sources within diverse ambient PM mixes that vast populations are subjected to—from traffic emissions on busy roads in urban areas to biomass smoke that fills homes in rural areas of the developing world.
Epidemiological data provide varying degrees of evidence for associations between prenatal exposure to ambient air pollutants and adverse birth outcomes (suboptimal measures of fetal growth, preterm ...birth and stillbirth). To assess further certainty of effects, this review examines the experimental literature base to identify mechanisms by which air pollution (particulate matter, nitrogen dioxide and ozone) could cause adverse effects on the developing fetus. It likely that this environmental insult impacts multiple biological pathways important for sustaining a healthy pregnancy, depending upon the composition of the pollutant mixture and the exposure window owing to changes in physiologic maturity of the placenta, its circulations and the fetus as pregnancy ensues. The current body of evidence indicates that the placenta is a target tissue, impacted by a variety of critical processes including nitrosative/oxidative stress, inflammation, endocrine disruption, epigenetic changes, as well as vascular dysregulation of the maternal‐fetal unit. All of the above can disturb placental function and, as a consequence, could contribute to compromised fetal growth as well increasing the risk of stillbirth. Furthermore, given that there is often an increased inflammatory response associated with preterm labour, inflammation is a plausible mechanism mediating the effects of air pollution on premature delivery. In the light of increased urbanisation and an ever‐changing climate, both of which increase ambient air pollution and negatively affect vulnerable populations such as pregnant individuals, it is hoped that the collective evidence may contribute to decisions taken to strengthen air quality policies, reductions in exposure to air pollution and subsequent improvements in the health of those not yet born.
In today's 'indoor generation', most human activities take place within an enclosed space, characterised by a chemically diverse and complex air quality. Although source control is the universally ...preferred approach to reduce contaminants, this is becoming increasingly insufficient, technically unfeasible or economically unviable. The provision of adequate ventilation is also being challenged by invariably poor outdoor air quality and our quest for a low carbon economy. Whilst the former directly adds to the burden of indoor air pollution, both factors attract mitigation measures that are leading to efforts to seal off indoor spaces, which can increase exposure to endogenous indoor air pollutants, heighten health risks and curtail concentration, learning and productivity. Research to date on the role of air purification technologies in key indoor microenvironments demonstrates that air filtration produces clear reductions in indoor pollution concentrations. To confirm the optimistic modelled health/performance benefits associated with air purification further research is required, evaluating longer term interventions particularly in vulnerable populations, employing real-time sensors to quantitatively assess complete exposure profiles and optimizing technologies/strategies to remove specific indoor air pollutants (eg infiltrated versus endogenous particles, gases, chemically transformed organics) within the unique spaces where people live, learn, work and travel.
•HEPA filter or electret air purifiers reduce indoor PM2.5 concentrations by 30–80%.•More consistent health improvements stem from studies in Asian megacity homes.•Studies should now evaluate longer interventions in vulnerable people with real-time sensors.•Modeling work reports significant health/performance/economic benefits of air filtration.
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