[Breathing: Ambient Air Pollution and Health - Part III]. / Atmen: Luftschadstoffe und Gesundheit ­ Teil III.

The third part of the DGP statement introduces the current body of knowledge on less studied health outcomes associated with exposure to ambient air pollution: the negative impact on metabolism leading to impaired glucose tolerance and diabetes as well as contribution to the development of neurodegenerative disorders and delayed cognitive function in children. Furthermore, prenatal exposure and adverse effects on mother and child are addressed. Finally, the currently discussed biological mechanisms underlying various health effects associated with exposure to air pollution are described.Differing, but often complementary biological mechanisms create the basis for the diverse health outcomes caused by air pollution. Oxidative stress and a subclinical inflammatory response in the lungs and on a systemic level ("low-grade systemic inflammation") are considered to be key mechanisms. They promote secondary alterations in the body, such as vascular or metabolic processes, and may also result in the currently studied epigenetic phenomena or neuroinflammation. In this context, the health significance of soluble particulate matter and the role of ultrafine particles translocated across biological membranes into blood vessel and transported via the circulation to secondary target organs, such as liver, brain or the fetus, are intensively discussed.Diabetes is one of the leading chronic diseases worldwide, with a prevalence of almost 14 % in Germany. Although lifestyle factors are the main causes, current evidence suggests that long-term exposure to air pollution may additionally increase the risk for type 2 diabetes. Supporting evidence for a causal role of air pollution is provided by studies addressing the regulation of the blood glucose levels in metabolically healthy participants, insulin sensitivity, or pregnancy-related diabetes. Experimental studies provide further support for plausible biological mechanisms. However, prospective studies are needed to gain more evidence, taking multiple lifestyle and environmental factors, such as green space and noise, and an improved individual exposure assessment into account.The aging population has an increased risk of neurodegenerative diseases. First studies point towards a contribution of chronic exposure to air pollution, specifically by particulate matter. Several studies report its association with decreased neurocognitive capacity or an increased prevalence of dementia or Alzheimer's disease in adults. However, the studies are inhomogeneous regarding design, exposure and outcome, leading to inconsistent results. With respect to the influence on neurocognitive development of children, first studies suggest an association between the level of air pollution, e. g. at school, and delayed cognitive development.Even though the evidence for the different biological endpoints during pregnancy is still heterogeneous, the studies generally point towards an adverse impact of air pollution on the maternal and fetal organisms. The strongest evidence exists for low birth weight, with small effect sizes of only some grams, and for a higher incidence of reduced birth weight (< 2500 g). An increased risk for gestational hypertension and preeclampsia underscores the possible impact of exposure to air pollution on the maternal organism. However, the current body of evidence does not yet allow a final conclusion on the influence of intrauterine exposure to air pollution regarding early childhood lung function and development of allergies, particularly in light of the fact that it is hard to distinguish in epidemiological studies between the effects of pre- and postnatal exposure.

[Breathing: Ambient Air Pollution and Health - Part II]. / Atmen: Luftschadstoffe und Gesundheit ­ Teil II.

The second part of the DGP-statement on adverse health effects of ambient air pollution provides an overview of the current ambient air quality in Germany and its development in the past 20 years. Further, effects of air pollution on the cardiovascular system und underlying pathophysiological mechanisms are introduced. Air pollutants form a highly complex and dynamic system of thousands of organic and inorganic components from natural and anthropogenic sources. The pollutants are produced locally or introduced by long-range transport over hundreds of kilometers and are additionally subjected to local meteorological conditions. According to air quality regulations ambient air quality is monitored under uniform standards including immission of particulate matter, up to 2.5 µm (PM2.5) or 10 µm (PM10) in aerodynamic diameter, and of nitrogen dioxide (NO2) or ozone (O3). The clean air measures of recent years led to a continuous decline of air pollution in the past 20 years in Germany. Accordingly, the focus is nowadays directed at population-related health hazards caused by low concentrations of air pollution. Exceeded limits for sulfur dioxide, carbon monoxide, benzene and lead are not detected anymore. Also the number of days with increased ozone concentration declined, although the annual mean concentration is unaltered. Decreasing concentrations of particulate matter and NO2 have been observed, however, about 40 % of the monitoring stations at urban traffic sites still measure values exceeding current limits for NO2. Moreover, the stricter, solely health-based WHO-standards for PM2.5, PM10 and NO2 are still not met so that an optimal protection from air pollution-related health hazards is currently not given for the German population. In recent years, the findings of numerous cross-sectional and longitudinal studies underscored adverse effects of air pollution on the cardiovascular system, especially for particulate matter, although the level of evidence still varies for the different health outcomes. Further, the studies show that cardiovascular health hazards on the population level are of higher relevance than those for the respiratory system. The existing evidence for cardiovascular mortality, hospitalization, ischemic heart diseases, myocardial infarction and stroke can be regarded as strong, while that for heart failure is rather moderate. While the evidence for air pollution-related short-term alteration of the cardiac autonomic balance can be considered as sufficient, long-term effects are still unclear. Likewise, the heterogeneous findings on air pollution-related arrhythmia do currently not allow a distinct conclusion in this regard. A large number of studies support the observation that both, short- and long-term air pollution exposure contribute to increased blood pressure, may impair vascular homeostasis, induce endothelial dysfunction and promote the progression of atherosclerotic lesions. These effects provide reasonable biological explanation for the fatal events associated with exposure to air pollution. Short-term exposure may not pose a significant risk on healthy individuals but may be considered as precursor for fatal events in susceptible populations, while repetitive or long-term exposure may contribute to the development of cardiovascular diseases even in healthy subjects.