Air pollution effects on chronic disease and the potential role of the microbiome

Another important factor influencing inflammation from cardiovascular disease, diabetes and chronic lung disease is air pollution. Increasing evidence is showing a quite substantial effect, even when the air pollution levels are below national standards[28–30], indicating a direct or indirect effect on lung pathology and quite possibly the microbiome. Although there are many potential effects of air pollution, this pattern is compatible with a role for the colonization/infection of microbes associated with air pollution, as described previously[12]. Little research has been done on this so far; however, changes in the nasopharyngeal microbiota were observed after a severe haze event in China[31]. It is also possible that hard-to-detect low-abundance microbes from the rare biosphere may also produce pro-inflammatory effects[12]. It has been observed that COPD exacerbations are often related to exposures to certain gases and particulate matter[32]. It seems possible that many of these gases and types of particulate matter, especially from the burning of fossil fuel, may have microbial strains associated with them that humans have not coevolved with. These relatively novel, potentially non-coevolved microbes (PHM) might be more prone to cause increased hypersensitivity reactions[12].
Not only are the above chronic diseases related to air pollution on a long-term basis, but increases in air pollution in the short-term lead to increases in emergency room visits, hospitalizations and deaths[33], including deaths from respiratory infections[34]. It is estimated that indoor and outdoor air pollution-related deaths annually exceed 7 million[35].
Recent studies in the U.S. and Italy also support a significant effect on mortality from COVID-19 from long-term air pollution exposure[36,37]. These potential COVID-19 mortality effects and the longer-term global effects mentioned above emphasize the need to reduce the use of polluting fossil fuels for health reasons in addition to avoiding the worst effects of global warming on many other facets of human health and well-being[38]. Smoking reduction is important, but it is also important to dramatically reduce and eventually eliminate unnecessary wood/biomass burning and fossil fuel-related pollution by adopting newer clean energy technologies.