In a new study published in Ecotoxicology and Environmental Safety, the researchers have shown that air pollution leads to lung function decline accompanied by lung and intestinal microbiome disbalances .
Air quality and longevity
It is widely accepted that both intrinsic and extrinsic factors influence lifespan. Extrinsic factors include both lifestyle choices and environmental factors such as air pollution, which can somewhat be controlled: theoretically speaking, one can choose to live in a place with cleaner air.
In reality, air quality is hardly on the top of the list of factors that people consider when deciding where to live. A disproportionally high number of job opportunities, more convenient infrastructure, and accessible healthcare make people move to big cities. As a result, more than half of the world population currently lives in urban areas, which are characterized by a high level of potentially harmful gaseous and particulate vehicular and industrial emissions.
Emitted particles with a diameter of ≤ 2.5 µm (PM2.5) are of particular concern, as they are associated with respiratory health issues. It was previously shown that PM2.5 contain trace metals capable of forming oxidants in the lungs, leading to lung injury. In addition, antibiotics and other drugs get dispersed into the air during the manufacturing process or get redistributed from soil and groundwater.
Although an adverse effect of air pollution on respiratory health is known, particularly in association with chronic obstructive pulmonary disease (COPD), the mechanisms are not clear. In this study, the researchers decided to investigate the effect of metals and several drugs on lung function in aging rats exposed to air pollution.
Air pollution, drugs, and metals
Thirty male 1.5-year-old rats were exposed for three months to either polluted air from a traffic-heavy urban area in Taiwan (experimental groups) or high-efficiency particulate air (HEPA)-filtered clean air (control group). The former were further subdivided into two groups: exposed to gaseous pollution (with HEPA filtration) or PM2.5 pollution (without HEPA filtration).
First, the lung function examination revealed a decline caused by air pollution in both experimental groups. Second, the concentrations of 12 drugs, including ketamine and ampicillin, became ~5-10 times higher in the HEPA group compared to controls, and ~3 times higher than that in the PM2.5 group as shown by liquid lung biopsies. Finally, there were differences in metal concentrations across the three groups, but none of them was significant.
Air pollution and microbiomes
The researchers then analyzed the lung microbiome diversity in the three groups of rats. Although all the groups contained three major bacterial phyla, with Protobacteria accounting for ~90% of all the bacteria, there were five bacterial groups significantly increased and one decreased in the PM2.5 group compared to controls.
Similar to the lung microbiome, the intestinal bacterial composition of all three groups contained three major bacterial phyla. There were differences in the bacterial abundances between all the three groups, with some bacteria increasing or decreasing depending on the exposure type.
Lastely, the researchers performed a series of correlational analyses. They showed that lung dysfunction caused by air pollution was correlated with lung and intestinal microbiome imbalances. Meanwhile, drugs and metals were correlated with lung functional decline as well as lung and intestinal dysbiosis.
We investigated the effects of antibiotics, drugs, and metals on lung and intestinal microbiomes after sub-chronic exposure of low-level air pollution in ageing rats. Male 1.5-year-old Fischer 344 ageing rats were exposed to low-level traffic-related air pollution via whole-body exposure system for 3 months with/without high-efficiency particulate air (HEPA) filtration (gaseous vs. particulate matter with aerodynamic diameter of ≤2.5 µm (PM2.5) pollution). Lung functions, antibiotics, drugs, and metals in lungs were examined and linked to lung and fecal microbiome analyses by high-throughput sequencing analysis of 16 s ribosomal (r)DNA. Rats were exposed to 8.7 μg/m3 PM2.5, 10.1 ppb NO2, 1.6 ppb SO2, and 23.9 ppb O3 in average during the study period. Air pollution exposure decreased forced vital capacity (FVC), peak expiratory flow (PEF), forced expiratory volume in 20 ms (FEV20), and FEF at 25∼75% of FVC (FEF25–75). Air pollution exposure increased antibiotics and drugs (benzotriazole, methamphetamine, methyl-1 H-benzotriazole, ketamine, ampicillin, ciprofloxacin, pentoxifylline, erythromycin, clarithromycin, ceftriaxone, penicillin G, and penicillin V) and altered metals (V, Cr, Cu, Zn, and Ba) levels in lungs. Fusobacteria and Verrucomicrobia at phylum level were increased in lung microbiome by air pollution, whereas increased alpha diversity, Bacteroidetes and Proteobacteria and decreased Firmicutes at phylum level were occurred in intestinal microbiome. Lung function decline was correlated with increasing antibiotics, drugs, and metals in lungs as well as lung and intestinal microbiome dysbiosis. The antibiotics, drugs, and Cr, Co, Ca, and Cu levels in lung were correlated with lung and intestinal microbiome dysbiosis. The lung microbiome was correlated with intestinal microbiome at several phylum and family levels after air pollution exposure. Our results revealed that antibiotics, drugs, and metals in the lung caused lung and intestinal microbiome dysbiosis in ageing rats exposed to air pollution, which may lead to lung function decline.
This important study revealed that air pollution, particularly a relatively high level of PM2.5, impaires the lung function and increases the concentration of various drugs in the lungs leading to microbiomial dysbiosis in aging rats. The PM2.5 concentration used in this study was 8.7 ± 4.2 μg/m3, which is the level of northern Taiwan. Meanwhile, WHO recommends that the annual average PM2.5 shouldn’t exceed 5 µg/m3. It may be wise to check the PM2.5 level in your home city and make sure your air conditioner or air purifier is equipped with a HEPA filter.
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 Laiman, V. et al. Effects of antibiotics and metals on lung and intestinal microbiome dysbiosis after sub-chronic lower-level exposure of air pollution in ageing rats. Ecotoxicol. Environ. Saf. 246, 114164 (2022)