Research progress on regulation of gut microbiota abundance induced by ambient particulate matter exposure

Particulate matter (PM) is the main air pollutant in China. Due to its wide distribution and difficulties in control, PM has been widely concerned. PM mainly enters human body through respiratory exposure and can cause a variety of health problems. Recent studies have shown that PM exposure is also associated with the occurrence and development of digestive system diseases, as it can enter human body indirectly through the respiratory tract or directly through the digestive tract. Gut microbiota (GM) is a group of microorganisms located in the intestinal epithelium mucosa and intestinal lumen. GM is large in number and rich in functions, and its homeostasis plays an important role in the intestinal health of individuals and even the health of the body. Because GM may mediate the health effects induced by environmental factors, more and more studies have focused on the effects of ambient PM on GM. In this review, we summarized the effects of a variety of ambient PM on GM homeostasis, focusing on five major phyla including Firmicutes, Bacteroidetes, Proteobacteria, Actinobacteria, and Verrucomicrobia, and discussed their main functions and the effects of PM on their homeostasis and abundance.