Investigation of Oral Toxicity Mechanisms of Low-Molecular-Weight Polycyclic Aromatic Hydrocarbons and Probiotic Interventions Under the Framework of the “Gut–Lung Axis”

Low-molecular-weight polycyclic aromatic hydrocarbons (LMW-PAHs), as ubiquitous contaminants in the environment and food processing, have attracted growing concern due to their systemic health hazards through oral exposure. Recent studies have demonstrated that the toxic effects of LMW-PAHs extend beyond the direct damage caused by inhalation exposure. They can induce pathological changes in distal organs by disrupting the bidirectional communication system known as the “gut–lung axis”. This review summarizes the major sources and health risks of LMW-PAHs and elucidates the communication mechanisms underlying the gut–lung axis, which comprises a bidirectional regulatory network involving gut microbial metabolites, circulating inflammatory factors, immune cell migration, and neuroendocrine signaling. Furthermore, the review explores the core mechanisms by which oral exposure to LMW-PAHs leads to pulmonary injury: primarily through triggering gut microbiota (GM) dysbiosis, compromising intestinal barrier integrity, and inducing intestinal inflammation, which collectively propagate lung injury via the “gut–lung axis”. In response to these toxic pathways, we propose probiotic intervention strategies that may antagonize the gut–lung-axis-mediated toxicity of LMW-PAHs through multiple mechanisms, including modulation of gut microbiota composition, reinforcement of intestinal barrier integrity, systemic immune regulation, and production of beneficial metabolites such as short-chain fatty acids (SCFAs). Finally, this review discusses the application prospects and existing challenges of probiotic interventions, aiming to provide a solid theoretical foundation and novel perspective for probiotic resource development and application based on the “gut–lung axis”.