Identification of priority gaseous component in biodiesel exhaust and its potential pulmonary hazards: a data-driven screening and validation strategy.

Biodiesel is increasingly adopted as a renewable low-carbon fuel, yet the pulmonary toxicity of its exhaust-particularly the gaseous components-remains a critical knowledge gap. To address this, we developed an integrative strategy combining data-driven prioritization with experimental validation. Herein, we employ a multidimensional risk-ranking system that predicts pulmonary fibrosis as the top-ranked adverse outcome (weighted score: 1.00) and ranks formaldehyde as the highest-priority toxicant (weighted score: 0.94). Component-outcome association analysis further predicts aldehydes, particularly formaldehyde, as the top candidate driving pulmonary fibrosis, with an estimated 28% contribution. Both in vivo and in vitro validations demonstrate that biodiesel exhaust (BDE) gas exposure induces substantial pulmonary fibrogenic toxicity, with formaldehyde directly driving epithelial-mesenchymal transition (EMT) in lung epithelial cells. By integrating quantitative proteomics with computational network toxicology, we identify TGF-β1 as a key mediator linking formaldehyde to fibrotic remodeling. This conclusion is further suppported by the upregulation of Tgfb1 expression both in vivo and in vitro. Moreover, analysis of a human Idiopathic Pulmonary Fibrosis (IPF) single-cell dataset highlighted immature neutrophils as a candidate immune subset enriched for the formaldehyde-pulmonary fibrosis-associated gene signature. Overall, this study systematizes the pulmonary toxicity profile of BDE gaseous components and provides an evidence-based foundation for incorporating BDE-derived aldehydes, specifically formaldehyde, into health risk assessments and future emission control policies for biodiesel.