Colon Effects of 7-Day Whole-Body Inhalation Exposure of Fischer 344 Rats to Emissions from First- and Second-Generation Biodiesel Fuels with and Without a Particle Filter

Biodiesel is projected to reduce greenhouse gas and particulate matter emissions relative to petrodiesel, but biodiesel engine emissions (DEEs) contain higher levels of nitrogen oxides, nano-sized particles, and specific oxygenated volatile organic compounds and aromatics that may increase health risks. Most research on DEE health effects has focused on respiratory, cardiovascular, neurodegenerative, and reproductive outcomes, leaving a considerable knowledge gap regarding gastrointestinal effects. We therefore examined and compared the colon effects of DEE produced by combustion of first-generation B7 biofuel (7% v/v fatty acid methyl esters, FAMEs) or second-generation SHB20 biofuel (7% v/v FAME plus 13% v/v hydrotreated vegetable oils, HVOs), with or without a diesel particle filter (DPF). Male Fischer 344 rats were exposed to DEE for 7 consecutive days (6 h/day; seven exposure sessions, 42 h in total) in whole-body inhalation chambers, at measured particulate matter concentrations of 2.19 and 2.13 mg/m3 without DPF and 0.17 and 0.19 mg/m3 with DPF for B7 and SHB20, respectively. Whole-body DEE exposure induced lipid peroxidation, oxidative-stress-associated and redox-related changes, mobilisation of the antioxidant defence system, and an inflammatory-associated response in colon tissue. These colon effects were blend-specific and only partly and endpoint-dependently mitigated by DPF use, with SHB20 DEE without DPF producing the most pronounced responses.