Benzo[b]fluoranthene Induces Mutation Accumulation and Cancer-Relevant Mutational Signatures in Mouse Lung Alongside...

Polycyclic aromatic hydrocarbons (PAHs) are well-known for their mutagenic and carcinogenic effects. Benzo[b]fluoranthene (BbF) is one of 16 PAHs prioritized by the US Environmental Protection Agency for toxicological evaluation due to pervasive human exposure. As part of a multi-stakeholder consortium, the genotoxic effects of BbF were evaluated in MutaMouse males exposed to five doses of BbF or a vehicle control via repeated oral gavage for 28, 60, 90, 120, or 180 days, with dose ranges adjusted by duration of exposure. Mutagenesis was evaluated in lung tissue (n = 4) at 28, 90, and 180 days using Duplex Sequencing (DS), and chromosomal damage (n = 8) was evaluated using the micronucleus assay in peripheral blood at all time points. Dose- and time-dependent increases in total mutation frequency (MF) and C:G > A:T mutations were observed in lung tissue after 28, 90, and 180 days of exposure. By 28 days, BbF exposure produced lung cancer-associated mutational signatures linked to tobacco smoking. Mutations accumulated over time in lung, whereas chromosomal damage in peripheral blood erythrocytes reached a steady state by 28 days. Benchmark dose (BMD) confidence intervals (CIs) narrowed with extended exposure only for MF. Collectively, the data demonstrate that BbF is a potent mutagen capable of inducing cancer-relevant mutations in lung, supporting its potential role in human lung carcinogenesis. By distinguishing early mutagenic responses from cumulative mutation effects over time, these findings highlight the value of integrating mutagenicity assessment into extended-duration studies to better inform the potential health effects of chronic genotoxic exposures.