RecruitingDrug trialExamining a Novel Gastrointestinal Intervention to Negate Environmental Toxicants (ENGINE)This randomized, placebo-controlled crossover trial will test the feasibility and acceptability of using colesevelam in male firefighters with high per- and polyfluoroalkyl substances (PFAS) exposure. This trial will also explore whether colesevelam lowers blood PFAS levels and urine environmental toxicant and mold mycotoxin levels.