Figure 1: Relative abundance of the most common bacterial genera for each sample. Samples are arranged according to treatment.

While the relative abundance of ASVs did not differ between control, solvent control, and brake dust, DEP treatment had 16 differentially abundant ASVs compared to the control, according to DESeq2 (Figure 2 , Table A1 ). Eleven ASVs had a higher abundance in the DEP treatment than control. Five ASVs had reduced abundance in comparison to the control treatment. A more conservative approach to identify differential abundance is ALDEx2, which revealed five ASVs with significantly altered abundance in the DEP treatment compared to the control: Snodgrassella 1 + 2, Neisseriacae,Lactobacillus bombicola , and Bombiscardovia (Table A2 ).