Bacterial diversity and health hazards associated with resuspended road matter transported by runoff into storm and combined sewers

Road surfaces accumulate anthropogenized sediments contaminated by animal waste, soil particles, and atmospheric deposits, raising hygienic concerns. During rainfall events, these sediments can be resuspended and transported via runoff into storm and combined sewers. This study investigated the bacterial diversity and potential health hazards associated with resuspended road-deposited matter in a peri-urban area. Quantitative PCR and metabarcoding analyses of 16S rRNA and <i>tpm</i> genes were performed to (i) identify the sources of bacterial taxa colonizing road surfaces, (ii) define core and specific taxa and assess their capacity to survive in downstream sewer environments, and (iii) explore their functional potential. Several taxa were linked to human and animal sources, with notable occurrences of bacterial pathogen DNA signatures. Amplicon sequence variant profiling revealed that resuspended road surface communities were more similar to those in storm sewage than in combined sewage. Functional annotation suggested that road surface taxa had enhanced pollutant degradation capabilities with some representing significant health hazards. Indicator taxa were identified to support the hygienic assessment of road-deposited sediments. These findings highlight the importance of monitoring road runoff as a vector of microbial contaminants in urban water systems.