Nanoplastics released from textile washing enrich antibiotic resistance and virulence genes in sewage sludge microbiomes.

The washing of synthetic textiles is a major source of microplastic pollution, contributing to the widespread presence of nanoplastics (NPs) in wastewater treatment plants (WWTPs). However, the role of laundry-released NPs in shaping microbial communities and facilitating the spread of antibiotic resistance genes (ARGs) and virulence factor genes (VFGs) in sludge remains unclear. Here, we quantified the concentration and size distribution of NPs released during the washing of polyamide (PA), polypropylene (PP), and polyethylene terephthalate (PET) textiles using nanoparticle tracking analysis. Substantial NP release was observed, with concentrations ranging from 3.4 × 10 to 1.7 × 10 particles mL, and sizes between 130 and 240 nm. We then evaluated their impact on ARG and VFG profiles, as well as bacterial communities in anaerobic sludge through metagenomic and 16S rRNA gene sequencing. Laundry-released NPs significantly increased the abundance of ARGs, VFGs, and mobile genetic elements (MGEs) in sludge, with D8A-2 and Halomonas identified as potential ARG and VFG hosts. Notably, the mechanisms driving ARG enrichment varied by NP type. PA-released NPs elevated reactive oxygen species levels in bacterial communities, facilitating horizontal gene transfer via MGEs, while PP- and PET-released NPs enhanced ARG enrichment through both horizontal gene transfer and shifts in bacterial community composition. These findings highlight the risks posed by laundry-released NPs accumulating in WWTPs, emphasizing the urgent need for improved wastewater management strategies to mitigate their environmental and public health impacts.