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Abstract AimsPremise plumbing systems are prone to biofilm development, and depending on municipal water source and infrastructure, may be susceptible to heavy metal exposure, including lead (Pb). We aimed to investigate the impacts of Pb on municipal water biofilms and to elucidate the interactive effects of time, pipe material, and Pb concentration of biofilms. Further, we aimed to understand if after a Pb-exposure event, microbial biomarkers indicative of previous Pb exposure may remain, which may assist public health and water regulatory agencies in triaging human health concerns postexposure. Methods and ResultsWe developed biofilms within pipe loops constructed from both cross-linked polyethylene (PEX-A) and high-density polyethylene (HDPE) plastics and exposed them to different concentrations of Pb (0, 5, and 500 µg l−1) for 4 and 8 weeks, followed by 4 weeks of exposure to lead-free water to examine community shifts following a lead exposure event. Using bacterial metabarcoding and biomarker analyses, we show that Pb exposure shifts community structure and we identified several key taxa associated with lead exposure events and demonstrate that these taxa persist even after lead is removed from the system. ConclusionsTaken together, this work provides a framework for identifying past Pb-exposure events that can be used for precautionary monitoring for human Pb exposures.