Assessing the sustainability and safety of polyethylene terephthalate (PET) liners for lead service lines (LSL) upgrades

Polyethylene Terephthalate (PET) liners have been proposed by industry as a more cost effective and less disruptive alternative to lead service lines (LSL) replacement. However, concerns have been raised about their aging under real-use conditions and their potential health and environmental impacts. In this study, two approaches were implemented. First, bench and pilot scale experiments were carried out to investigate the aging of a PET liner under conditions that simulate normal usage. Results show early surface oxidation and leaching of potentially hazardous metals (lead, zinc and titanium). No short-term fragmentation of the PET liner into microplastics was observed. Next, a life cycle assessment (LCA) compared the health and environmental impacts of three LSL upgrade alternatives: PET liners and full LSL replacement using either copper or PEX pipes. The installation phase was shown to be the main contributor to impact scores, while the benefits of PET liners are highly dependent on their lifespan. PEX pipes installed by torpedoing lower impacts as compared to PET liners and copper pipes for equal lifespan, while the use of PET liners remains less impactful regarding human health and ecosystem quality when a complete excavation is needed. LCA derived global human health effects due to ingestion of leached metals from PET liners, copper pipes and unreplaced LSL, and showed that PET liners and copper pipes significantly reduce health impacts by 14 and 80 DALY respectively compared to unreplaced LSL. Finally, the Integrated Exposure Uptake Biokinetic (IEUBK) model was used to assess the impact of lead exposure specifically for drinking water ingestion. Estimated Blood Lead Levels (BLL) in children and infants in households with long unreplaced LSL was up to 263.7% and 207.8% greater compared to either replacement with copper pipes or rehabilitation with PET liners, showing the clear benefits of corrective action. Combining experimental results, LCA and biokinetic modeling provides actionable information for utilities to select the best upgrade options, considering environmental, health and practical constraints, whilst identifying remaining data gaps. The relative benefits of PET liners should be carefully evaluated considering their lifespan under real-life conditions, the complete replacement costs after failure, and the growing evidence of micro- and nanoplastics (MNP) risks.