Rubber Dams: An Overlooked Source of Leachable Organic Contaminants within Water Infrastructure Systems

Inflatable rubber dams are used globally within water infrastructure, yet their potential as chemical contaminant sources remains overlooked. We investigated the occurrence of rubber additives and their transformation products within rubber dam materials (RDMs), including their organic extracts, aqueous leachates, and adjacent receiving waters, by employing targeted quantitative analysis combined with high-resolution mass spectrometry-based suspect and nontargeted screening. Targeted analysis revealed that substituted para-phenylenediamines (PPDs), their quinone/nonquinone products, and other rubber additives were abundant in RDM extracts and leachates. The antiozonant product N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine quinone (6PPDQ) was detected in laboratory leachates and receiving water adjacent to an in-service dam at toxic concentrations. Suspect and nontargeted screening of the RDM extracts and leachates identified 83 potential RDM-derived contaminants, with 75 structurally annotated (confidence level ≥3), including various hexa-(methoxymethyl)melamine analogues and 4-hydroxydiphenylamine homologues. To assess environmental health impacts, in silico toxicity predictions on unmonitored compounds prioritized from suspect and nontarget screening indicated high ecotoxicity potential, including aquatic neurotoxicity, revealing critical toxicological data deficits for rubber-derived contaminants. These findings demonstrate that water infrastructure materials can act as point sources of 6PPDQ and other contaminants, highlighting critical gaps in infrastructure risk assessment and emphasizing the need for environmentally benign rubber materials.