Exposure-scenario–dependent neurotoxicity and hepatic injury induced by complex byproducts from cured-in-place pipe materials

Cured-in-place pipe (CIPP) technology is widely used for pipeline rehabilitation, but curing emissions and leachates may introduce complex chemical mixtures into air and drinking water, raising environmental health concerns. In this study, we characterized gaseous emissions and aqueous leachates generated from simulated ultraviolet CIPP curing and evaluated their toxicological effects in mice under two controlled but environmentally informed exposure scenarios. Styrene was the dominant constituent of gaseous condensates, accounting for 99.5% of the detected composition, whereas aqueous leachates contained styrene, styrene oxide, benzaldehyde, and 2-ethylhexanol at 54.5%,16.06%, 17.62%, and 11.78%, and multiple released metal elements were also detected. To evaluate the toxicological relevance of these chemically distinct CIPP byproduct mixtures, mice were subjected either to a single nose-only inhalation exposure to gaseous CIPP byproducts at a styrene-equivalent concentration of 50 ppm or to a 28-day drinking-water exposure to CIPP-derived leachates across a dilution series reflecting practical material-contact conditions. A single low-dose inhalation exposure induced anxiety-like behavior, altered exploratory activity, and changes in selected liver-related indicators in mice. For endpoints showing significant sex-by-exposure interaction, follow-up sex-stratified analyses indicated that anxiety-like behavioral alterations and selected biochemical changes were more evident in female mice, whereas no significant corresponding behavioral differences were observed in males. DA levels were elevated in both the styrene-exposed and CIPP-exposed groups (P < 0.05), while IBA1 density was reduced in the CIPP-exposed group relative to both the control and styrene-exposed groups (P < 0.05). Brain lipidomics showed early divergence at 12 h, whereas only limited residual changes remained at the later time point; among these, PE(18:1/22:2), Hex1Cer(m17:0/20:4), and TG(18:1/11:1/18:1) remained elevated after exposure cessation. In contrast, drinking-water exposure was associated with delayed behavioral alterations, characterized by increased locomotor activity after the 14-day recovery period. Speed and total moving distance showed a trend toward sex-by-exposure interaction, and subsequent sex-stratified analyses indicated that both parameters were significantly increased in female mice after recovery, whereas no corresponding change was observed in males. Drinking-water exposure was also associated with altered neuroimmune-related indicators, reduced IBA1-positive cell counts and staining intensity after the recovery period, and persistent changes in selected brain lipid species, including reduced PEt(18:1/18:1), PEt(16:0/16:0), and PA(18:0/16:0). Pathologically, drinking-water exposure produced significant hepatocellular edema (χ² = 30.25, P < 0.0001) that remained evident after recovery, accompanied by delayed elevations in TP, ALB, T-BIL, and D-BIL. Collectively, these findings indicated that CIPP-derived byproducts produce exposure-scenario-dependent molecular, hepatic, and neurobehavioral effects under experimentally controlled conditions and cannot be fully interpreted on the basis of styrene concentration alone. These results support risk assessment strategies that consider both mixture complexity and exposure pathway when evaluating the environmental and health relevance of CIPP applications.