Advancing\nthe Effect-Directed Identification in Combined\nPollution: Using Pathways to Link Effects and Toxicants

The difficulty in associating diverse\npollutants with mixture effects\nhas led to significant challenges in identifying toxicants in combined\npollution. In this study, pathways were used to link effects and toxicants.\nBy pathways evaluated by the concentration-dependent transcriptome,\nindividual effects were extended to molecular mechanisms encompassing\n135 pathways corresponding to 6 biological processes. Accordingly,\nmechanism-based identification of toxicants was achieved by constructing\na pathway toxicant database containing 2413 chemical–pathway\ninteractions and identifying pathway active fragments of 72 pathways.\nThe developed method was applied to two different wastewaters, industrial\nwastewater OB and municipal wastewater HL. Although lethality and\nteratogenesis were both observed at the individual level, different\nmolecular mechanisms were revealed by pathways, with cardiotoxicity-\nand genotoxicity-related pathways significantly enriched in OB, and\nneurotoxicity- and environmental information processing-related pathways\nsignificantly enriched in HL. Further suspect and nontargeted screening\ngenerated 59 and 86 causative toxicants in OB and HL, respectively,\namong which 29 toxicants were confirmed, that interacted with over\n90% of enriched pathways and contributed over 50% of individual effects.\nAfter upgrading treatments based on causative toxicants, consistent\nremoval of toxicants, pathway effects, and individual effects were\nobserved. Mediation by pathways enables mechanism-based identification,\nsupporting the assessment and management of combined pollution.