Potential Ecological Risks of the Novel Alternative Plasticizer Di(isononyl)cyclohexane-1,2-Dicarboxylate via Metabolic Toxification in Earthworms

As legislative regulations on traditional plasticizers have been tightened globally, diisononyl cyclohexane-1,2-dicarboxylate (DINCH) gains widespread use owing to its environmental safety claims. Nevertheless, the emerging toxicological evidence raises concerns about its health and ecological risks. In soil earthworms, the dynamic bioaccumulation, biotransformation, and tissue-specific distribution of DINCH were first characterized using mass spectrometry imaging, and the major metabolites of monoisononyl cyclohexane-1,2-dicarboxylate (MINCH) and hydroxylated derivatives were primarily distributed in the earthworm coelom. Noticeably, the multilevel toxicological responses including growth inhibition, tissue damage, and oxidative stress were shown with a cascade of physiological and biochemical perturbations, particularly in endocrine and metabolic homeostasis. Disruption of peroxisome proliferator-activated receptor (PPARγ) signaling with downstream lipid biosynthesis and endocrine-metabolic homeostasis was further confirmed via integration of transcriptomics and metabolomics, while PPARγ was prioritized as a candidate biomarker for apparent exposure. Due to the stronger binding interactions of MINCH by in vitro/in silico studies, a metabolite-mediated mechanism whereby MINCH may mimic endogenous fatty acid-like ligands to regulate PPARγ was rationalized for lipid metabolism and endocrine disturbances. These findings provide early warnings of the ecological relevance and potential risks of DINCH to soil ecosystems and underscore the essentiality of incorporating bioactive metabolites into full environmental risk assessments.