Emerging Plastic-Derived Soil Contaminant AO168═O Impairs Nematode Development and Lifespan at Environmentally Relevant Concentrations

Emerging environmental contaminants increasingly accumulate in soil ecosystems, yet their chronic biological impacts on soil-dwelling organisms remain poorly understood. Here, we demonstrate that tris(2,4-ditert-butylphenyl) phosphate (AO168═O), a prevalent soil-borne contaminant formed through the oxidative transformation of the widely used plastic antioxidant (AO168), compromises nematode fitness at relatively low concentrations. Exposure of C. elegans to AO168═O induces pronounced developmental and physiological impairments, including suppressed somatic growth, delayed developmental progression, disrupted energy homeostasis, and reduced reproductive output at 400-10,000 ng/g. Transcriptomic profiling reveals a robust reprogramming of gene expression that molecularly corroborates growth and developmental restriction. Notably, longevity-regulating pathways centered on the conserved insulin/IGF-1 signaling (IIS) are consistently and significantly enriched. Integrated gene-set enrichment analyses further demonstrate that AO168═O-associated transcriptional signatures closely recapitulate established IIS- and DAF-16-regulated expression programs, which were functionally validated by pharmacological inhibition and genetic ablation. Furthermore, early-life exposure leads to persistent and long-lasting fitness deficits, such as impaired locomotor performance and a marked reduction in adult lifespan, detectable even at the lowest exposure concentration. Together, these findings identify AO168═O as a previously underrecognized factor compromising nematode fitness, providing essential laboratory-based evidence that highlights the potential vulnerability of soil biota to ubiquitous soil-borne contaminants.