Rubber Antioxidants Pose Mostly Low Ecological Risk in Chinese Freshwaters, Model Study Finds

A new modeling study has assessed the ecological risks that substituted p-phenylenediamines (PPDs) and their quinone derivatives (PPD-Qs) pose in major Chinese river basins, concluding that overall risks are low, though localized concerns emerged in two basins.

Interest in this class of chemicals intensified after N-(1,3-dimethylbutyl)-N’-phenyl-p-phenylenediamine-quinone, known as 6PPD-Q, was recognized as highly ecotoxic, drawing global attention to PPDs and their quinone derivatives. According to the study’s abstract, comprehensive evaluations of the toxicity and ecological risks of these compounds in aquatic ecosystems have remained scarce.

The research, published in the journal Ecotoxicology, was carried out by Tianwei Peng, Biao Song, Fang Li, Zhengqing Yang, Jie Yuan, Chen Yan, Yitian Min, Wenbin Li and Lin Tang. The team combined quantitative structure-activity relationship (QSAR) predictions with interspecies correlation estimation (ICE) models, species sensitivity distribution analysis, and ecological risk assessment to evaluate the compounds across major river basins of China.

Model performance was reported as acceptably reliable. QSAR predictions met r² values above 0.8 and q² values above 0.7 for all compounds, while ICE-based predictions yielded R² values of 0.66 to 0.99 and mean squared error values of 0.0070 to 0.46. The authors state that the integrated QSAR-ICE framework provided useful screening-level toxicity estimates.

Sensitivity distribution analysis based on Chinese native species identified 6PPD, 7PPD and 77PD as the compounds with the lowest predicted no-effect concentrations, meaning these substances were predicted to affect the most sensitive species at the lowest concentrations.

The ecological risk assessment found overall low ecological risks across the major river basins of China, with risk quotient values mostly below 0.1. However, the study reported that high exposure levels in the Pearl River and Tarim River basins suggested localized risks in those areas.

Beyond the risk findings, the authors describe the work as filling gaps in ecotoxicological data related to species sensitivity distribution and chronic toxicity endpoints for Chinese native species, and as offering scientific evidence for environmental management.

The study is a modeling-based assessment rather than direct toxicity testing, and its conclusions rest on predicted rather than measured toxicity endpoints, although the reported model performance statistics indicate acceptable predictive reliability for screening purposes.

Subject of Research: Ecological risk assessment of substituted p-phenylenediamines and their quinone derivatives in Chinese freshwater river basins using QSAR-ICE modeling.

Article Title: Ecological risk of substituted p-phenylenediamines and quinones in Chinese freshwaters using QSAR-ICE modeling

Article References: Peng, T., Song, B., Li, F., Yang, Z., Yuan, J., Yan, C., Min, Y., Li, W., & Tang, L. (2026). Ecological risk of substituted p-phenylenediamines and quinones in Chinese freshwaters using QSAR-ICE modeling. Ecotoxicology, 35(9), Article 191. https://doi.org/10.1007/s10646-026-03172-y

Image Credits: AI Generated

DOI: 10.1007/s10646-026-03172-y

Keywords: 6PPD-Q, p-phenylenediamines, quinone derivatives, QSAR, interspecies correlation estimation, species sensitivity distribution, ecological risk assessment, freshwater ecosystems, Chinese river basins, ecotoxicology, risk quotient, water pollution