Naphthenic acids as emerging petroleum-derived contaminants: Environmental fate, ecotoxicological effects, and human health implications

Oil pollution represents a significant global environmental threat, with naphthenic acids (NAs) - naturally occurring carboxylic acid derivatives in crude oil-emerging as critical pollutants due to their persistence, bioaccumulation potential, and multifaceted toxicity. This review critically synthesizes current knowledge on NAs, focusing on their scientific definitions, analytical characterization, environmental fate, toxicological mechanisms, and research challenges. These compounds have been detected in diverse environmental matrices across multiple regions such as Asia, Europe, and North America, with concentrations reaching mg/L levels in oil-impacted environments, particularly in oil sands regions. Increasing evidence indicates that NAs can migrate from environmental media into living organisms, and demonstrate a clear potential for bioaccumulation. By integrating evidence across multiple biological taxa, we proposed an adverse outcome pathway framework illustrating that membrane perturbation and reactive oxygen species accumulation represent critical initiating events leading to adverse outcomes at cellular, organism, and population levels.​ However, human health risks remain uncertain due to limited information on exposure pathways, internal exposure levels, and epidemiological evidence. Future research should prioritize field-deployable detection techniques, standardized toxicity assessment frameworks, and improved characterization of human exposure levels. This review underscores the need for globally coordinated monitoring strategies and rigorous regulatory standards to mitigate NAs-related ecological and public health risks.