Biological Effects and Environmental Behaviors of Medium- and Long-Chain Chlorinated Paraffins: A Brief Review

As short-chain chlorinated paraffins (SCCPs) have been classified as persistent organic pollutants (POPs), there has been a significant surge in the utilization of medium- and long-chain chlorinated paraffins (MCCPs and LCCPs) as potential alternatives. However, their environmental and ecological risks have gained more prominence. Consequently, the objective of this review is to provide a comprehensive overview of the biological effects, migration, and transformation of chlorinated paraffins (CPs), with a particular focus on comparing the similarities and differences among SCCPs, MCCPs, and LCCPs. According to the latest research findings, it has been discovered that MCCPs and LCCPs possess persistence, bioaccumulation, and long-distance migration abilities, similar to SCCPs. Moreover, these research results demonstrate that the toxicity of MCCPs and LCCPs, especially those components with high chlorine content, is equally significant as that of SCCPs. Furthermore, MCCPs and LCCPs in the environment can undergo biotransformation and photodegradation processes, resulting in the generation of toxic substances such as very short-chain chlorinated paraffins (vSCCPs), SCCPs, and chlorinated alcohols. This review comprehensively examines the biological toxicity, health risks, migration, and transformation of CPs with different chain lengths. In addition, the study analyzes the sources and trends of vSCCPs, SCCPs, MCCPs, and LCCPs in different environment media. It should be noted that SCCPs pose a greater health risk to aquatic organisms, whereas MCCPs are particularly concerning for infants. On the other hand, LCCPs present a higher health risk to terrestrial organisms, especially those situated at the top of the food chain. Based on the drawbacks of current research, outlook for future research was proposed. This review is expected to provide a reference for more scientific and reasonable evaluation of the CPs environment risk.