The toxicity effects and mechanisms of tris(1,3-dichloro-2-propyl) phosphate (TDCPP) and its ecological risk assessment for the protection of freshwater organisms

Tris (1,3-dichloro-2-propyl) phosphate (TDCPP) is a type halogenated organophosphate flame retardants (OPFRs), which has been identified as contaminants of emerging concern (CECs). The use and production of OPFRs began to increase gradually when brominated flame retardants (BFRs) were banned. Halogenated OPFRs, especially TDCPP have been considered to lead to mutagenicity and carcinogenesis and major concerns have been raised regarding their toxicity. In this study, the toxicity effects and mechanisms of TDCPP were summarized and ecological risk assessment was made regarding its potential impact on freshwater organisms. TDCPP has been widely detected in ecosystems throughout the world, with observed toxicity effects on both humans and freshwater organisms. Inhalation of the dust was found to be the main exposure for humans. TDCPP could be metabolized in the human body, and medium stability was achieved in human body with the main metabolite BDCPP. Aside from mutagenicity and carcinogenesis, TDCPP was also found to have the potential for endocrine disruption and impairing the human reproductive system. Furthermore, this study reviewed the results of previous toxicity experiments, including acute toxicity, growth and development toxicity, neurotoxicity, and hepatotoxicity in freshwater organisms. Risk assessment was made using the safety threshold method by comparing the toxicity data with the exposure data in freshwater. HC₅ (hazardous concentration for 5% of organisms) derived based on traditional endpoints of acute toxicity LC₅₀ (median lethal concentration) or EC₅₀ (concentration for 50% of maximal effect) was 877 μg/L. This value was much higher than the exposure concentration levels in the surface water with EXD₉₀ (exposure data with cumulative probability 90%) of 65.22 ng/L. However, based on the growth and development toxicity data, the derived HC₅ was 33.33 ng/L and the calculated MOS (margin of safety) was below 1. Therefore, the results validated the fact that the ecological risk of TDCPP could not be neglected for its growth and development toxicity.