Bioconcentration, metabolism and alterations of thyroid hormones of Tris(1,3-dichloro-2-propyl) phosphate (TDCPP) in Zebrafish

• The bioaccumulation and biotransformation of TDCPP in zebrafish liver was studied.
• High levels of TDCPP and its metabolite BDCPP were found in the zebrafish livers.
• Genes involved in phase I and II metabolism were upregulated after TDCPP exposure.
• Levels of thyroid hormones decreased in female zebrafish after TDCPP exposure.

Tris(1,3-dichloro-2-propyl) phosphate (TDCPP) is an organophosphate widely used as a flame retardant, and has frequently been detected in the environment and biota. The present study investigates the bioconcentration and metabolism of TDCPP in fish. Zebrafish embryos (from 2 h post-fertilization) were exposed to TDCPP (0, 4, 20 and 100 μg/L) for six months. Exposure to TDCPP significantly induced phase I metabolic enzymes 7-ethoxyresorufin O-deethylase (EROD) and 7-methoxyresorufin O-demethylase (MROD) in fish. The mRNA expression of genes related to Phase I and II metabolic enzymes, such as cyp1a1, cyp1b1, cyp1c1 and ugt1ab were also significantly upregulated. Exposure to TDCPP significantly reduced plasma thyroxine (T4) and 3,5,3′-triiodothyronine (T3) levels in females. Chemicals analysis indicated significant levels of TDCPP and its metabolite, bis (1,3-dichloro-2-propyl) phosphate (BDCPP), in the liver. The present study reveals that exposure to low concentrations of TDCPP can cause bioconcentration in fish, and TDCPP can be readily metabolized in liver.