Transformation of pyrene in aqueous chlorination in the presence and absence of bromide ion: Kinetics, products, and their aryl hydrocarbon receptor-mediated activities

To assess the endocrine-disrupting activity stemming from the presence of pyrene in drinking water, the kinetics of chlorination of pyrene was investigated at room temperature, the products of its aqueous chlorination with and without bromide ion were identified, and their aryl hydrocarbon receptor (AhR)-mediated activities were determined. It was found that the presence of bromide ion greatly promoted the reaction rate of chlorination of pyrene accompanied with the formation of brominated products. While the main product was 1-Cl-pyrene without the addition of bromide ion, di-Br-pyrene and 1-Brpyrene became the main products in the presence of bromide ion. GC-MS and NMR analysis identified three structures of dibromopyrene in chlorination with the addition of bromide ion as 1,3-di-Br-pyrene, 1,6-di-Br-pyrene, and 1,8di-Br-pyrene, and their molar ratio was determined to be approximately 0.3:1:1. Finally, 1-Br-pyrene, 1,3-di-Brpyrene, a mixture of 1,6-di-Br-pyrene and 1,8-di-Br-pyrene (di-Br-pyrene), 1-Cl-pyrene, and a mixture of 1,6-di-Cl-pyrene and 1,8-di-Cl-pyrene (di-Cl-pyrene) were fractionated by HPLC, and their AhR-mediated activities were assessed by a yeast assay. It was found that the effective molar concentrations (or mass concentration) showing half-maximal transcriptional response, EC50, for pyrene, 1-Br-pyrene, 1-Cl-pyrene, di-Cl-pyrene, and di-Br-pyrene were 5632 (1.14), 3089 (0.86), 1942 (0.46), 597.2 (0.21), and 147.3 (0.04) nM (mg/ L), respectively.