Relative Potencies of Individual Polychlorinated Naphthalenes and Halowax Mixtures To Induce Ah Receptor-Mediated Responses

Abstract

Polychlorinated naphthalenes (PCNs) are ubiquitous environmental pollutants that are structurally similar to other polychlorinated diaromatic hydrocarbons (PCDHs), such as polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), and biphenyls (PCBs). Despite being ubiquitous, much less is known about the fate, transport, and biological effects of individual PCN congeners than other PCDHs. The purpose of the current study was to utilize an in vitro assay (H4IIE-luc) to determine potencies relative to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) for 20 individual PCNs (from 75 possible congeners) and 6 Halowax mixtures. H4IIE rat hepatoma cells (H4IIE-Luc), which are stably transfected with an Ah receptor (AhR)-controlled luciferase reporter gene construct, respond specifically to AhR agonists and are thus a reasonable measure of AhR-mediated, or dioxin-like, activity. The most potent congeners were 1,2,3,4,6,7-hexa-CN (PCN 66), 1,2,3,5,6,7-hexa-CN (PCN 67), and 1,2,3,4,5,6,7-hepta-CN (PCN 73), with relative potencies as compared to TCDD of 0.004, 0.001, and 0.001, respectively. Significant structure−activity relationships were observed. For example, lateral substitution is an important determinant of AhR-mediated activity, but not sufficient, as illustrated by the inactivity of 2,3,6,7-tetra-CN to elicit AhR-mediated activity. Relative potencies of the Halowax mixtures with AhR-mediated activity were 0.0089, 0.000038, and 0.0000018 for 1051, 1014, and 1013, respectively. The relative potencies derived from this study were applied to literature-derived data on concentrations of PCN congeners in environmental mixtures to assess the potential contribution of PCNs to total TCDD equivalents (TEQs) in environmentally weathered complex mixtures.

Characterization of polychlorinated naphthalenes in stack gas emissions from waste incinerators

“…The concentrations of PCNs emitted from waste incinerators in this study were higher than those of five MSW incinerators reported by Abad et al (1999), but lower than that of raw gas from a MSW incinerator reported by Oh et al (2007). The dioxin-like toxicity of PCNs has been investigated in previous studies (Hanberg et al 1990;Blankenship et al 2000;Villeneuve et al 2000). The relative potency factors (RPFs) of individual PCN congeners to 2378-TCDD estimated in these studies have been used to evaluate the toxicity of PCNs (Noma et al 2004;Guo et al 2008;Liu et al 2009).…”

Occupational Exposure to Polychlorinated Dibenzo-p-dioxins and Dibenzofurans, Dioxin-like Polychlorinated Biphenyls, and Polychlorinated Naphthalenes in Workplaces of Secondary Nonferrous Metallurgical Facilities in China

“…The dioxin-like toxicity of PCNs has been investigated in previous studies. 21 −23 The relative potency factors (RPFs) of individual PCN congeners to 2378-TCDD estimated in these studies have been used to evaluate the toxicity of PCNs. 14,24,25 In this study, the TEQs of PCNs were defined by the sum of the products of the concentration of each congener multiplied by its RPF reported by Noma et al 24 (Table S2 of the Supporting Information).…”

Identification and characterization of the atmospheric emission of polychlorinated naphthalenes from electric arc furnaces

“…Polychlorinated naphthalenes (PCNs) are often termed as dioxin-like compounds given their similar properties (Weber et al 2008;Blankenship et al 2000). PCNs have attracted increasing attention due to their ubiquitous occurrence in environmental matrices and biota (Harner et al 2006;Bidleman et al 2010).…”