Declining Trends of Polychlorinated Naphthalenes in Seabird Eggs from the Canadian Arctic, 1975–2014

There are relatively few studies of polychlorinated naphthalenes (PCNs) for biota in polar regions and even fewer reports of temporal trends. We determined concentrations of PCNs in eggs of thick-billed murres (Uria lomvia) collected from the Canadian high Arctic between 1975 and 2014 and calculated their associated toxic equivalents (TEQs). Concentrations of Σ₆₇PCN decreased significantly in the murre eggs between 1975 and 2014 at an average annual rate of −14.9 pg g^–1 wet weight. Although the penta- and tetra-CNs (predominantly CN-52/60 and CN-42) dominated the PCN profile, the hexa-CNs (mainly CN-66/67) accounted for the majority of the Σ₆₇TEQ-PCN, concentrations of which also decreased significantly between 1975 to 2014. On average, Σ₆₇TEQ-PCN in the murre eggs accounted for only 1.9% of the total toxicity calculated for dioxin-like compounds measured in the murre eggs. As such, the TEQ-PCN concentrations calculated for the murre eggs in this study are several orders of magnitude lower than TEQ levels associated with reproductive effects in birds. This is the first published study of temporal trends of PCNs in Canadian Arctic biota.