Newly discovered methoxylated polybrominated diphenoxybenzenes have been contaminants in the Great Lakes herring gull eggs for thirty years.

We recently reported the discovery and identification of novel methoxylated polybrominated diphenoxybenzenes (MeO-PBDPBs) in herring gulls eggs from the Laurentian Great Lakes of North America. We presently investigated the temporal changes (1982-2010) in MeO-PBDPB concentrations and congener patterns, as well as chemical tracers of diet (ratios of carbon and nitrogen stable isotopes), in egg pool homogenates from five selected colony sites across the Great Lakes. Egg pool homogenates from the Channel-Shelter (C-S) Island (Lake Huron) contained ∑MeO-PBDPB concentrations orders of magnitude greater than those from other colonies, suggesting potential point contamination sources nearby. In the C-S Island egg pools, concentrations increased from the initial study year (31 ng/g wet weight) and peaked around the late 1990s, followed by a general decline until 2010. Over the period, concentrations generally increased in eggs from Fighting Island (Lake Erie), Toronto Harbour (Lake Ontario) and Big Sister Island (Lake Michigan) colonies, whereas the levels in Agawa Rock (Lake Superior) declined. Although other factors likely exist, changes over time in the carbon and nitrogen isotope tracers reflected a shift of the gull diet from aquatic to more terrestrial origins, and suggested this diet shift partially accounted for the temporal changes of ∑MeO-PBDPB levels in eggs from most colonies. The ratio of Br(6)- to Br(5)-MeO-PBDPB congeners generally decreased over time in the colonies at Channel-Shelter Island, Fighting Island and Agawa Rock. This suggested that Br(5)- versus Br(6)-MeO-PBDPB congeners and/or possibly their nonmethoxylated and higher brominated precursors may have been more abundant in diets of terrestrial origin. Notably, these MeO-PBDPB congeners are not "emerging" brominated substances, but rather "recently discovered" contaminants since, as of 2011, ∑MeO-PBDPB concentrations have been constantly in the range of 30-100 ng/g ww for at least the last 30 years.