Using glaucous-winged gull (Larus glaucescens) eggs from Canada's Pacific coast, we investigated spatial and temporal trends (2008-2022) of a suite of legacy and emergent contaminants, including 16 perfluoroalkyl substances (PFAS), 15 polybrominated diphenyl ethers (PBDEs), 7 alternative halogenated flame retardants (AHFRs), total mercury (THg), as well as stable isotopes of carbon (delta C-13) and nitrogen (delta N-15) to control for diet. Legacy organochlorines (OCs) were also measured in eggs in 2020 for a preliminary human health risk assessment (HHRA). Between 2008 and 2022, glaucous-winged gull eggs from more urban-influenced colonies (Mandarte Island) were up to similar to 2x more contaminated with PFAS, PBDEs, AHFRs, and THg than eggs from the offshore colony (Cleland Island), suggesting different source regions and dietary exposures. Concentrations of Sigma 15PBDEs declined linearly among colonies (p < 0.001), consistent with several North American phase-outs and regulatory restrictions dating back to the early/mid 2000s. Conversely, temporal trends for PFOS, Sigma 12PFCAs, Sigma(7)AHFRs, and THg were characterized by a combination of second-order declines and non-linear increases in recent years. After correcting THg for dietary shifts using delta N-15, THg concentrations followed a U-shaped trend at Mandarte and Cleland Islands, while those at Mitlenatch Island remained relatively constant over time. Increasing trends for some contaminants coincided with both an increase in delta C-13 and delta N-15. For the HHRA, all gull eggs collected in 2020 had hazard quotients (HQs) < 0.2, indicating no foreseeable risk or harm for First Nations consumers for certain contaminants. Our findings indicate that spatio-temporal trends of persistent organic contaminants and THg in Pacific glaucous-winged gull eggs are influenced by a combination of factors, including the impact of regulations on anthropogenic emissions, accompanied by changes in foraging behaviour and food-web structure.
