Halogenated flame retardants (HFRs) are chemical additives used in many household and commercial products. Due to their persistence, long-range transport, bioaccumulative potential, and toxicity, several HFRs were listed for elimination or restrictions under the international Stockholm Convention on Persistent Organic Pollutants (SC-POPs). To understand how levels of HFRs in the environment have changed since being listed under the SC-POPs, herring gull (Larus argentatus) eggs were collected from 17 colonies across Canada (Laurentian Great Lakes, Niagara and St. Lawrence rivers, and Atlantic and Arctic regions) from 2008-2023. Eggs were analyzed for SC-POPs-listed HFRs; total-α-hexabromocyclododecane (HBCDD), Σpolybrominated diphenyl ethers (PBDEs; sum concentration of 11 tri- to hepta-BDE congeners), BDE-209, and ΣDechlorane Plus (DP; sum concentration of syn- and anti-isomers). Overall, no significant temporal changes in concentrations of the four target classes of HFRs were found for most comparisons across colonies (75%, 51/68). Significant declines were found for 13% of class-colony comparisons while BDE-209 concentrations increased significantly at one colony. Evidence of a significant influence of the SC-POPs on concentrations was equivocal, with 6% of trends declining with the year of nomination, year of listing, or before the year of nomination, and 4% of trends showing increases. Despite more than a decade of regulation for some of these compounds, herring gulls continue to be exposed to HFRs, presumably from sources such as stockpiles, discarded products, or re-release from environmental reservoirs. Continued multi-site monitoring of HFRs is required to fully assess the effectiveness of regulations that may take several decades to show consistent evidence of reduced exposure in gulls.
© 2026. Crown.