Gulls foraging in landfills: Does atmospheric exposure to halogenated flame retardants result in bioaccumulation?

Contamination of aquatic ecosystems by persistent organic pollutants (POPs) originating from landfills in Canada and the United States: A rapid scoping review

Persistent organic pollutants (POPs) are organic chemical substances that threaten human health and the planet's ecosystems due to their toxicity and their ability to remain intact for a long time, wide distribution throughout the environment, and accumulation and magnification in living organisms through the food chain. Discarded products from landfills and dumpsites are potential sources of POPs due to their persistence for several decades and constant release to surrounding environment. POPs in aquatic systems signal input predominantly from landfills, wastewater treatment plants, sewage, and urban runoff, suggesting a research gap to guide policies to address these unabated releases. This scoping review aims to rapidly identify the key concepts underpinning the containment, translation, and migration of POPs in Canadian and US landfill leachate. The review targeted multidisciplinary perspectives on the topic and spanned forensic biology, environmental sciences, chemistry, and geology. Contaminated municipal solid waste (MSW) landfill characteristics, as reported by government agencies in Canada and the US, were synthesized and harmonized to illustrate the geographical scope of MSW landfills releasing POPs into the surrounding environment. The knowledge and data gaps summarized in this study highlight the need to address the inadvertent release of POPs from Canadian and US landfills, particularly in consideration of dated and degrading landfill infrastructure, the proximity of marginalized people, and the implications of climate change on the countries' more vulnerable landscapes. This review is applicable to the development of future studies that aim to guide environmental protective policies.

Dynamics and effects of plastic contaminants' assimilation in gulls

Polybrominated diphenyl ethers are persistent disrupters assimilated by organisms, yet little is known about their link to plastic ingestion and health effects. In an experiment, two groups of yellow-legged/lesser black-backed gulls (Larus michahellis/Larus fuscus) were fed plastics with BDE99 to assess leaching into brain, preen oil, liver and fat tissues and evaluate effects on health and stress parameters. Although most plastic was regurgitated, we observed a clear relation between plastic ingestion and chemical leaching. BDE99 exhibited higher levels in brain tissue of gulls from the plastic groups. Also, only values of cholinesterases measured in plasma were significantly reduced in the 'plastic' groups. Cholinesterase activity in the brain also tended to decrease, suggesting a negative effect in gulls' neurofunction. Results indicate that chemical leaching occurs, even when plastics stay in the stomach for a short period of time and showed that this can affect gulls' health.

Impact of landfill characteristics on the atmospheric exposure to halogenated flame retardants in gulls

Large amounts of consumer products containing halogenated flame retardants (HFRs) are disposed of annually in landfills, which may lead to significant releases of these semi-volatile contaminants into the environment. During their foraging activities in landfills, gulls can be exposed to elevated levels of HFRs in air. Ring-billed gulls (Larus delawarensis) breeding in the densely populated Montreal area (QC, Canada) are significantly exposed to air levels of polybrominated diphenyl ethers (PBDEs) in or in the vicinity of landfills. However, no information is currently available on the specific characteristics of these landfills that can modulate the atmospheric exposure of ring-billed gulls to HFRs. The objective of this study was to investigate how atmospheric exposure in ring-billed gulls to PBDEs and other HFRs is influenced by selected landfill characteristics (i.e., daily cover materials, waste types and tonnage). Miniature passive air samplers (PASs) combined with GPS dataloggers were deployed for ten days during six years on the back of wild-caught ring-billed gulls breeding in the Montreal area. Atmospheric levels of several PBDEs and other HFRs determined in PASs were found to increase with the presence probability of gulls in the two largest landfills using automotive shredder residues as daily cover material. Weather variables including relative humidity and wind speed had a weak influence on atmospheric levels of HFRs in the bird-borne PASs. Our results suggest that automotive shredder residues represent a significant emission source of HFRs into the air of landfills, thus influencing atmospheric exposure of gulls and other birds foraging in these sites.

Aging affects isomer-specific occurrence of dechlorane plus in soil profiles: A case study in a geographically isolated landfill from the Tibetan Plateau

Two major structural isomers in commercial dechlorane plus (DP) mixtures, anti-DP and syn-DP, generally displayed varied desorption and partitioning efficiencies in soils, which may be linked to their different aging rates. However, the molecular parameters that govern the degree of aging and its associated effects on the occurrence of DP isomers have not been comprehensively investigated. In this study, the relative abundance of rapid desorption concentration (R_rapid) was measured for anti-DP, syn-DP, anti-Cl₁₁-DP, anti-Cl₁₀-DP, Dechlorane-604 (Dec-604), and Dechlorane-602 (Dec-602) at a geographically isolated landfill area in the Tibetan Plateau. The R_rapid values were used as an indicator of aging degree, exhibiting a close correlation with the three-dimension conformation of the molecules for the dechlorane series compounds. This observation suggested that planar molecules may have a greater tendency to accumulate in the condensed phase of organic matter and undergo more rapid aging. The fractional abundances and dechlorinated products of anti-DP were found to be predominantly controlled by the aging degree of DP isomers. The multiple nonlinear regression model indicated that differences in aging between anti-CP and syn-DP were primarily driven by the total desorption concentration and soil organic matter content. Aging plays a significant role in both the transport processes and metabolism of DP isomers and should be taken into account to refine the assessment of their environmental behaviors.

Lead exposure in brown bears is linked to environmental levels and the distribution of moose kills

Lead (Pb) is heterogeneously distributed in the environment and multiple sources like Pb ammunition and fossil fuel combustion can increase the risk of exposure in wildlife. Brown bears (Ursus arctos) in Sweden have higher blood Pb levels compared to bears from other populations, but the sources and routes of exposure are unknown. The objective of this study was to quantify the contribution of two potential sources of Pb exposure in female brown bears (n = 34 individuals; n = 61 samples). We used multiple linear regressions to determine the contribution of both environmental Pb levels estimated from plant roots and moose (Alces alces) kills to blood Pb concentrations in female brown bears. We found positive relationships between blood Pb concentrations in bears and both the distribution of moose kills by hunters and environmental Pb levels around capture locations. Our results suggest that the consumption of slaughter remains discarded by moose hunters is a likely significant pathway of Pb exposure and this exposure is additive to environmental Pb exposure in female brown bears in Sweden. We suggest that spatially explicit models, incorporating habitat selection analyses of harvest data, may prove useful in predicting Pb exposure in scavengers.

Halogenated flame retardant exposure pathways in urban-adapted gulls: Are atmospheric routes underestimated?

Urban-adapted gulls can be exposed to flame retardants while foraging in landfills where elevated concentrations of polybrominated diphenyl ethers (PBDEs) and other halogenated flame retardants (HFRs) have frequently been measured in air. However, the contribution of atmospheric exposure has largely been overlooked compared to dietary exposure in birds and other wildlife. The overall objective of this study was to investigate the contribution of atmospheric exposure pathways relative to diet for PBDEs and other HFRs in ring-billed gulls (Larus delawarensis) nesting in the densely populated Montreal area (QC, Canada). Miniature passive air samplers (PASs) were deployed on the back of wild-caught ring-billed gulls for ten days. Concentrations of PBDEs and other HFRs were determined in PASs carried by ring-billed gulls as well as their lungs, stomach content, liver, preen oil, and onto the surface of their feathers. We evaluated the atmospheric and dietary exposure routes for the most abundant HFRs in samples using a structural equation model implemented in a Bayesian framework. Results indicated that lung concentrations of BDE-28 increased with its levels in air determined using bird-borne PASs. No association was found between BDE-28 concentrations in lungs and liver, whereas BDE-209 concentrations in liver increased with those in lungs. Moreover, BDE-28 and -47 concentrations in liver increased with those on feather surface, while liver BDE-47 concentrations were also positively related with those in stomach content. These findings suggested that, in addition to dietary exposure, atmospheric exposure pathways through inhalation and co-ingestion during feather maintenance (preening) significantly contribute to the accumulation of PBDEs in liver of ring-billed gulls. Atmospheric exposure to HFRs should therefore be considered in future landfill-foraging wildlife species as a potential exposure route compared to the traditional dietary exposure pathway.

Biotransformation of Dec-604 and potential effect on thyroid deiodinase activity in highly flame retardant-exposed gulls

Several halogenated flame retardants (HFRs) have been identified as thyroid disruptors in birds including the polybrominated diphenyl ether (PBDE) mixtures, which have been replaced with other HFRs such as Dechlorane-604 (Dec-604). Dec-604 Component B (Dec-604 CB), a putative debrominated product of Dec-604, has been frequently reported in urban-adapted ring-billed gulls (Larus delawarensis) breeding in the Montreal area (QC, Canada). The metabolic pathways of Dec-604 are yet to be characterized, although the occurrence of Dec-604 CB in gulls may suggest that enzyme-mediated dehalogenation may occur, potentially involving the thyroid deiodinases. The objective of this study was to investigate the effect of Dec-604 on type 1 deiodinase (DIO1) in the presence of thyroxine (T₄) in an in vitro DIO1 assay using liver microsomes of ring-billed gulls that are highly exposed to HFRs in the Montreal area, and to determine whether DIO1 is involved in the in vitro debromination of Dec-604. We tested the in vitro activity of DIO1 in gull liver microsomes in the presence of five concentrations of Dec-604 ranging from 0.86 to 86.21 nM. HFR concentrations (Σ₄₀HFR) were also determined in liver samples of gulls. Results showed that total DIO1 activity in gull liver microsomes was increased by three of the five concentrations of Dec-604. No relationship between liver Σ₄₀HFR concentrations and DIO1 activity was observed, except for T₂ formation rates that significantly decreased with increasing liver HFR concentrations. Moreover, greater Dec-604 CB to Dec-604 concentration ratios in activated gull microsomes (with the DIO1 cofactor dithiothreitol) were found at the intermediate Dec-604 concentration compared to controls. These results suggested that liver microsome DIO1 activity may be perturbed in ring-billed gulls exposed to Dec-604, and be involved at least in part, in the debromination of Dec-604 leading to the formation of Dec-604 CB.

First evidence of diverging migration and overwintering strategies in glaucous gulls (Larus hyperboreus) from the Canadian Arctic

Many seabird populations differ in their migration strategies, where individuals travel in different directions to separate wintering areas. These migratory strategies may expose individuals to different threats, thus understanding migratory connectivity is crucial to assess risks to populations. Glaucous gulls (Larus hyperboreus) are generalist predators with flexible migratory behaviour that may alter these behaviours in response to climate change and anthropogenic activities, such as access to landfills, yet little is known about their migration. We deployed GPS and GLS tracking devices on glaucous gulls from Coats Island, Nunavut, Canada to obtain the first insights into their migration and habitat use outside of the breeding season. Gulls used two migration strategies during the non-breeding season, where one migrated as far as the Sea of Okhotsk in the Pacific and the remainder (n = 7) wintered in the North Atlantic. Gulls primarily overwintered in pelagic (56%) and coastal (38%) habitats. While in coastal habitats, one gull visited one landfill once, but visits increased with a 1 km and 3 km buffer, suggesting that urban glaucous gulls primarily used non-landfill habitats. This research can be used as a baseline to explore changes in migratory behaviour and inform future conservation of Arctic-breeding gulls.

Spatial and temporal variations of halogenated flame retardants and organophosphate esters in landfill air: Potential linkages with gull exposure

Landfills represent important sources of local emissions of organic contaminants, including halogenated (HFR) and organophosphate ester (OPE) flame retardants used in a large variety of consumer products. Gulls foraging in landfills may be exposed to elevated atmospheric concentrations of HFRs and OPEs that may vary spatially and temporally within a landfill site, thus modulating their exposure. The objective of the present study was to investigate the spatial and temporal variability of HFR and OPE concentrations in air samples collected from a major landfill in the Montreal area (QC, Canada) that is frequently visited by gulls for foraging. Miniature stationary passive air samplers (PASs) and high-volume active air samplers (AASs) were deployed in six different areas within this landfill site for 34 days to collect HFRs and OPEs in air. During the same period, wild-caught ring-billed gulls (Larus delawarensis) were equipped on their back with a similar miniature PAS that was deployed in the landfill along with a GPS datalogger to monitor their movements for ten days. Elevated concentrations of certain OPEs (e.g., tris(2-chloroethyl) phosphate and tris(2-chloroisopropyl) phosphate) and brominated diphenyl ether (BDE)-209 were measured in stationary PASs and AASs, although they were homogenously distributed within this landfill site. Temporal variability was observed for concentrations of BDE-209, -99 and -47 measured in AASs as well as tributyl phosphate during the 34-day deployment period. Moreover, air concentrations of BDE-209, -207 and -206 and selected OPEs (tris(1,3-dichloro-2-propyl) phosphate and tris(methylphenyl) phosphate) determined using AASs were positively correlated with ambient air temperatures. Gulls that visited a landfill at least once exhibited significantly greater concentrations of BDE-47 measured in PASs they carried on their back, suggesting that landfill air may represent a source of exposure to PBDEs for these birds, and potentially other urban-adapted wildlife using these sites for foraging.