Spatial distribution and temporal trends of classical and emerging persistent organic pollutants (POPs) in black-tailed gull (Larus crassirostris) eggs from Korea

Enantioselective biomarkers of maize toxicity induced by hexabromocyclododecane based on submicroscopic structure, gene expression and molecular docking

Hexabromocyclododecane (HBCD), as a monitored chemical of the Chemical Weapons Convention, the Stockholm Convention and the Action Plan for New Pollutants Treatment in China, raises significant concerns on its impact of human health and food security. This study investigated enantiomer-specific biomarkers of HBCD in maize (Zea mays L.). Upon exposure to HBCD enantiomers, the maize root tip cell wall exhibited thinning, uneven cell gaps, and increased deposition on the cell outer wall. Elevated malondialdehyde (MDA) indicated lipid peroxidation, with higher mitochondrial membrane potential (MMP) inhibition in (+)-enantiomer treatments (47.2%-57.9%) than (-)-enantiomers (14.4%-37.4%). The cell death rate significantly increased by 37.7%-108.8% in roots and 16.4%-62.4% in shoots, accompanied by the upregulation of superoxide dismutase isoforms genes. Molecular docking presenting interactions between HBCD and target proteins, suggested that HBCD has an affinity for antioxidant enzyme receptors with higher binding energy for (+)-enantiomers, further confirming their stronger toxic effects. All indicators revealed that oxidative damage to maize seedlings was more severe after treatment with (+)-enantiomers compared to (-)-enantiomers. This study elucidates the biomarkers of phytotoxicity evolution induced by HBCD enantiomers, providing valuable insights for the formulation of more effective policies to safeguard environmental safety and human health in the future.

Partitioning of PFAS to serum, tissues, eggs, and hatchlings of an Australian freshwater turtle

Turtles are a potential sentinel species of aquatic ecosystem health as they inhabit aquatic ecosystems, are long lived, and potentially have high exposure to anthropogenic chemicals via food and water. This study investigated per- and polyfluoroalkyl substances (PFAS) tissue partitioning in female Emydura macquarii macquarii turtle, and the maternal offloading of (PFAS) into eggs and then hatchlings as well as the accumulation of PFAS in male and female Emydura macquarii macquarii serum. Significantly higher levels of perfluorosulfonic acids (PFSAs) and perfluorocarboxylic acids (PFCAs) were measured in the male serum compared to the female turtle serum, whereas perfluoroalkane sulfonamides (FASAs) were significantly higher in the female turtle serum. Perfluorooctane sulfonate (PFOS) was the predominant PFAS in the turtles whereas PFHxA was the predominant PFAS found in the surrounding water. PFHxA was not reported in any turtle tissue or the serum. The short-chain PFSAs and FASAs appeared to be highly associated with blood; long-chain PFSAs and PFCAs were more likely to be associated with tissue. Half of the PFHxS and all the long-chain PFSAs and PFCAs reported in the yolks were transferred into the hatchlings (by mass), suggesting a potential intergenerational effect.

Integrated approach for the isotope trophic position of black-tailed gull (Larus crassirostris) eggs over a decade: Combining stable isotopes of amino acids and fatty acids composition

Recently, compound-specific isotope analysis (CSIA) using the amino acid nitrogen stable isotope ratio (δ15NAAs) has been widely used for accurate estimation of trophic position (TP). In addition, a quantitative fatty acid signature analysis (QFASA) offers insights into diet sources. In this study, we used these techniques to estimate the TP for seabirds that rely on diverse food sources across multiple ecosystems. This allows for the proper combination of factors used in TP calculation which are different for each ecosystem. The approach involved the application of a multi-mixing trophic discrimination factor (TDF) and mixing β which is a Δδ15N between trophic and source amino acid of primary producer. Since the black-tailed gulls (BTGs) are income-breeding seabirds, which rely on energy sources obtained around their breeding sites, they and their eggs could be useful bioindicators for environmental monitoring. However, the ecological properties of BTGs such as habitats, diets, and TP are not well known due to their large migration range for wintering or breeding and their feeding habits on both aquatic and terrestrial prey. In this study, the eggs were used for estimating TP and for predicting TP of mother birds to overcome difficulties such as capturing birds and collecting non-invasive tissue samples. Eggs, sampled over a decade from three Korean islands, showed spatial differences in diet origin. Considering both the food chain and physiology of BTG, the TP of eggs was estimated to be 3.3-4.0. Notably, the TP was significantly higher at site H (3.8 ± 0.1) than at site B (3.5 ± 0.2), which indicated a higher contribution of marine diet as confirmed by QFASA. Using a reproductive shift of δ15NAAs, the TP of the mother birds was predicted to be 3.6-4.3, positioning them as the top predator in the food web. The advanced integration of multiple approaches provides valuable insights into bird ecology.

Toward a comprehensive understanding of alicyclic compounds: Bio-effects perspective and deep learning approach

The escalating use of alicyclic compounds in modern industrial production has led to a rapid increase of these substances in the environment, posing significant health hazards. Addressing this challenge necessitates a comprehensive understanding of these compounds, which can be achieved through the deep learning approach. Graph neural networks (GNN) known for its' extraordinary ability to process graph data with rich relationships, have been employed in various molecular prediction tasks. In this study, alicyclic molecules screened from PCBA, Toxcast and Tox21 are made as general bioactivity and biological targets' activity prediction datasets. GNN-based models are trained on the two datasets, while the Attentive FP and PAGTN achieve best performance individually. In addition, alicyclic carbon atoms make the greatest contribution to biological activity, which indicate that the alicycle structures have significant impact on the carbon atoms' contribution. Moreover, there are terrific number of active molecules in other public datasets, indicates that alicyclic compounds deserve more attention in POPs control. This study uncovered deeper structural-activity relationships within these compounds, offering new perspectives and methodologies for academic research in the field.

Levels of persistent organic pollutants (POPs) and the role of anthropic subsidies in the diet of avian scavengers tracked by stable isotopes

Persistent Organic Pollutants (POPs) have been identified as a significant factor driving declines in wildlife populations. These contaminants exhibit a dual tendency to biomagnify up the food chains and persist within tissues, rendering long-lived vertebrates, such as raptors, highly vulnerable to their adverse effects. We assessed the concentrations of polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) in fledglings of two vulture species, the Egyptian vulture (Neophron percnopterus) and the griffon vulture (Gyps fulvus), coexisting in northern Spain. Vultures, currently facing a severe threat with a population decline exceeding 90%, represent one of the most critically endangered avian groups in the Old World. Despite this critical situation, there remains a scarcity of research examining the intricate relationship between contaminant levels and individual foraging behaviors. In parallel, we analyzed stable isotope levels (δ15N and δ13C) in fledgling's feathers and prey hair to determine the association between individual dietary and contaminant burdens. Our findings revealed higher levels of PCBs in Egyptian vultures, while pesticide concentrations remained very similar between focal species. Furthermore, higher individual values of δ13C, indicating a diet based on intensive farming carcasses and landfills, were associated with higher levels of PCBs. While the levels of POPs found do not raise immediate alarm, the presence of individuals with unusually high values reveals the existence of accessible contamination sources in the environment for avian scavengers. The increasing reliance of these birds on intensive livestock farming and landfills, due to the decline of extensive livestock farming, necessitates long-term monitoring of potential contaminant effects on their populations.

Inulin alleviates perfluorooctanoic acid-induced intestinal injury in mice by modulating the PI3K/AKT/mTOR signaling pathway

Perfluorooctanoic acid (PFOA) is a widely used industrial compound that has been found to induce intestinal toxicity. However, the underlying mechanisms have not been fully clarified and effective interventions are rarely developed. Inulin, a prebiotic, has been used as a supplement in human daily life as well as in gastrointestinal diseases and metabolic disorders. In this study, male mice were exposed to PFOA with or without inulin supplementation to investigate the enterotoxicity and potential intervention effects of inulin. Mice were administered PFOA at 1 mg/kg/day, PFOA with inulin at 5 g/kg/day, or Milli-Q water for 12 weeks. Histopathological analysis showed that PFOA caused colon shortening, goblet cell reduction, and inflammatory cell infiltration. The expression of the tight junction proteins ZO-1, occludin and claudin5 significantly decreased, indicating impaired barrier function. According to the RNA-sequencing analysis, PFOA exposure resulted in 917 differentially expressed genes, involving 39 significant pathways, such as TNF signaling and cell cycle pathways. In addition, the protein expression of TNF-α, IRG-47, cyclinB1, and cyclinB2 increased, while Gadd45γ, Lzip, and Jam2 decreased, suggesting the involvement of the TNF signaling pathway, cell cycle, and cell adhesion molecules in PFOA-associated intestinal injury. Inulin intervention alleviated PFOA-induced enterotoxicity by activating the PI3K/AKT/mTOR signaling pathway and increasing the protein expression of Wnt1, β-catenin, PI3K, Akt3, and p62, while suppressing MAP LC3β, TNF-α, and CyclinE expression. These findings suggested that PFOA-induced intestinal injury, including inflammation and tight junction disruption, was mitigated by inulin through modifying the PI3K/AKT/mTOR signaling pathways. Our study provides valuable insights into the enterotoxic effects of PFOA and highlights the potential therapeutic role of inulin.

Gestational GenX and PFOA exposures induce hepatotoxicity, metabolic pathway, and microbiome shifts in weanling mice

Ammonium perfluoro (2-methyl-3-oxahexanoate) (GenX), a replacement for perfluorooctanoic acid (PFOA), has been detected in multiple environmental media and biological samples worldwide. Accumulated evidence implies that GenX exposure might exert adverse health effects, although the underlying mechanisms have not been fully revealed. In this study, pregnant BALB/c mice were exposed to GenX (2 mg/kg/day), PFOA (1 mg/kg/day), or Milli-Q water by gavage from the first day of gestation (GD0) until GD21. Necropsy and tissue collection were conducted in pups at 4 weeks of age. PFOA and GenX induced similar histopathological changes in both the liver and the intestinal mucosa, accompanied by higher serum levels of alanine and aspartate aminotransferase. Moreover, the capacity of hepatic glycogen storage and intestinal mucus secretion were significantly decreased, suggesting dysfunction of liver metabolism and the intestinal mucosal barrier. A total of 637 and 352 differentially expressed genes (DEGs) were identified in the liver tissues of GenX and PFOA group, respectively. Most of the enriched pathways from the DEGs by KEGG enrichment analysis were metabolism-associated. Moreover, overexpression of CYP4A14, Sult2a1, Cpt1b, Acaa1b, Igfbp1, Irs-2 and decreased expression of Gys2 were observed in livers of GenX exposed pups, supporting the hypothesis that there was metabolic disruption. Furthermore, DNA damage and cell cycle arrest proteins (Gadd45β, p21, Ppard) were significantly increased, while cell proliferation-related proteins (Cyclin E, Myc, EGFR) were decreased by gestational GenX exposure in the pups' liver. In addition, imbalance of gut microbiota and dysfunction of the intestinal mucosa barrier might contribute to hepatotoxicity at least in part. Taken together, our results suggested that gestational GenX exposure triggered metabolic disorder, which might be responsible for the hepatotoxicity in the pups in addition to dysfunction of the intestinal mucosa barrier. This study enriches the mechanisms of GenX-induced developmental hepatotoxicity by associating metabolic disorder with intestinal homeostasis.

Large-scale assessment of exposure to legacy and emerging per- and polyfluoroalkyl substances in China's shorebirds

Emerging per- and polyfluoroalkyl substances (PFAS) have become more widely applied, whereas legacy PFAS such as PFOS continue to distribute ubiquitously in the environment. Large-scale assessment of wildlife exposure to both emerging and legacy PFAS plays a key role in effective biomonitoring to better discriminate regional contamination patterns and provide early warnings. Using eggs of two closely-related shorebird species collected across China during the breeding season in 2021, we constructed contrasting PFAS levels and profiles in coastal versus inland populations. The highest ∑PFAS concentrations were found in two Kentish plover (Charadrius alexandrinus) populations from the Bohai Sea, a semi-enclosed shallow bay located in northeast China. These two populations showed exceptionally high PFOA concentrations (mean: 94 and 121 ng/g wet weight; West and North Bohai Sea, respectively) dominating the overall PFAS profile (66% for both). This pattern is characteristic, compared to that of other seabird eggs worldwide. By comparison, PFAS profile in the white-faced plover (Charadrius dealbatus) population at the South China Sea coast was dominated by PFOS (46%), which showed similar levels to those at the North Bohai Sea coast (mean: 29 and 20 ng/g, respectively). PFAS concentrations of Kentish plovers from the remote Qinghai Lake were lower compared to the three coastal populations, and were dominated by PFNA (mean: 2.6 ng/g, 29%) and PFOS (mean: 2.5 ng/g, 27%). None of the eggs analyzed in the present study exceeded estimated toxicity reference values for PFOS or PFOA. Additionally, the emerging 6:2 Cl-PFESA was detected in eggs from all regions, while its concentrations were highest in the Bohai Sea populations, and short-chain PFBS was only detected in the North Bohai Sea population. Our results indicate intensive local emissions of PFOA and emerging PFAS at the Bohai Sea region, and warrant further investigation and monitoring.

Global ocean contamination of per- and polyfluoroalkyl substances: A review of seabird exposure

Per- and polyfluoroalkyl substances (PFAS) have been extensively produced and used as surfactants and repellents for decades. To date, the global contamination pattern of PFAS in marine biota has seldomly been reviewed. Seabirds are ideal biomonitoring tools to study environmental contaminants and their effects. Here, we compiled and synthesized reported PFAS concentrations in various seabird species to reflect spatiotemporal patterns and exposure risks of major PFAS on a global ocean scale. Perfluorooctane sulfonic acid (PFOS) was the most studied PFAS in seabirds, which showed the highest level in eggs of common guillemots (U. aalge) from the Baltic Sea, followed by great cormorants (P. carbo) from the North Sea and double-crested cormorants (P.auritus) from the San Francisco Bay, whereas the lowest were those reported for Antarctic seabirds. The temporal pattern showed an overall higher level of PFOS in the late 1990s and early 2000s, consistent with the phase-out of perfluorooctane sulfonyl fluoride-based products. Maximum liver PFOS concentrations in several species such as cormorants and fulmars from Europe and North America exceeded the estimated toxicity reference values. Systematic evaluations using representative species and long time-series are necessary to understand contamination patterns in seabirds in South America, Africa, and Asia where information is lacking. In addition, limited research has been conducted on the identification and toxic effects of novel substitutes such as fluorotelomers and ether PFAS (F-53B, Gen-X etc.) in seabirds. Further research, including multi-omics analysis, is needed to comprehensively characterize the exposure and toxicological profiles of PFAS in seabirds and other wildlife.

Historical biomonitoring of pollution trends in the North Pacific using archived samples from the Continuous Plankton Recorder Survey

First started in 1931, the Continuous Plankton Recorder (CPR) Survey is the longest-running and most geographically extensive marine plankton sampling program in the world. This pilot study investigates the feasibility of biomonitoring the spatiotemporal trends of marine pollution using archived CPR samples from the North Pacific. We selected specimens collected from three different locations (British Columbia Shelf, Northern Gulf of Alaska, and Aleutian Shelf) in the North Pacific between 2002 and 2020. Comprehensive profiling of the plankton chemical exposome was conducted using liquid and gas chromatography coupled with tandem mass spectrometry (LC-MS/MS and GC-MS/MS). Our results show that phthalates, plasticizers, persistent organic pollutants (POPs), pesticides, pharmaceuticals, and personal care products were present in the plankton exposome, and that many of these pollutants have decreased in amount over the last two decades, which was most pronounced for tri-n-butyl phosphate. In addition, the plankton exposome differed significantly by regional human activities, with the most polluted samples coming from the nearshore area. Exposome-wide association analysis revealed that bioaccumulation of environmental pollutants was highly correlated with the biomass of different plankton taxa. Overall, this study demonstrates that exposomic analysis of archived samples from the CPR Survey is effective for long-term biomonitoring of the spatial and temporal trends of environmental pollutants in the marine environment.

Temporal trends (1968-2019) of legacy persistent organic pollutants (POPs) in seabird eggs from the northeast Pacific: Is it finally twilight for old POPs?

Legacy persistent organic pollutants (POPs), such as organochlorine pesticides (OCs) and polychlorinated biphenyls (PCBs), are known to persist in the marine environment; however, whether concentrations of these POPs have decreased or stabilized from Canada's Pacific coast in recent years is unclear. Here, we examined temporal trends of various legacy POPs in the eggs of five seabird species; two cormorants (Nannopterum auritum and Urile pelagicus), an auklet (Cerorhinca monocerata), a murrelet (Synthliboramphus antiquus), and a storm-petrel (Hydrobates leucorhous), sampled 1968 to 2019 from 23 colonies along the Pacific coast of British Columbia, Canada. The contaminant profile in the eggs of all species and sampling years was dominated by ΣPCBs, followed by ΣDDT (mostly p,p'-DDE), ΣHCH (β-HCH), ΣCHLOR (oxychlordane), and ΣCBz (HCB). ΣOC and ΣPCB concentrations were generally higher in double-crested cormorant eggs than in the other four species. The majority of legacy POPs are either significantly declining (e.g. p,p'-DDE, HCB, HE, oxychlordane, ΣPCBs) or showing no directional change over time (ΣMirex) in the eggs of our monitoring species. Contaminants such as α-HCH, cis- and trans-chlordane, p,p'-DDT, dieldrin, and octachlorostyrene also showed evidence of downward trends, largely influenced by non-detect values during more recent sampling periods. Increasing trends were observed for β-HCH in the eggs of some species; however, mean concentrations eventually returned to early 2000 levels by the end of the study period. Although bulk δ¹⁵N and δ¹³C egg values varied interannually, compound-specific amino acid analyses suggested no major changes in trophic position or baseline food web signature. Temporal trends observed here were comparable to those found in other seabird species and pelagic food webs. As most legacy POPs in our data set were at very low levels in recent years, we support the general consensus that it is indeed the twilight years for old POPs, and we attribute these declines largely to voluntary regulations and international restrictions on the production and use of these compounds, and thus their release into the marine environment.

Plastic debris as a mobile source of additive chemicals in marine environments: In-situ evidence

Plastic debris can act as a source of hazardous chemicals in the ocean, but the significance of its role in the environment is not yet known. To address this question, a comprehensive field study of highly contaminated and non-contaminated islands was conducted. Comparison of the plastic additive hexabromocyclododecanes and ubiquitous contaminants polychlorinated biphenyls in marine invertebrates showed that the load of stranded plastics plays a significant role in the bioaccumulation of plastic additives in the marine debris-contaminated island. Fugacity analysis indicates that net flow of hexabromocyclododecanes occurred from plastics to environmental reservoirs. Additionally, significantly higher levels of antioxidants, 2,4-di-tert-butylphenol and butylated hydroxytoluene, was found in the marine invertebrates inhabiting the marine debris-contaminated island than those inhabiting the marine debris-noncontaminated island, but ultraviolet stabilizers did not show the regional difference. This study provides the first field evidence that the movement of plastic debris in the ocean drives the dispersal of plastic additives to pristine waters.