Photoaging enhanced the adverse effects of polyamide microplastics on the growth, intestinal health, and lipid absorption in developing zebrafish

Induced aging, structural change, and adsorption behavior modifications of microplastics by microalgae

The effects of microalgal biofouling on microplastic (MP) may differ from bacterial biofouling. In this study, the influence of microalgae on MP surface alteration, structural change, and adsorption of organic micropollutants was evaluated. Virgin polyethylene (PE), polyvinyl chloride (PVC), and polyamide (PA) were each immersed in algal photobioreactor and river freshwater for 30 days to simulate algal and river microbe biofouling respectively. Consequently, their physicochemical changes and adsorption potential of a mixture of six bisphenol analogues (BPA, BPS, BPE, BPB, BPF, BPAF) and two parabens (propyl-paraben, benzyl-paraben) were investigated. Owing to the algal bioactive compounds, major microalgae-induced biofouling and more MP aging than the river microbe aging were observed through fractures, pits, cracks, and algal attachments. Intrusion of algal organic matter and scission of polymeric functional groups were revealed during microalgal immersion and the potential MP aging pathways were proposed. Algal biofouling considerably altered the intrinsic properties of the MPs, consequently the adsorption capacity of PE and PVC was enhanced by 3.04-6.72 and 2.14-8.72 times, respectively. Adsorption process onto algal-aged MPs was pH-dependent, endothermic, non-spontaneous, and favored by hydrogen bonds. Meanwhile, the amide group in PA structure was conducive to organic micropollutant adsorption, which was likely reduced by algal aging and the erosion of the N-H stretching. Moreover, higher adsorption capacities of organic micropollutants were shown by the algal-biofilm PE and PVC than virgin and river microbial biofilm MPs. This study discloses that, biofouling and aging of MPs by microalgae through their bioactive components would engender more incidences on MP properties, organic micropollutants adsorption with associated environmental and health hazards.

Developmental toxicity of glyphosate on embryo-larval zebrafish (Danio rerio)

Glyphosate (GLY) induces developmental toxicity in fish, but research on the toxicity mechanism is limited. In this study, zebrafish embryos were exposed for 120 hpf to 0.7, 7, and 35 mg L-1 GLY. The results show that GLY treatment induced developmental toxicity in the fish, including premature hatching, reduced heartbeats, pericardial and yolk sac oedema, swim bladder deficiency, and shortened body length, which was possibly due to a significantly decreased triiodothyronine (T3)/thyroxine (T4) ratio and the abnormal expression patterns of hypothalamic-pituitary-thyroid (HPT) (crh, tshβ, tr α, tr β, and t tr ) and growth hormone/insulin-like growth factor (GH/IGF) axis-related genes (gh, ghrα, ghrβ, igf1, igf1rα, and igf1rβ) in larvae exposed to GLY. In addition, GLY exposure altered the levels of SOD and CAT, increased ROS, promoted malondialdehyde (MDA) content, and significantly altered the levels of endoplasmic reticulum (ER) stress signalling pathway factors (perk, eif2α, gadd34, atf4, ire1α, xbp1, atf6, hspa5, and chop), suggesting that GLY treatment induced oxidative injury and ER stress in the larvae. Further research showed that treatment with a higher concentration of GLY upregulated the levels of iNOS, IL-1β, and TNF-α while inhibiting the expression of IL-10 and TGF-β, suggesting that GLY causes an inflammatory reaction in the larvae. In addition, we also found that apoptosis was induced in the larvae, which was determined by acridine orange staining and abnormal expression of p53, caspase-3, -8, and -9. Taken together, our results demonstrate that GLY exposure altered the T3/T4 ratio, disturbed the expression patterns of HPT and GH/IGF axis-related genes, and induced oxidative and ER stress, inflammatory reactions, and apoptosis in the zebrafish larvae. This investigation contributes to improved understanding of the developmental toxicity mechanism of GLY in fish.

Transcriptomic and metabolic responses of earthworms to contaminated soil with polypropylene and polyethylene microplastics at environmentally relevant concentrations

Examining transcriptomic and metabolic responses of earthworms to microplastic-contaminated soil is critical for understanding molecular-level toxicity of microplastics; yet very little research on this topic exists. We investigated influences of environmentally relevant concentrations (ERC) of polypropylene (PP) and polyethylene (PE) microplastic-contaminated soil on earthworms at the transcriptomic, metabolic, tissue and whole-body levels to study their molecular toxicity. The addition of PP and PE at ERC induced oxidative stress on earthworms, as indicated by the high enrichment of glutathione metabolism and increased glutamine at the transcriptomic and metabolic levels. Digestive and immune systems of earthworms were damaged according to the injuries of the intestinal epithelium, partial shedding of chloragogenous tissues and unclear structure of coelom tissues, which were confirmed by pathway analysis at the transcriptomic level. Significant enrichment of arachidonic acid and glycerolipid metabolisms indicated that PP and PE disturbed the lipid metabolism in earthworms. Significantly increased betaine and myo-inositol, and decreased 2-hexyl-5-ethyl-3-furansulfonate suggested that PP and PE caused differences in osmoregulation extent. In conclusion, most similar responses of earthworm might result from special size rather than type effects of PP and PE microplastics. Contamination of soils with microplastics even at ERC has health risks to earthworms; therefore, proper management of microplastics to reduce their input to the environment is key to reducing the health risks to soil fauna.

Key knowledge gaps for One Health approach to mitigate nanoplastic risks

There are increasing concerns over the threat of nanoplastics to environmental and human health. However, multidisciplinary barriers persist between the communities assessing the risks to environmental and human health. As a result, the hazards and risks of nanoplastics remain uncertain. Here, we identify key knowledge gaps by evaluating the exposure of nanoplastics in the environment, assessing their bio-nano interactions, and examining their potential risks to humans and the environment. We suggest considering nanoplastics a complex and dynamic mixture of polymers, additives, and contaminants, with interconnected risks to environmental and human health. We call for comprehensive integration of One Health approach to produce robust multidisciplinary evidence to nanoplastics threats at the planetary level. Although there are many challenges, this holistic approach incorporates the relevance of environmental exposure and multi-sectoral responses, which provide the opportunity to identify the risk mitigation strategies of nanoplastics to build resilient health systems.

Sub-acute exposure to nanoplastics via two-chain trophic transfer: From brine shrimp Artemia franciscana to small yellow croaker Larimichthys polyactis

This study investigated the trophic transfer of nanoplastics in marine food chains. We fed nanoplastic-exposed Artemia franciscana (brine shrimp) to Larimichthys polyactis (small yellow croaker) daily for eight days. Subsequently, the overall health condition, histopathological damage to the liver and digestive tract, and swimming ability of the fish were measured. After the sub-acute exposure to nanoplastics via trophic transfer, the fish showed inhibited growth, severe liver damage, as well as a poorer swimming ability compared to the control. The swimming ability was especially affected, in terms of the overall movement as well as thigmotaxis. The results thus clarified that even an indirect exposure to nanoplastics could induce neurotoxic effects and affect the swimming ability of the fish. As fish are well-known human food resources, the possibility of such trophic transfers affecting higher trophic level organisms, such as humans, cannot be ruled out.

Co-Exposure with an Invasive Seaweed Exudate Increases Toxicity of Polyamide Microplastics in the Marine Mussel Mytilus galloprovincialis

Plastic pollution and invasive species are recognised as pervasive threats to marine biodiversity. However, despite the extensive on-going research on microplastics’ effects in the biota, knowledge on their combination with additional stressors is still limited. This study investigates the effects of polyamide microplastics (PA-MPs, 1 mg/L), alone and in combination with the toxic exudate from the invasive red seaweed Asparagopsis armata (2%), after a 96 h exposure, in the mussel Mytilus galloprovincialis. Biochemical responses associated with oxidative stress and damage, neurotoxicity, and energy metabolism were evaluated in different tissues (gills, digestive gland, and muscle). Byssus production and PA-MP accumulation were also assessed. Results demonstrated that PA-MPs accumulated the most in the digestive gland of mussels under PA-MP and exudate co-exposure. Furthermore, the combination of stressors also resulted in oxidative damage at the protein level in the gills as well as in a significant reduction in byssus production. Metabolic capacity increased in both PA-MP treatments, consequently affecting the energy balance in mussels under combined stress. Overall, results show a potential increase of PA-MPs toxicity in the presence of A. armata exudate, highlighting the importance of assessing the impact of microplastics in realistic scenarios, specifically in combination with co-occurring stressors, such as invasive species.