In recent years, many new pesticides have been developed to meet the growing agricultural demands driven by global population growth. Unfortunately, this has led to their frequent detection in aquatic ecosystems, posing risks to non-target organisms and human health through environmental pollution and dietary exposure. Therefore, there is an urgent requirement to develop effective technologies to remove these pesticides from the environment. However, due to the complexity of pesticide structures, their degradation products are commonly unknown and may result in new environmental risks.

Permanganate is a strong oxidant and plays a vital role in drinking water purification, groundwater remediation, and wastewater treatment. It does not introduce new pollutants, and its reduction product, manganese dioxide, can also act as a coagulant to further remove pollutants.

In this study, we used experimental and theoretical methods to explore how potassium permanganate degrades pesticides. The reaction between permanganate and quinclorac was first studied, showing a bimolecular reaction mode, which is stable in a wide pH range. The UPLC-Q-TOF-MS analysis showed that the initial product was mono-hydroxylated quinclorac, which was formed by permanganate oxidation at the benzene ring and could be further oxidized to a less toxic catechol structure.

It is then hypothesized that permanganate oxidation is selective for certain functional groups, better than non-selective oxidants like hydroxyl radical. Then, the imidacloprid degradation by permanganate was further studied. The reaction was stable and efficient near neutral pH and different ion strengths. Background substances like humic acid and chloride ions in water barely affected degradation. UPLC-Q-TOF-MS analysis showed that the main pathway was C-H bond hydroxylation on the imidazole ring, finally leading to the breakage of the imidazole ring. Toxicity analysis with the ECOSAR program showed that the degradation products of imidacloprid by permanganate oxidation were less toxic to aquatic organisms.

Climate change-induced stress and increased aquatic pollution, including persistent pollutants such as polycyclic aromatic hydrocarbons (PAHs), disrupt biological functions. Although 3D cell culture systems can be used to better understand these effects, their use in fish studies is currently limited. In this vein, developing and characterising new models is of extreme importance, as these may help to disclose pollutant effects on temperature increase scenarios.

To generate spheroids from the rainbow trout liver-derived RTL-W1 cell line, four cell densities — 10,000, 20,000, 40,000 and 60,000 cells per well — were cultured in 96-well ultra-low attachment (ULA) plates at 18 ºC, with or without centrifugation after seeding. Over 18 days in culture, the spheroids were assessed for viability (using alamar blue and lactate dehydrogenase (LDH) assays), biometry (diameter, area and sphericity) and morphology (optical and electron microscopy). Protein expression of cytochrome P450 (CYP) 1A was assessed by immunocytochemistry (ICC) at 10, 14 and 18 days in culture. To determine its suitability for ecotoxicology research, spheroids (60,000 cells) were exposed from the 10^th to the 14^th day in culture to two concentrations of the model PAH benzo(k)fluoranthene (BkF), at 18 and 23 ºC. CYP1A immunolabeling and mRNA expression were evaluated after the exposures.

In all culture densities, spheroids' diameter and area decreased over time, while sphericity and viability increased. The biometric parameters remained stable from the 10^th day onward. Centrifugation did not impact the spheroids’ formation dynamics. Morphological analysis showed unscathed cells and organelle content compatible with hepatocytic differentiation. Spheroids expressed CYP1A in ICC, denoting its functionality. BkF-treated spheroids exhibited increases in both ICC and mRNA expression, but there were no variations in gene expression across temperatures.

The generated spheroids appear to be a promising alternative model for studying PAHs and warming effects on fish liver detoxification.

The increasing use of cobalt nanoparticles (CoNPs) in industrial and biomedical applications raises concerns about their environmental fate and impact on aquatic ecosystems. In this study, we evaluated the phytotoxicity and phytoremediation potential of CoNPs using Lemna minor, a macrophyte known for its metal accumulation capacity. Specifically, we investigated CoNP-induced oxidative stress, physiological responses, and nanoparticle uptake mechanisms. L. minor plants were exposed to CoNPs at concentrations ranging from 0.1 to 20,000 µg L⁻¹ for seven days. Growth rates, photosynthesis, and respiration were measured, while oxidative stress markers (H₂O₂ and MDA) and antioxidant enzyme activities (SOD, APX, and CAT) were analyzed. Cobalt accumulation in plant tissues was quantified using ICP-MS, and transmission electron microscopy (TEM) was used to assess ultrastructural changes and intracellular cobalt localization. Our results showed that CoNP exposure led to significant oxidative stress and metabolic impairment at concentrations ≥1000 µg L⁻¹, reducing photosynthesis by 85% and growth by 77%. TEM analyses revealed that CoNPs were internalized by L. minor and localized in chloroplasts, causing thylakoid disorganization and plastoglobuli accumulation. Interestingly, CoNPs were found in different subcellular locations than Co²⁺ ions, suggesting distinct toxicity mechanisms. Despite these effects, L. minor removed over 99% of CoNPs and Co²⁺ from the medium, highlighting its potential for nanoparticle remediation. This study provides novel insights into the uptake and impact of CoNPs in aquatic plants, reinforcing the role of L. minor as an effective phytoremediator in nanoparticle-contaminated environments. Future research should explore long-term accumulation dynamics and optimize phytoremediation strategies for sustainable nanoparticle management.

The widespread application of nanoparticles (NPs) in fields ranging from consumer products to industrial processes has led to increased concerns about their potential toxic effects on human health and the environment. While traditional toxicological studies often evaluate the effects of individual nanoparticles, real-world exposure scenarios typically involve mixtures of nanoparticles, where interactions between particles can significantly alter their toxicological profiles. This study focuses on addressing this critical gap by employing high-throughput screening (HTS) to evaluate the combined effects of nanoparticle mixtures under various exposure conditions. Our research investigated how metal oxide nanoparticles can provide advancements in commercial applications thanks to their cytotoxic, genotoxic, and oxidative stress-inducing effects. By leveraging HTS platforms, we rapidly screened multiple mixture ratios and exposure durations using human lung epithelial cells and zebrafish embryos as model systems. The results revealed a range of interactions, from synergistic effects, where the combined toxicity exceeded the sum of individual toxicities, to antagonistic effects, where toxicity was mitigated. Mechanistic analyses showed that oxidative stress and metal ion release were key drivers of toxicity, particularly in ZnO-dominant mixtures. This study highlights the importance of integrating HTS into nanotoxicology research to provide a more comprehensive understanding of nanoparticle mixtures' behavior. The large datasets generated through HTS enable predictive modeling, allowing researchers to anticipate toxicological outcomes and guide the development of safer nanomaterials. Furthermore, the findings emphasize the need for regulatory frameworks to incorporate mixture effects into nanoparticle risk assessments, moving beyond the current single-particle-focused approaches.

The present study presents, for the first time, results from comprehensive chemical analyses concerning heavy metals, toxic elements, various polychlorinated diphenyl ethers (PCBs), congeners, polycyclic aromatic hydrocarbons (PAHs), and pesticides in sediments, surface waters, and mussels from the Bulgarian Black Sea. In the samples from most of the investigated locations, iron, zinc, PCB-28, and PAHs (benz(a)anthracene, benzo(a)pyrene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(ghi)perylene, and chrysene) were detected in the waters; arsenic, copper, iron, and zinc in the sediments; and arsenic, copper, cadmium, iron, lead, zinc, and PAHs (acenaphtene, acenaphthylene, anthracene, bezno(b)fluoranthene, chrysene, dibenzo(a,h)anthracene, fluoranthene, fluorene, naphthalene, phenanthrene, and pyrene) in the mussels. No pesticides were detected in any of the analyzed matrices. According to Commission Regulation (EU) 2023/915 of 25 April 2023 on the maximum levels for certain contaminants in food and repealing Regulation (EC) No. 1881/2006, there are now human health hazards in terms of consuming bivalve mollusks because the levels of the contaminants that we investigated and are also included in the regulation—Cd, Pb, Hg, ∑PAHs (bezno(a)anthracene, bezno(a)pyrene, bezno(b)fluoranthene, and chrysene)—were less than the maximum permissible levels set by law. The findings suggest that despite the detectable contaminants, the levels in mussels remain below thresholds deemed hazardous to human health. Yet, a set of biomarkers should be assessed in future in order to determine the effects on mussels which seem to live in a chronically contaminated aquatic environment, even though the contaminant levels are lower than the ones set in Directive 2000/60/EC of the European Parliament and of the Council of 23 October 2000.

Acknowledgments: This study is financed by the European Union-NextGenerationEU, through the National Recovery and Resilience Plan of the Republic of Bulgaria, project № BG-RRP-2.004-0001-C01.

Bee products are widely consumed and valued for their nutritional and therapeutic properties. However, these products are increasingly at risk of contamination due to the routine use of acaricides in apiculture to control Varroa destructor, a major parasitic threat to honeybee colonies. When improperly applied or overused, these chemical treatments can leave residues in bee-derived foods, representing an emerging hazard to food safety and consumer health. This study presents a comprehensive review of acaricide residues in bee products across Europe and Turkey, emphasizing their potential impact on human exposure. The literature review covered a six-year period (2019–2024) and included original research articles published in English, retrieved from Scopus, Web of Science, and PubMed. Selection criteria included studies analyzing more than 15 samples, using validated analytical methods and covering a broad range of bee-related matrices (pollen, bee bread, honey, beeswax, royal jelly, and propolis). The review focused on residues from seven pesticide families, including neonicotinoids, fungicides, herbicides, acaricides, insecticides, inert ingredients, and glyphosate-related compounds. The data were compiled in collaboration with over 20 international researchers. The most frequently reported residues were fluvalinate, coumaphos, amitraz, and chlorpyrifos, frequently found in beeswax compared to other bee products. These compounds, some of which are persistent and bioaccumulative, may pose chronic toxicological risks, including endocrine disruption and neurotoxicity. This work emphasizes the need for continuous monitoring and risk assessment of apicultural contaminants and highlights the importance of integrating food safety considerations into pest management strategies in beekeeping.