Evaluation of Cyto-genotoxicity of Perfluorooctane Sulfonate (PFOS) to Allium cepa

A review of per- and polyfluoroalkyl substances (PFASs) removal in constructed wetlands: Mechanisms, enhancing strategies and environmental risks

PER: Polyfluoroalkyl substances (PFASs), typical persistent organic pollutants detected in various water environments, have attracted widespread attention due to their undesirable effects on ecology and human health. Constructed wetlands (CWs) have emerged as a promising, cost-effective, and nature-based solution for removing persistent organic pollutants. This review summarizes the removal performance of PFASs in CWs, underlying PFASs removal mechanisms, and influencing factors are also discussed comprehensively. Furthermore, the environmental risks of PFASs-enriched plants and substrates in CWs are analyzed. The results show that removal efficiencies of total PFASs in various CWs ranged from 21.3% to 98%. Plant uptake, substrate absorption and biotransformation are critical pathways in CWs for removing PFASs, which can be influenced by the physiochemical properties of PFASs, operation parameters, environmental factors, and other pollutants. Increasing dissolved oxygen supply and replacing traditional substrates in CWs, and combining CWs with other technologies could significantly improve PFASs removal. Further, CWs pose relatively lower ecological and environmental risks in removing PFASs, which indicates CWs could be an alternative solution for controlling PFASs in aquatic environments.

Genotoxicity and cytotoxicity assessment of 'forever chemicals' in zebrafish (Danio rerio)

Per- and polyfluoroalkyl substances (PFAS) comprise many chemicals with strong carbon-carbon and carbon-fluorine bonds and have extensive industrial applications in manufacturing several consumer products. The solid covalent bonding makes them more persistent in the environment and stays away from all types of degradation, naming them 'forever chemicals.' Zebrafish (Danio rerio) was used to evaluate the genotoxic and cytotoxic effects of legacy PFAS, Perfluorooctane sulfonate (PFOS), and its alternatives, such as Perfluoro-2-methyl-3-oxahexanoic acid ammonium (GenX) and 7H-Perfluoro-3,6-dioxa-4-methyl-octane-1-sulfonic acid (Nafion by-product 2 [NBP2]) upon single and combined exposure at an environmental concentration of 10 µg/L for 48-h. Erythrocyte micronucleus cytome assay (EMNCA) revealed an increased frequency of micronuclei (MN) in fish erythrocytes with a significant increase in NBP2-treated fish. The order of genotoxicity noticed was NBP2 > PFOS > Mixture > GenX in D. rerio. Fish exposed to PFOS and its alternatives in single and combined experiments did not cause any significant difference in nuclear abnormalities. However, PFOS and combined exposure positively inhibit cytokinesis, resulting in an 8.16 and 7.44-fold-change increase of binucleated cells. Besides, statistically, increased levels of reactive oxygen species (ROS) and malondialdehyde (MDA) content indicate oxidative stress in D. rerio. In addition, 'forever chemicals' resulted in cytotoxicity, as evident through changes in nucleus width to the erythrocyte length in NBP2 and mixture exposure groups. The findings revealed that PFAS alternative NBP2 is more toxic than PFOS in inducing DNA damage and cytotoxicity. In addition, all three tested 'forever chemicals' induced ROS and lipid peroxidation after individual and combined exposure. The present work is the first to concern the genotoxicity and cytotoxicity of 'forever chemicals' in the aquatic vertebrate D. rerio.

Per- and polyfluoroalkyl substances (PFAS) in little penguins and associations with urbanisation and health parameters

Per- and Polyfluoroalkyl substances (PFAS) are increasingly detected in wildlife and present concerning and unknown health risks. While there is a growing body of literature describing PFAS in seabird species, knowledge from temperate Southern Hemisphere regions is lacking. Little penguins (Eudyptula minor) can nest and forage within heavily urbanised coastal environments and hence may be at risk of exposure to pollutants. We analysed scat contaminated nesting soils (n = 50) from 17 colonies in lutruwita/Tasmania for 16 PFAS, plasma samples (n = 45) from nine colonies, and three eggs for 49 PFAS. We detected 14 PFAS across the sample types, with perfluorooctanesulfonic acid (PFOS) and perfluorohexanesulfonic acid (PFHxS) most commonly detected. Mean concentration of PFOS in plasma was 2.56 ± 4.3 ng/mL ( Collapse

Key Words

• Ecotoxicology
• Genotoxicity
• Human impacts
• Seabird sentinels
• Wildlife health

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MESH Headings

• Male
• Female
• Animals
• Spheniscidae
• Urbanization
• Alkanesulfonic Acids/analysis
• Environmental Pollutants/analysis
• Fluorocarbons/analysis
• Soil
• Sulfonic Acids

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Affiliation(s)

Melanie R Wells Department of Biological Sciences, School of Natural Sciences, University of Tasmania, Hobart 7001, Tasmania, Australia; Institute for Marine and Antarctic Studies, Battery Point 7004, Tasmania, Australia.
Timothy L Coggan Environment Protection Authority Victoria, 200 Victoria Street, Carlton 3053, Victoria, Australia; ADE Consulting Group, U 4/95 Salmon Street, Port Melbourne 3207, Victoria, Australia
Gavin Stevenson Australian Ultra-Trace Laboratory, National Measurement Institute, North Ryde 2113, New South Wales, Australia
Navneet Singh ADE Consulting Group, U 4/95 Salmon Street, Port Melbourne 3207, Victoria, Australia
Matthew Askeland ADE Consulting Group, U 4/95 Salmon Street, Port Melbourne 3207, Victoria, Australia
Mary-Anne Lea Institute for Marine and Antarctic Studies, Battery Point 7004, Tasmania, Australia; Centre for Marine Socioecology, University of Tasmania, Hobart 7001, Tasmania, Australia
Annie Philips Wildlife Veterinary Consultant, Hobart 7000, Tasmania, Australia
Scott Carver Department of Biological Sciences, School of Natural Sciences, University of Tasmania, Hobart 7001, Tasmania, Australia; Odum School of Ecology, University of Georgia, GA, USA 30602; Center for the Ecology of Infectious Diseases, University of Georgia, GA, USA 30602

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Ecotoxicity of single and mixture of perfluoroalkyl substances (PFOS and PFOA) in soils to the earthworm Aporrectodea caliginosa

Per and polyfluoroalkyl substances (PFAS) are persistent compounds that are massively used in industry, consumer goods and fire-fighting foams. Soil contamination by PFAS is a major environmental concern, and there is a lack of knowledge on both their ecotoxicological mechanisms and the concentrations that induce adverse effects especially to non-target organisms, particularly in the case of PFAS mixtures. This study contributes to filling these gaps by assessing and modelling the effects of PFAS (in single and in mixtures for PFOS and PFOA at different environmental doses) on juvenile endogeic earthworms of a common species in European soils (Aporrectodea caliginosa) at different levels of biological organization (sub-individual and individual). The results showed for the first time combined strong ecotoxicological effects of PFAS on earthworm survival, integumental integrity, growth, sexual maturity and on genomic stability notably with the induction of DNA breaks associated with no abnormal oxidative DNA-lesion levels. Our results demonstrated significant effects at 0.3 mg kg-1 and additive effects in case of mixtures.

Cytogenotoxic effects of 3-epicaryoptin in Allium cepa L. root apical meristem cells

Diterpenoid 3-epicaryoptin (C₂₆H₃₆O₉) is abundant in the leaves of Clerodendrum inerme, a traditionally used medicinal plant, and has insect antifeedant activities. Here, we aim to explore the cytogenotoxic effects of compound 3-epicaryoptin in Allium cepa root apical meristem cells. 3-epicaryoptin (concentrations of 100, 150, and 200 µg mL^-1) and the standard compound colchicine (200 µg mL^-1) were applied to A. cepa roots for 2, 4, and 4 + 16 h (4-h treatment followed by 16-h recovery). Cytogenotoxicity was analyzed by studying the root growth retardation (RGR), mitotic index (MI), and chromosomal aberrations. The result showed statistically significant (p < 0.01), concentration-dependent RGR effects of 3-epicaryoptin treatment compared with the negative control. A study of cell frequency in different phases of cell division observed a significant (p < 0.001) increase in the metaphase cell percentage (66.2 ± 0.58%, 150 µg mL^-1), which subsequently caused an increase in the frequency of MI (12.29 ± 0.34%, 150 µg mL^-1) at 4 h of 3-epicaryoptin treatment and that was comparable with the colchicine action. The cytological study revealed that the 3-epicaryoptin treatment could induce different types of chromosomal abnormalities, such as colchicine-like metaphase, vagrant chromosomes, sticky chromosomes, anaphase bridge, lagging chromosomes, multipolar anaphase-telophase, and an increased frequency of micronuclei and polyploid cells. These findings indicate that 3-epicaryoptin is cytogenotoxic, and thus, C. inerme should be used with caution in traditional medicine.

Efficient bioremediation of laboratory wastewater co-contaminated with PAHs and dimethylformamide by a methylotrophic enrichment culture

A methylotrophic enrichment culture, MM34X, has been assessed for its exceptional ability in biodegradation of dimethylformamide (DMF) and bioremediation of laboratory wastewater (LWW) co-contaminated with polycyclic aromatic hydrocarbons (PAHs). The culture MM34X tolerated high concentrations of DMF and efficiently degraded 98% of 20,000 mg L^-1 DMF within 120 h. LWW bioremediation was performed in stirred bottle laboratory-scale bioreactor. After 35 days of incubation, 2760.8 ± 21.1 mg L^-1 DMF, 131.8 ± 9.7 mg L^-1 phenanthrene, 177.3 ± 7.5 mg L^-1 pyrene and 39.5 ± 2.7 mg L^-1 BaP in LWW were removed. Analysis of post-bioremediation residues indicated the absence of any known toxic intermediates. The efficacy of bioremediation was further evaluated through cyto-genotoxicity assays using Allium cepa. The roots of A. cepa exposed to bioremediated LWW showed improved mitotic index, whereas original LWW completely arrested cell growth. Similarly, the alkaline comet assay indicated alleviation of genotoxicity in bioremediated LWW, as evidenced by significantly lower DNA damage in terms of tail DNA and Olive tail moment. In addition, oxidative stress assays, performed using fluorescent probes 2',7'-dichlorodihydrofluorescein diacetate, C11-BODIPY and dihydrorhodamine 123, revealed significant mitigation of oxidative stress potential in bioremediated LWW. Our findings suggest that the enrichment MM34X may prime the development of inexpensive and efficient large-scale bioremediation of LWW co-contaminated with PAHs and DMF.

Cyto-genotoxicity evaluation of pyroligneous acid using Allium cepa assay

Pyroligneous acid (PA) is a highly oxygenated organic condensate obtained by cooling the gases generated from the pyrolysis process. PA has been used in agriculture for several years with multiple beneficial effects, including plant health and yields, pest resilience, and seed germination. It is generally applied to agricultural soils in the dilution of 1:1000 to 1:100, corresponding to 0.1-1% PA concentration. In this study, the cyto-genotoxic potential of PA to Allium cepa meristematic root-tips (where all cells undergo repeated division and form primary root tissues) was examined. Exposure to PA concentrations of 0.1% and above showed a reduction in the mitotic index percentage, and at 5%, a complete arrest in the cell division was recorded. However, chromosomal aberrations at 0.5, 1, and 3% PA were reversible types such as bridges, vagrants, laggards, and multipolar anaphase, with a maximum of only 5.8% chromosomal aberration observed at 3% PA. Comet assay (single-cell gel electrophoresis) for genotoxicity assessment determined using PA exposed A. cepa root tips showed that it was not genotoxic. The absence of cyto-genotoxicity in A. cepa, even at concentrations far above what would be typically encountered in agricultural applications, strongly suggests that PA is unlikely to cause adverse effects on crops and ultimately on the biota and human health.

Genotoxic and cytotoxic effects of pethoxamid herbicide on Allium cepa cells and its molecular docking studies to unravel genotoxicity mechanism

Pethoxamid is chloroacetamide herbicide. Pethoxamid is commonly used to kill different weeds in various crops. Pethoxamid can leach in the water and soil and can cause toxic effects to other non-target species. Current study is therefore aimed to perform the investigation of the cytotoxic and genotoxic effects of pethoxamid on Allium cepa cells.The root growth, mitotic index (MI), chromosomal aberrations (CAs), and DNA damage were assessed through root growth inhibition, A. cepa ana-telophase, and alkaline comet assays, respectively. Furthermore, molecular docking was performed to evaluate binding affinity of pethoxamid on DNA and very-long-chain fatty acid (VLCFA) synthases. In root growth inhibition test, onion root length was statistically significantly decreased in a concentration dependent manner. Concentration- and time-dependent decreases in MI were observed, whereas increase in CAs such as disturbed ana-telophase, chromosome laggards, stickiness, anaphase bridges, and DNA damage was caused by the pethoxamid on A. cepa root cells. Molecular docking revealed that pethoxamid binds selectively to GC-rich regions in the minor groove of the DNA structure and showed remarkable binding affinity against all synthases taking part in the sequential biosynthesis of VLCFAs. It was concluded that the pethoxamid-induced genotoxicity and cytotoxicity may be through multiple binding ability of this herbicide with DNA and VLCFA synthases.

Turmeric (Curcuma longa L.) tends to reduce the toxic effects of nickel (II) chloride in Allium cepa L. roots

The immense protection potential of plant-derived products against heavy metal toxicity has become a considerable field of research. The goal of the present study was to evaluate the mitigative ability of turmeric against nickel (II) chloride (NiCl₂)-related toxicity in the roots of Allium cepa L. For this purpose, one control (treated with tap water) and five treatment groups (treated with 440 mg/L turmeric, 880 mg/L turmeric, 1 mg/L NiCI₂, 1 mg/L NiCI₂ + 440 mg/L turmeric, and 1 mg/L NiCI₂ + 880 mg/L turmeric, respectively) of Allium bulbs were established. Experimental conditions were maintained at room temperature for 3 days. Physiological, biochemical, cytogenetic, and meristematic integrity parameters were analyzed in all groups. NiCl₂ reduced germination percentage, root elongation, and weight gain. Following NiCl₂ application, the frequency of aberrant chromosomes and micronuclei increased, while mitotic index decreased. NiCl₂ caused an increase in oxidative stress, which was evident by increased malondialdehyde level and catalytic activities of superoxide dismutase and catalase. Epidermal and cortex cell injuries as well as deformed cell nuclei and indistinct transmission tissue were observed as a result of NiCl₂ treatment. When applied alone, turmeric, which did not cause any negative effects, led to an improvement in all parameters depending on the dose when applied together with NiCl₂. Data from the study suggests that turmeric has remarkable protection potential against NiCl₂ in Allium cepa.

Removal of per- and poly-fluoroalkyl substances (PFASs) by wetlands: Prospects on plants, microbes and the interplay

Per- and polyfluoroalkyl substances (PFASs) represent a large family of synthetic organofluorine aliphatic compounds. They have been extensively produced since 1940s due to enormous applications as a surface-active agent, and water and oil repellent characteristics. PFASs are made to be non-biodegradable, therefore, many of them have been found in the environment albeit strict regulations have been in place since 2002. PFASs are extremely toxic compounds that can impart harm in both fauna and flora. Recent investigations have shown that wetlands might be useful for their removal from the environment as a passive and nature-based solution. To this end, understanding the role of plants, microbes, and their combined plant-microbe interplay is crucial because it could help design a sophisticated passive treatment wetland system. This review focuses on how these components (plants, microbe, substrate) can influence PFASs removal in wetlands under natural and controlled conditions. The information on underlying removal mechanisms is mostly retrieved from laboratory-based studies; however, pilot- and field-scale data are also presented to provide insights on their real-time performance. Briefly, a traditional wetland system works on the principles of phytouptake, bioaccumulation, and sorption, which are mainly due to the fact that PFASs are synthetic compounds that have very low reactivity in the environment. Nevertheless, recent investigations have also shown that Feammox process in wetlands can mineralize the PFASs; thus, opens new opportunities for PFASs degradation in terms of effective plant-microbe interplay in the wetlands. The choice of plants and bacterial species is however crucial, and the system efficiency relies on species-specific, sediment-specific and pollutant-specific principles. More research is encouraged to identify genetic elements and molecular mechanisms that can help us harness effective plant-microbe interplay in wetlands for the successful removal of PFASs from the environment.

Perfluorooctanoic acid exposure in early pregnancy induces oxidative stress in mice uterus and liver

This study aimed to explore the mechanism of perfluorooctanoic acid (PFOA) toxicity on the uterus and liver of mice during early pregnancy. Pregnant mice were given 0, 1, 5, 10, 20, and 40 mg/kg PFOA daily by gavage from gestational day (GD) 1-7 and sacrificed on GD 9. Subsequently, several toxicity parameters were evaluated, including the uterus and liver weights, liver and uterine indexes, histopathological changes of the liver and uterus, and levels of malondialdehyde (MDA), superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px) in the liver. We also determined the expressions of FAS, FASL, Bax, Bcl-2, and Caspase-3 in decidual cells by immunohistochemistry and the TUNEL assay to detect apoptosis uterine cells. The results showed that PFOA increased the liver weights and reduced the uterus index in a dose-dependent manner. With increasing doses of PFOA, the levels of SOD and GSH-Px were significantly decreased, and MDA increased substantially in liver tissue. 20 mg/kg and 40 mg/kg of PFOA caused more substantial harm to the uterus, thus a higher probability for congestion and resorption. The expression of FAS, FASL, Bax, and Caspase-3 in decidual cells of the uterus in the PFOA treatment groups significantly increased in a dose-dependent manner. The expression of Bcl-2 was downregulated, decreasing the Bcl-2/Bax ratio. At gestation day 9, the control group had significantly fewer apoptotic cells in the uterus and shallower staining than the 40 mg/kg PFOA group. The findings of this study suggest that oxidative damage may be one of the mechanisms by which PFOA induces liver toxicity, and a subsequent increase in uterine cell apoptosis may cause embryo loss or damage.

Extenuating role of lycopene against 254-nm UV-C radiation-mediated damages in Allium cepa L. roots

UV-C exposure has become a crucial risk for living organisms due to its widespread use in sterilization. In this study, the mitigating potential of lycopene was investigated against UV-C-mediated toxicity in Allium cepa L. roots. Allium bulbs were separated into six groups which treated with tap water, 215 mg/L lycopene, 430 mg/L lycopene, 254-nm UV radiation, 215 mg/L lycopene + 254-nm UV radiation, and 430 mg/L lycopene + 254-nm UV radiation. Germination percentage, root length, weight gain, mitotic index, micronucleus frequency, and other chromosomal aberrations as well as meristematic cell damages were investigated in all groups. Malondialdehyde level and the activities of superoxide dismutase and catalase enzymes were also analyzed to understand the severity of oxidative stress. UV-C radiation was revealed to negatively affect all parameters investigated, while the mitigating activities of lycopene against UV-C-mediated toxicity were dose-dependent. Therefore, the study evidently demonstrated the promising potential of lycopene in the protection against the detrimental effects of UV-C exposure in A. cepa.

Cytotoxic and genotoxic effects of clopyralid herbicide on Allium cepa roots

Clopyralid is one of the synthetic pyridine-carboxylate auxin herbicides and used to control perennial and annual broadleaf weeds in wheat, sugar beets, canola, etc. In this study, dose-dependent cytotoxicity and genotoxicity of clopyralid at different concentrations (25, 50, and 100 μg/mL) have been evaluated on the Allium cepa roots. The evaluation has been performed at macroscopic (root growth) and microscopic levels [mitotic index (MI), chromosome aberrations (CAs) in ana-telophase cells, and DNA damage] using root growth inhibition, Allium ana-telophase, and comet tests. The percentage of root growth inhibition and concentration of reducing root growth by 50% (EC₅₀) of clopyralid were determined compared with the negative control by using various concentrations of clopyralid (6.25-1000 μg/L). The 96 h EC₅₀ of clopyralid was recorded as 50 μg/L. The gradual decrease in root growth and the MI reveals the cytotoxic effects of clopyralid. All the tested concentrations of clopyralid induced total CAs (polyploidy, stickiness, anaphase bridges, chromosome laggards, and disturbed ana-telophase) and DNA damage dose and time dependently. These results confirm the cytotoxic and genotoxic effects of clopyralid on non-target organism.