Toxicity of some aquatic pollutants to fish

Toxicological insight of metiram: immuno-oxidative, neuro-behavioral, and hemato-biochemical changes during acute exposure of Nile tilapia (Oreochromis niloticus)

BACKGROUND

The inappropriate use of pesticides including fungicides creates severe biological hazards that can endanger fish health and impede sustainable aquaculture.

OBJECTIVE

This study investigated the negative impacts of metiram (MET), a fungicide on the health status of Nile tilapia (Oreochromis niloticus) for a 96-hour duration as an acute exposure in a static renewal system.

METHODS

Three hundred fish (average body weight: 37.50 ± 0.22 g) were assigned into six groups (50 fish/group) with five replicates (10 fish/replicate). Fish were exposed to various six concentrations (0, 1.5, 3, 4.5, 6, and 7.5 mg/L) of MET as a water exposure to for 96-hour without water exchange. The fish's behavior, clinical signs, and mortalities were documented every day of the exposure period. Additionally, MET's impact on blood profile, stress biomarkers, hepato-renal functions, immune-antioxidant status, and brain biomarker were closely monitored.

RESULTS

The lethal concentration (LC50) of MET estimated using Finney's probit technique was 3.77 mg/L. The fish's behavior was severely impacted by acute MET exposure, as clear by an increase in surfacing, loss of equilibrium, unusual swimming, laterality, abnormal movement, and a decline in aggressive behaviors. The survivability and hematological indices (white and red blood cell count, differential white blood cell count, hematocrit value, and hemoglobin) were significantly reduced in a concentration-dependent manner following MET exposure. Acute exposure to MET (1.5-7.5 mg/L) incrementally increased stress biomarkers (nor-epinephrine, cortisol, and glucose), lipid peroxides (malondialdehyde), and brain oxidative DNA damage biomarker (8-hydroxy-2-deoxyguanosine). A hepato-renal dysfunction by MET exposure (4.5-7.5 mg/L) was evidenced by the significant increase in the alanine and aspartate aminotransferases and creatinine values. Moreover, a substantial decline in the immune parameters (lysozyme, complement 3, serum bactericidal activity, and antiprotease activity) and antioxidant variables (total antioxidant capacity, superoxide dismutase, and glutathione peroxidase) resulted from acute MET exposure.

CONCLUSION

According to these findings, the 96-hour LC50 of MET in Nile tilapia was 3.77 mg/L. MET exposure triggered toxicity in Nile tilapia, as seen by alterations in fish neuro-behaviors, immune-antioxidant status, hepato-renal functioning, and signifying physiological disturbances. This study emphasizes the potential ecological dangers provoked by MET as an environmental contaminant to aquatic systems. However, the long-term MET exposure is still needed to be investigated.

Long-term effects of embryonic exposure to benzophenone-3 on neurotoxicity and behavior of adult zebrafish

Benzophenone-3 (BP-3) is the most widely used ultraviolet filter (UV filter) in industries to avoid UV radiation damage. BP-3 is added to most sunscreens to protect the skin, hair, and lips from sun rays. It results in continuous discharge into aquatic environments, leading to aquatic biota and human's continuous exposure. Consequences of BP-3 exposure on the physiology and behavior of aquatic animals, mainly zebrafish, have been investigated, including their neurotoxic effects. However, little is known about its consequences in long-term developmental endpoints. This study aimed to investigate the long-term effects of embryonic BP-3 exposure on biomarkers of neurotoxicity in zebrafish. For this, we exposed embryos to 5, 10, and 20 μg∙L-1 BP-3 concentration and let fish grow to adulthood (5mpf). We evaluated anxiety-like behavior, social preference, aggressiveness, and enzymatic activity of the antioxidant defenses system and neurotoxic biomarkers (Glutathione S-transferase -GST, catalase -CAT, and acetylcholinesterase -AChE) in adult zebrafish. Enzymatic activities were also investigated in larvae immediately after BP-3 exposure. Animals early exposed to BP-3 presented anxiety-like behaviors and decreased social preference, but aggressiveness was not altered. In general, exposure to BP-3 leads to altered enzymatic activity, which persists into adulthood. GST activity increased in embryos and adults, while CAT activity decreased in both life stages. AChE activity enhanced only at the larval stage (96 hpf). The long-term behavioral and biochemical effects of BP-3 highlight the need for abolishing or restricting the compound from personal care products, which are continually disposed into the environment and threaten the biota and human health.

Method validation and dissipation kinetics of the novel HPPD-inhibiting herbicide cypyrafluone in winter wheat using QuEChERS method coupled with UPLC-MS/MS

Cypyrafluone, a novel hydroxyphenylpyruvate dioxygenase (HPPD)-inhibiting herbicide, can successfully control a wide species of grass and broadleaf weed in wheat fields. However, the dissipation behaviors and terminal residues of cypyrafluone in wheat fields remain unclear. Here, a simple, accurate, and dependable approach for the analysis of cypyrafluone in soil, wheat plant, and grain was constructed utilizing an adapted QuEChERS extraction combined with UPLC-MS/MS. For accurate quantification, matrix-matched calibrations with high linearity (R² >0.99) were employed to eliminate matrix interference. The method possessed high accuracy with recoveries in the range of 85.5%- 100.6% and precision with relative standard deviations < 14.3%, as well as high sensitivity with limits of quantifications of 0.001 mg kg^-1 in the three matrixes. The dissipation kinetics and terminal residues of cypyrafluone were determined at two separate locations with different climates, soil types and cropping systems in 2018. The half-lives of cypyrafluone in soil and wheat plant were 1.47-1.55 d and 1.00-1.03 d, respectively. At harvest, the terminal residue values of cypyrafluone detected in wheat plants were 0-0.0025 mg kg^-1 and 0.0044-0.0057 mg kg^-1 at the recommended dose and 1.5 times of the recommended dose, respectively, and 0.0049 mg kg^-1 of this herbicide was detected in grain at 1.5 times of the recommended dose, which was below the maximum residue limit (MRL). Finally, the risk quotient for cypyrafluone ranged from 0.33% to 0.81% (<1) for different age groups in China, indicating that the impact of residues from the cypyrafluone application on wheat was acceptable. These findings above will offer scientific guidelines for cypyrafluone application in the wheat field ecosystem.

Effects of ammonia exposure on anxiety behavior, oxidative stress and inflammation in guppy (Poecilia reticulate)

Ammonia is one of the most important aquatic environmental factors, which is of great concern. In order to evaluate the effect of ammonia on guppy (Poecilia reticulate), fish were exposed to increased concentrations (0, 12.50, 25.00, 41.67, 62.50 mg/L) of ammonia for 48 h. After exposure, we measured the anxiety behavior, antioxidant enzymes and pro-inflammation genes (TNF-α, IL-1β and IL-6) of guppy. The results showed that ammonia stress induced fish anxiety, which was manifested by the increased latency to enter the upper half and decreased time spent in upper half compared with control fish. The guppy showed oxidative stress after 48 h of ammonia stress as evidenced by decreases in the activities of antioxidant enzymes and an increase in lipid hydroperoxide content. With prolonged ammonia stress, the expressions of HSP70, HSP90, TNF-α, IL-1β and IL-6 mRNA at first had an increasing trend, and then decreased, all of which were significantly higher than the control levels at 12 h and 24 h after ammonia stress (P < 0.05). Ammonia significantly upregulated these genes mRNA levels after 48 h exposure, suggesting that heat shock proteins and innate immune system may try to protect cells from oxidative stress induced by ammonia stress. Our study showed that higher ammonia exposure induced oxidative stress in exposed fish, since inhibition of antioxidant enzymes activity and increases in lipid peroxidation, and inflammation occurred. Furthermore, the results will be helpful to understand the mechanism of ammonia toxicity in guppys.

Health Risk Assessment of Pesticide Residues in Drinking Water of Upper Jhelum Region in Kashmir Valley-India by GC-MS/MS

Globally growing demand for agricultural and farm foods has more or less become dependent on chemical pesticides to maintain the supply chain, which undoubtedly boosts agricultural production. However, pesticides not only impact the target pests but cause hazard to human health. Pesticides are ubiquitous and can be found in almost every component of the environment. They can therefore impair human and biota health when present over the threshold level. The present study assessed the concentration of commonly used pesticides for agricultural purposes but get mixed in different sources of water, as such fifteen sampling sites along the upper Jhelum basin of Kashmir valley were chosen. For the analysis, 60 water samples were obtained from different water sources. Gas chromatography coupled with tandem mass spectrometry (GC-MS/MS) was used to determine pesticide residues in water samples. Pesticide residues from 10 of the 26 commonly used pesticides were detected in water samples. Difenoconazole had the highest concentration among the pesticides detected, with a mean concentration of 0.412 ± 0.424 μg/L ranging from 0.0 μg/L to 0.8196 μg/L. The target hazards quotient (THQ) was used to quantify the possible noncarcinogenic health risks associated with drinking pesticide-contaminated water. Only chlorpyrifos and quinalphos were detected >1 in RWS3 (1.6571), RWS4 (1.0285), RWS14 (1.2571), and RWS15 (1.2000) sample sites, implying that the drinking water poses a health risk to humans. Hence, pesticide hazards should be mitigated and rigorous monitoring is needed to reduce pesticide residues in drinking water.

Mixture toxicity of pyraclostrobine and metiram to the zebrafish (Danio rerio) and its potential mechanism

The interplay between pesticides plays a critical role in ecotoxicology since these chemicals rarely emerge as single substances but rather in mixtures with other chemicals. In the present work, we purposed to clarify the combined toxic impacts of pyraclostrobine (PYR) and metiram (MET) on the zebrafish by using numerous indicators. Results exhibited that the 4-day LC₅₀ value of MET to fish embryos was 0.0025 mg a.i. L^-1, which was lower compared with PYR (0.019 mg a.i. L^-1). Combinations of PYR and MET presented a synergetic impact on fish embryos. Contents of POD, CYP450, and VTG were drastically increased in the plurality of the single and joint treatments relative to the baseline value. Three genes, including vtg1, crh, and il-8, related to the endocrine and immune systems, were also surprisingly up-regulated when fish were challenged by the individual and mixture pesticides compared with the baseline value. These results afforded valuable information on the latent toxicity mechanisms of co-exposure for PYR and MET in the early growth stage of fish. Moreover, our data also revealed that frequent application of these two pesticides might exert a potentially ecotoxicological hazard on aquatic ecosystems. Collectively, the present study provided valuable guidance for the risk evaluation of chemical combinations.

Multibiomarker approach in fish to assess a heavily polluted Brazilian estuary, Guanabara Bay

Brazil's Guanabara Bay (GB), located in Rio De Janeiro, is a deeply contaminated, eutrophic waterbody that challenges the understanding of the effects of pollutants on the biota. This paper presents a strategy to evaluate the impact of contamination utilizing a multibiomarker approach in two fish species: corvine (Micropogonias furnieri) and burrfish (Chilomycterus spinosus). The strategy is comprised of a general biomarker of fish' physical condition, the condition factor (CF), and specific biomarkers of pollutant exposure such as acetylcholinesterase (AChE), metallothionein (MT) activity and biliary polycyclic aromatic hydrocarbons (PAH) metabolites. Our results indicate that fish from GB are greatly affected by environmental pollution. CF values were lower in fishes from GB than in the reference site indicating that these fishes were under higher environmental stress. Lower AChE activity level in both species showed vulnerability to the presence of pesticide residues. Higher levels of MT in both species in GB reflect the consequences of heavy metal exposure in the bay, in spite of their bioavailability being restricted specially by the high organic matter content of GB. The levels of PAHs were higher in GB for both fish species, indicating exposure to these substances. However, the fish species showed different behavior regarding the origin of the PAHs. The multibiomarker approach used in this study evidently depicted effects on the health of fish in a waterbody with a complex polluted situation and further categorized the effects of anthropogenic activities in this aquatic system.

Mixture effects of imidacloprid and difenconazole on enzymatic activity and gene expression in small yellow croakers (Larimichthys polyactis)

Agrochemicals usually exist as mixtures in aqueous ecosystems and have harmful impacts on the natural environment. Nonetheless, the combined effects and underlying mechanisms of agrochemicals on aqueous organisms remain poorly understood. In the present study, the interactive effects of imidacloprid (IMI) and difenconazole (DIF) on the embryos of small yellow croakers (Larimichthys polyactis) were assessed using various toxicological assays, including acute toxicity, enzymatic activity, and gene expression changes. The results showed that DIF (72-h LC₅₀ value of 0.20 mg L^-1) had higher toxicity than IMI (72-h LC₅₀ value of 12.5 mgL^-1). Simultaneously, combinations of IMI and DIF exerted synergistic acute effects on the embryos of L. polyactis. In addition, the SOD, CAT, GST, and CarE activities were noticeably altered in most single and mixed exposures, relative to the untreated control. The expression of four genes (cyp19a1b, ngln2, klf2a, and socs3a) related to the immune system, endocrine system, and neurodevelopment was also surprisingly altered when the embryos of L. polyactis were subjected to individual and combined exposures relative to the untreated control. Changes in enzymatic activity and gene expression might provide early warning indices for the identification of agrochemical co-exposure. The results of this study provide valuable insights into the comprehensive toxicity of agrochemical mixtures to L. polyactis. Further studies on the long-term effects of agrochemical mixtures on marine fish should be conducted to formulate definitive conclusions concerning hazards.

Joint toxic effects of phoxim and lambda-cyhalothrin on the small yellow croaker (Larimichthys polyactis)

Although pesticides commonly exist as combinations in real-life situations of the aquatic ecosystem, the impact of the toxicity of their mixtures has remained largely unclear. In this study, we investigated the combined effects of two neurotoxic pesticides, including one organophosphate insecticide phoxim (PHO) and one pyrethroid insecticide lambda-cyhalothrin (LCY), on the embryos of the small yellow croaker (Larimichthys polyactis), and their potential pathways. LCY exhibited higher toxicity relative to PHO, with a 72-h LC₅₀ value of 0.0074 mg a.i. L^-1, while the corresponding value for PHO was 0.12 mg a.i. L^-1. The mixture of PHO and LCY exerted a synergistic effect on the embryos of L. polyactis. The activities of antioxidant enzyme CAT and apoptotic enzyme caspase 3 were substantially changed in most single and combined exposure groups relative to the baseline value. Under both single and combined exposures, more significant changes were found in the mRNA expression of five genes, including the immunosuppression gene ngln2, the apoptosis gene P53, the endocrine system gene cyp19a1b, as well as neurodevelopment genes of ap and acp2, relative to the baseline value. Furthermore, the non-target metabolomic analysis demonstrated that hundreds of differential metabolites, including two bile acids (taurodeoxycholic acid and tauroursodeoxycholic acid), were significantly increased in the exposure groups. The bile acids were closely associated with the gut microbiota, and 16S rRNA sequencing results demonstrated dysfunction of the gut microbiota after exposure, especially in the combined exposure group. Our findings indicated that there might be a potential risk connected to the co-occurrence of these two pesticides in aquatic vertebrates. Consequently, future ecological risk assessments should incorporate synergistic mixtures because the current risk assessments do not consider them.

A comprehensive review on electrochemical and optical aptasensors for organophosphorus pesticides

There has been a rise in pesticide use as a result of the growing industrialization of agriculture. Organophosphorus pesticides have been widely applied as agricultural and domestic pest control agents for nearly five decades, and they remain as health and environmental hazards in water supplies, vegetables, fruits, and processed foods causing serious foodborne illness. Thus, the rapid and reliable detection of these harmful organophosphorus toxins with excellent sensitivity and selectivity is of utmost importance. Aptasensors are biosensors based on aptamers, which exhibit exceptional recognition capability for a variety of targets. Aptasensors offer numerous advantages over conventional approaches, including increased sensitivity, selectivity, design flexibility, and cost-effectiveness. As a result, interest in developing aptasensors continues to expand. This paper discusses the historical and modern advancements of aptasensors through the use of nanotechnology to enhance the signal, resulting in high sensitivity and detection accuracy. More importantly, this review summarizes the principles and strategies underlying different organophosphorus aptasensors, including electrochemical, electrochemiluminescent, fluorescent, and colorimetric ones.

Physicochemical water quality of Karabel, Çaltı, and Tohma brooks and blood biochemical parameters of Barbus plebejus fish: assessment of heavy metal concentrations for potential health risks

The present study aims to comparatively examine the physical quality parameters of water samples taken from Karabel, Çaltı, and Tohma brooks in Sivas province and the blood biochemical parameters of blood samples of Barbus plebejus fish obtained from these waters. In periods when chemical pollution in water increased and decreased, it was determined that GLU and UA among blood biochemical parameters were significantly affected. Moreover, the potential risk levels of lead (Pb), copper (Cu), cadmium (Cd), and ferrous (Fe) for human health were compared to the international standards. Metal (Fe, Pb, Cu, and Cd) concentrations in the water were determined using atomic absorption spectrophotometer. The highest HQ_ingestion values of Cd were found in Brook Çaltı, which were 0.0018 for adults and 0.1980 for children. THQ upper limit set by the United States Environment Protection Agency (USEPA) is < 1. It was determined that HQ_ingestion, HQ_dermal, and THQ values of all the heavy metals were much lower than this limit. It was concluded that water quality parameters of samples taken from Karabel, Çaltı, and Tohma brooks on monthly basis for 12 months were not higher than the limits and the water qualities of brooks were determined to be "good".

Behavior evaluation of rainbow trout (Oncorhynchus mykiss) following temperature and ammonia alterations

In the study, we assessed how acute changes in water temperature and dissolved ammonia concentration can affect the swimming behavior pattern of rainbow trout (Oncorhynchus mykiss). The behavior was analyzed in three different stages: 1) increase stage, (where temperature and ammonia concentration increase during this step, respectively); 2) unchanged stage, (where levels of both factors do not change during this stage); 3) reduction stage, (where ammonia concentration and temperature during this stage are reduced), respectively. The results showed that both factors significantly changed the swimming pattern of the rainbow trout. There were significant differences in swimming parameters (distance from the center, swimming speed, total movement and the average of angular changes of movement) of treated fish in the comparison between treatments, and with the control group. The changes in the swimming pattern of fish in response to physicochemical parameters of water were confirmed to be a good tool in ecotoxicological studies.

The Chemical Compounds from Degradation of Profenofos and Malathion by Indigenous Bacterial Consortium

The Indonesian Pesticide Regulations state that Malathion and Profenofos have been restricted in their use for agriculture because of is bioaccumulative in ecological systems. Cleaning technology using microorganisms is an effective solution for cleaning pesticide residues. This study aims to identify the bacteria that degrade and the degradation process of Malathion and Profenophos into non-toxic compounds. The research method was experimental, identification of bacteria by 16S-rRNA gene analysis, degradation ability by GC MS. The results of phylogenetic tree analysis showed that the tested bacteria were closely related to Oceanobacillus iheyenis (RPL1) and Exiquobacterium profundum (RPL5) with a similarity level of 87% and 99%. The two bacteria are used as a consortium of test bacteria. The results of degradation based on the observation chromatogram T = 0 showed that the Malathion compound C10H19O6PS2 or butanedioic acid [(dimethoxyphosphinothioyl) thio]) was detected at peak 4, real-time = 19,675, area% = 7.37 and Profenofos compound C11H15BrClO3PSO-(4-Bromo-2-chlorophenyl)o-ethyl s-propyl thiophosphate, peak 8, real-time = 23,957, area% = 6.91. Likewise, the chromatogram results at T = 96 were still detected Malathion ((dimethoxyphosphinothioyl) thio) at peak 14, real-time = 19,675, area% = 2.25, and Profenofos (o- (4-Bromo-2-chlorophenyl)) o – ethyl. s – propyl thiophosphate) peak = 22 real-time = 23,951, area% = 2,2. However, the observation of T = 192 hours, Malathion and Profenofos compounds were not detected. The conclusion showed that the consortium bacteria were able to completely degrade Malathion and Profenophos within 192 hours.

Analysis of the biochemical and histopathological impact of a mild dose of commercial malathion on Channa punctatus (Bloch) fish

The intensive application of pesticides without proper disposal management has led their excess residues to reach the neighbouring aquatic ecosystem and its inhabitants mainly fish. In natural water body pesticides get diluted, and therefore to study the silent toxic effect, a low dose of malathion (0.4 mg/L; 1/20th of 96-h LC50 value) for the different duration (1, 4, 8, 12 days) was evaluated through biochemical and histopathological biomarkers of the blood and hepatorenal tissues of Channa punctatus. With the increase in pesticide exposure periods, the biometric indices: Condition Factor (K), HSI and KSI and hepatorenal tissues weight decreased. Among the biochemical alterations in malathion exposed fish, serum glucose levels reduced by 72.23 % while protein amounts increased by 29.03 % in 12 days malathion exposed fish. Other parameters, viz., cholesterol, albumin, and phosphorous, remained the same as control fish after malathion exposure. Though serum bilirubin (total and direct) followed a biphasic response, it reduced by 60 % after 12 days of malathion exposure compared to control. Biochemical changes are reflecting the induction of compensatory energy mechanism to cope up with the malathion stress. The transaminases and ALP biomarker enzymes used for liver functionality test declined in the order of AST > ALP > ALT in a time-dependent manner in malathion exposed fish serum, indicating liver injuries in fish due to malathion. The elevated levels of urea, BUN, creatinine, and Ca2+ in the serum of 12 days of malathion exposed fish revealed renal dysfunction. In the treated fish, antioxidative (SOD and CAT) and LPO activities were significantly higher in the liver followed by the kidney than their controls. Further, histological examination registered progressive damages in the hepatorenal tissues of malathion exposed fish with the increased exposure periods compared to control. Thus, even a small dose of malathion in water could severely deteriorate the structure and function of tissue on its prolonged exposure, and therefore utmost care should be taken to prevent their seepage into the water bodies.

Sediment records of polybrominated diphenyl ethers (PBDEs) in Huaihe River, China: Implications for historical production and household usage of PBDE-containing products

In recent decades, rapid development of industrialization and urbanization caused adverse impact on the aqueous ecology and environment of the Huaihe River basin, China. In this work, three ²¹⁰Pb-dated sediment cores extracted from the middle reach of Huaihe River in Anhui Province, China were analyzed to elucidate the temporal trends and sources of polybrominated diphenyl ethers (PBDEs). Source diagnostics indicated that commercial Deca-BDE, Penta-BDE and Octa-BDE products and debromination of higher brominated BDE compounds were likely the PBDE sources in the Huaihe River. The prevalence of BDE-47 in the sediment cores was attributed to the extensive use of commercial Bromkal 70-5DE and Bromkal DE-71 in the region. BDE-28 was another congener that was prevalent in all sediment samples, suggesting that reductive debromination occurred in the sediments. Dramatic increase of PBDE concentrations in both three cores since the post-1980s could be attributed to the rapid expansion of production of electronic and telecommunication equipment and household usage in China. PBDE temporal trends in core S1 located at rural area mainly reflected the regional and national inputs deriving from long distance atmospheric transport, and the positive correlations between PBDE concentration in core S1 and gross domestic product (GDP) and household appliances production volumes (HPVs) were observed. PBDE inputs at site S3 mainly include the transport of contaminated water and re-suspended fine sediment particles from the upstream site S2, which was located in the industrial area and adjacent to e-waste recycling area. The government efforts to protect the environment and improve the e-waste management resulted in the progressive decrease trends in PBDE concentrations in cores S2 and S3.

Temporal trends of polybrominated diphenyl ethers in the sediment cores from different areas in China

This paper presented the historical data on the temporal trends of polybrominated diphenyl ethers (PBDEs) in the sediment cores collected from the Huaihe River, Yellow River and Chaohu Lake, China. Among the 40 targeted PBDE congeners, only 10, 6, and 9 of them were detected respectively in the samples from the Huaihe River, Yellow River and Chaohu Lake. On average, the total PBDEs concentrations in sediments were highest in Chaohu Lake followed by the Huaihe River and the Yellow River. As compared to other PBDE congeners, BDE-209 had higher concentrations and detection rates. The similar down core variation between PBDEs and total organic carbon (TOC) suggests that TOC is an important factor influencing PBDEs distribution in the sediments. The total PBDEs concentrations showed an increasing trend from bottom to upper sediments before a decreasing trend in the topmost sediments. The rapid urbanization and industrialization of these regions in recent decades may cause the historically increasing concentrations of sedimentary PBDEs, especially BDE-209. The decreasing PBDEs concentrations in topmost sediments was probably related to the strict environmental policies at present.