Determination Of Median Lethal Concentration Research Articles

Classifying chemicals into toxicity categories based on LC50 values- Pros and cons

Classifying chemicals into toxicity categories based on LC50 values- Pros and cons

Determination of Median Lethal Concentration (LC50) for Endosulfan, Heptachlor and Dieldrin Pesticides to African Catfish, Clarias gariepinus and Their Impact on Its Behavioral Patterns and Histopathological Responses.

Pesticides such as endosulfan, heptachlor and dieldrin persist in aquatic environments as a result of their resistance to biodegradation. However, there is no adequate information about the toxicity of endosulfan, heptachlor and dieldrin to the aquatic organism, African catfish (Clarias gariepinus)—a high valued widely distributed commercially interesting species. The current experiment was performed with the aim to determine the median lethal concentration (LC50) of endosulfan, heptachlor and dieldrin to African catfish (Clarias gariepinus); their behavioral abnormalities and histopathological alterations in several vital organs. A total of 324 juvenile fish were exposed for 96 h to six concentrations of endosulfan and dieldrin at 0, 0.001, 0.002, 0.004, 0.008 and 0.016 ppm, and to heptachlor at concentrations of 0, 0.02, 0.04, 0.08, 0.16 and 0.32 ppm for dose-response tests. The study demonstrated that the species is highly susceptible to those contaminants showing a number of behavioral abnormalities and histopathological changes in gill, liver and muscle. The 96-h LC50 value of endosulfan, dieldrin and heptachlor for the African catfish was found as 0.004 (0.001−0.01) mg/L, 0.006 mg/L and 0.056 (0.006−0.144) mg/L, respectively. Abnormal behaviors such as erratic jerky swimming, frequent surfacing movement with gulping of air, secretion of mucus on the body and gills were observed in response to the increasing exposure concentrations. Histopathological alterations of liver, gill and muscle tissues were demonstrated as vacuolization in hepatocytes, congestion of red blood cells (RBCs) in hepatic portal vein; deformed secondary lamellae and disintegrated myotomes with disintegrated epidermis, respectively. These findings are important to monitor and responsibly manage pesticide use in and around C. gariepinus aquacultural areas.

Determination of median lethal concentration of two common heavy metal pollutants in rivers, potassium chromate and cadmium nitrate, to red zebrafish and their mortality causes

In order to investigate the toxicological properties of river pollutants, potassium chromate (K2CrO4) and cadmium nitrate tetrahydrate (Cd (NO3)2·4H2O) were selected as they are commonly discharged from industry to nearby rivers. This paper studied the Median Lethal Concentration (LC50) of the pollutants to the adult red zebrafish by acute toxicity experiments within 96 hours. 120mg/L, 130mg/L, 140mg/L, 150mg/L, 160mg/L, 170mg/L potassium chromate solutions and 16mg/L, 20mg/L, 24mg/L, 28mg/L 32mg/L, 36mg/L cadmium nitrate tetrahydrate solutions were prepared with triplicates to determine the LC50. The results of the preliminary experiments and the calibration curves suggested that the LC50 of potassium chromate and cadmium nitrate tetrahydrate were 165 mg/L and 28 mg/L respectively. The toxicity of thresholds and LC100 were also evaluated. Through the observations of the tested subjects in morphological, ethological and anatomical manners, behavioural alterations, oxidative stress, and immunotoxicity were probably their major causes of death.

Sublethal effects induced by captopril on Cyprinus carpio as determined by oxidative stress biomarkers

To our knowledge, this is the first study to evaluate captopril-induced oxidative stress in fish, and specifically in the common carp Cyprinus carpio. At present, very few studies in the international literature evaluate the sublethal effects of captopril on aquatic organisms such as fish, and available ones focus on determination of median lethal concentration in crustaceans and algae. Also, studies evaluating these effects do not make reference to the mechanism of action of this pharmaceutical or its toxicokinetics. This limits our knowledge of the characterization of the sublethal effects of this medication and of its potential ecological impact. The present study aimed to evaluate the sublethal effects induced by three different concentrations of captopril, on C. carpio), by determination of activity of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx), as well as indicators of cellular oxidation: hydroperoxide content (HPC), lipid peroxidation (LPX) and protein carbonyl content (PCC). Specimens were exposed for 12, 24, 48, 72 and 96h to three different captopril concentrations: 1μgL−1, 1mgL−1 and 100mgL−1 (the first one has been detected environmentally, the other two have been associated with diverse toxic effects in aquatic species), and brain, gill, liver, kidney and blood samples were evaluated. Significant increases in HPC and LPX were observed mainly in kidney and gill, while PCC also increased in brain. Modifications were found in the activity of SOD (mostly in kidney, brain and blood), CAT (all organs) and GPx (kidney and gill). In conclusion, captopril induces oxidative stress in C. carpio.

Exposure medium: key in identifying free Ag+ as the exclusive species of silver nanoparticles with acute toxicity to Daphnia magna.

It is still not very clear what roles the various Ag species play in the toxicity of silver nanoparticles (AgNPs). In this study, we found that traditional exposure media result in uncontrollable but consistent physicochemical transformation of AgNPs, causing artifacts in determination of median lethal concentration (LC50) and hindering the identification of Ag species responsible for the acute toxicity of AgNPs to Daphnia magna. This obstacle was overcome by using 8 h exposure in 0.1 mmol L−1 NaNO3 medium, in which we measured the 8-h LC50 of seven AgNPs with different sizes and coatings, and determined the concentrations of various Ag species. The LC50 as free Ag+ of the seven AgNPs (0.37–0.44 μg L−1) agreed very well with that of AgNO3 (0.40 μg L−1), and showed the lowest value compared to that as total Ag, total Ag+, and dissolved Ag, demonstrating free Ag+ is exclusively responsible for the acute toxicity of AgNPs to D. magna, while other Ag species in AgNPs have no contribution to the acute toxicity. Our results demonstrated the great importance of developing appropriate exposure media for evaluating risk of nanomaterials.

Histopathological changes resulted exposure the common carp fish Cyprinus carpioL. to diazinon pesticide

In the present study, the effects of diazinon on Cyprinus carpio L. were investigated according to the following parameters: determination of median lethal concentration (LC50), gross pathological lesions and histopathological changes. To simulate the situation in the nature regarding the possible mode of exposure of fishes to pesticide, experiments of acute and accumulate subacute exposures were designed. For acute exposure, groups of fish were exposed to 0.025, 0.050, 0.100, 0.150, 0.200, 0.250 and 0.300)ppm, respectively for 72 hrs. at 15 C° and pH7.5 to simulate the subacute exposure, a group of fishes were exposed to 0.006 ppm as an accumulated concentration during 15 days. The most prominent results was as following the LC50 was found to be 0.150 ppm. Gross lesions and microscopically examination of tissues of acutely or chronically exposed fish after 3, 15, 30 and 45day from the end exposure was conducted the examination revealed histopathological changes in (gills, livers and kidneys) damage of all the tissues were observed as inflammatory response of fish to get rid of the toxic material also proliferation of bile duct in liver was observed.

Comparative toxicity of methidathion and glyphosate on early life stages of three amphibian species: Pelophylax ridibundus, Pseudepidalea viridis, and Xenopus laevis

The assessments of pesticide toxicity on nontarget organisms have largely been focused on the determination of median lethal concentration (LC50) values using single/laboratory species. Although useful, these studies cannot describe the biochemical mechanisms of toxicity and also cannot explain the effects of pesticides on natural species. In this study, the toxic effects of glyphosate and methidathion were evaluated comparatively on early developmental stages of 3 anurans—2 natural (Pelophylax ridibundus, Pseudepidalea viridis) and 1 laboratory species (Xenopus laevis). The 96-h LC50 values for methidathion and glyphosate were determined as 25.7–19.6mg active ingredient (AI)/L for P. viridis, 27.4–22.7mg AI/L for P. ridibundus, and 15.3–5.05mg AI/L for X. laevis tadpoles. Furthermore, as early signs of intoxication, glutathione S-transferase (GST), acetylcholinesterase (AChE), carboxylesterase (CaE), glutathione reductase, lactate dehydrogenase, and aspartate aminotrasferase were assayed in 4-day-old tadpoles after 96-h pesticide exposure. The GST induction after 3.2mg AI/L methidathion exposure was determined to be 173%, 83%, and 38% of control, and the AChE inhibition for the same dose was determined to be 86%, 96%, and 30% of control for P. ridibundus, P. viridis, and X. laevis, respectively. Unlike the application of methidathion, all enzyme activities showed statistically significant increases on glyphosate exposure compared to controls. However, these increases in enzyme activities were not shown to be parallel with the increase of concentration. The levels of increases of GST and AChE were determined to be 111% and 31% for P. ridibundus, 13% and 51% for P. viridis, and 15% and 36% for X. laevis after 3.2mg AI/L glyphosate exposure, respectively. The findings of the study suggest that the most sensitive species to pesticide exposure is X. laevis. The selected biomarker enzymes AChE, CaE, and GST are useful in understanding the toxic mechanisms of these pesticides in anuran tadpoles as early warning indicators.

Toxicity bioassay of technical and commercial formulations of carbaryl to the freshwater catfish, Clarias batrachus

The acute toxicity of the carbamate insecticide, carbaryl, in technical and commercial formulations was investigated in the freshwater catfish, Clarias batrachus, after exposures of 24, 48, 72, and 96 hr. The “trimmed Spearman-Karber method” with 10% trimming was employed for the determination of median lethal concentration (LC(I) 50). The LC(I) 50 values of the commercial carbaryl (162.60, 134.08, 123.36, 107.66 mg/liter) decreased gradually with increase of exposure duration from 24, to 48, 72, and 96 hr, respectively. Similarly, the LC(I) 50 values of technical grade carbaryl (61.14, 53.65, 48.85 mg/liter) decreased with increasing length of exposure. This reflects a time-dependent adaptability of the fish to the toxicant. Further, the technical grade compound was 2.5 times more toxic than the commercial preparation. This demonstrates the involvement of carbaryl as the active principle in acute toxicity testing, rather than the additive substances. Dermal desquamation was observed as a characteristic change in response to carbaryl exposure.

Studies of the Syncopic Effect of Aniline Derivatives on Fish. I. The Problem Concerning the Determination of Median Lethal Concentration in Fish

Five kinds of aniline derivatives were chosen and subjected to LC50 test using both static and flow water systems. The flow water system was more appropriate than the static one for volatile compounds, because 37% of N, N-dimethyl aniline in the test solution was lost during LC50 test for 48 h. N-Methyl aniline, N, N-dimethyl aniline and 2, 6-xylidine were found to turn fish sideways producing syncope, and the states were observed during the test for 48h. Median syncopic concentration ; SC50 values of aniline derivatives for 48 h were determined and compared with LC50 values. Large differences were observed between SC50 and LC50 values in N, N-dimethyl aniline and 2, 6-xylidine. A rapid determination method of aniline derivatives in fish (killifish, gold fish and carp) using FTD-GC was developed and excretion of aniline derivatives accumulated in fish were determined. All compounds except N, N-dimethyl aniline were excreted within 4 h from fish body.