• YAKHAK HOEJI
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• v.46 no.2
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• pp.93-97
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• 2002

Methidathion is one of the organophosphorus pesticides commonly used for stamping out harmful pests in farming areas. This paper presents a fatality due to methidathion intoxication and describes the distribution of methidathion in postmortem blood and tissues obtained at autopsy. Qualitative identification of methidathion was achieved by TLC, GC and GC/MS, and quantitative analysis was performed by GC with thermionic specific detector (TSD). The analytes in postmortem specimens were extracted by liquid-liquid extraction (LLE) with ethylether. After the ethylether layer was evaporated, the residue was partitioned into hexane and acetonitrile, and the acetonitrile layer was used for analysis. Tissue specimens were homogenized with 4% perchloric acid and applied for LLE. After extraction, the extracts were reconstituted 100 $\mu\textrm{g}$ pyraclofos (IS, 100 $\mu\textrm{g}$/ml in methanol) for GC and GC/MS analysis. On analysis of postmortem specimens, methidathion was identified and quantitated. The methidathion concentrations were 2.0 $\mu$l/ml in blood, 24.4 $\mu\textrm{g}$/g in liver, 13.9 $\mu\textrm{g}$/g in lung, 21.8 $\mu\textrm{g}$/g in kidney, respectively.

• Toxicological Research
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• v.15 no.1
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• pp.47-53
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• 1999

The effects of methidathion on humoral immune response were studied in BALB/c mice. 0.5 or 5.0 mg/kg/day methidathion were administered orally for 14 days. The parameters examined to assess apparent toxicity of methidathion included changes of body weight, relative weight of spleen, thymus, sidney and liver, and viable spllenic cell numbers. To evaluate the humoral immune response, thymus, kidney and liver, and viable splenic cell numbers. To evaluate the humoral immune resopnse, the plaque forming cell(PFC) responses sheep the red blood cells (SRBC) and the lovels of serum IgG to hen egg lysozyme (HEL) were determined. No alterations were observed in changes of body weights, relative organ weights and the numbers of viable splenocytes by exposure to any dose of methidathion. At the dose of 0.5mg/kg only PFC response was decreased, whereas both PFC response and the level of serum IgG were decreased significantly at the dose of 5.0 mg/kg. These results indicate that exposure to methidathion may cause sup[pression of humoral immune reponse in mice without overt changed in lymphoid organ weight or viability of splenocytes.

• Toxicological Research
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• v.20 no.4
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• pp.329-337
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• 2004

Primiphos-methyl and methidathion as organophosphorus (OP) pesticides were tested for their immunotoxic effects on Balb/c mice. Three dose levels of primiphos-methyl (10, 60, or 120 mg/kg/day) and methidathion (0.5, 2.5 or 5.0 mg/kg/day) were administered orally in the mice for 4 weeks. After, changes in body weight gain, relative weight of spleen and thymus, viable splenic cell numbers, surface marker on immune cell, and proliferation activity were investigated. Results showed that neither Pirimiphos-methyl nor methidathion dosages changed significantly body weight, relative thymus and spleen weight, and thymus and spleen cellularities of the mice, but high dose treatment (120 mg/kg) of pirimiphos-methyl significantly decreased relative spleen weight and spleen cellularity of the mice. No alterations were observed in changes of LPS-proliferation response of splenocytes by exposure to any dose of pirimiphos-methyl and methidathion. However, pirimiphos-methyl dosages reduced ConA-proliferation response of splenocytes and both methidathion and pirimiphos-methyl decreased the ability of antibody production to SRBC. The results indicate that 28 days exposure to the high dose of pirimiphos-methyl suppress the function of splenic T and B cell function, and methidathion reduce the immune responsibility of B cell in mice without the changes in lymphoid organ weight or viability of splenocytes. Pirimiphos-methyl is more immunotoxic than methidathion although this has higher general toxicity than that.

• Toxicological Research
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• v.17 no.4
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• pp.317-323
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• 2001

The skin penetration rate of methidathion in vitro and pharmacokinetics of methidathion in vivo were studied with male Sprague-Dawley rats by dermal treatment. The in vitro skin penetration rates for Sprague-Dawley rats of methidathion technical (50 mg, 100 ${mu}ell$) and emulsifable concentrate (EC,40mg, 100${mu}ell$) were determined as 18.4 $\mu\textrm{g}$/c $m^2$/h (RSD : 6.5) and 18.5 $\mu\textrm{g}$/c $m^2$/h (RSD : 3.2), respectively. Dose-related systemic exposure (AUC) was observed in rats after dermal treatment. The corresponding AUC, $T_{max}$, $C_{max}$, and $T_{1}$2/ of methidathion in plasma were 1.5$\mu\textrm{g}$.hr/ml, 6 h, 0.10 $\mu\textrm{g}$/ml, and 16 h, for 116mg/kg doses, 3.2 $\mu\textrm{g}$. hr/ml, 8 h, 0.12 $\mu\textrm{g}$/ml, and 23 h, for 232 mg/kg doses and 10 $\mu\textrm{g}$. hr/ml, 12 h, 0.32 $\mu\textrm{g}$/ml, and 20 h, for 1,160 mg/kg doses respectively. The urinary excretion of methidathion, estimated wing an equation derived from the in vitro skin penetration study was 0.24~0.35% of the absorbed dose. The concentration of methidathion in kidney was higher than that in liver. Dose-dependent absorption and excretion of methidathion without saturation was observed under in vivo experimental condition.n.n.

• Journal of Food Hygiene and Safety
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• v.14 no.2
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• pp.146-152
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• 1999

The present study was performed to investigate the bioconcentration of BPMC, chlorothalonil, dichlorvos and methidathion. The BCFs(bioconcentration factors) and depuration rate constants for four pesticides in zebrafish(brachydanio rerio) were measured under semi-static conditions(OECD guideline 305-B) in a concentration of one-hundredth of the 96 hours LC50 of each pesticide at the equilibrium condition. The results obtained are summarized as follows : The BCFs of BPMC, chlorothalonil, dichlorvos and methidathion were 1.44$\pm$0.09, 2.223$\pm$0.063, 0.81$\pm$0.08 and 5.53$\pm$0.13, respectively. Depuration rate constants of BPMC, chlorothalonil, dichlorvos and methidathion were 0.028, 0.015, 0.220 and 0.152, respectively. The concentrations of BPMC, dichlorovs and methidathion in zebrafish reached an equilibrium in 3 days, and the equilibrium of chlorothalonil was reached after 14 days. Depuration rate of dichlorvos was the fastest followed by methidathion, BPMC and chlorothalonil. The lower BCF of BPMC was due to its relatively high KOW, slow KDEP, and low SW and VP, compared to chlorothalonil and methidathion. The BCF of chlorothalonil was much lower than that excepted on the basis of high KOW, slow KDEP, SW and VP. The reason is that the experimental concentration for chlorothalonil is 1/100~1/1000 lower than that of BPMC, dichlorvos and methidathion. The BCF of dichlorvos was lower than that of other pesticides due to its very rapid KDEP, very high VP and SW, and very low KOW. The BCF of methidathion was higher than that of other pesticides due to its very low VP and SW. Therefore, these data suggest that physicochemical properties of pesticides may be important in the bioconcentration.

• Journal of Food Hygiene and Safety
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• v.14 no.4
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• pp.339-345
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• 1999

The present study was performed to investigate photodegradation rate constants and degradation products of dichlorvos and methidathion by the USEPA method. The two pesticides were very stable in sunlight for 16 days from September 2 to 18, 1998 and humic acid had no sensitizing effect on the photolysis of each pesticide in sunlight. The photolysis rate was fast-est for methidathion, followed by dichlorvos in the presence of UV irradiation. Photodegradation rate constant and half-life of dichlorvos were 0.0208 and 33.3 min, respectively. Photodegradation rate constant and half-life of methidathion were 0.6789 and 1.0min, respectively. The two pesticides were degraded completely in the presence of UV irradiation and UV irradiation with TiO$_2$in about 3 hours. Therefore, it is suggested that UV treatment will be effective for the degradation of pesticides in the process of drinking water purification. In case of dichlorvos and methidathion, UV irradiation with TiO$_2$was more effective for degradation than W irradiation. In order to identify photolysis products, the extracts of degradation products were analyzed by GC/ MS. The mass spectrum of photolysis products of dichlorvos was at m/z 153, those of the photolysis of methidathion were at m/z 198 and 214, respectively. Photolysis products of dichlorvos was Ο, Ο-dimethyl phosphate(DMP), those of methidathion were Ο, Ο-dimethyl phosphorothioate(DMTP) and Ο, Ο-dimethyl phosphorodithioate (DMDTP).

• The Korean Journal of Pesticide Science
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• v.6 no.4
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• pp.244-249
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• 2002

This study was carried out to investigate the toxicities of 22 insecticides to Dichromothrips smithi. Insecticidal activity was evaluated by testing systemic action and residual effect in laboratory. All insecticides used in this study did not affect on the egg of D. smithi, although organophosphates such as fenitrothion, fenthion, methidathion, phenthoate, and phenthoate+ethofenprox suppressed the egg hatchability completely. On D. smithi larva fenitrothion, fenthion, methidathion, phenthoate, ethofenprox, thiamethoxam, abamectin, chlorfenapyr, emamectin benzoate, fipronil, spinosad, and phenthoate+ethofenprox showed 100% insecticidal activity. On D. smithi adult fenitrothion, fenthion, methidathion, phenthoate, ethofenprox, abamectin, emamectin benzoate, fipronil, spinosad, and phenthoate+ethofenprox showed 100% insecticidal activity. Root-uptake systemic effects of phenthoate on the larva of D. smithi was 43.3%. Whereas, systemic effect of other insecticides was less than 20%. Insecticide with more than 80% residual effect for 7 days after treatment were fenitrothion, fenthion, methidathion, phenthoate, ethofenprox, emamectin benzoate, fipronil, spinosad, and phenthoate.

• The Korean Journal of Pesticide Science
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• v.15 no.3
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• pp.329-334
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• 2011

Insecticidal activity of 31 registered insecticides was tested against Metcalfa pruinosa adults. All experiments were conducted at the recommended concentration (ppm) of each insecticide. Among them, 16 insecticides from organophosphates (dichlorvos, fenitrothion, fenthion, methidathion, phenthoate), carbamates (methomyl), pyrethroids (${\alpha}$-cypemethrin, deltamethrin, fenpropathrin, ${\gamma}$-cyhalothrin), neonicotinoids (acetamiprid, clothianidin, dinotefuran, imidacloprid, thiamethoxam), and other (endosulfan) showed 100% mortality by spraying on the body of M. pruinosa adults. Dichlorvos, fenitrothion, fenthion, methidathion, phenthoate and endosulfan showed 100% mortality by plant-dipping method. The residual effect was showed 100% mortality in four insecticides (fenitrothion, fenthion, methidathion, phenthoate) at one day after treatment, and three insecticides (fenitrothion, methidathion, phenthoate) were showed the mortality of 90% at three days after treatment.

• Journal of Environmental Science International
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• v.8 no.3
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• pp.379-386
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• 1999

The adsorption and leaching of organophosphorus pesticides (phenthoate, diazinon, methidathion) were investigated in Namwon soli(black volcanic soil), Aewol soil(very dark brown volcanic soil) and Mureung soil(dark brown nonvolcanic soil) sampled in Cheju Island. The Freundlich constant, K value, was 52.4, 31.3 and 27.7 for phenthoate, diazinon and methidathion in Namwonsoil, respectively and decreased in the order of phenthoate, diazinon and methidathion among the pesticides. The K value of phenthoate was 52.4, 15.9 and 5.9 for Namwon, Aewol and Mureung soil, respectively and was the highest for Namwon soil with very high organic matter content and cation exchange capacity(CEC). The Freundlich constant, 1/n, showed a high correlation with organic matter content, i.e., its value was less than unity for organic matter rich soil(Namwon soil) and greater than unity for organic matter poor soil(Mureung soil). Total recoveries of pesticides in soil and leachate with leaching in soil column, were in the range of about 74~86%. The leaching of pesticides was less for phenthate with high K values, and more for methidathion with low K values among the pesticides. It was slower for Namwon soil with high K values, and more for methidathion with low K values among the pesticides. It was slower for Namwon soil with high K values, and faster for Mureung soil with low K values among the soils.

• Journal of Environmental Health Sciences
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• v.25 no.3
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• pp.36-43
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• 1999

The present study was performed to investigate biodegradation rate of dichlorvos and methidathion. In the biodegradation test of two pesticides by the modified river die-away method from June 17 to August 22, 1998, the biodegradation rate constants and half-life were determined in Nakdong(A) and Kumho River(B). Biodegradation rate of dichlorvos was 4.51% in A sampling point, 6.88% in B sampling point after 7 days. Biodegradation rate constants and half-life of dichlorvos were 0.0066 and 105 days in A sampling point, 0.0102 and 67.9 days in B sampling point, respectively. Biodegradation rate of methidathion was 23% in A sampling point, 36% in B sampling point after 7 days. Biodegradation rate constants and half-life of methidathion were 0.0377 and 18.4 days in A sampling point, 0.0641 and 10.8 days in B sampling point, respectively. Biodegradation rate of methidathion was faster than that of dichlorvos. This suggested that the difference in biodegradation of pesticides was due to difference in the water quality and standard plate counts in the Nackdong and Kumho Rivers. The result of correlation analysis between biodegradation rate constants of the pesticides and water quality(DO, BOD, SS, ABS, NH$_3$-N, and NO$_3$-N) showed significant correlation with BOD, SS and NH$_3$-N at the 5% significant level. A significant linear equation was obtained from regression analysis at the 5% significant level, whereas, dependent variables were BOD, SS and NH$_3$-N, and the biodegradation rate constant was independent variable. It is suggested that dichlorvos will be mainly degraded by hydrolysis, and for methidathion was both hydrolysis and biodegradation. A significant QSAR equation was obtained from regression analysis at the 10% significant level, whereas, dependent variable is biodegradation rate constants of BPMC, chlorothalonil, dichlorvos and methidathion, vapor pressures, partition coefficients and water solubilities of the pesticides are independent variables. Also, a significant linear equation was obtained from regression analysis at the 1% significant level, whereas, dependent variable is biodegradation rate constants of BPMC, chlorothalonil, dichlorvos and methidathion, hydrolysis rate constants of the pesticides are independent variables. It is suggested that the pesticides will be degraded by main degradation factor when the pesticides was affected both hydrolysis and biodegradation.