Thiodicarb and methomyl tissue distribution in a fatal multiple compounds poisoning.

Thiodicarb is a nonsystemic carbamate insecticide whose acetylcholinesterase activity is related to its main methomyl degradation product. A 40-year-old woman was found dead in her car. Empty packages of medicines and an open bottle of Larvin containing thiodicarb were found near her body. No signs of violence nor traumatic injuries were noticed upon autopsy, and police investigations strongly suggested a suicide. Systematic toxicological analysis performed on postmortem specimens revealed the presence of various sedatives, hypnotics, and antipsychotic drugs in blood, urine, and gastric content. Some of the compounds identified were determined at blood concentrations well above the known therapeutic concentrations: zolpidem (2.87 mg/L), bromazepam (2.39 mg/L), nordazepam (4.21 mg/L), and levopremazine (0.64 mg/L). Specific analysis of thiodicarb and of its methomyl metabolite was then performed on all fluids and tissues collected during autopsy by liquid chromatography ion trap tandem mass spectrometry (LC-MS-MS). The anticholinesterase capacity of blood, urine, and gastric content collected at autopsy was 83%, 82%, and 32%, respectively (normal value: 0%). The presence of thiodicarb in the bottle found near the body corroborates the hypothesis of an intake of that compound. Although thiodicarb was only detected in gastric content (24.3 mg/L), its methomyl metabolite was quantified in most postmortem tissues and fluids: gastric content (19.9 mg/L), peripheral blood (0.7 mg/L), urine (8.5 mg/L), bile (2.7 mg/L), liver (0.7 mg/kg), kidney (1.7 mg/kg), lung (1.5 mg/kg), brain (9.3 mg/kg), and heart (3.6 mg/kg).

Degradation dynamics and persistence of Quinolphos and Methomyl in/on Okra (Ablemoschus esculentus) fruits and cropped soil.

Dissipation of Quinalphos (Ekalux 20 AF) and Methomyl (Lannate 12.5 L) residues were studied in/on Okra (var. Pusa Sawani) fruits and cropped soil at Baruipur, West Bengal, India. The insecticides were applied at 21 days after sowing by foliar spray at the recommended and double the recommended dose (i.e. 500 and 1,000 g a.i. ha(-1) in both the cases). Four sprays were given at 15 days interval in all the cases. The initial build-up residue on Okra fruits was to the magnitude of 3.20 and 7.50 microg g(-1) for Quinalphos, 5.61 and 8.42 microg g(-1) for Methomyl at lower and higher doses respectively. The half-lives (t(1/2)) in Okra fruit were found to be 1.25-1.43 days for Quinalphos and 0.88-0.94 days for Methomyl. The safe waiting period (T(MRL)) determined were 6.7 and 5.3 days at the lower dose of Quinalphos. The corresponding waiting period for Methomyl were 5.7 and 4.9 days. Decontamination process like washing and cooking dislodged 25.50%-81.50% residue depending on insecticides and doses, whereas 20.00%-69.60% surface residue was removed by washing alone. The residues of both insecticides in soil persisted for 6-8 days depending on dose. The half-lives in soil were found to be 1.07-1.20 days for Quinalphos and 0.97-1.25 days for Methomyl.

Role of selenium on antioxidant capacity in methomyl-treated mice

Methomyl carbamate is a pesticide widely used in the control of insects. The presentwork aims at studying the effect of selenium on the antioxidant system ofmethomyl-treated mice. Swiss albino mice were intraperitoneally administered a singledose of methomyl (7 mg/Kg body weight). Mice of another group were injectedwith sodium selenite (5 µmole/Kg b.wt.) 7 days before methomyl intoxication. After24 hours, methomyl exposure resulted in significant increase in lactic dehydrogenaseactivity (LDH). The antioxidant capacity of hepatic cells in terms of the activities ofsuperoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), glutathione-S-transferase (GST) and glutathione (GSH) content was diminished. Itappears that methomyl exerts its toxic effect via peroxidative damage to hepatic, renaland splenic cell membranes. Also, methomyl induced DNA damage in these organsas detected by alkaline filter elution technique. The distribution of methomyl in differentorgans of mice was detected by HPLC. Selenium administration prior tomethomyl injection produced pronounced protective action against methomyleffects. It is observed that selenium enhances the endogenous antioxidant capacity ofthe cells by increasing the activities of SOD, CAT, GR and GST as well as increasingGSH content. The activity of LDH was decreased in blood and the damage ofDNA was suppressed comparable to controls. In conclusion, the adverse effects ofmethomyl in mice could be ameliorated by selenium

Pesticide deposition in hair: preliminary results of a model study of methomyl incorporation into rabbit hair.

This work studied the incorporation of methomyl, a carbamate insecticide, into the hair of New Zealand white rabbits. A total of 600 mg methomyl was administered by drinking water over 4 mo, and acetylcholinesterase activity in serum was monitored. At the end of the dosing period, hair from the back of the rabbits was cut off, and the methomyl concentration was measured using ELISA and HPLC. A decrease of serum acetylcholinesterase occurred. The top cm of hair contained no methomyl, the second cm contained 0.9 ng/mg and the 3rd cm of hair contained 3 ng methomyl/mg. Methomyl was incorporated into the rabbit hair in a process independent of gender but dependent on the hair growth rate.