Fate of 14C-chlorpyrifos in stored soybeans and its toxicological potential to mice

Investigation of chronic toxicity of (14)C-fenitrothion and its degradation products on stored soybeans

Grains of soybeans were treated with the recommended dose of fenitrothion insecticide, 5mg/kg, and double that dose, before storage for 30 weeks under ambient local conditions. During the storage period, the penetration and distribution of insecticide residues were studied. The amount of surface residues on stored soybeans, internal extractable and bound residues were determined. Surface residues were found to decrease with the increase in time of storage, whereas internal residues showed a gradual increase with time to reach 56%, 54% of applied doses after 30 weeks. The amount of bound residues inside the matrix showed a slow increase with time. Toxicity of the total internal residues of fenitrothion in stored soybeans was studied in mice through a sub-chronic feeding experiment for 3 months. The maximum inhibition in plasma and erythrocyte cholinesterase activity was 37% and 13% after the first month, respectively. Treated mice suffered from deterioration of hepatic and renal functions as indicated by the increase level of blood serum esterase's and blood urea nitrogen. Percentage increase in alanine aminotransferase (ALT) and aspartate aminotransferase (AST) was reached to about 62% and 55%, respectively as compared with control animals with the end of feeding period.

Identification and characterization of chlorpyrifos-methyl and 3,5,6-trichloro-2-pyridinol degrading Burkholderia sp. strain KR100

A chlorpyrifos-methyl (CM) degrading bacterium (designated strain KR100) was isolated from a Korean rice paddy soil and was further tested for its sensitivity against eight commercial antibiotics. Based on morphological, biochemical, and molecular characteristics, this bacterium showed greatest similarity to members of the order Burkholderiales and was shown to be most closely related to members of the Burkholderia cepacia group. Strain KR100 hydrolyzed CM to 3,5,6-trichloro-2-pyridinol (TCP) and utilized TCP as the sole source of carbon for its growth. The isolate was also able to degrade chlorpyrifos, dimethoate, fenitrothion, malathion, and monocrotophos at 300 microg/ml but diazinon, dicrotophos, parathion, and parathion-methyl at 100 microg/ml. The ability to degrade CM was found to be encoded on a single plasmid of approximately 50 kb, pKR1. Genes encoding resistance to amphotericin B, polymixin B sulfate, and tetracycline were also located on the plasmid. This bacterium merits further study as a potential biological agent for the remediation of soil, water, or crop contaminated with organophosphorus compounds because of its greater biodegradation activity and its broad specificity against a range of organophosphorus insecticides.

Toxicological evaluation and bioavailability of (14)C-fenitrothion bound residues on soybeans towards experimental animals

Under local practice of Egyptian conditions, the application of (14)C-fenitrothion on soybeans at a dose of 10mg insecticide/kg grains, led to the formation of 21% of (14)C-bound residues (non-extractable) after 24 weeks of storage. The external residues were 20% and the internal extracts were 55% of the applied dose. Feeding studies on rats revealed that bound residues were bioavailable. After feeding rats for three days with bound (14)C-fenitrothion residues, the main portion of radioactivity was eliminated via expired air (42%), urine (20%) and feces (11.5%). About 15% of the administered radioactivity was distributed among various organs as, liver, kidney, lung, fat, intestine, blood, heart, and brain. Toxicity of bound residues of (14)C-fenitrothion in stored soybeans was studied in mice through feeding experiments for three months at a concentration of 1.9 mg/kg. The maximum inhibition in plasma and erythrocyte cholinesterase activity was observed 22.5%, 18.9% and 8.6%, 9% after one and seven days, respectively. The obtained results showed a slight significant elevation after three months in the activity of liver enzymes alanine amino transferase, aspartate amino transferase and alkaline phosphatase. A moderate increase in blood urea nitrogen and creatinine concentration was observed in the treated groups at the end of the experimental period. The detected levels of albumin and total protein showed no significant compared to the control values, of controlled animals, after three months.

Behavior of the organophosphorus insecticide fenitrothion in stored faba beans and its biological effects towards experimental animals

Sound whole-seed faba beans were treated with (methyl-(14)C) fenitrothion [O, O-dimethyl-O-(3-methyl-4-nitrophenyl) phosphorothioate] at 5 and 10 mg insecticide/kg seeds, a dose normally used in practice. During the 30 weeks of storage period, the penetration and distribution of insecticide residues were studied. The amount of surface residues, internal residues and bound insecticide residues was estimated. Surface residues were found to decrease with the increase in time of storage, whereas internal residues showed a gradual increase with time apparently not dose dependent. Grain-bound residues increased with time and reached to its maximum (14-18%) after 24 weeks of storage. Chromatographic analysis of the internal extracts revealed the presence of the parent compound together with three main metabolites which were found in both free and conjugated form. Feeding mice for 90 days with a diet mixed with total internal fenitrothion residues in stored faba beans led to a reduction in body weight gain, and an appreciable decrease in cholinesterase activity of 32% for plasma and 15% for red blood cells (RBC(S)) after two months of experiment. Also, a significant decrease was showed in both total protein and albumin concentration at the end of feeding period (90 days). Liver and kidney function, as well as lipid profile of treated mice significantly increased at the end of feeding period. After a one-month recovery period, all the examined blood parameters returned to about the control values except blood urea and serum triglyceride.

Characterization of a fungal strain capable of degrading chlorpyrifos and its use in detoxification of the insecticide on vegetables

A fungal strain capable of utilizing chlorpyrifos as sole carbon and energy sources was isolated from soil by enrichment cultivation approach. The half-lives of degradation (DT(50)) for chlorpyrifos at concentrations of 1, 10, and 100 mg l(-1) by the fungal strain DSP in mineral salt medium were measured to be 2.03, 2.93, and 3.49 days, respectively. Two cell-free extracts [E (1:10) and E (1:20)] from the fungal strain DSP in bran-glucose medium were prepared and used to enhance chlorpyrifos degradation on vegetables. Compared with the controls, the DT(50) of chlorpyrifos were reduced by 70.3%, 65.6%, 80.6%, 80.6%, and 86.1%, and by 53.8%, 43.2%, 66.0%, 54.3%, and 67.7% on E (1:20) and E (1:10) treated pakchoi, water spinach, Malabar spinach, haricot beans, and pepper, respectively. The 7-day residual values (R (7)) of chlorpyrifos on E (1:10) treated vegetables were all lower than the corresponding maximum residue levels of European Union (EU MRLs), except that the R (7) value on haricot beans was slightly higher than the corresponding EU MRLs. The results indicate that cell-free extracts could rapidly degrade chlorpyrifos residues on vegetables.

Determinants of temporal variability in NHEXAS-Maryland environmental concentrations, exposures, and biomarkers

The longitudinal NHEXAS-Maryland study measured metals, PAHs, and pesticides in several media to capture temporal variability. Questionnaires were concurrently administered to identify factors that influenced changes in contaminant levels over time. We constructed mixed-effects regression models for lead, phenanthrene, and chlorpyrifos (including metabolites) in indoor air, dust, dermal wipes, and biological fluids. Significant predictors represented time-varying activities as well as unchanging housing and demographic factors. There was little overlap among the models, with predictors generally reflecting the diverse characteristics of the target compounds. We estimated between- and within-person variance components to evaluate the reliability of the measurements. While only one measurement of lead in blood or chlopyrifos in dust was needed for a dependable estimate of an individual's average level, three to eight measurements were needed for most other compound/exposure medium combinations because of considerable temporal variability. Measurements in biological fluids and dust were generally more consistent than those in indoor air. The significant covariates in the full models preferentially reduced the between-person variance component. Since the regression models explained only 1-37% of the within-person variance, the questionnaires in this study provided only modest insight into the factors responsible for the temporal variability in the contaminant levels.