Inhibitor Report for: Triazophos

A laboratory incubation study was carried out to elucidate the dynamic response of insecticide (triazophos) on a paddy field soil health under controlled moisture (flooded soil) and temperature (25 degrees C). The insecticide was applied at five levels that were 0.0 (control), 0.5 field rate (FR), 1.0 FR, 5.0 FR, and 10.0 FR, where FR was 1500 ml/hm2, and the parameters were studied at 1, 4, 7, 14, and 21 days after treatments' addition. The electron transport system (ETS)/dehydrogenase activity exhibited a negative correlation with insecticide concentrations, and the activity affected adversely as the concentration increased. The higher doses of 5 and 10 field rates significantly reduced the ETS activity, while lower rates failed to produce any significant inhibiting effect against the control. The toxicity of insecticide decreased towards decreasing the ETS activity with the advancement of incubation period. The insecticide caused an improvement in the soil phenol content and it increased with increasing concentration of insecticide. The insecticide incorporation applied at various concentrations did not produce any significant change in soil protein content and it remained stable throughout the incubation period of 21-days. The response of biomass phospholipid content was nearly similar to ETS activity. The phospholipid content was decreased with the addition of insecticide and the toxicity was in the order: 10 FR (field rate) > 5 FR > 1.0 FR > 0.5 FR > control and it also decreased with incubation period.

Chronic occupational exposure to organophosphorus and carbamate-type pesticides significantly inhibits acetylcholinesterase activity and causes morbidity. This study on mice was designed to evaluate their amino profile and to identify signs of hepatic dysfunction following their chronic exposure to mixtures of organophosphorus pesticides. Laboratory mice were exposed to a formulated mixture of the six organophosphorus pesticides (Dimethoate, Chlorpyrifos, Profenofos, Pirimiphos methyl, Triazophos and Dimethoate) most commonly used in agriculture in this region of the Middle East. Doses (10% of LD50 of the mixture) were given once a week by gavage in corn oil for 7 weeks; the control group was given only corn oil. At the end of the exposure period, mice were culled and blood samples were collected to determine erythrocyte acetylcholinesterase activity, biochemical markers of liver function and concentrations of serum amino acids. Erythrocyte acetylcholinesterase activity and total serum proteins decreased significantly in the exposed group. Serum concentrations of alanine aminotransferase and aspartate aminotransferase, alanine, glutamic acid, glycine, isoleucine, leucine, methionine, ornithine, proline, serine, threonine and valine were significantly increased in the exposed mice, while serum levels of cystine were decreased significantly. There were also non-significant increases in serum alkaline phosphatase, gama-glutamyl transpeptidase and some of the other amino acids. Chronic exposure to mixtures of organophosphorus pesticides is associated with decreased acetylcholinesterase activity, hepatic dysfunction and disturbance of amino acids profile. Biochemical indices of hepatocellular injury and disturbed amino acid metabolism may be of value as markers of chronic exposure to such pesticides.

A rapid procedure has been developed that allows a single-step, selective extraction and cleanup of organophosphate (OP) pesticide residues from milk dispersed on solid-matrix diatomaceous material filled into disposable cartridges by means of light petroleum saturated with acetonitrile and ethanol. Recovery experiments were carried out on homogenized commercial milk (3.6% fat content) spiked with ethanolic solutions of 24 OP pesticides, viz., ethoprophos, diazinon, dimethoate, chlorpyrifos-methyl, parathion-methyl, chlorpyrifos-ethyl, malathion, isofenphos, quinalphos, ethion, pyrazophos, azinphosethyl, heptenophos, omethoate, fonofos, pirimiphos-methyl, fenitrothion, parathion, chlorfenvinphos, phenthoate, methidathion, triazophos, phosalone, azinphos-methyl, at levels ranging for the different OP pesticides from 0.02 mg/kg to 1.11 mg/kg. Average recoveries of four replicates were in the range 72-109% for the different OP pesticides, with relative standard deviations (R.S.D.) from ca. 1 to 19%, while dimethoate and omethoate were not recovered. Coextracted fatty material amounted to an average of about 4.0 mg/ml of milk. The extraction procedure requires about 30 min. The main advantages are that extraction and cleanup are carried out in a single step, emulsions do not occur, several samples can be run in parallel by a single operator, reusable glassware is not needed and simple operations are required.

A laboratory incubation study was carried out to elucidate the dynamic response of insecticide (triazophos) on a paddy field soil health under controlled moisture (flooded soil) and temperature (25 degrees C). The insecticide was applied at five levels that were 0.0 (control), 0.5 field rate (FR), 1.0 FR, 5.0 FR, and 10.0 FR, where FR was 1500 ml/hm2, and the parameters were studied at 1, 4, 7, 14, and 21 days after treatments' addition. The electron transport system (ETS)/dehydrogenase activity exhibited a negative correlation with insecticide concentrations, and the activity affected adversely as the concentration increased. The higher doses of 5 and 10 field rates significantly reduced the ETS activity, while lower rates failed to produce any significant inhibiting effect against the control. The toxicity of insecticide decreased towards decreasing the ETS activity with the advancement of incubation period. The insecticide caused an improvement in the soil phenol content and it increased with increasing concentration of insecticide. The insecticide incorporation applied at various concentrations did not produce any significant change in soil protein content and it remained stable throughout the incubation period of 21-days. The response of biomass phospholipid content was nearly similar to ETS activity. The phospholipid content was decreased with the addition of insecticide and the toxicity was in the order: 10 FR (field rate) > 5 FR > 1.0 FR > 0.5 FR > control and it also decreased with incubation period.

The degradation of triazophos in aqueous solutions was monitored at 205 and 254 nm after separation using high-performance liquid chromatography. An ODS column was used with a mobile phase of 60% acetonitrile and 0.04% phosphoric acid at a flow rate of 1.4 cm(3) min(-)(1). When dissolved in distilled water, approximately 30% of the original triazophos was detected. The effect of heating time and temperature on a 0.5 mg dm(-3) standard was investigated. Over a 150 min period at 100 degrees C the peak area detected for the standard decreased by 58.67 +/- 6.19 and 65.03 +/- 4.61% when measured at 254 and 205 nm, respectively. The precision of the absorbance detected at 205 and 254 nm was 3.54 +/- 2.8 and 3.86 +/- 3.9%, respectively. There was a significant difference (P = 0.10) between the precision of the results obtained at each wavelength. The t(calcd) value was -2.236 and the t(crit) value was 1.94. The most sensitive wavelength was 205 nm. A 54% difference in the gradients of the calibration graphs obtained at each wavelength was observed. The results suggest that approximately 72% of triazophos is degraded during a 20 min cooking period at 100 degrees C, due to ambient and elevated temperature hydrolysis. Therefore, the dose to the consumer of triazophos residues in cooked food is likely to be approximately 72% lower than in the raw food, with a concomitant reduction in toxicological risk.

Laboratory studies were undertaken in canal water (pH 8.3) spiked with Hostathion (triazophos 40 EC) at the rates of 0.25 (T(1)) and 0.50 (T(2)) microg a.i. ml(-1) to investigate its persistence, dissipation, and degradation kinetics. Water samples collected on 0 (1h), 2, 5, 10, 20, 30, 45, 60, and 90 days after spiking were processed for residues of triazophos by GLC. In T(1) the dissipation was 10.9, 19.1, 24.8, 40.4, 53.0, 73.0, and 83.0% in 2, 5, 10, 20, 30, 45, and 60 days. Corresponding dissipation in T(2) was 9.2, 17.4, 21.2, 37.1, 50.6, 72.1, and 82.4%. In 90 days the dissipation was about 91% in both treatments. The half-life values observed were 24.87 days in T(1) and 25.44 days in T(2). Kinetic studies revealed that dissipation of triazophos residues followed a first-order kinetics in both spiking levels.

As a result of routine monitoring data on carrots generated in the 1990s indicating MRL exceedances, further studies showed that residues of organophosphorus compounds in individual roots could vary up to 25 times the levels found in composite samples. Additional work found that this phenomenon also extended to other crops including apples, peaches and celery. Variability (defined as the highest residue level found in any one crop item divided by the level found in a composite sample from the same batch) of up to 34 times mean values was found in one batch of plums. Conventional deterministic methods used in consumer assessments were likely to give gross overestimates of short-term exposure because of the assumptions employed. This led to the development of probabilistic models which made the best use of all available information and was capable of indicating percentages of consumers that could exceed relevant toxicological end points. This indicated that there was unlikely to be serious health effects as a result of ingesting these residues and has subsequently proved to be a useful aid to regulatory decision making.

Chronic occupational exposure to organophosphorus and carbamate-type pesticides significantly inhibits acetylcholinesterase activity and causes morbidity. This study on mice was designed to evaluate their amino profile and to identify signs of hepatic dysfunction following their chronic exposure to mixtures of organophosphorus pesticides. Laboratory mice were exposed to a formulated mixture of the six organophosphorus pesticides (Dimethoate, Chlorpyrifos, Profenofos, Pirimiphos methyl, Triazophos and Dimethoate) most commonly used in agriculture in this region of the Middle East. Doses (10% of LD50 of the mixture) were given once a week by gavage in corn oil for 7 weeks; the control group was given only corn oil. At the end of the exposure period, mice were culled and blood samples were collected to determine erythrocyte acetylcholinesterase activity, biochemical markers of liver function and concentrations of serum amino acids. Erythrocyte acetylcholinesterase activity and total serum proteins decreased significantly in the exposed group. Serum concentrations of alanine aminotransferase and aspartate aminotransferase, alanine, glutamic acid, glycine, isoleucine, leucine, methionine, ornithine, proline, serine, threonine and valine were significantly increased in the exposed mice, while serum levels of cystine were decreased significantly. There were also non-significant increases in serum alkaline phosphatase, gama-glutamyl transpeptidase and some of the other amino acids. Chronic exposure to mixtures of organophosphorus pesticides is associated with decreased acetylcholinesterase activity, hepatic dysfunction and disturbance of amino acids profile. Biochemical indices of hepatocellular injury and disturbed amino acid metabolism may be of value as markers of chronic exposure to such pesticides.

UNLABELLED: High levels of triazophos residues detected in carrots during routine monitoring led to the discovery of a wide variability between levels in individual roots. Conventional point estimates of consumer exposure were carried out. Due to the assumptions used, these calculations were likely to give rise to gross overestimates. In 1997, data were obtained for individual apples, pears, peaches, nectarines, oranges, bananas, and tomatoes that showed similar levels of variability in a range of organophosphate and carbamate residues. Point estimate models that had previously been used for intake estimates for carrots were not appropriate since it was necessary to take account of not only the variation of residue levels from crop item to crop item but also the variation in eating patterns in individual consumers. Probabilistic modeling was identified as a suitable way to produce multifactorial submodels and address some of the problems of combining distributions of consumption and residues. Consumption data from 1675 toddlers were linked with residue distributions from individual crop items not only to allow combinations of fruit consumed but also to allow for the variability in residue levels that occur between individual crop items. The model was also capable of taking account of the percentages of crops that did not contain any detectable residues; this information was available from initial screens of bulked samples and percentage of crop not treated in the case of carrots. The outputs from the models were given as percentages of consumers that could exceed a toxicological end point; this could be the acute reference dose or a factor of the no-observable-adverse-effect level. Modeling in this way was considered to give a realistic view of the likely short-term exposure and the output was used as an aid to decision making in terms of necessary regulatory action. BACKGROUND: As a result of high levels of triazophos detected in carrots during routine monitoring, studies were carried out to determine the variability of organophosphate residue levels in individual roots. Results obtained indicated that the highest residue levels could be 25 times the mean level in bulked samples (which were used in routine monitoring). Since sufficient levels of organophosphate compounds can give rise to toxicological effects after a single exposure, it was considered necessary to carry out assessments of short-term or acute consumer risk. At that time, models available worldwide were designed only to carry out point estimates of long-term exposure. From consumption data, it was possible to derive the levels of carrot consumption during a single day and calculations were carried out assuming all carrots contained the highest levels of residues found in trials. This led to a gross overestimate of likely exposure but was considered to give to intakes that eroded margins of safety; these were not a cause for extreme regulatory action. Further studies were carried out on other crops that may be eaten whole, at one sitting, and without processing to consider whether the large variability of organophosphate residues was a phenomenon that was common to other fruits and vegetables.

Three multivariate calibration methods, partial least squares (PLS-1 and PLS-2) and principal component regression, were applied to the simultaneous determination of the five pesticides iprodione, procymidone, chlorothalonil, folpet and triazophos by high-performance liquid chromatography with diode array detection. Such detection gives multiwavelength chromatograms from a single analysis of one sample. In this paper, calibration models at two different wavelengths were developed to resolve mixtures of five pesticides with overlapping chromatographic peaks. The first model, carried out at 220 nm as detector compromise wavelength, yielded satisfactory sensitivity for accurate estimation of the concentration of iprodione, procymidone, chlorothalonil and folpet and the second model, at 200 nm, was used for accurate estimation of triazophos. Both calibration models were evaluated using the chromatograms and first-derivative (1D) chromatograms by predicting the concentrations of independent test set samples. Finally, the proposed 1D calibration models were successfully applied to the determination of these pesticides in groundwater and soil samples. In all cases, the PLS-1 calibration method showed superior quantitative prediction ability than the PLS-2 or principal component regression methods.

A rapid procedure has been developed that allows a single-step, selective extraction and cleanup of organophosphate (OP) pesticide residues from milk dispersed on solid-matrix diatomaceous material filled into disposable cartridges by means of light petroleum saturated with acetonitrile and ethanol. Recovery experiments were carried out on homogenized commercial milk (3.6% fat content) spiked with ethanolic solutions of 24 OP pesticides, viz., ethoprophos, diazinon, dimethoate, chlorpyrifos-methyl, parathion-methyl, chlorpyrifos-ethyl, malathion, isofenphos, quinalphos, ethion, pyrazophos, azinphosethyl, heptenophos, omethoate, fonofos, pirimiphos-methyl, fenitrothion, parathion, chlorfenvinphos, phenthoate, methidathion, triazophos, phosalone, azinphos-methyl, at levels ranging for the different OP pesticides from 0.02 mg/kg to 1.11 mg/kg. Average recoveries of four replicates were in the range 72-109% for the different OP pesticides, with relative standard deviations (R.S.D.) from ca. 1 to 19%, while dimethoate and omethoate were not recovered. Coextracted fatty material amounted to an average of about 4.0 mg/ml of milk. The extraction procedure requires about 30 min. The main advantages are that extraction and cleanup are carried out in a single step, emulsions do not occur, several samples can be run in parallel by a single operator, reusable glassware is not needed and simple operations are required.

The possible genotoxic effects of the organophosphorus insecticides methyl parathion and triazophos were evaluated by their ability to induce gene and chromosome mutations in male germ cells of Drosophila melanogaster. Sex-linked recessive lethal (SLRL), total and partial sex-chromosome losses (SCL), and non-disjunction (ND) assays were conducted. The routes of administration included adult feeding, injection, and larval feeding. Methyl parathion was unable to induce point mutations or chromosome mutations, although a small increase in the frequency of non-disjunction was detected after larval treatment. Triazophos induced point mutations when assayed in the SLRL test and induced a weak increase in the non-disjunction frequency, but gave negative results in the SCL test.

The residues of heptenophos and triazophos (active components of Hostaquick and Hostathion) were determined in several vegetable crops during the growing period. Heptenophos residues decreased below the limit of detection (0.001 mg/kg) in most of the crops one week after the treatment. However, the decline of triazophos in vegetables below the limit of detection (0.002 mg/kg) depended on the method of crop treatment.