The effect of certain intrinsic and extrinsic variables on the acute toxicity of selected organophosphorus insecticides to the mummichog, Fundulus heteroclitus.

The acute toxicity of two organophosphorus (OP) insecticides, azinphosmethyl and acephate, was evaluated in the mummichog, Fundulus heteroclitus. In addition, the effects of certain intrinsic (sex) and extrinsic (salinity and multiple toxicant interraction) variables on the toxic response were also investigated. Azinphosmethyl was by far the most toxic of the two OP insecticides with a 96h LC50 approximately 100,000 x lower than that for acephate. Slight sex differences were observed in the sensitivity of mummichogs to each of the OP insecticides with male fish being marginally more sensitive. Significant effects of low salinity stress were observed only with acephate exposure and, in this case, low salinity appeared to be slightly protective. In general, all of the insecticide mixtures (azinphosmethyl/endosulfan, azinphosmethyl/fenvalerate and acephate/fenvalerate) tested exhibited simple additive toxicity.     

The effect of certain intrinsic and extrinsic variables on the acute toxicity of selected organophosphorus insecticides to the mummichog,Fundulus heteroclitus

Abstract

The acute toxicity of two organophosphorus (OP) insecticides, azinphosmethyl and acephate, was evaluated in the mummichog, Fundulus heteroclitus. In addition, the effects of certain intrinsic (sex) and extrinsic (salinity and multiple toxicant interraction) variables on the toxic response were also investigated. Azinphosmethyl was by far the most toxic of the two OP insecticides with a 96h LC50 ～ 100,000 x lower than that for acephate. Slight sex differences were observed in the sensitivity of mummichogs to each of the OP insecticides with male fish being marginally more sensitive. Significant effects of low salinity stress were observed only with acephate exposure and, in this case, low salinity appeared to be slightly protective. In general, all of the insecticide mixtures (azinphosmethyl/endosulfan, azinphosmethyl/fenvalerate and acephate/fenvalerate) tested exhibited simple additive toxicity.     

In-vivo interaction of some organophosphorus insecticides with different biochemical targets in white rats

A comparative study between five organophosphorus insecticides: Leptophos, EPN, Cyanofenphos, Chlorpyrifos and Diazinon, was carried out for acute oral toxicity to white rats and for their in vivo interaction at 1/10th of LD50 doses with the activity of six serum enzymes after 4 wks from oral administration. Leptophos, Chlorpyrifos and diazinon exerted significant inhibition particularly to glutamic oxaloacetic transaminase (GOT), glutamic pyruvic transaminase (GPT), glutamyltransferase (GT) and lactate dehydrogenase (LDH). Adding ascorbic acid in the diet at 0.5% enhanced the acute oral toxicity of leptophos, chlorpyrifos and diazinon. For all the compounds, presence of ascorbic acid protected a number of the monitored serum enzymes from being inhibited except for leptophos. Ascorbic acid caused hypoglycemia with sublethal doses of leptophos, chlorpyrifos, and diazinon. The synergist piperonyl butoxide alone at 750 mg/kg dose inhibited the activity of the six serum enzymes. Presence of ascorbic acid in the diet intensified the inhibitory effect of piperonyl butoxide to all enzymes except for GOT.     

Neurotoxicity of organophosphorus insecticides Leptophos and EPN.

Phosfolan, chlorpyrifos, and stirophos when applied to white mice at sublethal doses did not induce any delayed neurotoxic effect. On the other hand, Leptophos and EPN when administered orally at sublethal or lethal levels clearly produced a delayed neurotoxic ataxia in treated mice. The five tested organophosphorus insecticides were compared for their ability to inhibit cholinesterase, neurotoxic esterases and monoamine oxidase. I50 values were estimated for each case. The results revealed that all five compounds were inhibitors of cholinesterase, but only Leptophos and EPN were shown to be potent inhibitors for both neurotoxic esterase and monoamine oxidase in the mouse brain. Additional particular properties of both Leptophos and EPN were found in their ability to cause delayed neurotoxic ataxia in chickens and sheep fed once on sublethal doses of these compounds. It is believed that the phosphonate ester configuration of EPN and Leptophos has a specific mode of toxic action which is mainly located at the central nervous system. It is also postulated that these delayed neurotoxic agents might inhibit postganglionic sympathetic neurons, thus resulting in chronic paralytic effects.     

Effect of ultraviolet-absorbing vinyl film on organophosphorus insecticides dichlorvos and fenitrothion residues in spinach

Dichlorvos and fenitrothion residues found in spinach grown in greenhouse covered either by regular vinyl film or UV-absorbing vinyl film (UV-A) were analyzed by gas chromatography. After one day, dichlorvos residues in spinach covered with regular vinyl film and UV-A degraded by 97% and 80%, respectively, and degraded 100% after three days covered with regular vinyl film and six days covered with UV-A. After three days, fenitrothion residue in spinach covered with regular vinyl film degraded by 72% and then by 97% after six days; residue in spinach covered with UV-A degraded by 50% after three days and by 95% after six days. These results indicate that UV-A used to prevent the occurrence of insects and fungi in greenhouses reduced the degradation rates of dichlorvos and fenitrothion.     

Solid phase microextraction applied to the analysis of organophosphorus insecticides in fruits

Trace amounts of organophosphorus pesticides (OPs) were determined in various fruits by headspace solid phase microextraction (HS-SPME) and gas chromatography–nitrogen phosphorous detection (GC-NPD). Sampling from the headspace enhanced method selectivity, whereas at the same time improved fiber life time and method sensitivity. Diazinon, parathion, methyl parathion, malathion and fenithrothion were determined in various fruits: more than 150 samples of 21 types of fruits were studied. SPME-GC-NPD provided a useful and very efficient analytical tool: method linearity ranged from 1.2 to 700 ng/ml. Limits of detection (LODs) and quantitation (LOQs) ranged from 0.03 to 3 ng/ml and 0.12 to 10 ng/ml respectively, values well below the residue limits set by the EU. Less than 2% of the samples were found positive containing amounts higher than the EU limits. The effect of fruit peeling and washing was also investigated.     

Photodegradation of organophosphorus insecticides - investigations of products and their toxicity using gas chromatography-mass spectrometry and AChE-thermal lens spectrometric bioassay

Four organophosphorus compounds: azinphos-methyl, chlorpyrifos, malathion and malaoxon in aqueous solution were degraded by using a 125 W xenon parabolic lamp. Gas chromatography-mass spectrometry (GC-MS) was used to monitor the disappearance of starting compounds and formation of degradation products as a function of time. AChE-thermal lens spectrometric bioassay was employed to assess the toxicity of photoproducts. The photodegradation kinetics can be described by a first-order degradation curve C=C0e(-kt), resulting in the following half lives: 2.5min for azinphos-methyl, 11.6 min for malathion, 13.3 min for chlorpyrifos and 45.5 min for malaoxon, under given experimental conditions. During the photoprocess several intermediates were identified by GC-MS suggesting the pathway of OP degradation. The oxidation of chlorpyrifos results in the formation of chlorpyrifos-oxon as the main identified photoproduct. In case of malathion and azinphos-methyl the corresponding oxon analogues were not detected. The formation of diethyl (dimethoxy-phosphoryl) succinate in traces was observed during photodegradation of malaoxon and malathion. Several other photoproducts including trimethyl phosphate esters, which are known to be AChE inhibitors and 1,2,3-benzotriazin-4(3H)-one as a member of triazine compounds were identified in photodegraded samples of malathion, malaoxon, and azinphos-methyl. Based on this, two main degradation pathways can be proposed, both result of the (P-S-C) bond cleavage taking place at the side of leaving group. The enhanced inhibition of AChE observed with the TLS bioassay during the initial 30 min of photodegradation in case of all four OPs, confirmed the formation of toxic intermediates. With the continuation of irradiation, the AChE inhibition decreased, indicating that the formed toxic compounds were further degraded to AChE non-inhibiting products. The presented results demonstrate the importance of toxicity monitoring during the degradation of OPs in processes of waste water remediation, before releasing it into the environment.     

Effects of atrazine on acetylcholinesterase activity in midges (Chironomus tentans) exposed to organophosphorus insecticides

Acetylcholinesterase activity was determined for midge larvae (Chironomus tentans) exposed to either organophosphorus insecticides (OPs) alone or OP insecticides in binary combination with atrazine (200 μg/l). Although atrazine by itself did not reduce the level of acetylcholinesterase activity, atrazine in combination with chlorpyrifos significantly decreased acetylcholinesterase activity as compared to chlorpyrifos only treatments. Although similar trends existed for malathion and methyl parathion, differences were not statistically significant. These results match previously published toxicity data where atrazine, although not acutely toxic even at much higher levels, decreased EC₅₀ values for chlorpyrifos by a magnitude of 4, decreased methyl parathion values by a magnitude of 2, and did not decrease values for malathion.     

Effects of atrazine on acetylcholinesterase activity in midges (Chironomus tentans) exposed to organophosphorus insecticides

Acetylcholinesterase activity was determined for midge larvae (Chironomus tentans) exposed to either organophosphorus insecticides (OPs) alone or OP insecticides in binary combination with atrazine (200 μg/l). Although atrazine by itself did not reduce the level of acetylcholinesterase activity, atrazine in combination with chlorpyrifos significantly decreased acetylcholinesterase activity as compared to chlorpyrifos only treatments. Although similar trends existed for malathion and methyl parathion, differences were not statistically significant. These results match previously published toxicity data where atrazine, although not acutely toxic even at much higher levels, decreased EC₅₀ values for chlorpyrifos by a magnitude of 4, decreased methyl parathion values by a magnitude of 2, and did not decrease values for malathion.     

Effects of two organophosphorus insecticides on some biochemical constituents in the nervous system and liver of rabbits

Abstract

Male Baladi rabbits were acutely and sub‐chronically intoxicated with cyanofenphos and profenophos. The levels of cholesterol, triglycerides, B‐lipoproteins and total proteins were determined in the serum, brain, spinal cord and sciatic nerve of rabbits. Moreover, the activities of alkaline phosphatase, acid phosphatase and glutamic‐pyruvic transaminase were determined in the liver of the animals. The whole Studie revealed that the biochemical constituents were highly affected by the tested insecticides. Also, the liver function suffered from adverse effects of the tested insecticides.     

Effects of two organophosphorus insecticides on some biochemical constituents in the nervous system and liver of rabbits

Male Baladi rabbits were acutely and sub-chronically intoxicated with cyanofenphos and profenophos. The levels of cholesterol, triglycerides, B-lipoproteins and total proteins were determined in the serum, brain, spinal cord and sciatic nerve of rabbits. Moreover, the activities of alkaline phosphatase, acid phosphatase and glutamic-pyruvic transaminase were determined in the liver of the animals. The whole studies revealed that the biochemical constituents were highly affected by the tested insecticides. Also, the liver function suffered from adverse effects of the tested insecticides.     

Bioavailability to rats and toxicity in mice of carbofuran residues bound to faba beans.

14C-carbofuran penetrated readily into seeds of Vicia faba and the rate of penetration was found to be dose dependent. The percentage of bound residues was generally low and did not exceed 3% of the applied dose. When the bound residues were fed to rats 46% of the radioactivity was eliminated via CO2 and urine, while tissues contained 25%. Carbofuran phenol and 3-hydroxy carbofuran represented the main metabolites in the urine. These data indicate that bean-bound carbofuran residues are highly bioavailable to rats. Feeding mice with bound carbofuran residues for 90 days led to inhibition of erythrocyte cholinesterase activity after 30 days (35-40%) while the plasma enzyme remained unaffected. Serum transaminases and blood urea nitrogen were significantly elevated, indicating injury to hepatic and renal structures. The results strongly suggest that the bound residues can induce adverse biological effects in mice.     

The acute toxicity of nickel to freshwater ciliates

The degradation of the (14)C-labelled fungicide dithianon in an orthic luvisol was investigated under standardized conditions in comparison to stimulated microbial activity by an amendment of maize straw. The compound is characterized by mineralization losses of approximately 33% and the formation of non-extractable bound residues of approximately 63% in 64 days. Despite the major role of microorganisms in mineralizing this compound, the formation of bound residues is not biotically induced. Gel permeation chromatography and polyacrylamide gel electrophoresis, as different size separation techniques of the humic acids fractions, showed differences in the distribution patterns of non-extractable residues depending on the addition of straw material. The results presented support the existence of humic substances in soil as a micellar system rather than as a biopolymer.     

Effect of quinalphos on blood enzymes and its acute toxicity in bubalus bubalis

Abstract

The acute toxic effects of quinalphos (0,0‐diethyl 0–2‐quinoxalyl phosphorothioata) uere investigated in male buffalo calves. Quinalphos was administered in single oral doses of 5, 7.5, 8.5 and 10 mg/kg body wt. and its effects on erythrocyte and plasma cholinesterases, serum aspartate aminotransferase and blood glucose were studied at various time intervals. The lowest dose (5 mg/kg) produced no apparent toxic symptoms. All the animals given highest dose (10 mg/kg) died within 60–82 hours after dosing. Quinalphos at all the dose levels markedly inhibited the erythrocyte and plasma cholinesterases (68–100%) and significantly elevated the levels of serum aspartate aminotransferase and blood glucose. Seven days after the administration of quinalphos, the blood cholinesterases in survivors remained inhibited to the extent of 41–77% whereas the levels of serum aspartate aminotransferase and blood glucose were comparable to control values.     

Toxic and developmental effects of organophosphorus insecticides in embryos of the South African clawed frog

Four organophosphorus insecticides and the active metabolites of two phosphorothionate insecticides were tested for their toxic and teratogenic effects on embryos of Xenopus laevis. All compounds caused dose-dependent developmental defects, such as abnormal pigmentation, abnormal gut development, notochordal defects and reduced growth. Malathion, malaoxon, parathion, and paraoxon produced severe defects, while monocrotophos and dicrotophos produced considerably milder defects. All compounds reduced NAD+ levels to a similar extent, regardless of the severity of the defects induced. Thus some commonly used organophosphorus insecticides and their metabolites are teratogenic to Xenopus embryos, but reduced NAD+ level does not appear to be important in causing the developmental defects.     

Biochemical effects of some organo‐phosphorus insecticides on new targets in white rats

Abstract

The three S‐n‐propyl phosphates and phosphothioates: RH 218, profenofos and prothiophos were compared with fenitrothion in their potential as inhibitors of rat liver and brain AChE. Fenitrothion was more potent as an inhibitor than the three S‐n‐propyl derivatives. Incubation of hepatic protein enhanced ChE inhibition in brain in the case of fenitrothion, while it reduced the inhibitory effect of the S‐n‐propyl derivatives. On the other hand, the four organophosphorus esters caused hypoglycemia in both male and female rats and also reduced their blood urea with different degrees.     

Effect of commercial formulation of four organophosphorus insecticides on the ovaries of a freshwater teleost, Mystus vittatus (bloch)--a histological and histochemical study

The chronic effect of an exposure to a sublethal concentration of commercial formulation of 4 organophosphorus insecticides such as birlane (chlorfenvinphos), gardona (tetrachlorvinphos), phosdrin (mevinphos) and malathion on midvitellogenic ovaries of Mystus vittatus was investigated using several histological and histochemical techniques. The loss of stage II and III oocytes accompanied by a significant decline in gonadosomatic index was recorded. The vitellogenesis in treated fishes was ceased as the oocytes did not advance to further stages as evidenced by the absence of lipid yolks and the lack of a PAS positive follicular layer. The RNA content of remaining stage I oocytes of exposed fishes resembled that of the stage I oocytes of the control fishes. The absence of delta 5-3 beta-hydroxysteroid dehydrogenase suggested the lack of steroidogenesis. Reduced glucose-6-phosphate dehydrogenase activity was also observed. The significance of these observations has been discussed in light of available literature.     

Effect of pulse frequency and interval on the toxicity of chlorpyrifos to Daphnia magna.

Due to the episodic nature in which organisms are exposed to non-point source pollutants, it is necessary to understand how they are affected by pulsed concentrations of contaminants. This is essential, as standard toxicity tests may not adequately simulate exposure scenarios for short-lived hydrophobic compounds, such as chlorpyrifos (CPF), a broad-spectrum organophosphate insecticide. Studies were conducted with 7-day old Daphnia magna for 7 days to evaluate the effect of pulse frequency and interval among multiple CPF exposures. Daphnids were exposed to a total exposure of either 12 h at 0.5 microg/l or 6 h at 1.0 microg/l nominal CPF, respectively, in all studies. For interval studies, D. magna were exposed to two pulses of CPF at each concentration, with 0-96-h intervals between pulses. For frequency studies, D. magna were exposed to each CPF concentration altering the pulse scheme by decreasing the exposure duration but increasing the number of pulses, keeping the total exposure time the same. The pulse interval between multiple pulses in these experiments was 24 h. Our results suggest that D. magna can withstand an acutely lethal CPF exposure provided that there is adequate time for recovery between exposures.     

The acute toxicity of arsenobetaine

The acute toxicity of arsenobetaine was studied in male mice. No deaths were observed with oral administration of 10 g/kg of arsenobetaine. Therefore the LD₅₀ value was higher than 10 g/kg. This compound was found in urine in the non-metabolized form. No particular toxic symptoms were observed following administration. These results suggest that arsenobetaine has low toxicity and is not metabolized in mice.