Acute toxicity and cholinesterase inhibition in chicks dosed orally with organophosphate insecticides

Acute toxic effects of three commonly used insecticidal preparations of the organophosphates chlorpyrifos, diazinon, and dichlorvos were examined in mixed breed broiler chicks, and cholinesterase activity in plasma and brain were measured. The acute (24 h) oral median lethal doses (LD50) of chlorpyrifos, diazinon, and dichlorvos were 10.79 mg kg(-1), 6.32 mg kg(-1), and 6.30 mg kg(-1), respectively, as determined by the up-and-down method in chicks. Signs of cholinergic toxicosis in the chicks appeared within two hours after dosing, and they included salivation, lacrimation, gasping, frequent defecation, drooping of wings, tremors, convulsions, and recumbency before death. Halving the oral LD50 of chlorpyrifos (5 mg kg(-1)), diazinon (3 mg kg(-1)), and dichlorvos (3 mg kg(-1)) caused immobility and wing drooping, but not the clinical signs of cholinergic toxicity. However, at full LD50 doses of these insecticides, chicks showed clinical signs of cholinergic toxicity similar to those seen in the LD50 experiments. Two out of six chicks died within two hours after treatment with LD50 doses of chlorpyrifos and dichlorvos, whereas LD50 dosing with diazinon caused death in three out of six chicks. Compared to control values, the insecticides reduced plasma and whole brain cholinesterase activities by 29% to 84% and 18% to 77%, respectively, depending on the dose. The decrease in plasma cholinesterase correlated well (r=0.82) with that of the brain. These data suggest that organophosphate insecticides administered orally at LD50 doses induce clinical signs of cholinergic poisoning and concurrently reduce brain and plasma cholinesterase activities in chicks.     

Hazards associated with aerial spraying of organophosphate insecticides in Israel.

Aerial application of organophosphates can result in exposure to drift and leaf residues for pilots, ground crews, field workers, and residents near sprayed fields. Exposure can be by either the airborne or dermal route, and can produce illness (headaches, fatigue, diarrhea, cramps, respiratory problems) even with low-grade depressions in cholinesterase. Alkyl phosphate metabolites have been shown to be "gold standard" measures of such exposures. Experience in Israel indicates that reduction of health hazards from exposure to drift and leaf residues may be attained by the use of a comprehensive "mix" of preventive measures. These measures include, first and foremost, reduction in total amount of organophosphates used, followed by substitution of less for more toxic organophosphates, reduction in length of spray season, banning the use of flaggers, and greater reliance on tractor spraying. Cotton yield per hectare cultivated has increased despite a reduction in use of pesticides of all kinds and organophosphates in particular. Enclosure and air-conditioning (to prevent heat stress) of cockpits, protective clothing, training and licensing of pilots have been implemented. Education and communication of information, in keeping with the right-to know principle on hazards and how they should be controlled and monitored, is a part of a comprehensive strategy. Aerial or ground spraying should produce no drift in adjacent residential communities. The criterion for achieving this goal is the absence of urine alkyl phosphate metabolites above the threshold of detection.     

Acute toxicity of locust insecticides to two indigenous invertebrates from Sahelian temporary ponds

During desert locust plagues large amounts of insecticides are used for control operations. Drift from these treatments and accidental overspraying may contaminate small surface waters such as temporary ponds. The present study describes methods for static acute toxicity tests with two abundant organisms that occur in temporary ponds in the African Sahel region: the fairy shrimp Streptocephalus sudanicus Daday (Branchiopoda, Anostraca, Streptocephalidae) and the backswimmer Anisops sardeus Herrich-Sch?ffer (Hemiptera, Notonectidae). The organisms were captured in the field and 48-h static toxicity tests were conducted in the laboratory. The assays were used to screen the toxicity of 11 formulated synthetic insecticides used in desert locust control and of spores of the mycopesticide Metarhizium anisopliae var. acridum. Most of the synthetic insecticides tested were highly toxic to both organisms (LC50 or EC50<1 mg/L). Exceptions were the toxicity of diflubenzuron to A. sardeus (moderately toxic: 1相似文献   

Increased toxicity to Ceriodaphnia dubia in mixtures of atrazine and diazinon at environmentally realistic concentrations

The acute toxicity of diazinon in combination with atrazine concentrations of 5, 10, 20, and 40 microg/L was evaluated using Ceriodaphnia dubia. Atrazine concentrations as low as 5 microg/L in combination with diazinon significantly increased toxicity to C. dubia compared to diazinon alone. Atrazine and diazinon residues within water samples collected from 65 subbasins throughout Denton, Texas, USA were used to assess the environmental relevance of pesticide concentrations. A geographical information system was used to examine the relationship between subbasin land uses and pesticide concentrations. Significant correlations were observed between in situ atrazine and diazinon concentrations and some subbasin land uses. Atrazine was significantly (P < 0.05) correlated to diazinon during some months. Of the 276 samples collected, 39% exceeded our experimentally derived diazinon LC(50) value, and 39% exceeded our minimum atrazine concentration of 5.0 microg/L. Results indicate the potential for increased toxicity from mixtures of compounds at environmentally realistic concentrations.     

Evaluation of humic-pesticide interactions on the acute toxicity of selected organophosphate and carbamate insecticides.

The ability of water resource managers to accurately predict the toxicity of agricultural chemicals in aquatic ecosystems is essential for the development of reliable water quality standards. At present, accurate predictions are difficult due to the paucity of data concerning the interaction of these chemicals with organic constituents of the freshwater chemical matrix. Dissolved humic materials are ubiquitous components of freshwater ecosystems and can affect the availability and toxicity of chemicals in the environment. In the present investigation, the influence of humic acid (HA) on the acute toxicity of selected organophosphate and carbamate insecticides was examined using a bacterial bioluminescence inhibition assay. EC50 values for the pesticides were determined in the presence of 0, 0.5, 5.0, 50, and 100 mg/liter HA. A combination of antagonistic and synergistic effects was observed with the selected organophosphate and carbamate insecticides examined. HA significantly reduced the toxicity of azinophos-methyl, chlorpyrifos, and carbofuran, while enhanced toxicity was observed with methyl parathion and carbaryl. These results indicate that humic-pesticide interactions can alter the toxicity of agricultural chemicals. Moreover, the influence of humic materials on the toxicity of these chemicals is dependent on temporal relationships and HA concentration.     

Susceptibility to organophosphate insecticides in larval Aedes albopictus

Larvae of 26 strains of Aedes albopictus were tested for susceptibility to 5 organophosphate insecticides. The recently collected geographic strains included 13 from the USA, 5 from Brazil, 3 from Southeast Asia and 5 from Japan. The greatest amount of variability was seen among U.S. populations, ranging from quite susceptible to potentially resistant. Brazilian samples were generally quite susceptible to all insecticides tested. Three Japanese strains showed tolerance or low level resistance to fenitrothion (2X, 3X and 8X), as did 2 U.S. strains (3X and 5X). Two U.S. strains showed tolerance to malathion (3X and 4X), while one strain from Chicago, Illinois, showed low level resistance (22X). Selection for resistance to malathion in a laboratory strain composed of multiple U.S. geographic strains resulted in a resistance ratio of 21X after 6 generations of selection.     

Safety measures associated with the use of organophosphate insecticides in the Haitian malaria control programme

A programme emphasizing intensive training, use of protective equipment and uniforms, daily supervision of safety measures at work, and weekly monitoring of blood cholinesterase levels by the tintometric method was instituted to prevent toxicity in Haitian malaria workers during spraying with the organophosphate insecticides fenitrothion and malathion. The programme functioned well, depressed cholinesterase activity (≤ 50% of normal) being detected rapidly prior to the development of serious symptoms. Evidence of fenitrothion overexposure appeared in spraymen early in the first spray cycle, and was associated with faulty protective clothing and a failure to observe strictly the recommended safety measures at work. After these deficiencies were corrected, insecticide application continued without serious incidents or interruption of the programme. No serious reduction of cholinesterase activity was seen in a more limited study of spraymen using malathion. It is strongly recommended that similar training and monitoring programmes should be instituted whenever organophosphate pesticides are used as residual sprays for malaria control. This is particularly important in areas where the more toxic compound, fenitrothion, is to be used.     

Characterization of a streptomycete growing on organophosphate and carbamate insecticides

A streptomycete bacterium was isolated from a field soil sample previously treated with the insecticide isofenphos and found to be capable of growing on several commercial carbamate and organophosphate insecticides. These included carbofuran, cloethocarb, trimethacarb, isofenphos, fonofos, ethoprop, and phorate but not terbufos. As shown by Chromatographic analyses, the bacterium reduced the levels of isofenphos by 65–75% in a four-week period. Although the exact mechanism of degradation is not known, apparently it occurs by either an incidental type of metabolism or an abiotic process. Taxonomic characterization of this bacterium indicated it most nearly resemblesStreptomyces pilosus. A single plasmid with a molecular weight of 9,700 base pairs was obtained from the organism. It is not yet known if the presence of plasmid DNA contributes to the ability of the organism to grow on the pesticides.Published as Journal Paper No. 2104 of the South Dakota Agricultural Experiment Station.     

Decreased toxicity to terrestrial plants associated with a mixture of methyl tert-butyl ether and its metabolite tert-butyl alcohol

The influence of the main fuel oxygenate methyl tert-butyl ether (MTBE) and its key metabolite, tert-butyl alcohol (TBA), on the growth of a plant seedling was studied separately and in combination. The test plants were mung bean (Phaseolus radiatus), cucumber (Cucumis sativus), wheat (Triticum aestivum), sorghum (Sorghum bicolor), kale (Brassica alboglabra), Chinese cabbage (Brassica campestris), and sweet corn (Zea mays). The growth of all the plants was adversely affected by TBA and MTBE. The 5-d median effective concentration (EC50) for the plants exposed to MTBE and TBA were in the range of 680 to 1,000 mg MTBE/kg soil (dry wt) and 1,200 to 3,500 mg TBA/kg soil (dry wt), respectively. The relative order of the sensitivity rankings is almost the same for MTBE and TBA. Methyl tert-butyl ether is more toxic than TBA to most of the test species. Based on the EC50 values, MTBE is approximately 1.5 to 3 times more potent than TBA. The sum of the toxic unit (TU) at 50% inhibition of the mixture (EC50mix) was calculated from the dose (TU-based)-response relationships using the trimmed Spearman-Karber method. The combined effect of MTBE + TBA on the plant growth was less than additive because the EC50mix values were greater than I TU. This phenomenon may be due to the competition of MTBE and TBA in terms of their intake by plants. The combined effects of MTBE and TBA should be taken into account to assess their risk in gasoline-contaminated sites.     

Tactile vibration thresholds after acute poisonings with organophosphate insecticides

This study evaluated the association between acute poisoning with organophosphate pesticides (OPs) and quantitative tactile vibration thresholds. Thresholds of the dominant index fingers and big toes of 56 men hospitalized for acute poisoning with OPs were measured at hospital discharge (1-24 days after poisoning) and around seven weeks later (24-176 days after poisoning), and compared with those of controls. Thresholds of the big toes of men with severe intentional poisonings due to neuropathic OPs (metamidophos and chlorpyrifos) increased between the first and second examinations. Threshold impairment was not detected in the index finger regardless of poisoning agent or severity. The development of threshold impairment as a consequence of severe intentional poisonings with neuropathic OPs is consistent with other reports indicating that only severe OP poisonings produce sensory peripheral nerve effects.     

Piperonyl butoxide as a tool in aquatic toxicological research with organophosphate insecticides

Experiments were conducted to determine the effects of piperonyl butoxide, a synthetic methylenedioxyphenyl inhibitor of cytochrome(s) P450, on the toxicity of organophosphate insecticides to three cladoceran test species: Ceriodaphnia dubia. Daphnia magna, and Daphnia pulex. Coadministration of piperonyl butoxide effectively reduced the acute toxicity of four metabolically activated organophosphates (parathion, methyl parathion, diazinon, and malathion) and did not affect the toxicity of three organophosphates not requiring metabolic activation (dichlorvos, chlorfenvinphos, and mevinphos). These results indicate that piperonyl butoxide may be an effective tool in toxicological research focused upon identifying specific compounds responsible for toxicity in complex aqueous mixtures.     

有机磷杀虫剂中毒致中间期肌无力综合征的遗传易感性研究

目的　探讨代谢酶基因多态性与有机磷杀虫剂 (OPs)中毒致中间期肌无力综合征(IMS)遗传易感性的关系 ,为IMS易感人群的筛选和保护提供依据。方法　以山东省某地区医院收治入院的 14 7位急性OPs中毒患者为研究对象 ,采集外周静脉血 ,检测全血胆碱酯酶 (ChE)活力 ,并以限制性片段长度多态性、等位基因特异性扩增和单链构象多态性PCR技术 ,分别对CYP2E1(10 91C→T)和GSTP1(313A→G )、CYP1A1(4889A→G)、PON1第 5 5位点 (L→M )、GSTM1和GSTT1进行基因分型。结果　急性OPs中毒者入院时全血ChE活力IMS患者为 (38 2 2±17 5 6 ) % ,非IMS患者为 (42 4 9± 16 2 3) % ,差异无显著性 ,但IMS患者入院后全血ChE活力恢复速度明显慢于非IMS患者。PON1第 5 5位点杂合子和突变纯合子、GSTM1缺失及其与GSTT1均缺失者在IMS患者的分布百分率分别为 4 1 7%、2 2 2 %、6 9 4 %和 4 1 7% ,显著多于非IMS患者的30 6 %、3 6 %、4 5 9%和 19 8%。结论　在有机磷及其混剂中毒患者中 ,PON1第 5 5位点含有突变型等位基因、GSTM1及其与GSTT1均缺失者发生IMS的危险性增高。     

急性有机磷农药及其混剂中毒患者单肌纤维肌电图的研究

目的探讨电刺激单肌纤维肌电图(SSFEMG)技术在急性有机磷农药(OPs)及其混剂中毒患者"中间期肌无力综合征"(IMS)诊断、分级及病情转归中的意义.方法对41例急性有机磷农药及其混剂中毒患者进行了SSFEMG和重频神经刺激肌电图(RNS)检测.结果(1)电刺激频率为5Hz和20 Hz时,SSFEMG检测所见单肌纤维动作电位平均连续差(MCD)增高与肌无力发生的一致性均较好(5 HzKappa系数=0.634,P=0.002;20 HzKappa系数=1.000,P=0.000),且以20 Hz者更好;RNS的检测结果与肌无力发生的一致性不如SSFEMG(5 HzKappa系数=0.153,P=0.400;20 HzKappa系数=0.188,P=0.319);(2)重型与轻型IMS患者MCD差异无显著性[5 Hz轻型(25.43±14.08)μs、重型(29.80±14.37)μs,P＞0.05;20 Hz轻型(34.30±11.19)μs、重型(39.40±18.98)μs,P＞0.05];(3)IMS患者肌力恢复后MCD明显下降,且趋于正常.结论 SSFEMG较同一频率的RNS敏感,可用于IMS的诊断与病情转归的评价,但在诊断分级中的意义还需进一步探讨.     

Responses of periphyton and invertebrates to a tetradecyl-pentadecyl sulfate mixture in stream mesocosms

Alkyl sulfates (AS) are anionic surfactants widely used in household and personal cleansing applications. Aquatic toxicity of AS under laboratory conditions indicated effects at relatively low concentrations (50-230 microg/L) for some sensitive species. A comprehensive stream mesocosm study of an AS mixture composed of tetra- (C14) and pentadecyl (C15) chain lengths was conducted to better understand effects on microbial and macroinvertebrate populations and communities. A 56-d exposure of AS was performed at concentrations ranging from 57 to 419 microg/L (analytically confirmed exposures) and was accompanied by detailed investigations of periphyton community function (autotrophy, heterotrophy, and metabolism of test chemical), periphyton structure (algal population and community dynamics based on taxonomic identity), and invertebrate structure (benthic abundance, drift, and insect emergence patterns based on taxonomic identity). A no-observed-effect-concentration (NOEC) of 222 microg/L was concluded for several individual algal and invertebrate species based on univariate statistical analyses. An apparent energetic subsidy from C14-15AS at the highest concentrations of 222 to 419 microg/L was observed and tied to changes in microbial community processing of AS when added at these high concentrations. A multivariate analysis based on principal response curves (PRC) indicated that communities in streams exposed to 222 to 419 microg/L were significantly different from the controls leading to an overall (multivariate and univariate) conclusion that 106 microg/L was the ecosystem NOEC. Exposure to AS in the environment has been demonstrated to be in the range of 5 to 21 microg/L in 100% wastewater treatment plant effluent. Potential environmental effects are at least 5 to 20 times above worst-case environmental exposures; therefore, C14-15AS does not pose a risk to the aquatic environment due to normal use patterns.