Dimethoate treatment

When dispersing the insectoacaracide dimethoate, widely used even today, from tractor-based sprayers, air concentration reached 9.0 mg/m3, a level unacceptable for humans (the old public health standard was 0.3 mg/ m3 the standard was then rounded up to 0.5 mg/m3 [10]). People are still permitted to carry out manual work in fields just 10-20 days after dimethoate treatment [7, A13]. 

The first field test was successful. Both dimethoate and malathion declined exponentially (Figure 9) and exhibited efficiency factors comparable to the efficiency factors found in the pilot tests. An efficiency factor could be calculated for baygon, but not for diazinon. Some sediment was present into the bottom of the holding tank which could have been slowly releasing baygon and diazinon in the bulk liquid. Nevertheless, after 24 hours of treatment, all pesticides were below the limit of detection. 

Earlier, there were contradictory functional disorders under exposure to OPs described, for which no appropriate interpretations were suggested from the point of view of molecular sources. For example, daily administration of DFP to rats for 20 days at a dose of 17% of LD50 caused an increase of velocity of nerve impulse conduction (Anderson and Dunham, 1985), though dimethoate or dichorvos treatment at subsymptomatic doses for at least 8 weeks caused reduction of peripheral nerve conductivity (Desi and Nagimajtenyi, 1999). 

Kusic et al. (1991) have tested the oxime HI-6 in OP pesticide poisoning in 60 patients. HI-6 was administered four times a day as a single i.m. injection of 500 mg with atropine and diazepam treatment. Oxime therapy was started on admission and continued for 2 to 7 days. Most patients were treated with HI-6 and nine patients severely poisoned with quinalphos were treated 2-PAM Cl (1,000 mg four times per day). HI-6 rapidly reactivated human red blood cell AChE inhibited by diethoxy OPs (phorate, pyr-idaphenthion, quinalphos) as well as that inhibited by dichlorvos (a dimethoxy OP). AChE inhibited with other dimethoxy OPs (dimethoate and phosphamidon) was reported to be resistant to HI-6 treatment, whereas reactivation with malathion was slow (reactivation half-time 10 h). Both HI-6 and 2-PAM successfully reactivated AChE in quinalphos-poisoned patients, with HI-6 acting as a faster AChE reactivator than 2-PAM. 

Problem 28.11 I p-Dimetho.xytrityl (DMT) ethers are easily cleaved by mild acid treatment. Show the mechanism of the cleavage reaction. 

Relapse of cholinergic symptoms and unconsciousness has also been reported following dimethoate intoxication (Molphy and Rathus, 1964). A tractor driver with. subacute dicrotophos poisoning probably through both skin contact and Inhalation recovered from a moderate cholinergic cri.sis after atropine and pralidoxime treatment. He further improved when atropine dosage was tapered, but tm day 7 after the last exposure, he relapsed with prominent respiratory paralysis. Response to drug treatment, if any, was not mentioned. The ultimate outcome was favorable (Perron and Johnson, 1969),... 

Sanderson (1961) studied the effect of intraperitoneally administered atropine 17.4 mg/kg given alone or combined with oximes on the survival of rats poisoned orally by 10 different OPs, excluding dimethoate. Atropine atone prevented the development of toxicity. Although the numbers of rats in each group were small (n = 6) and statistical analysis was not performed, this study dcmon.strafed that atropine treatment alone did reduce mortality. 

The study does not take into account a series of variables, such as the type of crop treated, the time lapse between the chemical treatment and the poisoning of the bees, and the botanical species visited. Nevertheless, it gives an idea of how the various pesticides may affect the insect and, above all, how bees capture them. The seven compounds detected achieve their effect through both contact (in particular dimethoate, parathion, and methylparathion) and ingestion ethiofencarb and monocrotophos are also systemic. 

In 1998, as in more recent years, the problem of dimethoate again came to the forefront. The widespread use of this compound (detected in 42.1 percent of the bee specimens analyzed), especially in the month of May, suggests that grain aphids are the target of the majority of the chemical treatments performed. This hypothesis has been further conhrmed by palynological analyses. The year in question also saw an extensive use of fenitrothion, which in some cases was detected in dead bees even several weeks after spraying took place due to the slow release of the compound from the microcapsules containing it. 

The toxicity of dimethoate to mice may be increased by pre-treatment with phenobarbitone [58] or pentobarbitone [59], whereas the toxicities of phos-phamidon, dicrotophos and their Ai-dealkylated derivatives are decreased [58]. Dimethoate requires oxidative activation, yet the vinyl phosphates do not. In vitro studies confirm the induction of mouse hepatic microsomal enzymes by phenobarbitone pre-treatment, which activate schradan, mala-thion and parathion [60]. Microsomal induction by pre-treatment with pentobarbitone stimulates not only the activation of certain organophos-phates, but also their catabolism, thereby reducing their toxicity, for example mipafox [59]. 

Malathion is a widely used member of a class of pesticides known as organophospate derivatives. It is biodegradable and less toxic (LDg for female rats is 1000 mg/kg) than DDT. Several other organophosphorus compounds are modifications of this basic structure. They include dimethoate (LD = 387 mg/kg), chlorpyrifos (LD q = 95-270 mg/kg), and methyl parathion (LD o = 18 -50 mg/kg). These organophosphates often are used in the treatment of many pests that are found on vegetables, or, in the case of methyl parathion, on cotton plants. 

Some OP insecticides were determined in green and dry tobacco leaves by TLC and gas chromatography. TLC detection required charcoal treatment, which diminished the recovery (88.5%) (59). Cardona content of fish tissues and water samples was established after chloroform or petroleum ether-chloroform extraction (9) (Table 3). Two solvent systems were reported for the separation of dimethoate, fonofos, and their oxygen analogs from disulfoton, fonofos, and oxydemeton meftiyl (60) (Table 3). Silica gel F254 or silica R (containing 5% 1102) layers were applied for the analysis of 10 OP insecticides (61). 

Duffield, S.J. and Aebischer, N.J. 1994 The effect of spatial scale of treatment with dimethoate on invertebrate... 

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