Pesticides malathion

The development of pesticides, for instance, led to the development of genetically engineered organisms and enzymes to handle particularly difficult or uncoimnon organics. Organophosphate pesticides (malathion, diazinon, parathion, etc.) are examples that will be discussed in detail in subsequent chapters. To develop this technology commercially, however, many of the microorganisms must be isolated because they are expensive or are not safe to release to effluent streams. 

However, in a study of pesticide workers exposed to combinations of four pesticides (malathion, parathion, DDT, and hexachloro-cyclohexane), 73% demonstrated alterations of serum immunoglobulin (Ig) levels (39). In another study, increases in serum IgG but decreases in serum IgM and the C-3 component of complement were reported to occur in 51 men exposed to chlorinated pesticides, as compared with a 28-man control group ( ). In the latter two studies, in spite of immune changes, a direct association between increased susceptibility to infection with changes in immune status was absent. 

Solanine and chaconine (the main natural alkaloids in potatoes) are cholinesterase inhibitors and were widely introduced into the hviman diet about 400 years ago with the dissemination of the potato from the Andes. They can be detected in the blood of all potato eaters. Total alkaloids are present in potatoes at a level of 15,000 Vig per 200-g potato, which is only about a six-fold safety margin from the toxic level for hximans ( .) Neither alkaloid has been tested for carcinogenicity. By contrast, the pesticide malathion, the main synthetic organophosphate cholinesterase inhibitor present in our diet (17 ug/day), has been thoroughly tested and is not a carcinogen in rodents. Plant breeders have produced an insect-resistant potato however, it had to be withdrawn from the market because of its acute toxicity to hvunans, a consequence of higher levels of solanine and chaconine. 

There are two principal pathways for the abiotic degradation of organic phosphorus compounds in the environment hydrolytic reactions and photolytic reactions. The importance of either mechanism depends to a substantial degree both on the nature of the particular compound of interest (Fig. 4.1), and on its location in the environment. Some compounds, such as the phosphorodithionate pesticide malathion, are readily broken down (malathion has a half-life of about 11 h in alkaline solution ... 

Within the framework of SPEED 98, Japan Environment Agency conducted PLC and/or FLC with 28 of 67 chemicals listed [3]. The results showed that only 3 chemicals, i.e., 4-nonylphenol, 4-t-octylphenol, and bisphenol A were suggested as EDCs. We also conducted sex reversal assay or PLC test (56-day exposure) to evaluate the effects of some pesticides (malathion, benomyl, cypermethrin, permethrin, esfenvalerate, fenvalerate) listed in SPEED 98. The results showed that these pesticides gave no endocrine-disrupting effects even at one-seventh to one-twentieth of the acute toxicity values (Table III). The effect of benomyl on hatchability is likely to be caused by inhibition of cell division. Based on these findings, it is unlikely that these chemicals listed affected as EDCs. 

To better define the role of blood flow in dermal pharmacokinetics, Williams et al. (1990) represented the skin vasculature as a three-compartment model with a fourth compartment for the skin surface (Figure 13.5). They then examined hypothetical changes in the absorption profile of the organophosphate pesticide malathion in the IPPSF fitted to the model as shown in Figure 13.6 (Rivirae and Williams, 1992). The amounts of solute in each compartment of this model are described by the following expressions (Equation 13.6 to Equation 13.9) (Williams etal., 1990) ... 

Controlled-release solid formulations of selected volatile organophosphorus pesticides (malathion, DDVP, sumithion, chlorpyriphos, and sulprofos) were studied by Szente [33]. These solid formulations exhibited negligible vapor pressure and preserved their entrapped pesticide content even at elevated temperature. Malathion and chlorpyriphos formulations showed increased physical stability, and resulted in an effective masking of the unpleasant smell while the complex formulations existed as dry solid. Sulfluramid is an expensive insecticide that is lost by volatilization, but complexation to j8-CyD reduced the loss [21]. 

Although more predictive approaches may be possible in the future, with the ethical considerations of utilizing humans in studies with pesticides, currently the laboratory rat appears to be a suitable model. Dermal absorption studies with the rat allow the calculation of a penetration rate and hence, assist in the estimation of a potential body burden in man. Indeed, the extrapolation of a dermal penetration rate in the rat to man may represent a worst case approximation. Studies with one pesticide, malathion, in the rat and man have revealed the absorption/ penetration rate in the rat to be approximately 3-fold higher than man ( ). 

The pesticide malathion is used as an insecticide and an acaricide. Sensitization has been reported in farmers. 

Organophosphate pesticides studied in this work were the model low-toxic OPC trichlorfon, and some common organophosphate pesticides malathion, parathion, dichlorvos, and diazinon (Table I). Calibration curves for these pesticides (dependences of the sensor inhibition response on the analyte concentration) were obtained for all of these OPCs. These calibration curves were obtained under conditions (time of inhibition, pH and temperature) optimize with the model analyte trichlorfon. All of the pesticide calibration curves are similar and Fig. 4 illustrate the method by the example of malathion. The lowest concentration of pesticide samples assayed with 10 min. of incubation of the electrode in inhibitor containing solution was 5 ppb. This resulted in approximately 10 % of the relative inhibition signal. Fig. 4 predicts much better performance of our system compared with the literature data. For example, trichlorfon detection by means of ISFET had a reported limit of detection of ca 250 ppb (5), while conductometric sensor assay registered trichlorfon at ca. 25 ppb (5), still an order of magnitude higher than the described sensor. An amperometric sensor was used to detect dichlorvos with a limit of detection of 350 ppb (2J) and a potentiometric (pH-sensitive) sensor was shown to detect parathion at 39 ppm and diazinon at 35 ppb (9). 

In contrast to the high toxicity of methyl parathion, malathion shows how differences in structural formula can cause pronounced differences in the properties of organophosphate pesticides. Malathion has two carboxyester linkages, which are hydrolyzable by carboxylase enzymes to relatively nontoxic products as shown by the following reaction ... 

Iediterranean and Mexican fruit flies are formidable pests that have the potential to seriously damage several important fruit crops. Because of this, there have been several widely publicized sprayings of residential areas in southern California with the pesticide malathion to try to control fruit flies. Now there may be a better way to kill fruit flies—with a blend of two common dyes (red dye no. 28 and yellow dye no. 8) long used to color drugs and cosmetics. One of the most interesting things about this new pesticide is that it... 

Chitosan-Pmssian blue-multiwall carbon nanotube-hollow gold nanosphere (Chit-PB-MWNT-HGN) films were fabricated to be employed in AChE biosensorsIncorporating MWNTs and HGNs into a Chit-PB hybrid film promoted the electron transfer reaction, enhanced the electrochemical response, and improved the microarchitecture of the electrode surface. Based on the inhibition of the AChE activity by the pesticides malathion, chlorpyrifos, monocrotophos, and carbofuran as model compounds, the biosensor showed a wide dynamic range, low detection limit, good reproducibility, and high stability. Moreover, the AChE/Chit-PB-MWNT-HGN/Au biosensor could also be used for the direct analysis of a practical samples, which would be a new promising tool for pesticide analysis. 

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