Carbaryl applications

Workers associated with the application of carbaryl (applicator, mixer-loader, bystander and aerial flagger) and re-entry workers (apple thinners) were monitored by a modification of the procedure of Durham and Wolfe (3). The workers were fitted with a disposable jacket (Safety and Supply Co., Seattle, WA) to which 10 x 10 cm pads were attached with masking tape. One pad was attached as close to the neck as possible on each shoulder and on the chest and the back of each subject. One pad was also placed on each forearm midway between the elbow and wrist. The pads were constructed by backing an 8 ply gauze compress with two pieces of heavy filter paper and attaching these together in the center with a staple. 

Volunteers were recruited from the community to make the carbaryl applications. No special attempts were made to Influence... 

A practical application of SEE-CEST coupling is shown in Eigure 6.13, which displays the electropherogram obtained for a tomato sample contaminated with a pesticide, i.e. carbaryl. The sample was placed in the SEE cell, extracted with CO2... 

Although previous applications of this technique in our laboratory had been concerned with aquatic animal metabolism of pesticides such as DDT, parathion, carbaryl, and trifluralin (14, 15), we also became interested in comparing metabolic routesljy means of a "metabolic probe". Such a compound ideally should be stable to nonbiological degradation, of low toxicity to maximize the dose, and subject to as many major routes of metabolism as possible without undue analytical complexity. 

Sud et al. (1972) discovered that a strain of Achromobacter sp. utilized carbaryl as the sole source of carbon in a salt medium. The organism grew on the degradation products 1-naphthol, hydroquinone, and catechol. 1-Naphthol, a metabolite of carbaryl in soil, was recalcitrant to degradation by a bacterium tentatively identified as an Arthrobacter sp. under anaerobic conditions (Ramanand et al., 1988a). Carbaryl or its metabolite 1-naphthol at normal and ten times the field application rate had no effect on the growth of Rhizobium sp. or Azotobacter chroococcum (Kale et al., 1989). The half-lives of carbaryl under flooded and nonflooded conditions were 13-14 and 23-28 d, respectively (Venkateswarlu et al., 1980). 

Carbaryl [65-25-2], 1-naphthyl ZV-methylcarbamate (111) (mp 142°C, d 1.232 g/cm3, vp 0.67 Pa at 20°C), is ca 95% pure as the technical grade and is soluble in water to 120 mg/L. Carbaryl has a rat oral LD5Q of 540 mg/kg and a dermal LD50 of >2000 mg/kg. It is a broad-spectrum insecticide registered on more than 100 crops. Carbaryl is rapidly detoxified and eliminated in animal urine and is neither concentrated in fat nor secreted in the butterfat of milk, thus it is favored for application to food crops. 

Carbamates (carbaryl, benomyl, carbofuran, aldicarb, methomyl). Symptoms of exposure were nausea, dizziness, b listers, dermatitis, malaise, sweating, tearing, breathing difficulty, and chest tightness. Usually, incidents have occurred within 1 to 2 days after application except for aldicarb (up to 4 days after application). 

Comer et al. (2) therefore evaluated the effect of exposure to carbaryl (1-naphthyl methylcarbamate) on formulating plant workers and on workers applying carbaryl to fruit orchards with a tractor-drawn air-blast sprayer. However, information was still needed on the persistence of carbaryl in apple orchards and on the resultant exposure of workers who re-enter treated orchards. Further, no studies had been done on other types of crops. The present study was undertaken to determine the exposure of agricultural workers to carbaryl as a function of type of formulation, application equipment, application method, and type of work performed (i.e., mixer-loader, applicator, flagman, bystander, and apple thinners). 

Applicators. The workers involved in the ground applications of carbaryl received considerably less exposure than the mixer-loaders. Most of the exposure was to the hands and was attributed to adjusting the nozzles on the spray equipment. Thus, for the ground application of the 80S formulation, the total HDE was 1.6 mg/h and the HDE to the hands was 1.5 mg/h. For a similar application of Sevimol-4, the total HDE was 2.8 mg/h and the HDE to the hands was 2.7... 

Bystanders. The bystander had the lowest exposure to carbaryl of all the workers monitored. In keeping the bystander within 100 feet and downwind of the ground applicator, the bystander often had to walk into the field while it was being treated. This practice resulted in exposure when the hands of the bystander touched the crop foliage. Thus, with peas, there was no exposure because the plants were too small at the time of spraying for any inadvertent contact, but with relatively mature potatoes, measurable residues were deposited on the bystander. For example, when 80S was applied to this crop, the bystander had a total HDE of 0.5 mg/h... 

Figure 1. Degradation of carbaryl residues on apple leaves plotted on semi-log graph. Key O, 0.5 lb/100 gal application rate and , 1.0 lb/100 gal application...

Figure 2. Residues of carbaryl found on thinners hands (Y) as a function of residues found on leaves (X) for 0.5 and 1.0 lb/100 gal application rates (2.0 lb AI and 4.0 lb Al/acre) (Y — 690X — 45 correlation coefficient (r) = 0.99).

Carbaryl. Carbaryl has been field tested in Canada at a rate of 0.28 kg/ha applied twice. This rate is considerably lower than application rates widely utilized for forest insect control programs in the United States. At this low application rate no... 

Abad, A. and A. Montoya. 1997. Development of an enzyme-linked immunosorbent assay to carbaryl. 2. Assay optimization and application to the analysis of water samples. J. Agric. Food Chem. 45 1495-1501. 

Nunes, G.S., M.P. Marco, M. Farre, et al. 1999. Direct application of an enzyme-linked immunosorbent assay method for carbaryl determination in fruits and vegetables. Comparison with a liquid chromatography-postcolumn reaction fluorescence detection method. Anal. Chim. Acta 387 245-253. 

Abad, A. and A. Montoya. 1995. Application of a monoclonal antibody-based elisa to the determination of carbaryl in apple and grape juices. Anal. Chim. Acta 311 365-370. 

The application of pesticides is also limited by regulation, which imposes wide buffer zones, and by community.action to veto pesticide application. Carbaryl (1-naphthyl N -methyl carbamate, Sevin ), acephate (0, S-dimethyl acetylphosphoroamido-thioate, Orthene ), diflubenzuron (N -[ [(A-chlorophenyl)amino]-carbonyl]-2,6-difluorobenzamide, Dimilin ), and other insecticides are effective against the larvae. 

Our first objective was to determine whether microencapsulated methyl parathion Is unique In Its property to be carried back to the hive by bees. To that end a mixture of three commonly used insecticides along with MMP was applied to a plot of blooming rape. The agents were azlnphos-methyl (Guthlon), parathion, and carbaryl (Sevin). By using a mixture on a single plot the effects of variation In bee visitation were eliminated and the tendencies to be carried to the hive could be measured by the relative residue levels in the pollen samples. Five applications were made over a period of seventeen days. Pollen samples were collected from hives placed near the field after two, three, four, and five successive applications approximately two days after each application was made. The application rates were doubled for the last two applications. The data are shown In Table I. 

Although the residues found cannot be correlated with the application rates, the results nevertheless demonstrate that all insecticides used in this test were absorbed on the pollen and carried back to the hive. These observations have been confirmed using other approaches by USDA and university researchers at the University of Wisconsin, who reported that foraging bees have brought back to their hives permethrln, carbaryl, and methyl parathion emulslfiable concentrate (MPEG) when applied to shedding corn.Q)... 

Another area of concern is the residual life of a pesticide once it is brought back to the hive. Microencapsulated methyl parathion was at one time believed to represent a special hazard because of its controlled release feature. Thus methyl parathion from MMP was reported to persist in stored pollen for up to 17 months.( ) Unfortunately, little is known about the persistence of insecticides in honey bee combs etnd the subsequent effects of their residues on the honey bees. Carbaryl has been shown to persist for at least eight months in colonies ( ) euid permethrln for at least seven months.O) Recently, USDA researchers at the University of Wisconsin studied samples from two bee kills that apparently Involved methomyl and MMP applied to sweet com. Samples were collected to determine, among others, whether methomyl persisted in combs. Analysis demonstrated that eight months after the insecticide application, residues of 0.03 ppm of methyl parathion and 0.03 ppm of methomyl ( 5) remained, even though the latter is considered to be a short-residual pesticide. 

Studies comparing MMP with other pesticides have also shown that it does not represent an unusual hazard to bees. In Wisconsin application on pollen-shedding corn of carbaryl plus parathion... 

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