Carbaryl workers

Workers exposed to carbaryl dust at levels that occasionally reached 40mg/m had slight depression in blood cholinesterase activity but no clinical symptoms. In general, cases of occupational poisoning by carbaryl are rare because mild symptoms appear long before a dangerous dose is absorbed, furthermore. 

Most of the older methods of fluorimetric analysis of pesticides involved hydrolysis to form fluorescent anions. Co-ral (coumaphos) [147] was hydrolyzed in alkali to the hydroxybenzopyran, which was subsequently determined by means of its fluorescence. Guthion (azinphosmethyl) was hydrolyzed to anthranilic acid for fluorimetric analysis [148,149]. A method was developed [150] for Maretin (N-hydroxynaphthalimide diethyl phosphate) in fat and meat which involved hydrolysis in 0.5 M methanolic sodium hydroxide followed by determination of the fluorescence of the liberated naphthalimide moiety. Carbaryl (1-naphthyl N-methylcarbamate) and its metabolites have been determined by a number of workers using base hydrolysis and the fluorescence of the resulting naphtholate anion [151-153]. Nanogram quantities of the naphtholate anion could be detected. Zectran (4-dimethylamino-3,5-xylyl N-methylcarbamate) has been determined by the fluorescence of its hydrolysis product [154]. The fluorescence behaviour of other carbamate insecticides in neutral and basic media has been reported [155]. Gibberellin spray used on cherries has been determined fluorimetrically after treatment with strong acid [156]. Benomyl (methyl N-[l-(butylcarbamoyl)-2-benzimidazolyl]carbamate) has been analyzed by fluorimetry after hydrolysis to 2-aminobenzimidazole [157]. 

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). 

Table 1 shows the number and types of workers and the various situations in which these workers were monitored for dermal exposure to carbaryl. Formulations of carbaryl that were evaluated included 80S, a wettable powder containing 80% active carbaryl 50W, a wettable powder containing 50% active carbaryl Sevimol 4, a liquid suspension of carbaryl in molasses containing 40% active ingredient and XLR, a water based flowable containing 4 lbs active carbaryl per gallon. 

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. 

Table I.—Operations in which workers were monitored for dermal exposure to carbaryl.

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... 

Thinners. Carbaryl is applied to apple trees as a thinning agent, but sometimes it is necessary to send workers into the treated orchard to finish the thinning by hand. For this situation, we studied the relationship between the persistence of carbaryl on apple leaves and the exposure to thinners working in this orchard. 

A.2. The work described by McFadden and co-workers is an extension of the wire transport detector (section Z.A.l). Because the wire will transport only about It of the total effluent into the vacuum locks, sample utilization is low. Therefore, the wire was replaced with a stainless-steel ribbon (3.2 mm wide, 0.05 mm thick) such that effluent was carried into the vacuum lock at a rate of 1 ml/min, thus achieving efficient sample transport to the ion source region (Fig. 2). Depending on the nature of the sample, the efficiency of sample vaporization and other operational processes, sample utilization in the range 30-50% was achieved. The detection limit for the system was less than 1 ng for carbaryl,... 

The use of carbaryl has not resulted in illnesses among workers mixing-loading or applying the pesticide and no reentry interval has been established for this pesticide in California. Cholinesterase inhibition is considered to be the major toxic effect of carbaryl. Carbaryl (500 mg/kg) topically applied to the back of the rabbit inhibited 50% of the red cell ChE activity 24 hr after application and activity returned to pretreatment values after 72 hr (21). In the rat study reviewed in this paper, a topical dose of 417 mg/kg did not produce ChE inhibition 24 hr after application indicating that the rate of absorption was low or carbaryl was metabolized in the skin to non-OiE inhibiting products. 

Thlodicarb is a new insecticide being marketed by Union Carbide as Larvin for the control of insects on cotton. Thiodicarb is metabolized in the rat to acetamide, acetonitrile, CO, methomyl, and methomyl metabolites. No illnesses have been reported among applicators or field workers coming in contact with this carbamate insecticide. Thiodicarb is somewhat more persistent on crops than methomyl and is less toxic dermally in rabbit studies. The dermal dose-CliE response study showed that a dose of 33 mg/kg produced 50% ChE inhibition 24 hr. after the application of the dose, while a dose of 87 mg/kg of thiodicarb did not produce more inhibition than a dose of 44 mg/kg. The poor solubility of this carbamate in water/lipid most likely prevented the absorption of additional quantities of thiodicarb, thereby reducing its toxicity. Thiodicarb was found in lower concentrations in skin than either parathion or carbaryl during the percutaneous absorption studies. The concentrations in plasma. 

Dermal exposure to captan and benomyl by strawberry harvesters has been the subject of several previous studies (1.2.3). This field study was designed to test a number of hypotheses and the reproducibility of dermal exposure rate measurements taken under field conditions. Most of our past studies have not been designed for a particular pesticide but were modified to accommodate the pesticide chosen by the grower to control a certain pest. In this case, the pesticide was carbaryl (1-naphthyl N-methylcarbamate) an insecticide used to control the spittlebug and leafroller. Our results could then he compared with those obtained by Maitlen and co-workers (A) who studied workers exposed to carbaryl in an apple orchard. Furthermore, attempts will be made to test possible positive correlations between age and dermal dose rate versus productivity and dermal dose rate versus age of harvesters. Difference of dermal exposure due to age or... 

Leonard and Yeary (230) studied the occupational exposure to four insecticides and two fungicides among workers using handheld equipment when spraying pesticides on trees and shrubs. They reported concentrations of 0.01-0.07, 0.001-0.04, and 0.001-0.007 mg/m for carbaryl, diazinon, and dicofol, respectively. These levels were well below the acceptable ACGIH exposure limits of 5.0, 0.1, and 1.0 mg/m for these pesticides, respectively. 

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