Exposure carbaryl

Davidson, C., Benard, M.F., and Shaffer, H.B. et al. (2007). Effects of chytrid and carbaryl exposure on survival, growth and skin peptide defenses in foothill yellow-legged frogs. Environmental Science and Technology 41, 1771-1776. 

There are, however, several apparent discrepancies. The first is the ratio calculated from literature values dealing with carbaryl exposure to pesticide applicators and fruit thinners in an apple orchard (4) This ratio (about 0.6x10 cm h ) was considerably lower than the range seen in Table IX. The difference may be due to the fact that Maitlen et al. (4) measured total and not dislodgeable foliar residues, thus leading to lower values than those obtained by us and others. 

Rut ser gloves worn applicators qpparently mlnlinized hemd exposure DDVP application euid handling resulted in 0.024 pg/cs /hr. Hand contamination accounted for 0.9% of tot d. dermal exposure (Table 1) as oompared with 87% in carbaryl exposure studies (11, 13) where hand protection was not worn. The fact that DDVP was recovered from the hands of the lioators in all 20 treatments denonstrated the need to stress hand protection and decontamination even when ruliher gloves are worn. 

Use of oximes is well accepted for OP exposures, but their role in carbamate poisoning is controversial. Animal studies have shown oxime use can increase toxicity when treating carbaryl exposure (Lifshitz et al., 1994). Therefore, there is a general guideline that oximes should be avoided if a carbamate exposure is suspected. One case series reported the routine use of oxime therapy for carbamate exposures in children (Lifshitz et al., 1994). Marked clinical improvement was observed in all patients, regardless of whether they were exposed to an OP or a carbamate. In addition to the retrospective review of cases, the authors completed an in vitro study of oxime use with carbamate toxicity and discovered that oximes play a minor role in direct reactivation of human carbamylated AChE. Due to this finding, the authors concluded that the current guideline to avoid oxime use in a carbamate exposure is valid. 

Johnston, G.O, Walker, C.H., and Dawson, A. (1994). Potentiation of carbaryl toxicity to the hybrid red-legged partridge following exposure to malathion. Pesticide Biochemistry and Physiology 49, 198-208. 

Stoner, A., W.T. Wilson, and J. Harvey. 1985. Honey bee exposure to beeswax foundation impregnated with fenvalerate or carbaryl. Amer. Bee Jour. 125 513-516. 

Edmiston, C.E., Jr., Goheen, M., Malaney, G.W., and Mills, W.E. Evaluation of carbamate toxicity acute toxicity in a culture of Paramecium multlmlcronucleatum upon exposure to aldicarb, carbaryl, and mexacarbate as measured by a Warburg respirometry and acute plate assay. Environ. Res., 36(2) 338-350, 1985. 

The general chemical structure of N-methyl carbamate is shown in Fig. 4.4. Common N-methyl carbamates in use today include aldicarb, carbofuran, methiocarb, oxamyl, and carbaryl. N-methyl carbamates share with organophosphates the capacity to inhibit cholinesterase enzymes and, therefore, share similar symptomology during acute and chronic exposure. 

National Institute for Occupational Safety and Health Criteria for a Recommended Standard. .. Occupational Exposure to Carbaryl, DHEW (NIOSH) Pub No 77-107, pp 17-96, 109-117. Washington, DC, US Government Printing Office, 1976... 

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). 

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. 

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

Analytical Procedures. The extracts from exposure pads, hand rinses, and apple leaves were evaporated to dryness in the 40-45°C water bath, and the carbaryl residues were determined by the procedure of Maitlen and McDonough (4). In this procedure, the residues were hydrolyzed with methanolic potassium hydroxide to 1-naphthol which was then converted to the mesylate derivative by reaction with methanesulfonyl chloride. The carbaryl mesylate was quantitated with a Hewlett Packard Model 5840A gas chromatograph (GLC) equipped with a flame photometric detector operated in the sulfur mode. The GLC column was a 122 cm x 4.0 mm I.D. glass column packed with Chromosorb G (HP) coated with 5% OV 101. The column was operated at a temperature of 205°C with a nitrogen flow rate of 60 ml/min. 

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. 

Iwata et al. (5) published a procedure for the extraction of dislodgable residues from foliage. It involved the extraction of residues with a water-detergent solution and then partitioning the residues from this solution into dichloromethane. In our work, the total carbaryl residues were extracted directly from apple leaves with dichloromethane, and are not equivalent to dislodgeable residues. Nevertheless, because the total extractable residues correlate with HDE, they have the same value for predicting human exposure as... 

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