Carbaryl variation

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. 

The stratum comeum, composed of keratinized dead cells that are continually being replaced, is the first major barrier to chemical agents. The barrier qualities of the stratum comeum depend on a number of factors, including its location on the body, which affects thickness, and how much hair is present. Thus, hair follicles and sweat glands can either provide charmels through the stratum comeum, and thereby bypass its barrier attributes, or at least provide increased surface area for penetration of compounds, since a number of compounds were shown to penetrate faster in hair follicle-rich areas (lUel et al, 1991). Maibach studied three radiolabeled pesticides -parathion, malathion, and carbaryl - for their permeability at 13 different anatomical sites in humans (Maibach et al, 1971). Variations in percutaneous penetration were observed higher penetration of the pesticides occurred at the abdomen and dorsum of the hand. 

Internationally recognized food standards, i.e.. Codex standards, have been established for more than three decades as standards for facilitating international trade and solving trade disputes. One of the many standards established by Codex is the maximum residue limit (MRLs) for pesticides on food commodities in international trade. Codex MRLs are used as national standards by many countries however, some countries continue to establish their own MRLs or tolerances and impose zero tolerance to residues of pesticides on imported crops which do not have nationally/regionally agreed-upon MRLs. Therefore, the acceptance of Codex MRLs among countries is different. An example of the variation in MRLs for carbaryl in some commodities is shown in Table 1. 

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