Thiabendazole Risk Characterization Document

Thiabendazole (TBZ) is a fungicide that is used for postharvest application to fruit and vegetables. It can also be mixed with paint to inhibit the growth of mildew. During 1982 to 1992, a total of 17 human illness/injury cases associated with exposure to TBZ were reported in California. Most of these cases were skin rashes that occurred following handling treated fruit in packing facilities. When given orally, TBZ is rapidly absorbed and almost completely metabolized by humans. The two major metabolites are the glucuronide and the sulfate ester of 5-hydroxy thiabendazole. TBZ was used for several years as a human anthelmintic in the U.S., and is still used for this purpose in some countries. No dermal absorption study is available to indicate the dermal absorption rate. Therefore, a dermal absorption of 100% was assumed to estimate human exposure in terms of absorbed dosage. There were no worker exposure studies for TBZ. Surrogate data and the pesticide handler exposure data base (PHED) version 1.1, were used to estimate exposure to workers potentially exposed to TBZ. The estimated absorbed daily dosage (ADD) for packers and sorters handling treated fruit and painters applying paints mixed with TBZ ranged from 16 to 100 μg/kg/day. This exposure assessment document was prepared because animal toxicology studies have shown that TBZ may be a teratogen. It will be a part of the risk characterization document for TBZ. Department of Pesticide Regulation Worker Health and Safety Branch Human Exposure Assessment