ETHYLENETHIOUREA: A Special Report on the Occurrence of Ethylenethiourea as a Terminal Residue Resulting from Agricultural Use of Ethylenebisdithiocarbamate Fungicides

Abstract

- Ethylenethiourea (ETU) is a manufacturing, processing, and metabolic. product of the ethylenebisdithiocarbamate (EBDC) fungicides. Toxicological studies indicate that ETU may produce goiterogenic, tumorogenic, and teratogenic effects in laboratory animals, raising the concern that residues may be found on agricultural commodities. Thin-layer chromatography, polarography, and radioisotopic methods are used for ETU analysis, though electron capture or flame photometric gas-liquid chromatography are the preferred methods because of their greater sensitivity, specificity, and accuracy. Derivatization of ETU is usually necessary prior to gas liquid chromatography. ETU is degraded by oxidative reactions in biological systems and by photolytic reactions, especially in the presence of photosensitizers. Degradation products of ETU detected in photochemical, soil, and plant systems include 2-imidazolidinone (EU), 2-imidazoline, 2,4-imidazolidinedione (hydantoin), and 3-(2-imidazolin-2-yl)-2-imidazolidinethione (Jaffe's base). Ethyleneurea, oxalic acid, glycine, and urea have been detected in animal urine. The amount of ETU residue detected in the environment depends on the amount applied with the EBDC fungicide, the rate of formation as a result of EBDC degradation, and the rate of degradation. Residues of ETU have been detected in crops receiving EBDC fungicides. Levels of ETU detected are well below 0.1 ppm and occur primarily as surface residues.