Summary of Toxicity Data on Methyl Isothiocyanate (MITC)

Abstract

In order to investigate the toxicological properties of MITC and its formulations, a number of animal toxicity studies were conducted. In conclusion MITC is a toxic substance and shows severe corrosive effects and inflammation to skin and mucous membranes. In addition, it's vapours irritate mucous membranes and are lachrymatory.
In a sensitization test in guinea pig, the test substance showed a mild skin sensitizing potential. In sub-chronic studies administered by oral gavage to rats and mice, MITC gave considerable dose-related toxic effects (e. g. stomach lesions, small round cell infiltration of the liver, slight spermatogenic disorder, decreased body weight gain, decreased ovary weight in mice, etc.) particularly at higher doses. A repeat study on mice to assess the effect on ovaries did not give any treatmentrelated effects in these organs. Long term chronic oral toxicity/oncogenicity studies in which MITC was administered to rats or mice in the drinking water, did not show any of the dose-dependent or substance-related effects that had been found in the sub-chronic studies. The only significant changes in the long term studies were a decreased body weight gain and water consumption in the high dose groups.
MITC showed no oncogenic activity and had no adverse effect on reproductive capacity or in teratogenicity studies. In a number of mutagenicity studies, Rec-assay, reverse mutation, mouse micronucleus test, unscheduled DNA synthesis, sister chromatid exchange and forward mutation, MITC was negative although a in vitro chromosome aberration in Chinese hamster's cells was positive. Whilst in human lymphocytes it was negative. Di-Trapex and Trapexide were initially registered as soil fumigants in 1976 and 1982, respectively.
Withholding values for registration have been set at 0.05ppm on fruits, 0.2ppm on vegetables and tea, and 0.5ppm on potatoes. MITC is a toxic substance with severe irritant effects on skin and mucous membranes, therefore, proper application in accordance with the recommended handling precautions including the use of full protective clothing must be followed. Then products containing MITC may not only be useful but also safe to users and applicators.