William F. Grant
1979
Citations
0
Influential Citations
51
Citations
Journal
Mutation research
Abstract
Abstract 2,4,5-T (2,4,5-trichlorophenoxyacetic acid) is a herbicide that is used primarily for brush and weed control on rangelands and pastures, and rights-of-way. Commercial formulations contain up to 0.1 ppm of the contaminant dioxin (TCDD) which has been shown to cause birth defects and tumors in animals when administered in concentrations below 100 ppt. In many studies (especially in literature prior to 1970) it is not clear whether the reported genotoxic effects are the result of the 2,4,5-T per se, the TCDD contaminant, or a combination of both. The possible harmful effects of 2,4,5-T to humans and wildlife came into prominence during the Vietnam war when the American Army used Agent Orange (equal parts of 2,4-D and 2,4,5-T) for defoliation purposes. The reported increases in the incidence of congenital malformations and certain types of cancer in defoliant-treated regions led to the Bionetics Research Laboratory study in which 2,4,5-T was reported to cause developmental abnormalities in rats. Subsequent research showed that 2,4,5-T is a clastogen producing chromosome aberrations including bridges and micronuclei in a variety of animal and plant species. In addition, 2,4,5-T induces cell enlargement, lengthens the duration of the mitotic cycle, extends DNA synthesis, induces mitosis and causes chromosome contraction, stickiness, and sticky bridges, all at low concentrations. C-Mitoses, multinucleate cells, polyploidy, reduced fertility, and species resistance have also been reported. In vivo production of chromosome aberrations in humans is inconclusive. The emulsifiers and solvents in commercial preparations of 2,4,5-T have also been shown to induce chromosome aberrations. 2,4,5-T is only weakly mutagenic with positive reports recorded in only 2 of 4 sex-linked lethal tests in Drosophila and in one of two studies on Saccharomyces cerevisiae . Only two studies on carcinogenicity from 2,4,5-T are reported with contradictory results. While the data on teratogenicity are not clear-cut, the number of positive reports suggest that 2,4,5-T is definitely teratogenic both with and without TCDD and that 2,4,5-T and TCDD may potentiate teratogenic activity. Further studies, including epidemiological investigations of human groups exposed to 2,4,5-T, are required to supplement insufficient data and to resolve contradictory evidence.