Herbicide exposures attributed

TCDD, the most toxic of the 75 dioxin isomers and possibly the most toxic manufactured chemical, contaminates phenoxy herbicides during the production process (Demers and Perrin 1995 Klaassen 1985). Conflicting literature addresses TCDD lethality in humans. Some reviews deny that human deaths result from systemic effects of TCDD (Demers and Perrin 1995). Others describe successful suicides with phenoxy herbicides (Nielsen et al. 1965). Despite extensive reports of numerous medical conditions from TCDD, the literature confirms only chloracne and transient mild hepatotoxicity in humans. Table 1-6 lists the various, but unconfirmed, signs and symptoms associated with human poisonings. Table 1-7 lists the unconfirmed psychiatric symptoms attributed to TCDD exposure. 

It is estimated that 18% of all new Wilms tumours, affecting the kidneys of Brazilian children, are attributable to pesticide exposure of their parents. Consistently elevated risks were seen among children whose fatlier or mother carried out farm work which involved the frequent use of pesticides. As elsewhere, many pesticides are used in Brazil and researchers estimated that 73 insecticides, 42 fungicides and 59 herbicides are in use. Atrazine and dichlorvos are particularly widely used and both are rated as possibly carcinogenic by the International Agency for Research in Cancer. 

Like most other classes of pesticides and herbicides, the degree of toxicity of triazines has been found to vary with compounds. Thus, the toxicity may not be solely attributed to the triazine ring. For example, while substances such as atrazine, metribuzin, and cyanazine are moderately toxic by all routes of exposure, compounds such as prometryn and propazine have a very low order of toxicity. However, no cases of human poisonings have been reported. A few selected triazine herbicides are discussed individually in the following sections. 

Metam-sodium, a broad-spectrum soil fumigant, is a fungicide, insecticide, nematocide, and herbicide. Richter [55] states that allergic contact dermatitis to metam-sodium (methyl isothiocyanate) may be significant among exposed persons. In his opinion, metam-sodium is a potent sensitizer. He also attributed hepatitis in one patient to exposure to metam-sodium. 

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