Herbicides and congenital malformations: a review for the paediatrician

The herbicides 2, 4, 5-T and 2, 4-D are relatively non-toxic to primates, in acute exposure. Dioxins, which have occurred as impurities in these two herbicides, manifest universal biological toxicity. The best understood dioxin TCDD, has, in susceptible strains of mice, a very low teratogenic minimal effective dose of 1-10 micrograms/kg. This fact has engendered an era of uncertainty about the potential teratogenic effects of herbicides, in the context of potential human exposure. This paper reviews current knowledge concerning herbicide teratogenesis following maternal exposure. Because of species specificity of teratogenic agents, it is not possible to extrapolate from effects in lower animals to potential effects in humans. It remains a fact however that all proven human teratogens have parallel animal models. Following maternal exposure to herbicides and to dioxins, it has not been possible to produce teratogenic effects in primates, although fertility may be affected. Epidemiological reports from Hungary, Italy (the ICMESA accident), New Zealand, the United States, Europe and Australia have not revealed any positive evidence to indicate that a human herbicide teratogenic syndrome exists.