Teratogenicity dioxins

The detection of a potent dioxin impurity in a major herbicide has focused attention on the nature of chlorinated impurities in pesticides, and in a larger sense, impurities in all chlorinated industrial compounds used extensively in man s environment. The present 2,4,5-T controversy is overshadowed by the dioxin problem. Major disagreement still exists on their relative contributions to the teratogenic effects observed in chicks and the validity of interpretation of high dosage rates used to achieve these effects. We have avoided any assessment of the health-related aspects of dioxins but have dealt almost exclusively with dioxins as an environmental entity. 

Wannemacher, R., A. Rebstock, E. Kulzer, D. Schrenk, and K.W. Bock. 1992. Effects of 2,3,7,8-tetrachlorodibenzo-/>-dioxin on reproduction and oogenesis in zebrafish (Brachydanio rerio). Chemosphere 24 1361-1368. Webb, K.E. (ed.). 1984. Dioxin lessons from the Missouri experience. Bull. Environ. Contam. Toxicol. 33 629-734. Weber, H., M.W. Harris, J.K. Haseman, and L.S. Bimbaum. 1985. Teratogenic potency of TCDD, TCDF, and TCDD-TCDF combinations in C57BL/6N mice. Toxicol. Lett. 26 159-167. 

At doses of 0,01-0,05 mcg/kg, dioxin has mutagenic effect on lymph cells in mice. Embryo- and gonado-toxicity, as well as teratogenicity, are also observed. 

TCDD (a dioxin derivative) tested positive as a teratogen in rats. 

After TCDD (dioxin) had been found to be a contaminant in the herbicide 2,4,5-T and was tested as a teratogen in rats in 1968, the herbicide was outlawed by the EPA on most food crops. A complete discussion of this chemical and its history is given in Chapter 22, Section 4.1. 

The teratogenic potential of chlorophenoxyacetic acid derivatives cannot be unambiguously evaluated without consideration of the dioxin contaminants formed from the monomers by a 2-step condensation at elevated temperatures ... 

Perhaps the most catastrophic industrial accident involving dioxin occurred in S6veso, Italy in July, 1976. Here an entire community surrounding a trichlorophenol feedstock plant was contaminated 736 individuals were in the maximum exposure zone 4699 were in a less exposed zone, and 31.800 individuals were in the zone of least exposure. There were four spontaneous abortions and thirty voluntary interrupted pregnancies. The dose-related increase in chloracne occurred, but the spate of voluntary abortions obscured the teratogenicity data. 

Dioxins - global superecotoxicants, which have strong mutagenic, immunosuppressive, carcinogenic, teratogenic, and embryotoxic activity. 

Couture LA, Abbott BD, Bimbaum LS. 1990. A critical review of the developmental toxicity and teratogenicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin Recent advances toward understanding the mechanism. Teratol 42 619-627. 

Hassoun E, D Argy R, Dencker L, et al. 1984a. Teratogenicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin in BXD recombinant inbred strains. Toxicol Lett 23 37-42. 

Sparschu GL Jr, Dunn FL Jr, Row VK Jr. 1971b. Study of the teratogenicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin in the rat. Food Cosmet Toxicol 9 405-412. 

Recent studies have indicated that humans may be exposed to 2,3,7,8-tetrachlorodibenzo-p- dioxin(2,3,7,8-TCDD), a toxic and teratogenic substance in laboratory animals (1). A fraction of beef fat samples from cattle known to have grazed on pasture treated with herbicide 2,4,5-T (which contains trace quantities of 2,3,7,8-TCDD) have been reported to contain low part per trillion (ppt) levels of 2,3,7,8-TCDD (2,3) Two studies of bovine milk reported no detectable chlorodioxins however (4,5). Combustion processes have been reported to produce chlorinated dioxins which enter the air as fly ash and soot (6.7.8). Three different studies of human milk have been carried out by various workers to determine if humans contain detectable concentrations of 2,3,7,8-TCDD (9,20,22). 

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