A survey of the embryotoxic effects of TCDD in mammalian species.

Only limited data are presently available on the embryotoxic effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). This is true for the number of animals used per experimental group, especially in the higher dose range, as well as for the number of different species of experimental animals tested. There has been an understandable reluctance to investigate these highly toxic compounds, because of the hazards of contaminating animal quarters and the risk to personnel. Nevertheless, we feel that the data available allow a rough estimate of the dangers that may be encountered with exposure to such dioxins during pregnancy. The possibility that TCDD might have certain types of embryotoxic effects was realized for the first time when Courtney et al. (1) reported their data on the teratogenic effect of 2,4,5-T. Substances like TCDD have been known for some time (2-4) to be contaminants of chlorinated phenols and derivatives of such compounds and they were thought to be responsible for an intoxication called chloracne (5). Some commercial samples of 2,4,5-T apparently were rather highly contaminated with these extremely toxic substances.