TOXIC AND SUBLETHAL EFFECTS 



GENERAL 



Information is lacking or scarce on the biological properties of PCDD 

 isomers, except 2,3,7,8-TCDD. The latter has been associated with lethal, 

 carcinogenic, teratogenic, reproductive, mutagenic, histopathologic, and 

 immunotoxic effects. There are substantial inter- and intraspecies 

 differences in sensitivity and toxic responses to 2,3,7,8-TCDD. Typically, 

 animals poisoned by 2,3,7,8-TCDD exhibit weight loss, atrophy of the thymus 

 gland, and eventually death. The toxicological mechanisms are imperfectly 

 understood. 



TERRESTRIAL INVERTEBRATES 



Reinecke and Nash (1984) reported that two species of earthworms 

 ( Allolobophophora caliginosa , Lumbricus rubellus ) showed no adverse effects 

 when held for 85 days in soils containing grossly elevated levels of 5 ppm of 

 2,3,7,8-TCDD, but both species died at 10 ppm. In soils containing lower 

 concentrations of 50 ppb of 2,3,7,8-TCDD, earthworms accumulated 5X soil 

 levels in 7 days. There was no avoidance of soils contaminated with 

 2,3,7,8-TCDD, suggesting indifference. No surface penetration of dioxins into 

 the body of earthworms was noted, and there was no biological breakdown of 

 2,3,7,8-TCDD during digestion as judged by the absence of mono-, di-, and 

 tri-CDD's in excrement. Worm-worked soils had 2,3,7,8-TCDD retention times of 

 80 to 400 days, suggesting that earthworms may significantly alter half-time 

 patterns of 2,3,7,8-TCDD in soils (Reinecke and Nash 1984). 



Mutagenic responses were produced in Escherichia coli and certain strains 

 of Salmonella typhi murium bacteria by 2,3,7,8-TCDD, but not by octa-CDD (Vos 

 19787^ Further, chromosomal aberrations were induced in at least one species 

 of higher plant and mammal (Ramel 1978). It must be concluded at this time 

 that 2,3,7,8-TCDD is mutagenic or has mutagenic potential. 



AQUATIC ORGANISMS 



No data were available on lethal and sublethal effects of any PCDD isomer 



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