Hamster, 2,3,7,8-TCDD toxicity

Dioxins are extremely toxic compounds. LD50 for the most toxic dioxin (2,3,7,8-TCDD) at intragastric injection was 0,6-2,0 mcg/kg for guinea pigs, 3000-5000 mcg/kg for various species of hamsters, about 70 mcg/kg for monkeys and 25-45 mcg/kg for rats. 

Toxicity data in animals indicated that similar effects occur after exposure to CDDs by oral, dermal, or parenteral routes. Toxicokinetic data in mice showed that 2,3,7,8-TCDD hepatic levels were similar following oral, intraperitoneal, and subcutaneous exposure (Nau and Bass 1981). However, recent data in rats showed that intratracheal administration of a 2,3,7,8-TCDD dose resulted in a relatively higher accumulation of 2,3,7,8-TCDD in the liver than after oral administration of the same dose (Diliberto et al. 1996). Intraperitoneal administration of 2,3,7,8-TCDD was less toxic than oral dosing in acute-exposure experiments with hamsters (Olson et al. 1980a). 

The comparative data on the acute lethality of the chlorinated dibenzo-p-dioxins and furans in laboratory animals are included in Table I. Evaluation of these data indicates that TCDD is the most toxic of this series. For the guinea pig, the single dose oral LD50 value is reported to be 0.6-2.0 yg/kg B.W., while in the hamster the single dose oral LD50 value is reported to be 1157-5051 yg/kg B.W. 

The biologic factors that account for this large difference (up to 5000 fold) in species susceptibility in acute toxicity have not yet been defined. The other laboratory animal species (mouse, rat, monkey, rabbit and dog) in which TCDD has been tested have single dose oral LD50 values that are found to be somewhere between the most sensitive species (guinea pig) and the least sensitive species (hamster). 

Berg et al ( 4) reported that uptake of TCDD and other dioxins and furans from dietary fly ash was less than H% in rats, 3.7% in guinea pigs, and 2.4 % in hamsters. Kuehl et al ( ) showed a minimum of 37.5% uptake of TCDD from contaminated lake sediments into carp. In an aquarium study, Kuehl et al ( ) found a maximum bioavailability of 2.1% to fish. Silkworth et al ] ) demonstrated toxicity of soot from a PCB fire however, the extremely low levels of TCDD in these materials make it difficult to relate these results to bioavailability of dioxins. 

The carcinogenic action of 2,3,7,8-TCDD has been studied on Syrian golden hamsters, which otherwise, showed maximum resistance to the toxic effect of this compound (Rao et al. 1988). TCDD was fully carcinogenic in hamsters, developing squamous cell carcinomas of the skin of the facial region from a total dose of 600 /irg/kg by a subcutaneous or intraperitoneal route within... 

Acute toxicity studies with 2,3,7,8-TCDD have shown marked differences - up to 8400 times - between the single oral LD50 dose for the guinea pig and the hamster (Cricetus sp.). The acute oral LD50 value of 0.6 xg/kg BW for guinea pigs suggests that 2,3,7,8-TCDD may be the most toxic compound ever tested on small laboratory animals. The unusual resistance of hamsters may be associated with its enhanced rate of metabolism and excretion of... 

Table 4.1 shows that the toxicity data vary in a huge range for different animal species, which mandates extreme caution in drawing conclusions. Human toxicity data are not known for dioxins, but some observations imply that people are more resistant to poisoning than hamsters. The right side of the table shows toxicity data for other substances. It is clear that TCDD is not among the most poisonous substances. 

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