Generally, exposure to dioxins in mammals has a greater effect on growth, survival, and reproduction of animals than on tumor formation. Atrophy of the thymus appears to be the most consistent ecotoxicological effect in mammals. The developing mammalian fetus is especially sensitive to dioxins, and maternal exposure to high environmental levels has been shown to result in increased frequencies of stillbirths. At lower exposure levels, response in offspring generally involves teratogenic effects such as cleft palate and spinal deformities.
While laboratory findings using mice and rats appear to be applicable when extrapolating exposure to wild populations of mammals in field observations and experiments, there is some debate whether laboratory rodents are representative of all wild mammal species, or even the most sensitive species. It is generally recognized that mink is the most sensitive mammalian species to dioxin exposure, and may be about 1 order of magnitude more sensitive than laboratory rodents.
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