  If the Unnaturalness Argument is intended to be an extrinsic objection, the link between unnaturalness and wrongness will most likely be supported by pointing to possible adverse consequences for the environment, public health, or the animal subject itself. Adverse environmental consequences have not received much discussion, probably because they are presumed to be adequately managed through standard guidelines and regulations regarding the use of animals in laboratory research. The possibility of a public health crisis arising from a transmissible infection crossing species boundaries, a significant concern with xenotransplantation, is greatly reduced when the source of the biological material is human and the recipient a non-human animal confined to a laboratory. (It should be noted, though, that transmission of a porcine virus to human cells in a human/porcine chimera has already been demonstrated (Ogle et al. 2004).) Adverse consequences for the animal are important to address, but their implications will depend on the moral status of the animal, an issue addressed by the Borderline-Personhood Argument. On any of these bases of support, the proponent of an extrinsic unnaturalness argument would not be committed to the conclusion that everything unnatural is unethical, since unnaturalness is not necessarily connected with these kinds of bad consequences, and even when it is connected with bad consequences, the act may be justified on other grounds. 