My headcanon is that Australium is a rare isotope of gold because it has the same electron configuration as gold.
Gold is Au because of the word ‘Aurum’. Australium could very well be the same element as gold except a difference in neutrons, hence it may be an isotope.
Which leads to the question.. is it a stable isotope? Or is it radioactive?
The harmful effects of radioactivity were not discovered until the late 40′s. So the Administration might possibly know whether or not Australium is actually harmful.