Originally posted by @wildgrass
... until you inhale a couple of them and we see what concentration of Molybdenum and Tungsten and Selenium causes cancer.
Maybe, if those substances can actually interact with the body. They might be bound so they can't touch human cells. It's still a new field and they night find human compatible components.
Like the study of catalytic converters which usually has some platinum and the like, now have found much cheaper alternatives that work almost as well as platinum but for 1% of the price, like iron oxides and such.
Just saying this is just the beginning of a new technology and there is no way to predict what will come of it in 50 years.