We don't know if it can be a long term exposure. We don't know at what rate they are expelled from a live person. And One thing is for sure. Cell Death that this experiment showed off at the unreasonbly hight concentration is still quite the opposite of Cancer. Cancer is Uncontrolled cell multiplication not death. So according to this we could use nanaplastics to kill cancer. See How easy it is to draw any conclussion that you want if you forget to factor the real conditions?