# Is the flint used in disposable lighters toxic?

Especially the sparks that result when using them. I heard this from a friend and can't seem to find an answer on Google.

If you rub such an alloy on a rough surface, tiny metal particles are formed, which are instantly ignited and produce metal oxides. Neither of the expected products are particularly toxic: lanthanoid oxides, particularly $$\ce{CeO2}$$ and $$\ce{La2O3}$$, are not toxic and can only cause mild irritation when swallowed, and iron oxide $$\ce{Fe3O4}$$ is basically rust.