It's more about breathing in screws and especially the nuts, which is unfortunately very common with kids and small objects.

In my city the ER departments in the hospitals regularly deal with kids having their airways blocked e.g. due to small Lego pieces. I nearly got myself killed at the age of three or something like this by inhaling a small stone...

I came pretty close to choking (whilst home alone) as a young kid when I thought it'd be a great idea to try to swallow a peach pip.

I like to think I'm not that dumb now, but as a kid I did some really idiotic things that seriously jeopardized my safety. I'm willing to believe I'm not alone there.

Again, this seems to be a problem that could be solved by locking up your project when you're done working with it.