In second grade, 14-15 years ago, I accidentally stabbed myself in the knee with a pencil while fiddling with it under my desk. I remember feeling embarrassed because I had to go to the nurse and I had a crush on the girl sitting next to me.
There is still a little gray dot where the pencil penetrated the skin, although it’s migrated a few inches as I’ve grown. I noticed it today for the first time in years, and it got me thinking. How could the lead that is causing that stain remain in my body for so long? I assume it is either in the skin or right below the skin because of how visible it is. I know skin cells are replaced very frequently, and everything else in the body is also replaced with new cells within months or years. Shouldn’t the lead have been flushed out of my body by now?
I could imagine something big and solid remaining there (I’ve heard of bullets and shrapnel remaining inside the human body for years), but I assume the lead that’s in my body is a powder.
First lead in a pencil is not the metal lead. Your pencil from 15 yrs ago was probably mostly graphite (carbon) with some clay and maybe other binders.
Carbon is normally colored black and will not degrade or change into anything else, like you might expect organic dyes to do. Its essentially in its elemental state and will stay there barring some interesting chemistry not typically found in your body.
Second its probably embedded underneath your skin below the live layer of cells that continually push new dead cells to the exterior. So the graphite isn’t going to be pushed out.
Third, its like a tatoo. Tatoos are normally still visible after several years and decades.
For years and years I had a small piece of cinder in my hand, from when my kindergarten teacher was pushing me on a swing . . . and I let go, and went flying onto the playground surface. That was 59 years ago, and I just noticed that I can no longer find that little black speck.
I had one for many years. But I can no longer find mine. I have no idea when/where I lost it.