When we were young, we’ve always been warned not to put the pencil in our months or eat with our lead covered hands, and we should always wash our hands after using pencils. The reason behind that is lead in pencils can lead to poisoning. Well, not only that.
Researches have shown that lead can kill brain neurons (never cells). Which means when exposed to excess of lead at a young age could lead to a smaller size of brain (smaller gray matter of brain, to be more precise). And since brain size have been argued to be connected with intelligence, lead could lead to less intelligent people!
So apparently, lead can make you stupid. Gee, and I used to wonder why now that we have better education, the generation is getting stupider. It’s the pencils! (*holding sarcasm sign*)