The average candy bar ranks fourth for highest lead content in a food. Don't panic yet, though; lead occurs naturally in everything, even wholesome vegetables and grains, and while there is no amount of lead that isn't harmful to the human body, a little bit of the stuff in our bloodstream is more or less unavoidable and probably won't do anything bad enough that we'll ever notice.
Infants and children, on the other hand, are basically screwed. Because they're already stupid, kids absorb higher concentrations of lead into their system than the rest of us, just through their day to day activities of eating dirt and inhaling paint chips. Also, they breathe faster than an adult, which further draws in whatever lead happens to be floating around and sends it toward their sensitive little brains. Even before they start wailing on that candy, they have more lead in their bodies than Vito Corleone. Then comes Halloween.