The answer is "lead poisoning".
Lead poisoning as a rule happens over a time of months or years. It can cause extreme mental and physical hindrance. Young children are generally defenseless.
Kids get lead in their bodies by putting the lead containing objects in their mouths. Contacting the lead and after that putting their fingers in their mouths may likewise harm them. Lead is more hurtful to kids on the grounds that their brains and sensory systems are as yet creating.
Lead poisoning can be dealt with, however any harm caused can't be reversed.