A child will usually get lead poisoning by eating things such as lead paint that flakes off such as in old houses with lead paint that is peeling.
Young children will put just about everything in their mouths so you have to watch what they do closely and if your child has eaten some lead paint then you need to take them to the emergency room to be safe because the lead poisoning could be deadly pretty soon.
A child can also get lead poisoning by breathing in lead dust or putting anything else in their mouths that can contain lead or even by swallowing batteries which is also dangerous.
If your child swallowed a battery then you need to get the child to the emergency room because the battery can eat at the child's stomach along with the lead poisoning.
Young children are especially at risk for lead poisoning due to them putting things in their mouths which they shouldn't.
So that's one reason that very young children under 5 years old really need a lot of supervision.