Answer:
Mostly in the old paint, dust and eating contaminated chickens. Chickens eat the lead paint because it is looks like the broken down egg shells. Also chicken feed had a lot of lead in the past. FDA do not inspect animal feed usually. Cat food and dog food has a lot of lead. ( do not get surprise if you dog get stupid). FDA hires oil and far-ma CIOs to run there government agency. They do not protect public from big farma and oil Co. No protection for food for your kitty or doggy or you. Genetically modify foods sold without labeling. You may become mad or get cancer from it. Was no studies.