Lead is extremely toxic when ingested (even small amounts). It's documented and proven that lead will adversely affect the human body. Companies mixed lead into paint to begin with and refused to acknowledge its danger until it was banned.

As for blocking radiation, you can do that with copper to create a faraday cage. If you're referring to xrays (like dental clinics), there isnt a point to shielding against that as there aren't many sources of xrays in the wild currently