That claim is usually sourced to a guy named Bernard Cohen, who once volunteered to eat as much pure plutonium as Ralph Nader did caffeine. Nader demurred, and

That claim is usually sourced to a guy named Bernard Cohen, who once volunteered to eat as much pure plutonium as Ralph Nader did caffeine. Nader demurred, and most people disavow Cohen, because who'd actually do that? That said, consider Albert Stevens. He was (unknowingly) injected with 131 kBq of Pu, accumulating a lifetime dose of ~64 Sv, and died of heart disease some 20 years later.