From Wikipedia:
Isotopes
Main article: Isotopes of bismuth
The only naturally occurring isotope of bismuth, bismuth-209, was traditionally regarded as the element with the heaviest stable isotope, but it had long been suspected to be unstable on theoretical grounds. This was finally demonstrated in 2003 when researchers at the Institut d'Astrophysique Spatiale in Orsay, France, measured the alpha emission half-life of 209Bi to be 1.9 × 1019 years,[7] over a billion times longer than the current estimated age of the universe. Owing to its extraordinarily long half-life, for all presently known medical and industrial applications bismuth can be treated as if it is stable and non-radioactive. The radioactivity is of academic interest, however, because bismuth is one of few elements whose radioactivity was suspected, and indeed theoretically predicted, before being detected in the laboratory. Bismuth has the longest known alpha decay half life, although tellurium-128 has a double beta decay half-life of over 2.2×1024 years.
Several isotopes of bismuth with short half-lives occur within the radioactive disintegration chains of actinium, radium, and thorium, and more have been synthesized experimentally.
That's good enough for me. I checked with a geologist, and he said I'd get more radiation driving down the street past a doctor's office than I'll get from handling bismuth shot or eating birds shot with it.
