Naturally occurring strontium is nonradioactive and nontoxic at levels normally found in the environment, but Sr is a radiation hazard. Sr undergoes β decay with a half-life of 28.79 years and a decay energy of 0.546 MeV distributed to an electron, an antineutrino, and the yttrium isotope Y, which in turn undergoes β decay with a half-life of 64 hours and a decay energy of 2.28 MeV distributed to an electron, an antineutrino, and Zr (zirconium), which is stable. Note that Sr/Y is almost a pure beta particle source; the gamma photon emission from the decay of Y is so infrequent that it can normally be ignored.
Sr has a specific activity of 5.21 TBq/g.