Original sentence: Due to the elements being sufficiently similar chemically, the stable forms of strontium might not pose a significant health threat, but the radioactive 90Sr can lead to various bone disorders and diseases, including bone cancer
Edited sentence: Due to the elements being sufficiently similar chemically, the stable forms of strontium might not pose a significant health threat -- in fact, the levels found naturally may actually be beneficial (see below) -- but the radioactive 90Sr can lead to various bone disorders and diseases, including bone cancer