The radioactive strontium - 90 can lead to various bone disorders and diseases, including bone cancer. It emits high energy beta radiations. Phosphorus -32 also emit high energy beta radiations but they cannot penetrate human skin. Caesium - 137 (beta emitter) and iodine -131 ( β and γ emitter) also pose danger to human health but not as much as strontium - 90 which is a long-lived radioactive element and tends to cycle like calcium.