Iodine-131 is a radioactive isotope of the element iodine.
sealed radioactive source means the radioactive isotopes which is encapsulated with a stainless steel to avoid higher LET radiation condamination .typically source may be used in brachytherapy to treat the cancer and unsealed source used to in nuclear medicine which is the radioactive source is not sealed examble IODINE131
Since there is no strontium-185, and strontium-85 is rarely encountered, I am assuming you mean strontium-90, which is similar in its health effects to iodine-131 and cesium-137. All of these are readily absorbed by the body. All are strong negative beta emitters, and all either are or produce strong gamma emitters. It is the gamma emission that is particularly problematical. Gamma rays penetrate much deeper in living tissue than alpha or beta emissions. This causes cellular damage throughout the body, which can lead to a variety of symptoms of radiation poisoning. These include a range from headache, weakness and fatigue for limited exposure; nausea, vomiting, diarrhea (possibly bloody), and hair loss for greater levels of exposure, or death for heavy exposure. There is a chance of cancer, which increases with exposure.