Final answer:
After NaI 131 treatment, exposure to others should be reduced if they are likely to be subject to doses causing temporary sterility (0.35 Sv for women, 0.50 Sv for men), significant reduction in blood cell counts, or potentially lethal effects (LD50/32). Other serious effects can occur at higher doses, including fatal outcomes. I-131 has a half-life of approximately 8 days, but safety precautions are advised for several weeks after treatment.
Step-by-step explanation:
When treated with NaI 131, it's important to reduce exposure to others if they are experiencing doses that lead to significant health effects. According to the information provided, individuals should particularly be concerned if they or others are experiencing effects from doses that cause temporary sterility (0.35 Sv for women, 0.50 Sv for men), significant reduction in blood cell counts, or effects that could be lethal to 50% of the population within 32 days after exposure, known as LD50/32. The immediate effects of radiation also include nausea, vomiting, hair loss, severe blood damage, hemorrhage, and fatalities, particularly at higher doses. The worst effects can include malfunction of the small intestine and blood systems with limited survival, and exposure to doses over 600 rem is invariably fatal due to the collapse of the central nervous system.
For smaller doses, such as those used for thyroid imaging, the I-131 has a half-life of approximately 8 days, and most of the radioactive iodine will leave the patient's system within a few weeks. However, during this time, precautions should still be taken to limit exposure to others, especially vulnerable groups such as pregnant women and children, due to potential health risks including thyroid cancer.