1 Becquerel is by definition the same amount of decay events. However, the amount of an isotope that is needed for that one Bq is directly dependent on the half

1 Becquerel is by definition the same amount of decay events. However, the amount of an isotope that is needed for that one Bq is directly dependent on the half-life of that isotope. Exactly twice as many nuclei are needed to produce the same Bq amount when using an isotope that has twice the half-life. The limit for ingestion for I-129 is 5 uCi. From the formula of radioactivity: m/m0 × NA × ln(2)/t½ = A, the amount of I-129 that is needed for 5uCi is ~28mg, which is also ~= the amount of Iodine in a normal human body. That is, if an evil wizard suddenly converted every atom of iodine in your body to I-129, you would be right about at the epa limit.