@bojacobs
Just in case someone is getting the wrong picture here, I'll point out that 1 gram of caesium 137 has an activity of 3.2 terabequerel.
The upper red box starts at 1.4 megabequerel, so that's less than one 2 millionth of a gram.
There are measurable radioisotopes there, but you do need special equipment to find them. Also, about half of the stuff is gone now due to decaying into stable elements.
@TheSneakySneaker @bojacobs that. Also note that the scale is logarithmic...