That is a fallacy. I'm talking about a dirty nuclear bomb which consists of the worst radioactive material you can find (which doesn't have to be "weapons grade

That is a fallacy. I'm talking about a dirty nuclear bomb which consists of the worst radioactive material you can find (which doesn't have to be "weapons grade" btw) dispersed by conventional explosives. This can be achieved anywhere there is a nuclear reactor for power generation or research purposes. ISIS contemplated doing this. Biological weapons are actually much harder. It does not just take "a lab". What are we talking about? Weaponizing anthrax? Unless you have access to the secret "weaponized" strains you'd need a pretty big lab to "breed" it yourself. At the very least animal testing, maybe human testing, definitely some mass production. That takes time. Also the dispersal methods aren't as simple as one might think. In theory bioweapons sound easy, in practice they haven't proven to be very effective.