Radiation has a very bad health effect, I would still do it if it's interesting but just know the dramatic risks that involve it. Now Resp, and Dental is a GREAT choice in career. Dental Hygenist make good pay (atleast they do here in cali) and There is quite a demand for them. Respitory therpay is pretty much the same, it's very interesting and will give you a better paycheck then most will. Again, if I had a choice, I would go for the dentistry one just because it's more of a calming job than RT, BUT that is entirely up to you. Reverting back to the radiation one, I'm sure it pays well and will be a good career if you decide on that one also. Like I said though, I'd go for the dental out of all of them just based on both the comfort-ability and the lack of exposure to extremely harmful diseases/chemicals etc.