But for the sake of argument Ill assume you just care about ionizing radiation (UV, Xray, Gamma, Neutron, etc). In that case I agree consent should be needed for medium to high dose. It's unfeasible to get the consent of everyone for low doses (x-ray machine x-rays can travel for miles and theoretically infinitely far).
In this case it appears the dose is only about that of eating a banana. Hard to argue you need to consent to that for radiation concerns unless you also agree that everyone should consent to every xray scan that every hospital executes, or every time your colleague brings in bananas to work. Privacy concern is valid though. Radiation one is just fear mongering if OP is correct.