They don't. Hey Matt! This is a good question and I'm glad to reassure you. A typical CT scan delivers maybe 3mSv, the same as the extra radiation a pilot gets each year. Pilot dose is cumulative and nobody has shown increased cancer in pilots. Up to 20 mSV/year is okay for radiation workers and they don't get extra cancer either. Relax and give yourself a break from worrying.
None. Ct scan will not cause cancers , although there is very small potential due to minimum radiation exposure. Humans are unknowingly exposed to ionizing radiation like prolonged repeated air travel more than any diagnostic test , just don't worry about getting cancer from xray tests, it only a precaution for un indicated tests.