Regarding CT scans, they routinely save lives. And yes, there is measurable risk with each scan, and yes, it is a problem in terms of causing cancer.
How much of a problem? Modern CT scanners are built to minimize radiation exposure. According to the FDA:
“…The effective doses from diagnostic CT procedures are typically estimated to be in the range of 1 to 10 mSv. This range is not much less than the lowest doses of 5 to 20 mSv received by some of the Japanese survivors of the atomic bombs….”
According to the FDA, 400 out of every 2000 people will develop a fatal cancer in their lifetime. That’s without CT scans in the mix. How many more cancers will we see if everyone in the group of 2000 gets a CT scan? Turns out the number is 401.
Admittedly, that’s a small increase in risk. However, the risk adds up if you’re getting a number of scans. If your doctor says you need a CT scan and you’ve already had a few, you can ask if there are other imaging options that can do the job without radiation. Sometimes the answer is yes. If the answer is no, you and your doctor will want to weigh the risks and benefits of having or forgoing the CT scan.
Better news is that the younger you are, the more dangerous radiation exposure is, with in utero and early childhood being the most vulnerable periods. In turn, young adults are more sensitive than are elders. One of the few physical perks of aging, I guess.
Reference: What are the Radiation Risks of CT?