Answer to Question #12342 Submitted to "Ask the Experts"
The following question was answered by an expert in the appropriate field:
I recently asked a question about how many mSv I received from a chest computed tomography (CT) scan and a barium swallow. The total was around 7.5 mSv for both procedures.
At how many mSv do cells start to die? Under what mSv can the cells repair themselves? I understand that a chest x ray is much less radiation than a CT scan, but do our bodies repair themselves the same way compared to a large or small dose? Do cells immediately begin repair right after exposure or is it an ongoing mechanism?
I did read that some scientists believe that some radiation boosts immunity and possibly protecting us from radiation harming us in the future. How true is this?
Cells are constantly dying and being replaced. It's an issue when they die faster than they can be replaced. A CT scan results in low doses, a chest x ray in lower doses. Radiation therapy for cancer treatment results in high doses. It takes radiation therapy type doses to kill cells faster than they can be replaced. It's not an issue with radiation exposures from diagnostic imaging.
Cells, or more specifically, DNA molecules in cells, are constantly being damaged and repaired. This happens all the time, every second of every day, in every cell in the body.
While some studies have shown positive health effects from low-dose radiation, at low doses the epidemiological evidence is not consistent.
Thank you for using the Health Physics Society's ATE feature.
Kent Lambert, CHP, FHPS