A CT scan generally exposes a person to **more radiation than a typical air travel flight**. While both involve exposure to ionizing radiation, the amount and type differ significantly.
To understand this, it helps to know what radiation exposure means in these contexts. Radiation is measured in units called millisieverts (mSv), which quantify the effect of ionizing radiation on the body. Everyone is exposed to some natural background radiation annually, roughly about 3 mSv on average.
**CT scans** use X-rays to create detailed images inside the body. Because they produce cross-sectional images, they require multiple X-ray exposures, which add up to a higher radiation dose than a single X-ray. The radiation dose from a CT scan varies depending on the body part scanned but typically ranges from about 2 to 10 mSv per scan. For example, a chest CT scan might deliver around 7 mSv, which is more than twice the average annual natural background radiation. This level of exposure is significant enough that medical professionals carefully weigh the benefits of the scan against the small but real risk of radiation-induced effects, such as a slight increase in lifetime cancer risk.
On the other hand, **air travel exposes passengers to cosmic radiation** from outer space, which increases with altitude. At cruising altitudes, the atmosphere is thinner, so more cosmic rays reach the aircraft. The radiation dose from a typical long-haul flight (say, 8 to 10 hours) is about 0.03 to 0.05 mSv, which is roughly equivalent to a few days of natural background radiation. Even frequent flyers accumulate only small doses compared to a single CT scan.
Putting these numbers side by side:
| Exposure Type | Typical Radiation Dose (mSv) |
|——————–|————————————-|
| Natural background | ~3 mSv per year |
| Single chest X-ray | ~0.1 mSv (about 10 days background) |
| Typical CT scan | 2 to 10 mSv (varies by scan type) |
| Long-haul flight | 0.03 to 0.05 mSv per flight |
This means a **single CT scan can deliver radiation equivalent to several months or even years of natural background radiation or hundreds of long-haul flights**.
Despite the higher radiation dose from CT scans, the risk to an individual remains low, especially when the scan is medically justified. CT scans have become indispensable in diagnosing and managing many health conditions, saving countless lives. However, the increase in CT scan use over recent decades has raised concerns about cumulative radiation exposure at the population level, with some studies projecting a small increase in future cancer cases linked to medical imaging radiation.
In contrast, radiation exposure from air travel is generally considered minimal and not a significant health risk for most people, even frequent flyers. Airline crew members, who spend much more time at altitude, receive higher doses but still within regulated safety limits.
In summary, while both CT scans and air travel expose people to ionizing radiation, **CT scans deliver a much higher dose of radiation in a short time compared to the relatively low dose accumulated during a flight**. This difference is why medical imaging protocols emphasize minimizing unnecessary CT scans and using dose reduction technologies to keep radiation “As Low As Reasonably Achievable.”