A CT scan delivers a dose of ionizing radiation that is significantly higher than the natural background radiation a person receives annually, even in a high-altitude city like Denver. While Denver’s elevation means its residents are exposed to more cosmic radiation than those at sea level, the radiation dose from a single CT scan still far exceeds this background exposure.
To understand this, it helps to compare the numbers. The average natural background radiation dose in the United States is about 3 millisieverts (mSv) per year, but because Denver is at a high altitude, the background radiation there is somewhat higher—roughly around 4 to 5 mSv annually due to increased cosmic rays. In contrast, a typical CT scan can deliver anywhere from about 2 to 10 mSv in a single session, depending on the type of scan and the body part imaged. For example, a chest CT scan might give around 7 mSv, which is roughly equivalent to one to two years of background radiation in Denver.
This means that a single CT scan can expose a person to radiation doses that are multiple times higher than what they would naturally accumulate over a year living in Denver. The difference is not trivial because CT scans use ionizing radiation, which has enough energy to damage DNA and potentially increase cancer risk over a lifetime. However, it is important to keep in mind that the risk from one scan is still relatively low in absolute terms, especially when weighed against the diagnostic benefits CT scans provide.
The radiation from background sources like cosmic rays, radon gas, and terrestrial sources is continuous and unavoidable, but it is generally low-level and spread out over time. CT scans, on the other hand, deliver a concentrated burst of radiation in a short period. This concentrated dose is why medical experts emphasize the ALARA principle—keeping radiation exposure “As Low As Reasonably Achievable”—to minimize unnecessary scans and use the lowest effective dose.
In Denver, the higher background radiation does not make CT scan radiation less significant; rather, it adds to the total radiation dose a person receives. The cumulative effect of background radiation plus medical imaging is what matters most for long-term health risk. While living at higher altitudes like Denver’s does increase natural exposure, it does not negate the fact that CT scans contribute a substantial additional dose.
Modern CT technology has improved to reduce radiation doses compared to older machines, and protocols are designed to limit exposure while still obtaining high-quality images. Still, the radiation from a CT scan remains many times higher than daily or even yearly background radiation, even in places with elevated natural levels like Denver.
In summary, CT scan radiation is indeed worse than background radiation exposure in Denver when comparing dose amounts directly. The natural background radiation in Denver is elevated compared to sea level but remains far lower than the dose from a typical CT scan. This difference underscores the importance of using CT scans judiciously, balancing the clear diagnostic benefits against the small but real radiation risks.