Radiation Sources, Doses, & Cancer

We will now combine information from various other charts in this section. First, though, remember that without radiation exposure, the odds of getting cancer are 1 in 2.4 (or 42 percent). This means that of 100 average people I know, including me, 42 of us may get cancer at some time in our lives. In addition, if I go to the doctor and have a pelvic CT scan (dose <= 1 rem), my cancer odds stay 1 in 2.4 (or 42 percent). If I have 10 CT scans, my cancer odds are now 1 in 2.3 (or 43.7 percent). If I live next to the perimeter fence around a nuclear power plant for 40 years, my cancer odds are 1 in 2.4, the same as baseline with no extra radiation exposure.

With that information we now have a better understanding of the approximate risks of radiation doses. We can see that radiation doses less than 10 rem are unlikely to cause harmful effects and only slightly increase our chances of getting cancer. Whether to be concerned or not is still a personal decision. Taking steps to keep our exposure to any potentially harmful agent reasonably small is important. It is a personal responsibility for ourselves and our families.

We must, however, try to make informed decisions based on the real and not the perceived risks in our everyday lives. When we do that, we can lower or eliminate the higher risks over which we have control and not agonize over lowering risks that are already low. Often, we believe that if radiation is present there is a high risk. As can be seen from the charts and the information in this section, we know this is not true. To compare the chances of getting cancer from radiation exposure to other more common chances of diseases or accidents, see our Probability Table.

X Rays & Cancer

Let’s look at the risk of cancer, then, from some basic x rays. Here are the radiation sources, the approximate dose of radiation you get from them, and how much your chances of getting cancer increases in your lifetime as a result of that radiation dose. Remember, with no extra radiation dose, your odds of getting cancer in your lifetime are about 10 out of 24 (or 1 in 2.4) or 42 percent.

Radiation Source Effective Dose Additional Chances of Getting Cancer‡*

bitewing dental film

annual dose living at nuclear power plant perimeter

skull x ray

chest x ray

Less than (<) or equal to (=) 0.01 rem

<=1 in 60,000

spine x ray

abdominal x ray

pelvis x ray

hip x ray


<=0.1 rem

<=1 in 6,000

kidney series of x rays

most barium-related x rays

head CT +

any spine x-ray series

one year’s worth of natural background radiation

most nuclear medicine liver, kidney, bone, brain, or lung scans

<=0.5 rem

<=1 in 1,200

barium enema

chest, abdomen, or pelvic CT +

<=1.0 rem

<=1 in 600

cardiac catheterization

coronary angiogram

other heart x-ray studies

most nuclear medicine heart scans

<=5.0 rem

<=1 in 120

‡The “odds” numbers in this column are estimated numbers of increased cancers; the real number in each case may be zero up to the number cited. For instance, the odds of 1 in 120 really are “zero up to 1” in 120.

*Numbers from the National Radiation Protection Board (now the United Kingdom Health Protection Authority)

+CT = computerized tomography; a specialized x-ray exam.

So, you can see that even with many types of radiation exposures and medical exams, the ordinary everyday odds of getting a cancer (1 in 2.4) are much higher than the added chances of getting cancer from radiation exposure.