Are X-rays safe?

A common notion is that all X-rays are harmful. We (in the x-ray business) actually adopt that as a principle when using radiation in medical diagnosis. The thing is, while it is useful as a safety-first approach, it has never been proven to be true, and it is probably wrong.

 The idea that the X-ray (and its twin, the gamma ray) are dangerous came about when people began to handle radioactive materials at their workplace or placed their hands in an X-ray beam (for minutes or hours at a time). The deleterious effects on the health of Japanese survivors of the WWII atomic and hydrogen bombs has been extensively documented and analysed. These two examples, however, involved exposure to enormous radiation levels compared to those used in medical diagnosis. We just don’t know if very low levels of exposure are proportionately less harmful.

 Could some radiation levels be even totally harmless? There are several clues that this could be the case. We know that the human body doesn’t react in a proportional or linear way to other environmental hazards. A simple example is heat. A short exposure to very high temperatures, say 2500 degrees, is lethal, but a daily dose of 25 degrees clearly isn’t. Similarly with atmospheric pressure, gravitational forces etc. With mineral intake, high levels can be toxic but trace levels are essential to good health. Even water can be toxic if you drink too much.

 But surely radiation isn’t natural! Well, in fact it is. It may be surprising to learn that we are all continuously exposed to a level of background radiation much greater than that we would get with a medical examination. The solid earth, the air we breathe, the sky overhead, and even our own bodies are sources of ionising radiation due to naturally occurring isotopes of common elements e.g. potassium. (The contribution of nuclear fallout to this is minuscule). These are naturally occurring rays which give every one of us an annual dose of around 2mSv (milliSievert). This is the equivalent of having 100 chest X-rays each year! We can’t avoid it; the human race has grown up with it and maybe has developed a tolerance for this level of radiation exposure.

 There are variations in levels locally, particularly with altitude; this means that by jetting to London equates to having 3 chest x-rays because of the extra cosmic rays you are exposed to in the thinner atmosphere. The bomb victims, those who died of radiation-induced cancers, received doses of the order of 2000 – 5000 mSv over a very short period. In other words, equal to at least 1000 years of background exposure or 100,000 medical X-rays. The X-rays we encounter in our health care will barely register against our background exposure. So relax.

 Can radiation even be good for us?? Certainly….if you are a cockroach. Laboratory studies exposed different groups of these insects to a range of radiation levels. At high levels, they died. At very low levels there was no effect identified, but a brief low level exposure resulted in a group who lived longer than average! They are still looking for human volunteers to repeat the study…. Sorry, bad joke. This experiment could never be performed on people under modern science guidelines. So we’ll probably never know.

 I don’t want my baby anywhere near x-rays! It’s true, an unborn baby is about twice as sensitive to radiation, particularly during the 2 – 4 month stage of pregnancy. But the risk to your baby from you having X-rays is still negligible; a much greater risk would come from improper treatment of his mother because an X-ray wasn’t done.

Possible adverse effects on a baby exposed to radiation include a small head, mental impairment, or the development of cancer in childhood. It is observed that these conditions occur spontaneously (i.e. in cases where there was no additional radiation), and a dose of the order of 50 – 150mSv would be required to significantly increase the risk of abnormality. It is calculated that a CT scan of Mum’s pelvis (i.e. directly over the unborn baby) carries a dose of 10mSv, equal to 500 chest X-rays, but still below the danger threshold.

We would prefer to avoid CT scans during pregnancy, but if you need one, the chances of harming the baby are very slim. In the above case (with a CT scan in early pregnancy) the prediction would be 0.3 point reduction in IQ (i.e from 100 average to 99.7), a 1 in 3300 risk of fatal childhood cancer and an even smaller risk of chromosome damage causing heritable disease. 


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