United Nations Radio

Radiation Exposure

Human exposure to medical radiation is rapidly increasing, especially in well developed countries. In fact, according to a new report issued by the UN Scientific Committee on the Effects of Atomic Radiation, medical-related radiation exposure accounts for 98 percent of the contribution from artificial sources of radiation. UN Radio's Gail Walker spoke to Committee member Fred Mettler who explains that there are at least three reasons for the increase.

Duration: 4'17"

Mettler: One is of course the population has gotten larger. If we just go between 1980 and 2005, the world population went from about 4.5 million to about 6.5 million. So that will count for some of the increase. The second increase we saw was a lot of countries have been getting more developed, doing in those countries has basically doubled. And then in the very well developed countries or highly developed countries like US, Japan and so forth, the major increase is from CT and nuclear medicine.

Walker: What is the impact of this increase of radiation exposure, I mean does that naturally mean we see more cases of cancer or something along those lines?

Mettler: Of course a lot of the exposures are very low, and it's always been very difficult to discern whether a single chest x-ray actually causes an increased risk of cancer. But a number of the higher dose studies like CT scans, we actually do think those are at the level of-where we have seen small increases in cancer. I think on the other hand though, one has to look at the whole thing in terms of benefit as well and actually taking radiology into countries that don't have it, may actually save more lives. So you have to look at both sides of the equation.

Walker: Are we at a level where higher quality medical care will put people at some level of disadvantage, where we're seeing people who are getting maybe too many CAT scans or x-rays because of technology being so readily available, are we overdoing it?

Mettler: And I think that the increase in particularly CT scans sort of caught people by surprise that there we really that many going on and that most of the people who were doing the CT scans didn't really realize that you know a chest CT scan is at least 100 chest x-rays worth. And so I think that caught a lot of people by surprise, from radiologists to regulators, to patients, and the media too. So at this point one of the difficulties is how much benefit are we giving people and in some cases I think, like looking for appendicitis with CT scans is clearly beneficial and we're doing a lot less operating on people who have a normal appendix. On the other hand there other things like doing CT scans for kidney stones that a lot of patients just get a repeated scan every time they come in and whether they need it is questionable. So I think in general, for example in the US, the numbers you hear are around maybe 30% or of the number of x-ray studies that are done probably don't need to be done. And then the other issue is, the ones that are done in many cases could be done with a lower dose.

Walker: Can you talk a little bit about the natural sources of radiation and what the level of changes have been with the natural sources of radiation?

Mettler: Generally, I would say that the natural background doses pretty much in the US and around the world haven't changed measurably. And, I think that's the important point, a lot of the natural sources don't change over time and in fact there isn't much you can do about them. And, actually our report points out that worldwide, if you look at all the man-made sources, other than the natural, medicine accounts for over 99.9%. So, when people think about nuclear reactors and, they think about research activities and things like that: I mean that's less than 1/10 of 1 percent of what the exposure is from man made sources.

Walker: Now, is their a difference in, what is the difference in the body reacts to lower and higher level of radiation?

Mettler: There's no question that at relatively high doses of radiation, we know that there's an increase of cancer of various types and leukaemia. The question that a lot of people have is at these really low doses, is there a risk of cancer? We generally think there is a risk, but it is so small that we never been able to actually see it. And, there some studies now that have been started in Europe looking particularly at children who have had CTC scans and looking for leukaemia. Children are more sensitivity to radiation and leukaemia tends to show up before the other types of tumours, so that's why they're beginning to look for it now.