Radiation: separate the fact from fiction - Nidhal Guessoum - April 15, 2011

The recent earthquake and tsunami in Japan produced the second-worst nuclear accident in human history. This brought the spectre of ‘radiation' exposure, ‘radioactive clouds', and contaminated water, milk, and food upon millions of people, as everyone has heard that "radiation causes cancer". Though a physicist, and not a physician, I am constantly asked how dangerous radiation is and how one can protect against it.
Radiation has become part of our lives. Google the word and you will get ‘background radiation', ‘thermal radiation', ‘radiation damage', ‘radiation therapy', ‘radiation poisoning', and many more related concepts. Read these again and you will realise that some refer to scary situations (poisoning from large doses), others relate to our normal environment (thermal radiation is just heat), while others indicate beneficial applications (therapy).
But what is radiation? Physics defines radiation as either particles (such as electrons) or electromagnetic waves (X-rays, ultraviolet rays, microwaves) carrying substantial amounts of energy.
Even heat (infra-red) can be termed radiation. More often, however, the term is used for highly energetic emissions, such as X-rays and gamma rays, which emanate from atomic and nuclear processes.
In small doses, and if used under medical conditions, radiation can be useful to kill malignant cells or simply imaging organs in our bodies. In very large doses, however, radiation can damage cells, particularly their DNA, leading them to chaotic multiplication, i.e. cancer.
Specialists use several units to measure the doses of radiation received by a person. In Europe and Asia, the sievert (or millisievert) is used; in the US, the rem (Roentgen Equivalent Man) is used. On an average, humans receive 0.3 rems (three millisieverts) a year from background radiation.
A lethal dose is in the range of 400-450 rems. Between those two levels (the background radiation doses we are normally exposed to and the lethal doses that one receives if hit by a nuclear blast upfront), it is difficult to clearly spell out the risks.
There is no data for any effects on people receiving up to 10 rems, and specialists are divided about whether there is a threshold below which there would be no effect on the body, or whether very tiny amounts can always have an effect. Indeed, it only takes one ray to damage a cell's DNA, but on the other hand, if we worry about such tiny exposure, then no one should get even a dental X-ray.
Now, what is the situation in Japan and how does it affect the world? Japanese officials have now raised the severity of the accident at the Fukushima Daiichi nuclear power plant to level 7 (‘Major Accident'), the highest on the scale used by the International Atomic Energy Agency. The infamous Chernobyl disaster, 25 years ago, had also reached this level, but there is no question that, as long as none of the Japanese reactors have melted or exploded, Chernobyl was a much greater catastrophe (if the scale was extended, Chernobyl would probably be a 9 or a 10).
The main difference is that the Japanese reactors were much better encased, keeping most of the radiation inside when the reactor heated up, as the cooling pumps could not be run, due to power failures. Chernobyl was a huge disaster because not only did the reactor blow up, its contents were spewed far and wide. Still, international reports claim fewer than 100 deaths (too many, of course) directly attributed to the accident, but also that some 6,000 people will have gotten cancer from the intense radiation and many of them will die from it. Actually, many people got cancer from Chernobyl due to lack of awareness of the risks. As has been done in Japan, people should have immediately been advised not to drink the milk of or eat the meat of cows from the contaminated region, not to drink tap water unless it has been checked and declared free from radioactive elements (particularly iodine, which leads to thyroid cancer, especially in children), and to stay away from the vicinity (a few kilometres) of the damaged nuclear reactor(s).
So what conclusions can we draw from these facts about radiation? First, that it is always important to be well-informed, to replace half-truths and irrational fears with scientific knowledge and rational behaviour.
Secondly, governments have moved to examine and strengthen ageing nuclear power plants and prepare workers and residents for any such accidents in the future, just as we prepare for earthquakes and other natural disasters. We human beings learn from our mistakes, and the sad episodes of Chernobyl — and, to a much lesser extent, Three Mile Island — have taught us good lessons, particularly how to react to such accidents.

Nidhal Guessoum is a professor of Physics and Astronomy at the American University of Sharjah.

Source : http://gulfnews.com/opinions/columnists/radiation-separate-the-fact-from-fiction-1.792580

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