Sieverts and the Fukushima Crisis

Terrible loss and suffering in Japan has been overshadowed in the media by the edge-of-your-seat drama of its stricken Nuclear Power Plants.  The combination of drama, potential dangers beyond Japan’s borders, and the continuing debate over nuclear power make the story irresistable.  Confusion about the dangers of leaking radioactive materials abounds, especially when news media meet science in trying to report the measurements used to assess radiation levels and risks. 

It is a measure of importance to humanity when something gets its own units of measure designed to quantify its effect on human life.  Hurrcanes, earthquakes and nuclear radiation are among the few things in our world that merit such treatment.  We’ve become familiar with the Safir-Simpson scale of 1 to 5 for the destructive power of hurricanes, and the Richter scale for earthquakes, but the Sievert, used to measure radiation dosage has thrown us for a loop. 

The problem lies with the Sievert itself.  While most of us don’t know a lot about radiation, we do know that it involves little particles streaming at us and messing up our molcules as they zoom through.    Thus, the natural measure we expect to use would reflect the intensity of that stream.  Like the sun and sunburn, if its really bright, you don’t stay out long.  The Sievert is instead a measurement of how much radiation you have already absorbed.  It is a measure of dosage.  So if you want a measure of intensity, that would be Sieverts per hour.   The following sound-bite from a news article:

“The radioactive radiation at Japanese nuclear power plant Fukushima 1 reached new record levels. It is the value of 1000 mSv (1 sievert) was measured, says government spokesman Edano.”

doesn’t tell us what we want it to.  Does it mean that a person standing near the plant would by now have received 1 Sv dose?  More likely it means a person standing there now would receive 1Sv every hour.  When you hear “it’s no more than a chest X-ray”, that has the same problem.  Is the amount hitting a person near the plant like a chest X-ray every hour?  Every minute?  Like one long contiuous chest X-ray as long as you are standing there?

For us readers thousands of miles away, it really doesn’t matter.  I guess the pace of today’s reporting precludes running such facts by the science editor, and I can’t help thinking that this is only a reflection on the editorial process news lacks in general.  But from the Numerator’s point of view, lets at least get the units right!