On “Radiation risky, but at what level?”
Here is a syndicated newspaper article (Written by Denise Grady of New York Times) titled “Radiation risky, but at what level?” which discusses one aspect of the difficulty in coming up with a guideline radiation dose in the context of public health.
US EPA’s Protective Action Guideline (PAG) (http://www.epa.gov/rpdweb00/rert/pags.html and http://www.epa.gov/rpdweb00/docs/er/400-r-92-001.pdf) states that, following a nuclear incident, if the projected, net (total) dose over a 4-day period is 1 rem (10 mSv) or above, the population should be evacuated. It also recommends that the population be relocated long-term if the projected dose over the first one-year period exceeds 2 rem/year (20 mSv/year). For subsequent years, the relocation guideline tolerates much lower figure, 0.5 rem/year (5 mSv/year).
However, the above article talks about the huge uncertainty in determining the radiation dose guideline, as described by Dr. Evan B. Douple, the associate chief of research at the Radiation Effects Research Foundation in Hiroshima. Current guidelines were developed based on the existing radiation exposure studies, most of which come from studying the Hiroshima and Nagasaki atomic bomb survivors. The a-bomb survivors received virtually all of the radiation as a one-time dose whereas people in the vicinity of the Fukushima Daiichi nuclear power plant are subjected to low-level doses for a prolonged period. There is no clear consensus as to how the different modes of radiation may affect human health differently.
I suppose much of the current confusion and frustration is due to the fact that nobody really knows how much is too much. Public health experts cannot say anything more definitive than “may likely be harmless.” However, I do realize that these statements are indeed inevitable because there is no explicit data that illustrates the effect of prolonged low-dose exposures.
Where can we go from here? First, we need to ensure that the Japanese government fund a long-term monitoring of the physical health of Fukushima people for many years to come. This is not only to ensure good health and high quality of life for the affected people (which is an absolute priority), but also to provide data for future nuclear incident guidelines. Also, we need to make sure that the Japanese government fund a comprehensive, long-term characterization of the radionuclide levels in soils, air, surface/ground water and public facilities for many years to come so that the public health data can be interpreted in the environmental context. The guidelines must be revised as needed as more health effect data become available. Finally, we need to make sure that the Japanese government prepare an evacuation plan based on the most up-to-date guidelines available, and the plan be put to use without delay if needed.
We have an unprecedented, albeit unfortunate, opportunity to reduce the uncertainty.