Assessing potential radiological harm to fukushima recovery workers

Abstract

A radiological emergency exists at the Fukushima Daiichi (Fukushima I) nuclear power plant in Japan as a result of the March 11, 2011 magnitude 9.0 earthquake and the massive tsunami that arrived later. News media misinformation related to the emergency triggered enormous social fear worldwide of the radioactivity that is being released from damaged fuel rods. The heroic recovery workers are a major concern because they are being exposed to mostly gamma radiation during their work shifts and life-threatening damage to the radiosensitive bone marrow could occur over time. This paper presents a way in which the bone marrow equivalent dose (in millisieverts), as estimated per work shift, could be used along with the hazard function model previously developed for radiological risk assessment to repeatedly check for potential life-threatening harm (hematopoietic system damage) to workers. Three categories of radiation hazard indication are proposed: 1, life-threatening damage unlikely; 2, life-threatening damage possible; 3, life-threatening damage likely. Categories 2 and 3 would be avoided if the whole body effective dose did not exceed the annual effective dose limit of 250 mSv. For down-wind populations, hormetic effects (activated natural protective processes) are much more likely than are deleterious effects.

Keywords: hormesis; radiological emergency; risk assessment.

FIGURE 1.

Predicted median lethal dose (D₅₀(y)) for the hematopoietic mode of death for different mammals (Sprague-Dawley rats, white non-inbred mice, dogs, swine, goats, sheep, and humans) as a function of the external low-LET radiation dose rate y to bone marrow in Gy/h. Dose rate is presented as a categorical variable and is not aligned to tick marks.