The following story originally appeared in NEI’s Nuclear Energy Overview.
Radiation health experts said at a Washington press briefing that based on the radiological data collected, the health effects of the Fukushima accident should be very minimal for both the public and workers.
“From a radiological perspective, we expect the impact to be really, really minor,” said Kathyrn Higley, professor of radiation health physics in the department of nuclear engineering at Oregon State University. “And the reason for that is we understand how radionuclides move through the environment, how they disperse and how people can be exposed. Because we understand that we are able to make decisions to block exposure.”
At the event hosted by the Health Physics Society, Higley said that prompt evacuations and food monitoring by the Japanese authorities had helped reduce the public’s exposure.
“Because of those actions, the Japanese government was able to effectively block a large component of exposure in this population,” Higley said.
Dr. Robert Gale, visiting professor at Imperial College London, pointed out that although approximately 20,000 people died from the 2011 Tohoku earthquake and subsequent tsunami, none of those deaths are attributable to radiation from the Fukushima accident.
However, Gale said, “The fact that everyone is here today, shows that the public’s focus is really on Fukushima. You hear very few things about the earthquake and tsunami.”
Gale presented preliminary data on the 10,000 inhabitants near the Fukushima plant thought to have received the highest doses of radiation showing that:
- 5,800 received doses less than 1 millisievert (mSv).
- 4,100 received doses between 1 and 10 mSv.
- 71 received doses between 10 mSv and 20 mSv.
- 2 received doses between 20 mSv and 23 mSv.
By comparison, each year a resident of the United States receives an average total dose from background radiation of about 3.1 mSv.
Gale said it was important to translate these doses into something the general public could easily understand. These radiation doses indicate an “incredibly small” increase in risk of death from cancer of only 0.001 percent for a member of the Japanese public, he said. The increased risk of cancer incidence would be only 0.002 percent for a member of the Japanese public.
Such a small increase in the cancer rate would make it very hard to scientifically verify an increase in cancers that could be directly linked to the Fukushima accident.
“The exposures to the population are very, very low,” said John Boice, professor of medicine at Vanderbilt University School of Medicine and President Nominee of the National Council on Radiation Protection and Measurements. “As such, there is no opportunity to conduct epidemiological studies that have any chance of detecting excess [cancer] risk. The doses are just too low.”
Despite this, the Japanese government is conducting various large-scale studies of the public’s exposure to radiation to “reduce anxiety and provide assurance to the population,” Boice said.
These studies include:
- A health study of all 2 million residents in the Fukushima prefecture, with a 30-year follow-up study planned. This includes a 10-page questionnaire sent to residents.
- A study of 360,000 children under the age of 18 who are having their thyroid glands scanned.
- A health exam of people in the proximal area, including blood exams.
- A special survey of 20,000 pregnant and nursing mothers.
The health effects for workers at the Fukushima nuclear power plant would also be minimal, Boice said. The average radiation dosage for a worker at the plant was 9 mSv. (See above for comparative dosages for the public.) He added that out of 17,000 workers involved in “reactor containment and reactor cleanup”—including both TEPCO employees and contractors—only 37 workers had received external doses greater than 100 mSv. He said that up to 100 workers had received more than 100 mSv combining internal and external doses.
Boice added that these internal doses would have a “minimal” health effect because of the way the adult human body reacts to Iodine-131, one of the major byproducts of a reactor accident.
“In terms of health effects, these would be minimal because most of the internal, the ingested radiation, was radioactive iodine to adult thyroid glands,” he said. “Adult glands are relatively insensitive to cancer-producing effects of radiation, in particular, to Iodine-131. We have lots of studies of adults exposed to Iodine-131 where there is no effect.”
Boice said that among the small number of workers that had received over 100 mSv of radiation doses, the increased cancer risk in their lifetime would be one or two percent. He added that these workers would be studied throughout their lives.
Asked what role the Fukushima accident should play in licensing nuclear power plants in the United States, panelists said lessons learned should be applied.
“This event is being dissected for ramifications for old designs, [and] what we can learn in terms of seismic safety for new designs,” Higley said. “You really do need to look at the knowledge that is coming out of this event and decide what is relevant to reactors here in the United States.”
Boice praised the actions of the Japanese government, but hinted at improvements.
“It was a very appropriate response. What the Japanese authorities failed to do was communicate effectively,” Boice said. “And that still remains a problem—xplaining what was being done in terms of radiation exposure.”
The Health Physics Society is a scientific organization of professionals who specialize in radiation safety. Its mission is to support its members in the practice of their profession and to promote excellence in the science and practice of radiation safety.
The HPS shortly will release a white paper on the radiological effects of the Fukushima accident.