Researchers to study long-term effects of radiation on Fukushima workers via The Mainichi

Following the Fukushima No. 1 Nuclear Power Plant disaster, Japan has a large number of radiation-exposed workers. To learn more about the health effects of this exposure, a study will be conducted this spring to follow the health of these workers throughout their lives.

Meanwhile, while rules to protect nuclear plant workers and workers involved in radiation decontamination efforts have been advanced, a look at the reality now, four years after the disaster, shows there have been safety lapses and workers who have fallen through cracks in the system.

One Fukushima Prefecture man, 34, received an envelope in the mail in early February this year. It was from the Radiation Effects Research Foundation (RERF), a name unfamiliar to him. Inside the letter was a six-page pamphlet. It was a request for cooperation with “epidemiological research on workers involved with emergency work at the Fukushima No. 1 Nuclear Power Plant.”
The man and his colleagues evacuated and sought radiation screenings at a company within the TEPCO business group, but they were rejected. Furthermore, it was only after the disaster that the men were educated about radiation and given radiation management booklets. Inside the man’s booklet, it was written that he had experienced 9 millisieverts of combined external and internal radiation exposure. It was only an estimate, however, likely calculated from the concentration of radiation in the area at the time and the length of time the man spent on site.

In late May that year the man and his colleagues underwent internal radiation dose screenings, but too much time had passed for detecting substances like iodine-131, which has a half-life of around eight days.

“We all complained and finally we underwent a screening, but I wish they had responded more quickly,” says the man.

As he looked again at the pamphlet that came in the mail, he added, “Until I know how much I was really exposed to, I’ll be anxious.”

RERF, which receives funding assistance from the Ministry of Health, Labor and Welfare, will start its investigation into Fukushima workers’ health this spring to follow them for life and study the relationship between their radiation exposure and illnesses they may develop, like cancer. The study aims to cover around 20,000 people who worked at the plant up through Dec. 16, 2011, the day that the radiation exposure limit for workers involved in emergency work was raised from 100 millisieverts to 250 millisieverts. During this time, the greatest radiation exposure for an individual worker was 679 millisieverts.

First, for an initial study, at the end of January the RERF sent pamphlets to around 5,000 of these workers currently living in Fukushima Prefecture, but many of the pamphlets were returned because the addressee couldn’t be found, says Okubo. By the reply deadline at the end of February, only around 1,000 people had responded.

As for why the study is starting four years after the disaster, the health ministry says that one reason is that it took a long time to estimate radiation exposure, but it also notes that health effects from the Chernobyl disaster in the former Soviet Union took five years to appear, so it is not too late to start such a study.

However, Okubo says, “There are workers whose addresses we don’t know, or who have died.” The degree of cooperation the RERF can get from the workers will determine what becomes of the survey.

Furthermore, accurate radiation exposure amounts are vital for the study. TEPCO said that, “From around March 15, 2011, to the end of that month, some work groups only had their leader carry a dosimeter, but outside of that we always lent dosimeters to everyone.” However, those devices can only detect external radiation exposure. The internal radiation exposure screeners at the plant became unusable due to the disaster, and it was not until July 2011 that internal radiation screeners were set up at a location where the workers gather outside the plant.

Many workers did not get their internal radiation exposures screened soon after the disaster, so they have to be estimated. New assessments will be made in the RERF study, but Okubo, explaining the difficulty in making those estimates, says, “Even at the same workplace, if one person breathed twice the amount of another during their work, they will have twice the radiation exposure.”

The number of workers who have been involved in radiation-related work for the Fukushima disaster, including workers at the plant itself, was over 40,000 as of the end of January this year. Of them, 174 had radiation exposure over 100 millisieverts, which is said to be a threshold over which the risk of developing cancer grows. Currently, there have been only nine applications for workplace-related accidents in connection with work at the Fukushima plant, but that number could increase.

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