Two nuclear plant workers have exceeded Japan's radiation exposure limit for men and others who toiled without sufficient protection in the earliest days of the disaster could show high levels as well, the government and plant operator said Friday.
The two control room operators at the Fukushima Dai-ichi plant are the first men to surpass the government-set limit. About 40 workers are being tested further after preliminary findings showed high exposures, TEPCO spokesman Junichi Matsumoto said.
The two men are not showing immediate health problems but have an increased lifetime risk of cancer. TEPCO will take care of their long-term health monitoring, he said.
Doctors at the National Institute of Radiological Sciences examined them and said the two men don't require current health treatment and can live normally, Matsumoto said.
Workers have been fighting to get the Fukushima Dai-ichi plant under control since the March 11 earthquake and tsunami knocked out power and crucial cooling systems, largely melting the cores of three reactors. Several explosions have scattered highly radioactive debris around the plant and leaked radiactivity into the environment around it.
The two men, one in his 30s and the other in his 40s, were responsible for the central control room for Unit 3 and 4 reactors the day the disasters struck and in the days that followed. About 150 other control room operators worked early in the crisis and are being examined.
Overexposed workers most likely inhaled radioactive particles while battling the initial crisis without sufficiently covering themselves with masks and radiation-proof gear, Matsumoto said.
"Monitoring of internal exposures has been slow. I'm afraid we'll see more people exceeding 250 millisieverts," Goshi Hosono, director of the government's crisis management taskforce, urging TEPCO to speed up monitoring of workers' health and take appopriate steps.
Soon after the tsunami damaged the plant, the government raised the limit for men to 250 millisieverts from the earlier 100 millisieverts so workers could tackle the emergency.
Total exposures of the two male workers may be as high as 580 millisieverts _ nearly 1,000 abdominal X rays _ if they were almost entirely irradiated in the first two days, when a first explosion occurred at the plant, Matsumoto said.
The total exposure would depend on whether they wore masks, their location inside the facility and other factors. Officials are still examining details to finalize the results.
A massive single whole-body exposure of 500 millisieverts could decrease lymphocyte cells in some people, which would compromise their immune systems.
The exposure limit for women is much lower to avoid harming a fetus of any pregnant worker. The limit for women certified to work in controlled areas is 5 millisievert for three months, and the cap for other women is 1 millisievert. Two women in the first category have exceeded that limit, and two in the second category.
The two men, and the four women whose exposures were disclosed earlier, have been removed from working at the plant.
TEPCO has been criticized for not fully disclosing the extent of radiation exposures by the plant workers or their working conditions.
When TEPCO revealed the preliminary results on the two men this week, the health ministry ordered TEPCO to check exposure levels of everyone who worked closely with them and to remove them from plant duties.
TEPCO has promised to bring the plant under control by January, but fears are growing that was too optimistic.
TEPCO has been also struggling to contain tons of radioactive water leaking out of the damaged reactors, but the water that has pooled across the plant is now threatening to overflow temporary storage tanks, Matsumoto said.
Workers are scrambling to complete a reprocessing system by June 15 to eventually reuse the water as coolant in the reactors. The schedule is extremely tight, as the water could start overflowing around June 20, or even earlier in case of heavy rain, Matsumoto said.