By Kiyoshi Takenaka, Shinichi Saoshiro and Kevin Krolicki
TOKYO (Reuters) - Two workers at Japan's crippled nuclear power plant may have exceeded the government's radiation exposure limit, the plant operator said, adding to concerns about health risks for those fighting the world's worst nuclear disaster in 25 years.
If confirmed, it would mark the first cases of excess radiation exposure among the hundreds of emergency workers who have struggled to bring Tokyo Electric Power Co's Fukushima Daiichi plant under control after it was wrecked by a massive earthquake and tsunami two and half months ago.
Both the government and the utility, Tepco, have come under fire for not disclosing enough information about radiation doses and the risks. Some experts question whether workers have been fully informed of the potential dangers.
"The problem is that too much policy has been focused on p rotecting Tepco and not enough on the public," said Kiyoshi Kurakawa, a medical doctor who served as a science adviser to the government from 2006-2008.
Measurements of external exposure and radioactive iodine in their thyroid glands suggested that the two male workers, one in his 30s and the other in his 40s, had surpassed the maximum set by the government of 250 millisieverts over the life of the control and clean-up project.
Exposure to 250 millisieverts of radiation is equivalent to more than 400 stomach X-rays. That is below the level for acute radiation sickness. Experts are divided about the long term health effect but agree higher levels of exposure correspond to higher risk of cancers.
The government relaxed its upper limit for exposure for the Fukushima disaster, allowing 250 millisieverts for male emergency workers compared with the conventional maximum of 100 millisieverts for nuclear-related emergencies.
Health checks about a week ago did not reveal any abnormalities in the two workers. More detailed exams are planned, Tepco said.
Japan's nuclear regulator pressed Tokyo Electric for more information and said it would monitor the situation to ensure adherence to government guidelines.
The two worked in the central control room for the plant's No.3 and No.4 reactors and conducted inspections of the plant on March 11 after a magnitude 9.0 earthquake and tsunami disabled its cooling systems and triggered fuel meltdowns in three reactors. They had been stationed at the plant until recently.