Out of close to 900 full-time workers from the Fukushima Daiichi power plant, almost half reported psychological distress, including nervousness, hopelessness and depression, two to three months after the March 2011 earthquake and tsunami that damaged the plant.

Just under one-third of Daiichi workers had symptoms of post-traumatic stress disorder, or PTSD.

One of the study researchers said those effects could be due to explosions at the plant and other workplace stressors during the emergency, which lasted weeks, as well as to the workers' fears of losing family, friends and their homes.

In addition, said Dr. Takeshi Tanigawa, an occupational physician for both the Daiichi and the nearby Daini power plants, the workers were targets of discrimination by the community after the disaster.

"We were expecting Daiichi workers to be higher (on psychological stress measures) than Daini, because of the higher degree of stress they had experienced from plant explosions and radiation release," Tanigawa, also from the Ehime University Graduate School of Medicine, told Reuters Health in an email.

"But the responses for Daini workers were not low by all means. Their experiences were horrific as well. They had worked day and night to prevent (their plant's) meltdown."

The researchers surveyed 885 workers from the Fukushima Daiichi plant and 610 from the Daini plant in May and June 2011.

On a mental health scale from 0 to 24, where a score of 13 or higher signals psychological distress, 47 percent of Daiichi workers and 37 percent of Daini workers had high scores. Thirty percent of Daiichi workers also showed signs of post-traumatic stress, compared to 19 percent of Daini employees.

Being evacuated because of the tsunami, losing property and facing slurs and discrimination in the community were all tied to a higher chance of psychological distress, the researchers reported Tuesday in the Journal of the American Medical Association.

Evelyn Bromet, who has studied the psychological effects of disasters at Stony Brook University Medical Center, said the study was noteworthy.

"It's not that the findings are surprising - the stress these workers are under is enormous and of course it takes a toll - but it's very important to show it empirically so that appropriate mental health intervention programs can be put into place," she told Reuters Health in an email.

Gerard Jacobs, head of the Disaster Mental Health Institute at the University of South Dakota in Vermillion, agreed.

"It's very important that we look at these things and respond to these things," he said.

"If you have workers that are operating under these levels of stress, one of the consequences we know… is that cognitive functioning is affected, and so your ability to make good decisions, your ability to make good judgments, those things can be seriously impaired," Jacobs, who along with Bromet wasn't involved in the new study, told Reuters Health.

LOW RADIATION IN THE COMMUNITY

In a second research letter, another group of Japanese researchers found that cesium levels - a measure of radiation exposure - were low in more than 9,000 residents of a town located 14 miles north of the Daiichi plant. Those residents were evacuated after the March 2011 disaster but many returned later that year.

The tests were done between September 2011 and March 2012.

About 35 percent of the population had detectable levels of cesium, but only one person had enough to suggest a radiation dose above common recommended limits, according to Dr. Masaharu Tsubokura from the University of Tokyo and colleagues.

"No case of acute health problems has been reported so far; however, assessments of the long-term effect of radiation requires ongoing monitoring of exposure and the health conditions of the affected communities," they concluded.

SOURCE: bit.ly/JjFzqx Journal of the American Medical Association, online August 14, 2012.

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