However, Misao Fujita, a doctor who performs thyroid scans at a clinic in Iwaki, about 30 miles south of the nuclear plant, says a connection between the cancers and radiation exposure cannot be ruled out and the screening effect is no reason to disregard the examinations.

“What we do know is that after Chernobyl, many children developed thyroid cancer, and if you take that into account and consider the high risk that Fukushima children were exposed to radiation then I think we should carry out such tests,” Dr Fujita says, adding that thyroid cancer normally occurs in one in one million children.

Noriko Tanaka, whose son is one of Dr Fujita’s patients, says exams revealing cysts in her son’s thyroid are a concern, not least because iodine-131 – a substance that causes thyroid cancer – was contained in the plume released by the Fukushima plant that landed on Iwaki after the disasters. At the time, she was pregnant with her son. “I worry because nobody knows for sure what the future holds,” she says.

Such uncertainty about the future has been shown to be a major cause of psychological stress among Fukushima residents, especially the tens of thousands stuck in temporary housing.

One 2018 study undertaken by researchers at Hirosaki University showed stress levels of evacuees increased with the length of time spent in interim accommodation while also indicating that “evacuees in radiation disasters have different stressors from other natural disasters, which may accelerate mental and physical stress.”

Profs Allison and Thomas believe it is for this reason that residents should have been allowed to return home within weeks of the disaster, but excessively strict regulations prevented this from happening.