Four years ago today Japan was hit with a magnitude 9.0 earthquake and massive tsunami that caused widespread destruction, leaving almost 22,000 people dead or missing and triggering a crisis at the Fukushima Daiichi nuclear plant.

Sorry, this video has expired Fukushima residents take cancer testing into their own hands ( Matt Carney )

The triple nuclear meltdown was the world's worst nuclear disaster since Chernobyl.

About 120,000 people still cannot return their homes because of high radiation levels, but the issue of long-term health implications like cancer are causing the greatest concern and controversy in Japan.

Before the disaster, there was just one to two cases of thyroid cancers in a million Japanese children but now Fukushima has more than 100 confirmed or suspected cases, having tested about 300,000 children.

Megumi Muto's daughter Nana has undergone scans to determine if the lumps in her thyroid glands have grown. In a small number of cases, these lumps can develop into cancer.

Ms Muto is convinced the growths were caused by exposure to high radiation levels after the Fukushima nuclear meltdown in March 2011.

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"I feel angry. I think the authorities hide the real dangers and now many more children are being diagnosed," she said.

Engineer says Fukushima cancer spike needs to be investigated

Some scientists have said the rise is just because they are simply doing more testing with more sensitive equipment. This view is backed by a United Nations report, but other credible scientists said the spike in thyroid cases was significant and had to be thoroughly investigated.

It is expected that thyroid cancers could turn up about four to five years after a nuclear disaster.

In Chernobyl about 6,000 children contracted thyroid cancer but the radiation released there was greater than in Fukushima.

Ms Muto said her daughter and son, like many other children, had not been the same since experiencing the Fukushima fallout.

"They had rashes on their bodies then nose bleeds. My son's white cells have decreased and they both have incredible fatigue," she said.

"They may not have cancer now but they both have multiple nodules around their thyroids. I'm really worried."

Ms Muto is part of about 100 Fukushima residents taking the local and central governments to court.

They claim both governments failed to protect the children and they do not trust what the government or TEPCO, the operator of the crippled nuclear plant, are telling them about radiation levels and safety.

So they are conducting their own radiation tests. Near a school in Fukushima city they record three microsieverts an hour, around 100 times the rate in Tokyo.

Sumio Konno has worked as a engineer at nuclear plants for 29 years and said the levels needed to be investigated.

"I have to investigate and inform the public of the facts, that is why I have become one of the plaintiffs of the court cases," Mr Konno said.

"They're still not decontaminating areas where children live or near schools, even after four years."

Smoke rises from the earthquake and tsunami damaged the Fukushima nuclear plant on March 14, 2011. ( DigitalGlobe: AFP )

Mr Konno said he would not be able to return to his home as the radiation levels were far too high.

"I lost my hometown of Namie to the disaster and I cannot see any future," he said.

"A lot of people are depressed, they feel isolated."

The Fukushima government has recorded more than 1,800 stress-related deaths to the March 11 disaster of 2011.

Ms Muto wanted to move her family out of Fukushima city but she said she could not afford to.

"Fukushima was a rich farming area and we used to live off the local produce given to us by relatives and friends but now I buy food from other prefectures of Japan," she said.

"It's more expensive so I'm stuck here."