Japan should do more to address fears over radiation in the area around Fukushima, a UN health expert said Monday, urging it to consult those affected by nuclear pollution.

Anand Grover, UN Special Rapporteur on the right to health, told reporters the government needed to depend less on experts and give more information directly to people living with nuclear fears.

"Everything should be done with the participation of communities," he told reporters at the end of a 12-day tour of Japan that included Fukushima and Miyagi prefectures.

The Fukushima crisis, where reactors went into meltdown after cooling systems were swamped by the tsunami of March 2011, was "a man-made disaster", said Grover, echoing the Japanese parliament's own finding.

Grover said the failure of the government and plant operator Tokyo Electric Power Co to disclose key information on radiation limits had added to the confusion and hurt.

The government's initial threshold for evacuation of 20 millisieverts per year "conveyed the message that effective radiation doses up to" that level were safe.

He said the "inconsistency" between that limit and the 5-millisievert dose allowed around Chernobyl before mandatory resettlement after its nuclear catastrophe "created confusion among a significant number of the local population, who increasingly doubt government data and policy".

Asked about how to clear up the confusion and reassure people, he urged the government not to rely too much on specialists. "I personally think experts know only part of the situation. Communities must be involved," he said.

"During the visit, I have also heard from the affected residents, and particularly from such groups as persons with disabilities, young mothers and pregnant women, children and older persons, that they have had no say in decisions that affect them," Grover said.

"I urge the government to ensure that the affected people, particularly the vulnerable groups, are fully involved in all decision-making processes" including in the formulation of health management surveys, designing of evaluation shelters and implementation of decontamination, he said.

Grover also said the government should widen the area over which it tests people for the effects of radiation, rather than limit it to residents of and visitors to Fukushima prefecture at the time of the disaster.

"The scope of the surveys is unfortunately narrow as they draw on the limited lessons from the Chernobyl accident and ignore epidemiological studies that point to cancer as well as other diseases in low-dosage radiation, even in areas of exposure below 100 millisieverts per year," he added.

"As for internal radiation exposure... there is a view among scientists legitimately that there is no danger from exposure between zero and 100 millisieverts, but that is controversial," he said.

"The government has to err on the side of caution and be inclusive."