Tokyo, Japan - "Hot spots" of nuclear radiation still contaminate parts of Fukushima Prefecture, according to findings from the latest Greenpeace radiation monitoring mission near the Daiichi nuclear power plant that experienced a melt down after an earthquake and tsunami in March 2011.

Experts from the environmental organisation also claim that authorities have consistently underestimated the amount of contamination and the health risks involved.

Greenpeace will use these results to try to persuade local governments with nuclear power plants in their districts to resist lobbying from the central government to have them reactivated. All 50 of Japan's remaining nuclear plants were shut down following the 2011 disaster.

Greenpeace began independently monitoring radiation in Fukushima within a few days of the nuclear accident, and it has conducted field trips each year since then. The latest such trip took place from October 24-27.

Heinz Smitai, a nuclear physicist, Greenpeace campaigner and participant in the radiation monitoring mission, told foreign journalists at an October 30 press conference in Tokyo that radiation hot spots exist as far as 60 kilometres from the site of the disaster.

For instance, one street in front of a hospital in Fukushima City "is quite contaminated", Smitai said, measuring 1.1 microsieverts of radiation per hour. Although this was one of the highest readings, Greenpeace found 70 other places in the city where the amount of radiation recorded exceeded the Ministry of Environment's long-term target of 0.23 microsieverts per hour.

A sievert is the standard unit for measuring the risk of radiation absorbed by the body. A millisievert is equal to one-thousandth of a sievert, while a microsievert is one-millionth of a sievert. A typical CT scan can deliver from 2 to 10 millisieverts of radiation, depending on the area being scanned.

Radiation 'hot spots'

Greenpeace also monitored contamination in Miyakoji and Kawauchi, the first two locations in the 20-kilometre exclusion zone around the Daiichi plant where the government has lifted its evacuation advisory.

Nevertheless, Greenpeace found numerous points on roads in these areas that exceeded the target of 0.23 microsieverts per hour.

"And when you leave the roads and go into the fields and surrounding forests, the radiation levels go up very strongly," said Jan van de Putte, a radioactivity safety advisor in Greenpeace who also participated in the Fukushima monitoring mission. Most of these areas therefore have "not been decontaminated, and cannot be decontaminated because, for instance, a forest can't be decontaminated, practically speaking", he added.

Fukushima residents want to know what the radiation effects are in their local areas. Ritsuo Yoshioka, President of the Japan Functional Safety Laboratory

Japan's Ministry of Environment (MOE) disputes Greenpeace's claim that it is underestimating radiation contamination and its risks. It points out that radiation in Fukushima has steadily diminished over time, as indicated by the most recent Nuclear Regulation Authority (NRA) airborne monitoring survey, conducted in December 2013. An MOE spokesperson told Al Jazeera that radiation rates "around Fukushima have significantly decreased [compared to October 2012 NRA survey] due to physical decay, weathering, and decontamination efforts".

Critics, however, charge that these results were found by averaging the radiation measurements, meaning that individual "hot spots" such as those Greenpeace claims to have found could go unstated.

"There can still be buildups of [radiation doses] higher than the average result," said Ritsuo Yoshioka, an expert in nuclear reactor engineering and safety, and president of the Japan Functional Safety Laboratory. "Fukushima residents want to know what the radiation effects are in their local areas."

The government says such a means of testing is already being provided. "At the end of 2013, individual exposure rates measured with individual dosimeters were less than 1 millisievert [annualised] for more than 93 percent of Fukushima City residents," the MOE spokesperson pointed out.

Natural decay

In dealing with different monitoring methods and their results, it's important to maintain a sense of perspective, Azby Brown, a member of Safecast, told Al Jazeera. Safecast is an apolitical, independent radiation monitoring group made up of volunteers including radiation engineers, software and hardware designers and university professors.

"Yes, it's easy to find locations in Fukushima City and elsewhere that are still above 0.23 microsieverts an hour," said Brown. "But in almost every conceivable case, even if nothing is done to clean up a place that currently gives 1 millisievert exposure per year, it will give 0.5 millisieverts or less a year after 30 years, due to natural radioactive decay."

On the other hand, Brown agrees that Fukushima residents have justifiable grievances. "While experts on both sides tell me the increased risk of fatal cancer with few exceptions is likely to be less than one percent over their lifetimes, this is not the point. It's the injustice of having this risk thrust upon them, and the turmoil the accident has caused, that matters."

Greenpeace, which wants to eliminate all nuclear power, immediately presented its findings to the Kagoshima prefectural government. Kagoshima, located in the southernmost part of the island of Kyushu, is host to the Sendai nuclear power plant.

Gearing up for a fight In September the plant's two reactors were declared safe to operate the first in the country to be so designated by Japan's Nuclear Regulation Authority, after the plant met strict new safety criteria. As a result, Kagoshima has been the focus of lobbying by the central government on the one hand and by organisations opposing it, like Greenpeace, on the other.

The central government wants to restart the Sendai plant and others, to cut down on expensive natural gas and oil imports and diversify the country's energy mix. But antinuclear groups say the risks are unacceptably high, pointing to what happened in Fukushima.

After debating the issue, the Kagoshima prefectural assembly voted on November 7 to restart the plant, which is operated by Kyushu Electric Power Company. The yes vote echoed a similar decision a week earlier by the Satsuma Sendai assembly, which hosts the plant.

In a press conference following his decision, Kagoshima Governor Yuichiro Ito said that after considering every possible factor, "restarting the plant had to happen" citing Japan's limited natural resources and the need to keep industry moving.

NHK, Japan's public radio and TV broadcaster, conducted a phone survey on the subject from October 31 to November 3. In Satsuma Sendai 49 percent approved, while 44 percent disapproved. But in the surrounding areas only 34 percent approved, with 58 percent opposed. In the rest of the country, the figures stood at 32 percent for, versus 57 percent against.

Yoshioka, the safety expert, said groups opposed to reactivating nuclear plants in their respective areas would be able to argue their cases more strongly if they banded together. He mentioned that in Hakodate, the city assembly filed suit in April to stop the construction of the new Oma nuclear plant, which is 23 km away in a different prefecture.

With operators of Japan's 48 other nuclear reactors also fighting for their plants to be reactivated, it's clear this battle has only just begun.

(Editor's note: This story originally appeared on the website on November 13, 2014, but was briefly taken down due to technical difficulties.)