New research has found that radioactive material in parts of northeastern Japan exceeds levels considered safe for farming.
The results are reported in the Proceedings of National Academy of Sciences Journal and, according to the BBC, provide the first comprehensive estimates of contamination across Japan following the nuclear accident in 2011.
In the wake of the accident at Japan's Fukushima nuclear power plant, radioactive isotopes were blown over Japan and its coastal waters.
Fears that agricultural land would be contaminated spurned research into whether Japanese vegetables and meat were safe to eat.
An early study had suggested that harvests contained levels of radiation well under the safety limit for human consumption.
The latest research measured radioactive caesium-137 in grass and soil samples from all but one of Japan's 47 regions and combined these results with simulations based on weather patterns following the meltdown.
Using this information they calculated that radioactive levels close to the Fukushima plant were eight times the safey limit, while neighbouring regions were just under the limit.
Most areas of the country were judged to be well below the safety limit due, the researchers, believe to the mountainous nature of Japan.
As a result, the scientists are urging the Japanese government to carry out a more thorough assessment of radioactive contamination across the country before considering future plans for decontamination.
