Perilous
Times
Large land areas in Japan too radioactive to farm: study
by Staff Writers
Tokyo (AFP) Nov 15, 2011
Large Swaths of Farmland in parts of Japan is no longer safe
because of high levels of radiation in the soil, scientists have
warned, as the country struggles to recover from the Fukushima
atomic disaster.
A team of international researchers said food production would
likely be "severely impaired" by the elevated levels of caesium
found in soil samples across eastern Fukushima in the wake of
meltdowns at the tsunami-hit plant.
The study, published in the Proceedings of the National Academy of
Sciences journal, suggests farming in neighbouring areas may also
suffer because of radiation, although levels discovered there were
within legal limits.
"Fukushima prefecture as a whole is highly contaminated,"
especially to the northwest of the nuclear power plant, the
researchers said.
The study looked at caesium-137, which has a half life of 30 years
and therefore affects the environment for decades.
The legal limit for concentrations in soil where rice is grown of
the sum of caesium-134 and caesium-137, which are always produced
together, is 5,000 becquerels per kilogram (2.2 pounds) in Japan.
"The east Fukushima prefecture exceeded this limit and some
neighbouring prefectures such as Miyagi, Tochigi and Ibaraki are
partially close to the limit under our upper-bound estimate," the
study said.
"Estimated and observed contaminations in the western parts of
Japan were not as serious, even though some prefectures were
likely affected to some extent," it added.
"Concentration in these areas are below 25 becquerels per
kilogram, which is far below the threshold for farming. However,
we strongly recommend each prefecture to quickly carry out some
supplementary soil samplings at city levels to validate our
estimates."
The study said "food production in eastern Fukushima prefecture is
likely severely impaired by the caesium-137 loads of more than
2,500 becquerels per kilogram".
It is also likely production is "partially impacted in
neighbouring provinces such as Iwate, Miyagi, Yamagata, Niigata,
Tochigi, Ibaraki and Chiba where values of more than 250
becquerels per kilogram cannot be excluded", it said.
The study was led by Teppei Yasunari of the Universities Space
Research Association in the US state of Maryland.
He and his team used daily observations in each Japanese
prefecture and computer-simulated particle dispersion models based
on weather patterns.
Japan has been on alert for the impact of radiation since an
earthquake and resulting tsunami struck the northeast of the
country on March 11, crippling the Fukushima Daiichi nuclear power
plant.
Its cooling systems were knocked offline and reactors were sent
into meltdown, resulting in the leaking of radiation into the air,
oceans and food chain.
Shipments of a number of farm products from the affected regions
were halted and even those that were not subject to official
controls have found little favour with Japanese consumers wary of
the potential health effects.
An official in charge of soil examination for the agriculture
ministry said government tests had been conducted on soil in
Fukushima and five other prefectures earlier this year.
He said contamination levels in Fukushima had exceeded 5,000
becquerels per kilogram, but were below that level elsewhere.
"We are now conducting further checks covering 3,000 spots in
Tokyo and 14 prefectures and plan to publish the results later,"
he said.