Fallout at Fukushima -- Part 3
What impact will Japan's nuclear woes have on the country's ecology and agriculture?
The most recent estimates from the US Department of Energy (DOE) assert that the levels of radiation outside the Fukushima Daiichi nuclear plant are well below the threshold that would pose an immediate risk to the local residents. But reports of radionuclides in soil, water and food products are raising concerns among consumers and importers alike. While the levels of radioisotopes being detected in soil and crops are above legal standards, they are still below dangerous levels, according to most reports. The United States became the first country to linkurl:block the import;http://www.trust.org/alertnet/news/us-halts-milk-produce-imports-from-areas-of-japan-near-crippled of milk and fresh produce from the areas around the plant, however, followed quickly by linkurl:Hong Kong.;http://www.bloomberg.com/news/2011-03-23/hong-kong-bars-some-japan-produce-after-finding-elevated-radiation-levels.html What does this mean for Japan's food industry, as well as the local flora and fauna?
Effects on agriculture
The 1986 Chernobyl disaster released radionuclides that spread to some 125,000 square kilometers of land in Belarus, Ukraine and Russia, more than a third of which was in agricultural use. This meant widespread contamination of farm lands, with radioisotopes ending up in crops and pasture land. The dairy industry was particularly hard hit, as cows grazing on affected grass produced contaminated milk. Four years after the accident, as many as 50,000 cows were still producing milk with radionuclides that exceeded permissible levels.
|Daikon and wind farm in Koriyama, Fukushima, Japan. How will farms like these by affected by radiation from the nuclear power plant?|
Image: Wikimedia Commons, contri
Current estimates of the direct radiation levels from the Fukushima Daiichi nuclear plant are significantly lower than those that occurred during the Chernobyl accident, and few details have been released on the type of radiation being emitted, said radioecologist linkurl:Nick Beresford;http://www.ceh.ac.uk/staffwebpages/NickBeresford.html of the Centre for Ecology & Hydrology at the Lancaster Environment Centre. So whether or not Japan will struggle with similar agricultural consequences is pure speculation at this point. But "any of them can pose a threat to the agricultural industry -- iodine, strontium, cesium -- depending on the nature of the incident," he said. "Radioactivity as a pollutant is slightly different from most other things -- [there's] the external dose, and then there will be uptake into plants via the roots or animals via the diet."
Late last week, for example, Japanese chief cabinet secretary Yukio Edano announced the government's decision to ban shipments of milk from the immediate region and spinach from several surrounding prefectures after detecting iodine-131 in the food products from farms within 90 miles of Fukushima. Yesterday, that list grew to a total of 11 different vegetables, including cabbage, radish, parsley, cauliflower, and broccoli, and reports over the last couple of days have reported elevated radiation levels in the area's soil and in tap water as far away as Tokyo.
The amount of radiation found in the affected crops, water and soil, however, is highly uncertain. NHK
, Japan's sole public broadcaster, linkurl:reported;http://www3.nhk.or.jp/daily/english/23_28.html yesterday that soil samples collected 40 kilometers away from the plant had 1,600 times the normal level of "radioactive substance." But the DOE linkurl:reports;http://blog.energy.gov/content/situation-japan/ that while the immediate vicinity of the plant is seeing exposures of up to 12 millirem per hour (a rate at which it would take 17 days of continuous exposure for a worker to accumulate the maximum annual dose of 5000 millirem), just 20 kilometers away from the plant, those levels drop to just 1.2 millirem per hour (though the report did not specify soil) -- a level that's not a cause for immediate concern.
Beresford said he had seen reports of radiation levels in soil that were "obviously 'higher than normal,'" but not more than he measured from samples in the United Kingdom following the Chernobyl accident. Plus, he added, it's important to keep in mind that "if normal is very low, then x-times normal need not be a cause for concern."
The variation in the reports regarding the radiation levels may stem from how different soil types affect the transfer of radionuclides to plants, and subsequently meat or milk, he said. "High clay contents and/or available potassium concentrations lead to comparatively low transfers whereas high organic matter soils and those with low available potassium concentrations have comparatively high transfers."
But Beresford still urges caution. "The higher values which are being reported require that food products are monitored, and this should be continued as animal management changes with season and different crops are harvested."
Impacts on local ecology
The Chernobyl disaster was the "worst case scenario," said Timothy Jannik, technical advisor at the linkurl:Savannah River National Laboratory.;http://srnl.doe.gov/ Fire ignited the nuclear fuel, dispersing radioactive particles across 200,000 square-kilometer landscape around the nuclear plant in the former Soviet Union.
But the degree to which local flora and fauna suffered from the accident remains a topic of much debate. Journalists and scientists visiting the area regularly cite the great diversity of life within the Chernobyl exclusion zone, the most contaminated area within 30-km of the power plant, declaring it a wildlife preservation with sightings of moose, deer, and wild boar. However, this anecdotal evidence doesn't necessarily mean that the accident was a boon for biodiversity, said University of South Carolina biologist linkurl:Timothy Mousseau,;http://cricket.biol.sc.edu/mousseau/mousseau.html who has spent the last decade studying organisms in Chernobyl. While much of the vegetation destroyed by the initial nuclear blowout has grown back and the area may appear at first glance to be a lush environment for wildlife, "I can count on two hands the number of those animals we've seen over a 10 year period," he says.
|Chernobyl barn swallows (Hirundo rustica) normal (left) and with radiation-caused albino spots (right)|
Image: Courtesy of Timothy Mousseau
Indeed, the data that Mousseau and his team have collected suggests that the accident resulted in population declines and decreased diversity in linkurl:birds;http://rsbl.royalsocietypublishing.org/content/3/5/483 and linkurl:insects;http://f1000.com/1161029?key=1jyccjwqyq86qnn inhabiting high-radiation areas. The radiation also caused linkurl:mutations;http://rsbl.royalsocietypublishing.org/content/3/4/414.full in the barn swallows that created albino patches in their bright plumage, impairing their ability to attract mates, and a recent linkurl:study;http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0016862 even found a decrease in the brain size of the radiation-exposed birds. linkurl:Studies;http://onlinelibrary.wiley.com/doi/10.1002/etc.5620190209/abstract by linkurl:Ron Chesser;http://firstname.lastname@example.org of Texas Tech University and colleagues, on the other hand, found no effects on small mammal populations in the area.
"There are very contradictory points of view on the same issue," says Eduardo Farfan, principle engineer at the Savannah River National Laboratory, who has worked with scientists at Chernobyl.
Regardless of the diagnosis for Chernobyl's wildlife, there is one thing on which everyone seems to agree: At this point there is no evidence that Japan's animal populations should suffer from the radiation currently leaking from the plant in Fukushima. Current reported levels are quite low compared to those following the Chernobyl disaster, and as long as the workers are "able to control the fuel and keep most of it from escaping," the local plant and animal populations should remain safe, says linkurl:Ward Whicker,;http://www.cvmbs.colostate.edu/erhs/faculty/whicker/w_whicker.htm one of the founders of radioecology from Colorado State University.
The risks for the local marine populations are similarly low, he adds: The ocean's size will dilute any radiation that does make it to the water, and the high concentration of potassium and calcium will compete with the chemically similar cesium-137 and strontium-90 radionuclides, preventing any significant marine impacts or bioaccumulation in the sea products consumed by humans.
"Certainly there will be many interesting questions to address in the coming months and years to determine what the impact of that event will be," said Mousseau. But for now, the risks appear minimal for Japan's ecological communities.
**__Related stories:__*** linkurl:Fallout at Fukushima -- Part 2;http://www.the-scientist.com/news/display/58087/
[23rd March 2011]*linkurl:Fallout at Fukushima;http://www.the-scientist.com/news/display/58085/
[22nd March 2011]
**__Related F1000 Evaluations:__** *linkurl:Reduced abundance of insects and spiders linked to radiation at Chernobyl 20 years after the accident;http://f1000.com/1161029?key=1jyccjwqyq86qnn
A. Moller et al., Biology Letters
, 5(3):356-9, 2009. Evaluated by Andrew Clarke, British Antarctic Survey, UK.*linkurl:Transgenerational accumulation of radiation damage in small mammals chronically exposed to Chernobyl fallout;http://f1000.com/1033562?key=5qhpsgq7z0ljs81
N. Ryabokon et al., Radiat Environ Biophys
, 45(3):167-177, 2006. Evaluated by Russell Bonduriansky, University of New South Wales.