Radioactive material released during Japan’s Fukushima nuclear disaster, which unfolded in March 2011 as the result of a powerful earthquake and devastating tsunami, probably caused little long-term harm to wildlife within 100 km of the power plant, a new study suggests.

A team of scientists modeled radiation exposure caused by the crippled nuclear plant and found that the doses weren’t high enough to prevent populations of plants and animals from reproducing and surviving (Environ. Sci. Technol. Lett. 2014, DOI: 10.1021/ez500019j).

The work challenges previous studies that suggested Fukushima would lead to serious effects on wildlife, says Kathryn A. Higley, a radioecologist at Oregon State University. One such study reported a link between elevated radiation levels and abnormalities in insects (Sci. Rep. 2012, DOI: 10.1038/srep00570).

Fukushima ’caused mutant butterflies’ in Japan

Genetic mutations have been found in three generations of butterflies from near Japan’s crippled Fukushima nuclear plant, scientists said on Tuesday, raising fears radiation could affect other species.

http://www.telegraph.co.uk/news/worldnews/asia/japan/9474312/Fukushima-caused-mutant-butterflies-in-Japan.html

But the new study’s use of more accurate modeling methods to estimate organisms’ radiation doses has allowed a better assessment of the radiation effects, says Higley, who wasn’t involved in either study.

After a tsunami damaged the Fukushima Daiichi Nuclear Power Station, three of its reactors melted down, causing radioactive nuclides to spew into the air and spread to nearby areas. Since the start of the incident, scientists have tried to estimate whether wildlife had been exposed to radiation levels that might hurt the ability of populations to reproduce and survive. [And poop – Arclight2011]

Using the Hagan-Poiseuille-equation for dynamic pressure, they determined that the pressure needed to project the poop depended on the viscosity of said poop. Observe Figure 2 (below), which illustrates the dependence of pooping pressure on viscosity.

This necessitated that the authors measure the penguin poop’s viscosity with a high-performance viscosimeter (not one of those cheap-o low-performance viscosimeters!). However, the readings were inconsistent due to all the fishbones and shrimp shells in the poop, but their best estimate was that the poop’s viscosity matched somewhere around that of olive oil. (Ew ew.) After this final value was obtained, they were able to complete the equation and estimate that the power of a penguin’s fart was somewhere in the range of 10kPa to 60 kPa.

http://scienceblogs.com/retrospectacle/2007/07/07/science-vault-projectile-pengu-1/

Most previous studies relied on dosimeters that measure only external dosage to wildlife. In the new study, Justin E. Brown of the Norwegian Radiation Protection Authority and his colleagues used a model to estimate doses organisms received internally from ingesting radioactive material, which they say is a more accurate way to assess long-term risks.

Image source ; http://theinternetpost.net/2013/05/20/nuclear-cover-up-at-fukushima-to-save-money-u-n-s-c-e-a-r-obliges-icrp-dose-advice-increased/

Their model used thousands of measurements of postmeltdown radionuclide concentrations collected by other scientists throughout the first year after the accident. They looked at concentrations in air and soil, as well as in organisms that represent diverse wildlife, including macroalgae, grass, and deer. The data mainly came from monitoring stations that were set up by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR).

Brown and colleagues compared the estimated total internal doses from their model to established benchmarks for harmful radiation exposure in wildlife. In the short term, some individuals in a population may have received levels that exceeded the benchmarks, the researchers say. But among the population studied, exposure to harmful doses for almost all species was short-lived: It fell off within a few months, and within one year, total dose exposure fell below benchmarks for all organisms but macroalgae.

The study helps researchers estimate the range of radiation doses that organisms received, says Deborah H. Oughton, a radioecologist at the Norwegian University of Life Sciences. And more work is needed to learn how radiation and other stressors, such as the tsunami itself, affected wildlife in the area, she says.