According to a new report published in the highly-respected journal PNAS, the levels of radiation caused by the Fukushima nuclear disaster and experienced by marine organisms throughout the food chain are “well below levels which could cause harm to ocean biodiversity, and even in the most part below levels experienced due to naturally-occurring radionuclides.” However there are other factors that could have a greater impact on wildlife.
Yesterday, we published an article that reported levels of Fukushima radiation found in Bluefin tuna off the coast of California, but this new report states that the radiation levels have not caused as much damage to the ecosystems as we may have feared.
Of course, it all comes down to numbers and how they compare to natural levels of radiation found in the sea. According to the report, the radiation released into the sea was a “tenth as much radiation as was released by Chernobyl”. That’s a significant amount, and the report states that two caesium isotopes (Cs-134 and Cs-137) were found in the seawater at concentrations up to 1,000 times greater than before the disaster. They were also found in an area of the Pacific Ocean covering 150,000 square kilometres off the coast of Japan.
However once you go 30 km offshore, the radiation levels drop down by 50 times, to about 600-800 becquerels per cubic metre on average. This is well below Japanese regulatory limits for the ocean of 90,000 Bq/m3, and also 15 times lower than the radiation released naturally by the most common natural radionuclide in the ocean, potassium-40 (which on average measures in at 12,000 Bq/m3).
But what about the 30 km of ocean between Japan and the levels were it’s ‘relatively’ safe? The report seems to indicate that marine life will be fine. Again, numbers are important – but as radionuclides are ever-present in the environment, it would seem that living organisms are well-accustomed to dealing with them. It also states that the waters 30 km from Fukushima are still dominated by the naturally-occurring radionuclides polonium-210 and potassium-40. In order for the radiation to reach the levels emitted by natural polonium, caesium-137 levels in fish would have to be 1-3 orders of magnitude (10-1000x) higher than they observed in the waters off Japan.
In short, “these levels are several orders of magnitude lower than those used in one study that assumed exposure to the most heavily impacted water discharged from the Fukushima NPPs to predict marked reproductive effects and possible mortality in marine biota.”