It’s been almost eight years since a major earthquake and the resulting 15-metre tsunami caused a severe nuclear accident at Japan’s Fukushima Daiichi Nuclear Power Station. The fuel meltdown and subsequent explosion released massive amounts of radioactive material into the environment – including iodine-131, cesium-134 and cesium-137 (Cs-137) – heavily contaminating the Pacific Ocean.
Most of the damage was done in reactors 1, 2 and 3 where some 300 tons of fuel melted through the reactors’ steel vessels, penetrating so deep into the ground that operators weren’t sure about its whereabouts and how to extract the molten fuel. Not to mention that the decommissioning and clean-up efforts were soon marred by poor decision and mishandling by the authorities (storage tanks still leaking contaminated water into the ocean, black bags filled with radioactive debris sitting dangerously at the site, and an underground ice wall built at a staggering cost).
Now, a new study revealed that the Cs-137 which spewed out during these meltdowns will continue to contaminate the food supply for a long time. However, the researchers were quick to offer reassuring statements, claiming that radioactivity will persist in foodstuffs for many decades, but at the same time these levels are too low to present any serious risk to our health.
Dr. Keiko Tagami, the study’s co-author from the Japanese National Institute of Radiological Sciences said “This study gives us the evidence to explain to people how contamination levels will change over time. It gives us confidence that radiation doses in the average diet in the Fukushima region are very low and do not present a significant health risk now or in the future. But we have to continue monitoring foodstuffs, particularly “wild” foods such as mushrooms, new shoots of edible plants, and game animals where contamination levels remain high.” 
Is there really a safe dose? Many experts don’t agree. They believe that even small doses of radiations carry profound long-term health risks that we should be aware of.
Dr. Ian Fairlie, a London-based independent consultant on radioactivity in the environment, “Stochastic means an all-or-nothing response: you either get cancer or you don’t. As you decrease the dose, the effects become less likely and your chance of cancer declines all the way down to zero dose. The corollary is that tiny doses, even well below background, still carry a small chance of cancer: there is never a safe dose, except zero dose.” 
We have addressed this in detail in one of our previous blog posts titled, Risk of Low Dose Chronic Radiations. Recent epidemiological studies also show that low dose radiations have detrimental effects of your health, increasing the relative risk of ischemic or non-ischemic heart diseases, cerebrovascular disease, and cataracts.  
Another research published in the International Journal of Radiation Biology found that exposure to doses even as low as 0.5 Gy has the potential to increase the risk of cardiovascular damage, up to decades after exposure. 
The study highlighted how low dose radiation affects heart health through a number of molecular and cellular mechanisms – including reduced levels of Nitric oxide (an anti-inflammatory molecule that helps blood vessels to dilate) and increased generation of free radicals (leading to oxidation of important cellular structures such as DNA and lipids. This oxidative damage results in chronic inflammation), among others.
Another 2017 study examined whether low-dose irradiation affected the functions of mesenchymal stromal/stem cells (MSCs), derived from bone marrow (BM). The result suggested that “acute exposure to low-dose (0.1 Gy) radiation can transiently affect the functional characteristics of human BM-MSCs.” 
Effects of small amounts of Cs-137 in your food?
Cs-137 is one of the most prevalent, also one of the most dangerous, radionuclides released after a nuclear fall-out. With a half-life of 30 years, Cs-137 stays in the environment for roughly 300 years. It dissolves in water and quickly enters and accumulates in the food chain. That’s why consumption of locally produced foods carries high risk of internal exposure. Wild fungi, game meat and to some extent berries and dairy, have a high capacity to accumulate Cs-137.
In 2015, researchers evaluated radiocesium concentrations in wild mushrooms collected in Kawauchi Village after the Fukushima accident. The village is located less than 30 km from Fukushima plant. The team found that radiocesium is often detectable.  A similar research conducted in 2016 concluded that “the internal radiation doses of ingesting foods are acceptably low compared to the public dose limit, although the potential for radiation exposure still exists. Attention should be paid when consuming foods harvested from forests in order to avoid unnecessary chronic internal exposure.” 
Once released into the environment, Cs-137 decays into both beta particles and gamma radiation. Studies show that consuming food contaminated with Cs-137 causes the radionuclide to accumulate throughout the body; in endocrine tissues, thyroid, heart, kidneys, stomach, small intestines, pancreas, liver, spleen, brain, lung and skeletal muscles. Children and pregnant women are more susceptible to the damage caused by Cs-137. What is alarming in that Cs-137, in the tissues, mimics potassium and most of it becomes concentrated in muscle, and that includes your heart.
New and unexpected discoveries
A new study published in the Proceedings of the National Academy of Sciences reveals how nuclear disasters can impact our environment in the most unexpected ways. Scientists found that highest levels of Cs-137 from the 2011 disaster have been accumulating in the sands and brackish groundwater (mixture of fresh water and salty water) underneath beaches over tens of kilometres away from the site; not in the in the ocean, rivers, or potable groundwater as was expected.
It was generally believed that after the accident, high levels of radioactive cesium were carried along the coast. However, some of this became stuck to the sands, loading the beaches and permeating the brackish water underneath. Interestingly, it has been found that cesium no longer remains sticky in the presence of salty water. So, with new waves bringing salty seawater from the ocean, the brackish water turned salty and rendered cesium loose, which is now slowly making its way into the oceans of the world.
The scientists estimated that this discharge of cesium from the groundwater under the beaches into the ocean is occurring at the rate which is at par with direct leakage from the Fukushima power plant itself and runoff from the rivers. While this may not pose an immediate health concern, the study authors wrote that, “this new unanticipated pathway for the storage and release of radionuclides to ocean should be taken into account in the management of coastal areas where nuclear power plants are situated.” 
In 2016, another finding came into the limelight. Until this time, scientists believed that Cs-137 existed in water soluble form. But now researchers found that Cs-137 fallout on Tokyo following the 2011 nuclear meltdown was in an insoluble form. This cesium was found enclosed within super tiny glass microparticles, formed when concrete and metal in the buildings was shattered and liquified due to high heat. Not much is yet known about how these microparticles act in the environment or how our bodies react to them.
According to Professor Bernd Grambow, Director of SUBATECH laboratory, Nantes, France, these findings are important, changing the “way we assess inhalation doses from the caesium microparticles inhaled by humans. Indeed, biological half- lives of insoluble caesium particles might be much larger than that of soluble caesium“. 
Going by these observations, one thing is clear: many things about radioactive contamination are still unknown and unpredictable. This means that how we look at the resulting health implications could also change.
- University of Portsmouth. After Fukushima: Radiation Levels in Food Predicted. Lab Manager. 2017
- Ian Fairlie. 2015. Fukushima: Thousands Have Already Died, Thousands More Will Die. Counter Punch.
- Little et al. Systematic review and meta-analysis of circulatory disease from exposure to low-level ionizing radiation and estimates of potential population mortality risks. Environ Health Perspect. 2012
- Chodick et al. Risk of cataract after exposure to low doses of ionizing radiation: a 20-year prospective cohort study among US radiologic technologists. Am J Epidemiol. 2008
- Azimzadeh et al. Proteome analysis of irradiated endothelial cells reveals persistent alteration in protein degradation and the RhoGDI and NO signalling pathways. Internation Journal of Radiation Biology. 2017
- A Fujishiro et al. Effects of acute exposure to low-dose radiation on the characteristics of human bone marrow mesenchymal stromal/stem cells. Inflammation and Regeneration 2017.
- Nakashima K, Orita M, Fukuda N, Taira Y, Hayashida N, Matsuda N, Takamura N. Radiocesium concentrations in wild mushrooms collected in Kawauchi Village after the accident at the Fukushima Daiichi Nuclear Power Plant. Peer J. 2015
- M Orita et al. Concentrations of Radiocesium in Local Foods Collected in Kawauchi Village after the Accident at the Fukushima Dai-ichi Nuclear Power Station. Scientific Reports 2016.
- Sanial et al. Unexpected source of Fukushima-derived radiocesium to the coastal ocean of Japan. PNAS 2017.
- Radioactive cesium fallout on Tokyo from Fukushima concentrated in glass microparticles. Phys.org. 2016.