Stony Brook and Stanford Universities link radioactive bluefin tuna caught off California coast to Fukushima

A study, published by the universities at Stony Brook and Stanford, has scientifically linked  radioactive contamination in bluefin tuna caught off the coast of California in August 2011, to the massive releases of radionuclides into ocean waters from Japan's Fukushima Dai-ichi nuclear catastrophe which began in March 2011. The scientific report concludes that Fukushima has "caused significant local and global concern regarding the spread of radioactive material."  The authors with Hopkins Marine Station at Stanford University and the School of Marine and Atmospheric Sciences at Stony Brook University jointly published "Pacific bluefin tuna transport Fukushima-derived radionuclides from Japan to California” in the Proceedings of the National Academy of Sciences.

The authors report "unequivocal evidence" that the radioactive cesium-137 and cesium-134 contamination in the bluefin tuna is from the Fukushima Dai-ichi nuclear catastrophe.  The bluefin tuna spawn in the waters of the Western Pacific off the coast of Japan each year and then migrate across the Northern Pacific to the eco-systems in the Eastern Pacific off the coast of California.   Radioactive cesium accumulates in the muscle tissue of fish.  The report states, “Because bluefin tuna are harvested annually in the Eastern Pacific Ocean (EPO) at 1.7 – 9.9 x 10³ metric tonnes (between 1700 and 9900 metric tonnes) for human consumption (2000 to 2010), the possibility of radioactive contamination raises public health concerns.”

The report further states that the samples showed a 10-fold increase in radiocesium concentrations in the commercial fish and, presently, would likely only provide low doses of radioactivity through consumption relative to other naturally occurring radionuclides in those same fish.

However, the study appears to have measured only one kind of radiation: gamma. The researchers do not mention measuring beta or alpha radiation, two types that deliver a much higher dose once inside a human body. This means that any radioactive decay level (usually given in becquerels - Bq) would under represent the actual level of radioactivity. Additionally, the researchers attempt to compare radiocesium contamination with that of naturally occurring radiation. However, such comparisons should be avoided because studies show that cesium can behave very differently, collecting in unexpected places in the body and residing there longer than expected.

The study represents the first evidence that radiation from the Fukushima nuclear catastrophe, coming by way of the Pacific Ocean marine food chain, can ultimately end up increasing internal radioactive exposure and body burden for humans in the US. Since publishing the study, the authors have now caught more bluefin tuna that have completed additional migrations between Japan and California.  These commercial fish will be tested for increased bioaccumulation of radioactive isotopes. Additional bio-magnification of radioactive isotopes like cesium-137 can be expected to continue to increase in the fish food stock in these contaminated eco-systems. The average life span of bluefin tuna can be up to 15 years, meaning that additional fish migrations into these contaminated eco-systems can increase as the result of bio-magnification, bio-accumulation and  the uptake and retention of radioactivity in muscle and organ tissue.