One of the positive things about moving to Oregon was that we would have access to fresh fish and seafood. The events at Fukishima, however, have caused me and many here on the west coast a lot of concern. How toxic will our seafood become now? Are there other health risks?
I asked Graham to do some research. His first PhD is in oceanography so he understands the scientific information being published now. Please take the time to read through this. More scientific info at the beginning and regular “people-speak” at the end.
My summary: There is radiation in all bananas because the absorption of chemicals that are absorbed from the earth’s crust. Eating a banana gives you the same exposure as eating fresh tuna caught off the west coast.
The Sky is NOT falling! Over-reaction regarding radiation detected in seafood off Western US By Graham Rankin
There has been much published in the media about radioisotopes found in fish (specifically tuna) caught off the west coast of the US. These reports are the result of measurements on a few specimens caught off California in 2012 (Madigan et al, 2012). Blue fin tuna are migratory fish that are known to spend part of the year off Japan in the eastern Pacific and part of their time off the west coast of the US (see Figure 1 below). They are some of the “top predators” in the food chain feeding on smaller fish which in turn feed on plankton and other small organisms. Tuna are known to concentrate the element cesium in their bodies so the radioisotopes of cesium that are produced during nuclear fission are of most concern. The study cited two particular cesium isotopes (134Cs and 137Cs). The 134 isotope has a short half-life of 2.1 years (half of the isotope will decay in that time; after another 2 years the remaining isotope will be ¼ the original amount and so on). The 137 isotope has a half-life of about 30 years. Much of the background amounts of 137Cs are due to residual fallout from the atomic testing in the Pacific in the 50s and 60s.
One important fact often overlooked in media is that the instruments used to detect these radioisotopes are very sensitive so “detection” does not mean that the levels are necessarily dangerous. One has to consider what the type of radiation is occurring, how the person is exposed (ingestion in the case of fish), the amount ingested over a particular time, etc. The Fisher et al (2013) does a good job of calculating the amount that a person might be exposed to who either eats tuna occasionally and who eats tuna daily. Further they compare the amount of radiation exposure as compared to other naturally occurring radioisotopes in the environment, specifically polonium-210 (210Po) from the decay of uranium-238 and potassium-40 (40K) which is found in the earth’s crust. Potassium is an essential element needed by the body, important in a number of bodily processes including recovery from strenuous exercise. That is why runners will often eat a banana at the end of a race.
Fisher et al (2013) calculate that a human who eats blue fin tuna occasionally (based on the average measured amount of cesium isotopes in the samples collected in 2012) would receive less radiation than from the naturally occurring 40K in a single banana. Further they acknowledge there is a lot of controversy about the effects of exposure to very low levels of radiation. Using the higher levels for a human that ingests tuna daily, they calculate that the maximum increased likelihood of developing cancer at 8 individuals in 10.000,000 as a result of eating these fish.
Three points need to be made:
- These studies are based on a few fish collected and analyzed in 2012. As a former oceanographer, I feel confident that additional samples are being collected and analyzed and will be reported in the scientific literature over the next few years. Reporting in scientific literature is not a fast process as it takes time to collect and analyze the data, write the report and for the peer-review process to take place. This does not mean that the government is hiding anything!
- There is continued leakage of water from the Fukushima reactor. Short lived isotopes like 134Cs are decaying rapidly and are not being produced now that the reactor is shutdown. The volume of water, its radioactivity and the dilution by the mass volume of the Pacific Ocean are all factors in the amount of potential exposure to the west coast. I have not stopped eating seafood from the Oregon coast, but will continue to monitor what is published in the scientific literature rather than the press which generally is more interested in sensational headlines than facts.
- I have been told of reports in the press about detection of radiation in rainwater along the west coast. I personally have not seen these, nor have found anything in the scientific literature. Again, it is important to realize that instruments are very sensitive and what isotopes are being measured, at what levels and how that relates to health risks are important facts that must be understood in order to make informed decisions.
There is a known phenomenon called Confirmation Bias, where someone tends to believe only those things that confirm preexisting beliefs and ignore evidence and facts that refute that belief. I am sure that there are those who will continue to believe the “sky is falling” in spite of the evidence that is readily available to the contrary. I encourage everyone to check out the Wikipedia reference to confirmation bias. It is quite extensive and includes a number of well-respected studies of the phenomenon.
References: (all are available for free on the Internet)
Daniel J. Madigan, Zofia Baumann, and Nicholas S. Fisher, Pacific Bluefin tuna transport Fukushima-derived radionuclides from Japan to California. Proceedings of the National Academy of Sciences, 2012, Vol 9, No. 24, pp 9483-9486,
Nicholas S. Fisher, Karine Beaugelin-Seiller, Thomas G. Hinton, Zofia Baumann, Daniel J. Madigan, and Jacqueline Garnier-Laplace, Evaluation of radiation doses and associated risk from the Fukushima nuclear accident to marine biota and human consumers of seafood. Proceedings National Academy of Science, 2013, vol. 110 no. 26, pp 10670–10675
Jing Chen, Evaluation of radioactivity concentrations from the Fukushima nuclear accident in fish products and associated risk to fish consumers, (Ed.), Radiation Protection Dosimetry (2013), Vol. 157, No. 1, pp. 1–5.