Fukushima Radiation in U.S. West Coast Tuna
In March 2011, in association with the Great Tohoku earthquake and resultant tsunami, there was an accident at the Fukushima Daiichi nuclear power plant on the east coast of Japan.
This accident released the radionuclides cesium 134Cs and 137Cs into the ocean next to the plant, exposing marine life to radioactive materials.
Pictured below are model simulations (using dye) on the long-term dispersal of 137Cs released into the Pacific Ocean off Fukushima following the Daiichi nuclear accident, 43 days, 367 days, and 1412 day after (up to down).
While many of the exposed marine organisms remain around Japan, a number of species are highly migratory and swim across the North Pacific to the West Coast of North America.
Pictured above are model simulations (using dye) of the long-term dispersal of Cs-137 released into the Pacific Ocean off Fukushima following the Daiichi nuclear accident, 43 days, 367 days, and 1412 day after (left to right). Image credit: E. Behrens, F.U. Schwarzkopf, J.F. Lübbecke and C.W. Böning, GEOMAR. Study and full-length simulation can be found at http://iopscience.iop.org/1748-9326/7/3/034004/
Two examples of these migratory fish are Pacific bluefin tuna (Thunnus orientalis) and albacore tuna (Thunnus alalunga), and both134Cs and 137Cs have been detected in these species caught in the eastern Pacific. For public health, the levels of radiation are very low and far below levels that are considered cause for concern. In a recent study of fifty bluefin tuna sampled off the U.S. West Coast in 2012, the smaller bluefin (recent migrants from Japan) had 134Cs (0.7 ± 0.2 Becquerels (Bq)/kg) and elevated 137Cs (2.0 ± 0.5 Bq/kg) in their white muscle tissue, while most larger, older fish had no 134Cs and only background levels of 137Cs.1 For scientists the 134Cs and 137Cs served as a marker indicating migratory pathways. If, for example, a Pacific bluefin tuna had detectable levels of 134Cs (which decays relatively quickly), it indicated that they recently migrated from Japan; this has provided important insight into the dynamics of tuna migration in the Pacific.
The Basics of Radiation
- Ionizing radiation: has so much energy, it can knock electrons out of atoms and create an ion, or unbalanced atom. This process can change living cells and cause mutations in DNA and damage in tissues, which poses health risks for humans. Examples include x-ray machines, cosmic rays, and nuclear radioactive elements.
- Non-ionizing radiation: does not have enough energy to cause ionization, but can move atoms around. Examples include radio waves, microwaves, and visible light.
4. International Bureau of Weights and Measures (BIPM), http://www.bipm.org/metrology/ionizing-radiation/units.html
5. Mathews, T., Fisher, N. S. "Dominance of dietary intake of metals in marine elasmobranch and teleost fish." Sci. Total Environ. 2009, 407 (18), 5156−5161.