This week at Ecocentric, we've been following news that Bluefin tuna caught off California’s coast had low levels of cesium-134 and cesium-137 in their systems. The timing of the findings suggests that radioactivity was picked up by tuna swimming in waters off the tsunami-damaged Fukushima Daiichi nuclear power plant in Japan in March 2011. Scientists and the FDA immediately stressed that the tuna are still safe for humans to consume—even raw. Besides, tuna, ocean life and people already have low levels of cesium in their tissues.
Remember the Cold War between the United States and the former Soviet Union after World War II? In the corresponding arms race, the U.S. and other nations detonated thousands of nuclear devices above ground (including our atmosphere) and also eventually underground. Though the practice peaked during the 1950s and 1960s, testing continued for many years as partial and total international test ban treaties were proposed, signed and ratified. (For more on this fascinating, important policy issue and topic, please see the international Preparatory Commission for the Comprehensive Nuclear-Test-Ban Organization, which is affiliated with, though not a part of the United Nations.) Those tests are the single greatest source of radioactive cesium in the environment. Over time, radioactive isotopes will decay, while the effects of radiation exposure can take decades to manifest in the environment.
Hence the concern for those exposed to fallout from the Fukushima disaster. That tuna swam across the Pacific to California (as tuna are wont to do) further demonstrates connections among populations through food (and water, and in this case, energy) systems. Ahem.