"January 28, 2014
The first results from seawater samples come from La Jolla and Point Reyes, Calif., and Grayland and Squium, Wash. Four samples from these three locations show no detectable Fukushima cesium. We know this because Fukushima released equal amounts of two isotopes of cesium: the shorter-lived cesium-134 isotope (half-life of 2 years) and the longer-lived cesium-137 (half-life of 30 years). Cesium-137 was found at levels of 1.5 Bq per cubic meter (Bq/m3), but this was already detectable prior to releases at Fukushima and came primarily from nuclear weapons testing in the Pacific during the 1950s and 1960s.
This so-called "negative" result has two immediate implications. First there should be no health concerns associated with swimming in the ocean as a result of Fukushima contaminants by themselves or as a result of any additional, low-level radioactive dose received from existing human and natural sources of radiation in the ocean (existing levels of cesium-137 are hundreds of times less than the dose provided by naturally occurring potassium-40 in seawater).
Secondly, and just as important from a scientific perspective, the results provide a key baseline from the West Coast prior to the arrival of the Fukushima plume. Models of ocean currents and cesium transport predict that the plume will arrive along the northern sections of the North American Pacific Coast (Alaska and northern British Columbia) sometime in the spring of 2014 and will arrive along the Washington, Oregon, and California coastline over the coming one to two years. The timing and pattern of dispersal underscores the need for samples further to the north, and for additional samples to be collected every few months at sites up and down the coast.
For this reason, we are also pleased to report that funds are already in hand to continue sampling at both the La Jolla and Pt. Reyes locations thanks to the foresight and generous donations of the groups who volunteered to adopt these sites. We expect levels of cesium-134 to become detectable in coming months, but the behavior of coastal currents will likely produce complex results (changing levels over time, arrival in some areas but not others) that cannot be accurately predicted by models. That is why ongoing support for long-term monitoring is so critical, now and in the future.
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