Fukushima update—the plume and fish come to North America, part 3

Some of the oddest accusations about the Fukushima accident imply that it has affected or will affect health of Americans.

Tsunami debris

Marine debris from the tsunami is expected to hit Hawaii this winter, and the US mainland in 2014. This is unrelated to the nuclear accident, but will it have health effects? Harm other species?
marine debris
Marine debris, see NOAA for more information

The plume

A number of unrelated figures, such as this NOAA picture of tsunami height on March 11, 2011, have been alleged to represent a radioactive plume moving east across the Pacific:

Tsunami height becomes radiation?
Snopes says nope, NOAA’s picture of tsunami height is not also a picture of the amount of radioactivity.

The current expectation is that the plume will reach Hawaii in the first half of 2014, and the West Coast of the US some years later. Estimates of Hawaiian radioactivity is 10 – 30 becquerel/cubic meter, but it will be more dilute when it hits the mainland, some 10 – 22 Bq/m3, according to Multi-decadal projections of surface and interior pathways of the Fukushima Cesium-137 radioactive plume. This radioactivity adds to >12,000 Bq/m3 in the ocean water itself (the great majority of this is potassium-40, also a large part of natural radioactivity in our body).

Lots of stuff travels to other hemispheres through the ocean and air—California gets enough Chinese coal pollution to challenge the state’s air pollution standards. (More interesting and less discussed, but why?)

Radioactive fish are traveling as well

The US, like a number of countries, requires tests of food if there is reason to think that food standards might not be met. So far as I know, the US isn’t bothering to test Pacific Ocean fish for radioactivity.

A partial list of odd assertions:

Cecile Pineda, a novelist, has stayed in that genre with her recent discussions of Fukushima. She spoke recently in the SF East Bay on fish purportedly showing signs of radiation disease washing up in Vancouver, Oregon, and LA. Yet as we see below, the major radioactivity in almost all fish traveling to North America is natural.
• The Daily Mail offers radioactivity as an explanation for malnourished seal pups in CA. See the front page of The Daily Mail if you wonder about its general reliability.
• Bluefin tuna caught in CA last August are 10 x as radioactive as normal, according to a Huffington Post interpretation of a paper in the Proceedings of the National Academy of Sciences. NOT. Interestingly, the link the article provided gives different information: the fish, which were young and in Japan at the time of the accident were 5 x as radioactive as normal if you count just the cesium (5 becquerel rather than 1). This is in part because cesium washes out unless the fish keep ingesting it.

The actual facts are not frightening. According to Evaluation of radiation doses and associated risk from the Fukushima nuclear accident to marine biota and human consumers of seafood in the Proceedings of the National Academy of Sciences,

Abstract: Radioactive isotopes originating from the damaged Fukushima nuclear reactor in Japan following the earthquake and tsunami in March 2011 were found in resident marine animals and in migratory Pacific bluefin tuna (PBFT). Publication of this information resulted in a worldwide response that caused public anxiety and concern, although PBFT captured off California in August 2011 contained activity concentrations below those from naturally occurring radionuclides.

To link the radioactivity to possible health impairments, we calculated doses, attributable to the Fukushima-derived and the naturally occurring radionuclides, to both the marine biota and human fish consumers. We showed that doses in all cases were dominated by the naturally occurring alpha-emitter 210Po and that Fukushima-derived doses were three to four orders of magnitude below 210Po-derived doses….

Their report begins,

Recent reports describing the presence of radionuclides released from the damaged Fukushima Daiichi nuclear power plant in Pacific biota have aroused worldwide attention and concern. For example, the discovery of 134Cs and 137Cs in Pacific bluefin tuna (Thunnus orientalis; PBFT) that migrated from Japan to California waters was covered by >1,100 newspapers worldwide and numerous internet, television, and radio outlets. Such widespread coverage reflects the public’s concern and general fear of radiation. Concerns are particularly acute if the artificial radionuclides are in human food items…

The “three to four orders of magnitude” says that the added radioactivity from the Fukushima accident is, give or take, 1,000 – 10,000 times less important than natural radioactivity. The relative interest in bluefin tuna radioactivity over Chinese air pollution in North America appears to be explained in the opening paragraph.

Table 1 provides mean radioactivity decay rates for the following elements:

Bluefin tuna arriving in San Diego, August 2011
cesium (both Cs-134 and Cs-137), 10.3 becquerel/kg dry
potassium-40, 347 Bq/kg dry
polonium-210, 79 Bq/kg dry

Japan, April 2011
cesium, 155 Bq/kg dry
potassium-40, 347 Bq/kg dry
polonium-210, 79 Bq/kg dry

The polonium will have significantly more health effects per becquerel—polonium is an alpha emitter, stored differently in the body, etc.

In the same table, the authors assume that Americans get their entire average annual sea food consumption, 24.1 kg = 53 pounds/year, from bluefin tuna, and calculate health effects. They do the same for the Japanese, assuming 56.6 kg = 125 pounds consumption/year. It is not clear that the authors consider how long radioactive atoms remain in our body, since we excrete them along with other atoms; the numbers below may overstate the case as the authors assume a residence time as long as 50 years.

San Diego, August 2011
cesium, 0.9 µSv (microsievert, see Part 2 for more on units)
potassium-40, 12.7 µSv
polonium-210, 558 µSv

in Japan April 2011
cesium, 32.6 µSv
potassium-40, 29.7 µSv
polonium-210, 1,310 µSv

Radioactivity due to cesium in tuna, in Japanese waters and elsewhere, has declined dramatically since 2011.

Bottom line

The accident at Fukushima added an insignificant level of radioactivity to that already in seawater and fish, at least for those of us who are far away. As mentioned in Part 2, a small number of bottom feeders in the area immediately adjacent to the plant have levels of radioactivity which don’t meet international standards.

A good portion of the American Fukushima discussion I’m seeing asks, “How will Fukushima affect me?” The answer: if it is unhealthy for Americans, the effects in Japan would be more dramatic. Contrast this with Chinese air pollution, affecting CA air quality after killing many hundreds of thousands yearly in China.

Part 1 Bottom line numbers
Part 2 The state of the evacuation, food and fish
Part 4 The history of predictions on spent fuel rods
Part 5 The current state of F-D cleanup

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