Fukushima Fallout Not Affecting U.S.-Caught Fish

While this was published on the National Geographic website, it's written by a regular writer on the Think Progress website.  Both are highly trusted sources.

He starts by noting the extreme fear stories that were published in August/September 2013.  Those were based on reports from TEPCO of several accidents and on-going releases of radioactive water into the ocean.  It looks like an untenable situation, because they have an ever-growing need to store radioactive water that comes from having poured water onto the radioactive pile to keep them cool.  Since this will be what they're doing for the next 40ish years required for the decommissioning, we all wonder just how they're going to store 40 years worth of water?

Anyway, he went to Dr. Ken Buesseler, senior scientist in marine chemistry and geochemistry at the Woods Hole Oceanographic Institution for some hard data.  Their FAQ page is downplaying the risk of radiation in the ocean from Fukushima - http://www.whoi.edu/page.do?pid=83397&tid=3622&cid=94989 - not because they're closing their eyes to the potential, but that they've tested samples in their lab and on ships at sea including close to the site, and are not finding dangerous levels of radioactivity. 

How is the federal government testing Pacific Ocean seafood?

The lead U.S. agency testing seafood for contamination is the Food and Drug Administration, or FDA. As of June 20, the FDA has tested 1,313 samples of food imported from Japan, including 199 seafood samples. Of those, just one—a sample of ginger powder—exceeded the level considered safe for consumption.

When contacted about its testing of domestically caught seafood, an FDA spokesman responded in an email, saying that “the FDA is not aware of any evidence suggesting that the domestic seafood catch contains harmful levels of radiation.” He further referenced a 2012 study from the Proceedings of the National Academy of Sciences, which found levels of cesium-137 and cesium-134 in bluefin tuna to be, according to an email from the FDA, “roughly 300 times lower than levels that would prompt FDA to investigate further to determine if there were a health concern.”

Source: http://newswatch.nationalgeographic.com/2013/09/11/fukushima-fallout-not-affecting-u-s-caught-fish/

http://thinkprogress.org/climate/2013/09/12/2612961/fukushima-seafood/

Re: West Coast of North America to Be Hit Hard by Fukushima Radiation

Radiation levels in the ocean are expected to concentrate in pockets.  That's because ocean currents will ensure the radioactive water doesn't disperse evenly, but the dispersion will be based on where the currents go.

The people on Washington's Blog are rightfully concerned about the situation, but are presenting the negative portion of results from a study of probable dispersion into the ocean. 

The way they portray it is by saying "The paper shows that the West Coast of North American could end up with 10 times more radioactive cesium 137 than the coastal waters off of Japan itself."

It does say that, and it also says the radiation should be homogeneous across the North Pacific, but it also says: "The magnitude of additional peak radioactivity should drop to values comparable to the pre-Fukushima levels after 6–9 years (i.e. total peak concentrations would then have declined below twice pre-Fukushima levels)."

Is that so bad?

Here's the entire quote.

In the following years, the tracer cloud continuously expands laterally, with maximum concentrations in its central part heading east. While the northern portion is gradually invading the Bering Sea, the main tracer patch reaches the coastal waters of North America after 5–6 years, with maximum relative concentrations ( > 1 × 10−4) covering a broad swath of the eastern North Pacific between Vancouver Island and Baja California. Simultaneously some fraction of the southern rim of the tracer cloud becomes entrained in the North Equatorial Current (NEC), resulting in a westward extending wedge around 20°N that skirts the northern shores of the Hawaiian Archipelago. After 10 years the concentrations become nearly homogeneous over the whole Pacific, with higher values in the east, extending along the North American coast with a maximum (~1 × 10−4) off Baja California. The southern portion of the tracer cloud is carried westward by the NEC across the subtropical Pacific, leading to increasing concentrations in the Kuroshio regime again.
***
With caution given to the various idealizations (unknown actual oceanic state during release, unknown release area, no biological effects included, see section 3.4), the following conclusions may be drawn. (i) Dilution due to swift horizontal and vertical dispersion in the vicinity of the energetic Kuroshio regime leads to a rapid decrease of radioactivity levels during the first 2 years, with a decline of near-surface peak concentrations to values around 10 Bq m−3 (based on a total input of 10 PBq). The strong lateral dispersion, related to the vigorous eddy fields in the mid-latitude western Pacific, appears significantly under-estimated in the non-eddying (0.5°) model version. (ii) The subsequent pace of dilution is strongly reduced, owing to the eastward advection of the main tracer cloud towards the much less energetic areas of the central and eastern North Pacific. (iii) The magnitude of additional peak radioactivity should drop to values comparable to the pre-Fukushima levels after 6–9 years (i.e. total peak concentrations would then have declined below twice pre-Fukushima levels). (iv) By then the tracer cloud will span almost the entire North Pacific, with peak concentrations off the North American coast an order-of-magnitude higher than in the western Pacific.

Source: West Coast of North America to Be Hit Hard by Fukushima Radiation

Estimation of the spread of radioactive material from Fukushima

A scientific study report talking about the dispersal of material into the northern Pacific Ocean from Fukushima.  It's meant to guesstimate the spread of the radioactive material from that site.

Study source: Model simulations on the long-term dispersal of 137Cs released into the Pacific Ocean off Fukushima 

Abstract

A sequence of global ocean circulation models, with horizontal mesh sizes of 0.5°, 0.25° and 0.1°, are used to estimate the long-term dispersion by ocean currents and mesoscale eddies of a slowly decaying tracer (half-life of 30 years, comparable to that of 137Cs) from the local waters off the Fukushima Dai-ichi Nuclear Power Plants. The tracer was continuously injected into the coastal waters over some weeks; its subsequent spreading and dilution in the Pacific Ocean was then simulated for 10 years. The simulations do not include any data assimilation, and thus, do not account for the actual state of the local ocean currents during the release of highly contaminated water from the damaged plants in March–April 2011. An ensemble differing in initial current distributions illustrates their importance for the tracer patterns evolving during the first months, but suggests a minor relevance for the large-scale tracer distributions after 2–3 years. By then the tracer cloud has penetrated to depths of more than 400 m, spanning the western and central North Pacific between 25°N and 55°N, leading to a rapid dilution of concentrations. The rate of dilution declines in the following years, while the main tracer patch propagates eastward across the Pacific Ocean, reaching the coastal waters of North America after about 5–6 years. Tentatively assuming a value of 10 PBq for the net 137Cs input during the first weeks after the Fukushima incident, the simulation suggests a rapid dilution of peak radioactivity values to about 10 Bq m−3 during the first two years, followed by a gradual decline to 1–2 Bq m−3 over the next 4–7 years. The total peak radioactivity levels would then still be about twice the pre-Fukushima values.

Effects of Tohoku Tsunami and Fukushima Radiation on the U.S. Marine Environment

The following is a Congressional Research Service report from August 2012.

High levels of radioactive iodine-131 (with a half-life of about 8 days), cesium-137 (with a half-life of about 30 years), and cesium-134 (with a half-life of about 2 years) were measured in seawater adjacent to the Fukushima Dai-ichi site after the March 2011 events. EPA rainfall monitors in California, Idaho, and Minnesota detected trace amounts of radioactive iodine, cesium, and tellurium consistent with the Japanese nuclear incident, at concentrations below any level of concern. It is uncertain how precipitation of radioactive elements from the atmosphere may have affected radiation levels in the marine environment.

Scientists have stated that radiation in the ocean very quickly becomes diluted and would not be a problem beyond the coast of Japan. The same is true of radiation carried by winds. Barring another unanticipated release, radioactive contaminants from Fukushima Dai-ichi should be sufficiently dispersed over time that they will not prove to be a serious health threat elsewhere, unless they bioaccumulate in migratory fish or find their way directly to another part of the world through food or other commercial products. Radioactive contamination of seafood from the nuclear disaster in Japan has not emerged as a food safety problem for consumers in the United States. According to the U.S. Food and Drug Administration (FDA), the damage to infrastructure in Japan limited food production and associated exports from areas near the Fukushima nuclear facility. FDA and Customs and Border Protection continue to screen imported foods from Japan, including seafood, before they can enter the U.S. food supply.

Based on computer modeling of ocean currents, marine debris from the tsunami produced by the Tohoku earthquake was projected to spread eastward from Japan in the North Pacific Subtropical Gyre. Approximately two to three years after the event, the debris plume was projected to reach the U.S. West Coast, dumping debris on California beaches and the beaches of British Columbia, Alaska, and Baja California. However, initial debris is already arriving. Although most of the radioactive release from Fukushima Dai-ichi is believed to have occurred after the tsunami, there is a slight possibility that some of the tsunami debris might also be contaminated with radiation. A related concern is the transport of nonnative, and potentially invasive, species from Japan to U.S. shores on marine debris. Legislation (H.R. 1171, H.R. 6251, and S. 1119) has been introduced in the 112th Congress to address marine debris concerns.

Source: Effects of Tohoku Tsunami and Fukushima Radiation on the U.S. Marine Environment

Fukushima-derived radionuclides in the ocean and biota off Japan

The Tohoku earthquake and tsunami of March 11, 2011, resulted in unprecedented radioactivity releases from the Fukushima Dai-ichi nuclear power plants to the Northwest Pacific Ocean. Results are presented here from an international study of radionuclide contaminants in surface and subsurface waters, as well as in zooplankton and fish, off Japan in June 2011. A major finding is detection of Fukushima-derived 134 Cs and 137 Cs throughout waters 30–600 km offshore, with the highest activities associated with near-shore eddies and the Kuroshio Current acting as a southern boundary for transport. Fukushima-derived Cs isotopes were also detected in zooplankton and mesopelagic fish, and unique to this study we also find 110m Ag in zooplankton. Vertical profiles are used to calculate a total inventory of ∼ 2 PBq 137 Cs in an ocean area of 150,000 km 2. Our results can only be understood in the context of our drifter data and an oceanographic model that shows rapid advection of contaminants further out in the Pacific. Importantly, our data are consistent with higher estimates of the magnitude of Fukushima fallout and direct releases [Stohl et al. (2011) Atmos Chem Phys Discuss 11:28319 – 28394; Bailly du Bois et al. (2011) J Environ Radioact, 10.1016/j.jenvrad.2011.11.015]. We address risks to public health and marine biota by showing that though Cs isotopes are elevated 10-1,000× over prior levels in waters off Japan, radiation risks due to these radionuclides are below those generally considered harmful to marine animals and human consumers, and even below those from naturally occurring radionuclides


Source: http://www.pnas.org/content/early/2012/03/26/1120794109.full.pdf+html