I am writing this post is to bring the public up to date on monitoring efforts of my research program into the impact of the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident on environmental and public health here in North America. This post is part of an ongoing series summarizing work carried out by the Integrated Fukushima Ocean Radionuclide Monitoring (InFORM) project. Eight years since the peak in releases to the environment our project continues to measure radioisotopes released from the FDNPP that have the potential to present radiological health risks to living things. InFORM makes measurements of levels in seawater and common marine organisms as consumption of seafood is one of the most likely ways that residents of North America could be exposed to Fukushima derived contamination. We have found that:
Maximum contamination levels in seawater from Fukushima measured in waters offshore (~1500 km) and onshore British Columbia are now known to be about 8 to 10-fold lower than levels present in the North Pacific during the height of atmospheric nuclear weapons testing in the 1950’s and 1960’s. These levels are roughly 1000-fold below the maximum allowable drinking water standards for these isotopes.
Levels in Pacific salmon returning to North America have not changed in a statistically significant way since before the disaster and are lower than peak levels measured in the 1960’s.
Every month since about December 2014 volunteer citizen scientists in 15 coastal communities up and down the shores of British Columbia have collected seawater samples at the beach and returned them to our laboratories for analysis. The sampling network is shown below.
Since monitoring began coastal seawater concentrations have increased as the Fukushima contamination plume arrives. For the first time we can report that contamination levels have ceased increasing near the coast and are beginning to diminish. The activity of 137Cs leveled off at ~4 Bq per cubic meter of seawater which is about 2-4 times the background from weapons testing that existed here before Fukushima. Both the open ocean and coastal monitoring data are summarized in the figures below.
Offshore levels of 137Cs peaked at a little less than 10 Bq per cubic meter and have been diminishing as less contaminated water moves across the Pacific from the west. Coastal activities have peaked at lower levels likely because freshwater runoff from the continent is less contaminated than the seawater and dilutes the Fukushima contamination.
Monitoring of Pacific Salmon
Since 2014 we have collected and analyzed ~100 Pacific salmon and steel head trout per year returning to rivers up and down the BC coast from the Pacific Ocean. There has been no statistically significant increase in the levels of human-made isotopes in the fish since before the Fukushima disaster. Below we plot the maximum levels we have detected in fish returning to BC from 2011-2017 compared to levels measured in Pacific salmon during the 1960’s when weapons fallout levels were highest surface waters.
On average our Pacific salmon have ~0.2 Bq per kilogram wet weight and it is important to note that there is no statistically significant different in the average contamination level in the fish in years 2011-2017. We are only showing the maximum value detected in each year and have not shown how much variability exists in the yearly data for clarity. Levels of contamination in the 1960’s were >10-fold higher than our average levels in years post-Fukushima. The dose of ionizing radiation experienced by consumers of Pacific fish and shellfish is still dominated by the presence of naturally occurring radioisotopes in the Uranium and Thorium decay series (principally 210-Polonium) and remains well below levels that might represent a health risk.
We will continue our monitoring efforts likely through the end of this calendar year and continue to report our results as they are generated. As always I am happy to answer any questions related to the project and our findings.
Last evening I spoke at the monthly meeting of Surfrider Vancouver Island, one of InFORM’s non-governmental organization partners, to provide them with an update on our most recent results and progress. Surfrider VI helps to coordinate our citizen science volunteers who sample coastal seawater every month to monitor for Fukushima derived contamination along our beaches from Victoria in the south to Lax Kw’alaams in the north of BC. Surfrider VI is primarily responsible for sampling in Port Renfrew BC which is on the southwest coast of Vancouver Island.
I was pleasantly surprised by Lynn Wharram (Volunteer Coordinator and Combing the Coast BCU team lead) who had produced a short video chronicling her family collecting InFORM’s August 2016 seawater sample from the dock near the Port Renfrew Hotel. You can watch the video below.
You can read more about our citizen science program methods here, our NGO partners here , and our citizen science volunteers here. Thanks again to our volunteers and to Surfrider VI for all the work they do. Go and check them out if you are interested in ocean health (and surfing).
The amount of 137Cs released from the plant was ~50-fold less than the fall out from nuclear weapons testing in the 20th century and ~5-fold lower than that released from Chernobyl in 1986. Total releases from Fukushima are similar to the discharges of 137Cs from the nuclear fuel reprocessing plant Sellafield in the UK
Initial releases in the weeks to months after the disaster which began on March 11, 2011 dwarf those from aggregated ongoing releases from the plant site
The majority of radionuclide releases ended up in the Pacific Ocean with most deposition and input occurring close to the FDNPP
Current range of estimates of the total 137Cs ocean source term are 15-25 PBq (PBq = 1015 Becquerel where a Bq is one nuclear decay event per second). While many other radionuclides were released from FDNPP, the most likely isotopes to represent a health risk to the marine ecosystem and public are those of Cs given their longer half-lives for radioactive decay (134Cs = ~2 yrs; 137Cs = ~30 yrs) and higher relative abundance compared to other isotopes of concern in the FDNPP source term
Because Cs is very soluble it rapidly dispersed in the ocean after the disaster given mixing, transport and dilution by ocean currents. Peak levels of 137Cs occurred close to the plant in 2011 where activity concentrations near FDNPP was tens of millions of times higher than before the accident. By 2014 137Cs concentrations in the central North Pacific was about six times the remaining weapons testing fallout and about 2-3 times higher than prior fallout levels in the northeast Pacific near to North America. Most of the fallout remains concentrated in the top few hundred meters of the ocean. Measurements being made by the Fukushima InFORM project indicate that maximum 137Cs levels off the North American coast are likely to occur this year before declining to levels associated with background nuclear weapon testing before the accident by about the end of this decade
There are unlikely to be measurable effects on marine life with the exception of coastal areas very close to FDNPP immediately after the disaster. Monitoring of fish species in Fukushima Prefecture show that about 50% of samples in coastal waters had radiocesium levels above the Japanese 100 Bq kg-1 limit, but that by 2015 this had dropped to less than 1% measuring over the limit. High levels continue to be found in fish around and in the FDNPP port
Given levels in seawater and marine organisms measurable impacts to human health through contact with the ocean and the consumption of seafoods are very unlikely
There are many informative graphics and moderately technical summaries of available studies found in the new paper. The authors highlight the difficulty of monitoring radionuclides in the ocean given the dynamic nature of the sea and logistical challenges presented by the temporal and spatial scales and low levels of FDNPP derived contamination going forward. In addition to providing ongoing assessments of risk to the environment from the disaster it is likely that useful information about ocean circulation will be obtained through continued monitoring efforts.