The purpose of this post is to bring the public up to date on monitoring efforts of a 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 which I led from 2014-2022. Radioactive contamination of the Pacific Ocean following the FDNPP accident raised public concern about seafood safety, particularly in coastal Indigenous communities in British Columbia where I live. To address this, InFORM along with Health Canada, Department of Fisheries and Oceans Canada and First Nations partners have collected and analyzed a total of 621 samples of commonly consumed salmon, ground fish, and shellfish from the Canadian west coast from 2011 to 2018. We examined the activities of cesium radioisotopes (134Cs half-life ~2 years and 137Cs half-life ~30 years) that were released in relatively large quantities from the Fukushima Dai-ichi Nuclear Power Plant (FDNNP) disaster in 2011 and would be most likely to pose radiological health concerns for human consumers of marine animals. Through careful analysis to determine the amount of radioactive isotopes in the seafood we have been able to carry out a health impact assessment. I wish to thank the following First Nations from British Columbia, Canada, for their generous donation of fish: Tr’ondëk Hwëch’in, Selkirk, Champagne and Aishihik, Taku River Tlingit, Tahltan, Nisga’a, Wet’suwet’en, Wuikinuxv, ‘Namgis, Hupacasath, Syilix, and Vuntut Gwich’in. I also thank Kayla Mohns and Brenna Collicutt of the Hakai Institute for assistance with the collection of shellfish samples. These results have recently been published in the peer-reviewed scientific literature in the Journal of Environmental Radioactivity and can be accessed here.
Highlights of the paper and key findings:
- the vast majority of fish and shellfish did not have detectable levels of 137Cs or 134Cs where the minimum detectable level was 0.7 — 1.0 Bq kg-1 fresh weight for 6 hours of analysis by counting with a sensitive gamma emission spectrometer
- 19 fish that had detectable levels of 137Cs were freeze dried and recounted for 336 hours and found to have an average 137Cs content of 0.29±0.02 Bq kg-1 fw
- 2 of these 19 fish had detectable levels of 134Cs, the short-lived isotope, which showed clearly that fallout from the FDNPP was present in these particular fish. Given that the ratio of 137Cs:134Cs in the releases from the FDNPP was 1:1 we determined that the contribution of contamination in these fish from the nuclear accident was 49% and 24% respectively with the majority of caesium contamination coming from other sources like nuclear weapons testing and the Chernobyl disaster in the 20th century
- 38 shellfish showed no contamination from FDNPP in either their shells or meat
- 8 years of measurements showed that radioactivity in fish was dominated by naturally occurring radioisotopes and that levels of human-made radioisotopes remained small in the Pacific off North American following the FDNPP disaster
- upper bounds for ingested doses of ionizing radiation from 137Cs was determined to be ~0.26 micro-Sieverts per year and far below the annual effective dose of 2400 micro-Sieverts from exposure to other sources of radiation
- we conclude that fish and shellfish from the Canadian west coast are not a radiological health concern despite the FDNPP accident of 2011
