Tuesday, February 12, 2019

Radiation Exposure from Fukushima Daiichi Nuclear Disaster Under-Estimated

It seems that inadvertent errors were made measuring radiation exposures for residents of Date Japan in the aftermath of the Fukushima Daiichi nuclear disaster:
Radiation doses underestimated in study of city in Fukushima (2019, January 9) THE ASAHI SHIMBUN http://www.asahi.com/ajw/articles/AJ201901090057.html?iref=pc_ss_date

A nuclear physicist who has drawn attention for tweeting about fallout from the Fukushima nuclear disaster has admitted that he and a colleague underestimated radiation doses in an article for an international scientific journal. Ryugo Hayano, professor emeritus at the University of Tokyo, said the error, which he recognized on Jan. 8, was “unintentional.” The article, carried in the Journal of Radiological Protection’s online edition in July 2017, listed average radiation doses that were one-third of the actual levels for people in Date, a city around 60 kilometers northwest of the crippled Fukushima No. 1 nuclear plant, he said.

Measuring exposure is a tricky business with many uncertainties. I applaud the scientists for acknowledging their error. The admission was made after a letter to the editor identified a questionable calculation of radiation exposure from dosimeters worn by Date residents.

Apparently, Hayano and his colleagues had: "mistook a monthly dose recorded on a dosimeter as the figure for three months of exposure."

I think this is the article where radiation exposure levels for Date, Japan were under-estimated:
Makoto Miyazaki1 and Ryugo Hayano (2016). Individual external dose monitoring of all citizens of Date City by passive dosimeter 5 to 51 months after the Fukushima NPP accident (series): 1. Comparison of individual dose with ambient dose rate monitored by aircraft surveys. Journal of Radiological Protection, 37(1) https://iopscience.iop.org/article/10.1088/1361-6498/37/1/1/meta

Date (da'te) City in Fukushima Prefecture has conducted a population-wide individual dose monitoring program after the Fukushima Daiichi Nuclear Power Plant Accident, which provides a unique and comprehensive data set of the individual doses of citizens. The …

Ryugo Hayano is also a co-author on a highly cited article measuring radiation exposure, posted below. I'm not clear whether the under-estimation found in the Journal of Radiation Protection has relevance for the estimates provided in other articles

…, K Uehara, A Sugimoto, S Nomura, R Hayano… - Plos one, 2013 - journals.plos.org
Resettlement to their radiation-contaminated hometown could be an option for people displaced at the time of a nuclear disaster; however, little information is available on the safety implications of these resettlement programs. Kawauchi village, located 12–30 km …

…, M Tsubokura, S Gilmour, RS Hayano… - Health policy and …, 2015 - academic.oup.com
After a radiation-release incident, intake of radionuclides in the initial stage immediately following the incident may be the major contributor to total internal radiation exposure for individuals in affected areas. However, evaluation of early internal contamination risk is …

…, M Tsubokura, T Furutani, RS Hayano… - Journal of radiation …, 2015 - academic.oup.com
After radioactive incidents, the exposure risk in daily activities among children is a major public concern. However, there are limited methods available for evaluation of this risk, which is essential to future health risk management. To this end, this study assessed the …

…, S Nomura, T Matsumura, M Miyazaki, R Hayano… - Health …, 2013 - journals.lww.com
THE FUKUSHIMA Daiichi nuclear disaster involved a series of equipment failures, nuclear meltdowns, and release of a large amount of radioactive material following the Great East Japan Earthquake on 11 March 2011. The Japanese government initiated the …

S Nomura, M Tsubokura, R Hayano… - … science & technology, 2014 - ACS Publications
After a major radioactive incident, accurate dose reconstruction is important for evaluating health risks and appropriate radiation protection policies. After the 2011 Japan Fukushima nuclear incident, we assessed the level of agreement between the modeled and directly …

…, T Oikawa, Y Kanazawa, M Kami, R Hayano - PloS one, 2014 - journals.plos.org
Maintaining low levels of chronic internal contamination among residents in radiation-contaminated areas after a nuclear disaster is a great public health concern. However, the efficacy of reduction measures for individual internal contamination remains unknown. To …
RS Hayano, YN Watanabe, S Nomura… - … of Radiological …, 2014 - iopscience.iop.org
Using the first WBC unit installed in Fukushima Prefecture after the accident, the radiocesium body burdens of 566 high-risk residents of Minamisoma city were measured in July 2011 at the Minamisoma Municipal General Hospital. The analysis of the data was …

I'd also like to note that using badges to measure exposure is itself considered to under-estimate biological exposure because badges don't capture internal exposure.

Kodama Tatsuhiko, head of the Radioisotope Center at the University of Tokyo, emphasized the special risks posed by radiation to children when speaking before Japanese Diet members in July of 2012, explaining that their rapid cell division makes them more vulnerable to DNA mutations:
K. Tatsuhiko (2011) ‘Radiation Effects on Health: Protect the Children of Fukushima’, The Asia-Pacific Journal 9.32.4, http://japanfocus.org/-Kodama-Tatsuhiko/3587
Tatsuhiko cautioned that radiation badges and whole body scans are inadequate for measuring risks because internally ingested radioisotopes such as cesium and iodine are not found uniformly across the body, but rather are concentrated in organs. He explained that it takes years for cancers to develop after exposure and that efforts to prove that exposure caused subsequent illnesses require data from control groups, allowing comparisons to be drawn from baseline normal incidences of disease rates within populations. 
Ryugo Hayano's 2016 talk can be found here:


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