This paper proposes a meteorological mechanism for large increases in dose rate based on the findings from a high dose rate event that occurred during rainy season in northern Kyushu, Japan. The gamma-ray energy spectrum obtained by NaI(Tl) scintillation spectrometry confirmed the contribution of short-lived 222Rn decay products, such as 214Pb and 214Bi. The locations of monitoring posts, at which the large increases in dose rate were observed, corresponded to rainfall areas. Infrared satellite images and surface weather charts indicate that the intense precipitation was caused by cumulonimbus clouds along a stationary front, which accompanied a low pressure system. The low pressure system had formed in central China approximately 18 to 36 hours before the high dose rate event. Analyses of the backward trajectory and a long-range atmospheric transport model suggest that the low pressure system raised an air mass containing 222Rn to 1 to 2 km altitude above ground level. Then, the air mass that contained the 222Rn was transported laterally to Japan, as the low pressure system advanced to the east along the stationary front. Thus, the high dose rate event was attributed to the eastward advance of the low pressure system that carried the 222Rn and wet deposition of 222Rn decay products.
The health effects of low-dose or low-dose rate of radiation are still controversial. There is little evidence to show if radiation risk is greater than other risks, such as lifestyle or socio-economic factors, including smoking. This study aimed to directly compare radiation and smoking risk on cancer mortality by deriving both risk factors simultaneously from one cohort. The study population was Japanese nuclear workers who were engaged until the end of March, 1999. A lifestyle questionnaire was distributed in 1997 and 2003 and smoking information was obtained. Radiation dose was supplied by Radiation Dose Registration Center in Radiation Effects Association. Poisson regression was used to derive radiation excess relative risk (ERR) per 100 mSv and smoking (ERR) per 20 pack-years. Radiation doses were lagged by 10 years. There were 71,733 subjects. The total person-years was 591,000, and the number of deaths for all cancers excluding leukemia was 1,326. For all cancers excluding leukemia, the ERR of radiation per 100 mSv was 0.08 (90% CI: −0.08, 0.28), and the ERR of smoking per 20 pack-years was 0.57 (90% CI: 0.44, 0.73). In addition to all cancers excluding leukemia, stomach cancer, lung cancer, smoking-related cancers showed significantly smaller radiation ERRs than smoking ERRs. These results suggest that, even if a low-dose radiation risk existed, it was much smaller than smoking risk.
A lot of people concerns about radiation exposure by Fukushima nuclear accident. But no method that we effectively understand people’s anxiety because we grasped people’s needs about radiation exposure with individualism (ex. Telephone, questionnaire). In this paper, we suppose that it is possible to efficiently collect more people’s needs by utilizing twitter, which is one of Social Network Service, easier than before. Firstly, we search tweet including words of (“radiation” and “exposure”), normalize unicode, process pointless words (ex. URL, html tags, @NAME). Secondly, we extract tweets with anxious words dictionary that there are low dependency on texture and annotate 999 tweets to Anxious or Nonanxious. Thirdly, we extract tweets by sentiment analysis. Finally, we analysis tweets by utilizing KHCoder. In this dataset, about 40 % opinion data are anxiety about medical exposure. We infer that people are concerned about radiation exposure related to medical treatment, which is relatively close to everyday life. In this paper, we developed the system, which from collecting anxious opinion about health effects due to radiation exposure by using Twitter to doing dataset tendency analysis on about 60% Precision and Recall, by utilizing anxiety dictionary and sentiment analysis.
An international framework for environmental radiation protection has been developed over the last few decades. From 2005 to 2017, the International Commission on Radiological Protection (ICRP) established a committee on environmental protection and published several reports. ICRP developed a protection framework which was based on the Reference Animals and Plants corresponding to the Reference Man in radiation protection of humans, and the Derived Consideration Reference Level which is the band of dose rates corresponding to the possibility of adverse effect of each animals and plants. The present review summarized the current state of the environmental protection system focusing on the activities of ICRP first and then of other international organizations. The current issues about environmental protection were also discussed.
An efficient Monte Carlo computational model has been used to calculate the radiation transport when radioactive materials are deposited on an infinite plane surface, in which the geometrical shapes of the plane source and the point detector are interchanged. This transformation was verified by comparing the calculation results with the theoretical values only for the primary (unscattered) photons. It is desirable to confirm the validity of the transformation for both unscattered and scattered photons. The extension of the transformation to a finite plane source has not been verified yet. In this study, we performed calculations with and without transformation via the Monte Carlo method, and the results were compared with each other, then confirming the validity of the transformed model.