Comparing the risks of environmental carcinogenic chemicals in Japan using the loss of happy life expectancy indicator.

In this study, we aimed to use the loss of happy life expectancy (LHpLE), an indicator that enables risk assessment considering wellbeing, to compare the risks of environmental carcinogenic chemicals in Japan. First, we surveyed Japanese people to determine their emotional happiness by age and sex and evaluated whether cancer incidence reduced emotional happiness. Questionnaires were administered to a general population panel and a panel of patients with cancer in 2022, recruiting a predetermined number of responses of 5000 and 850, respectively. Second, using the survey data, LHpLE was calculated for radon, arsenic, and fine particulate matter (aerodynamic diameter <2.5 µm; PM2.5) and compared to psychological distress, considering increased mortality and decreased emotional happiness due to these risks. We discovered no significant decrease in emotional happiness due to cancer incidence and no significant associations between emotional happiness and cancer type, history, or stage. LHpLE was calculated to be 6.4 × 10-3 years for radon, 2.6 × 10-3 years for arsenic, 1.1 × 10-2 years (2012 exposure) and 8.6 × 10-4 years (2020 exposure) for PM2.5, and 9.7 × 10-1 years for psychological distress. The fraction of losses caused by these carcinogenic chemicals to HpLE exceeded 10-5, suggesting that risk reduction for these chemicals is important in environmental policies. The LHpLE indicator allows for comparing different types of risks, such as environmental chemicals and psychological distress. This is the first study to compare chemical risks using the LHpLE indicator.

Japanese physicians' perceptions of conflicts of interest with pharmaceutical companies: Estimating two different questioning approaches.

Despite being one of the world's largest pharmaceutical markets, interactions between Japanese physicians and pharmaceutical companies often remain opaque. Importantly, potential conflicts of interest associated with these interactions can compromise patient care and increase costs. We conducted an online survey of Japanese physicians to elucidate perspectives on pharmaceutical company promotional activities and how these influence physician prescribing patterns. Anticipating that physicians might downplay their reliance on, or the value of, pharmaceutical company-provided information, the survey incorporated a direct questioning method and an unmatched count technique (UCT) to identify hidden perceptions on factors likely to influence prescribing. Overall, 1080 eligible physicians participated. Of these, 105 (9.7%) self-identified as hospital directors or managers. Surprisingly, nearly twice as many participants responding to direct questioning (18.9%) versus those responding to the UCT (10.1%) asserted that information provided by pharmaceutical companies was important when prescribing medicine. Hospital directors or managers (adjusted odds ratio [adjOR] 2.56, 95% confidence interval [95% CI]: 1.00-6.54, reference = physician without title) and frequent interactions with pharmaceutical sales representatives (adjOR 5.96, 95% CI: 1.88-18.9, reference = rare interaction) significantly valued the information from sales representatives and sponsored lectures when considering prescribing decisions. Additionally, 77.1% of respondents believed that sales representatives provide fair, neutral, or relatively honest and unbiased information about their products. Few Japanese physicians acknowledged the influence of industry-provided information on prescribing patterns. Our study uniquely applies two distinct question formats, providing a novel approach to understanding the depth of physician-industry relationships and the effectiveness of various survey methodologies.

Public Attitudes toward the Final Disposal of Radioactively Contaminated Soil Resulting from the Fukushima Daiichi Nuclear Power Station Accident.

Radioactively contaminated soil from the Fukushima Daiichi nuclear power station accident in 2011 is required by law to be finally disposed of outside Fukushima Prefecture by 2045. To gain public acceptance of this policy, it is essential to promote understanding and nationwide discussion. We conducted a web-based survey of 2000 people in Japan to examine public attitudes toward final disposal of the contaminated soil outside Fukushima Prefecture. Results show that policy approval was negatively correlated with perceived risk of a final disposal site, sense of inequity associated with building a final disposal site near residential areas, and values that are absolutely non-negotiable or protected from trade-offs with other values (protected values). Policy approval was positively correlated with high levels of interest in the Fukushima accident and subjective knowledge of decontamination and the policy. Respondents' comments and opinions about the policy indicated that respondents who approved of the policy accepted burden sharing, while those who disapproved were unconvinced by the rationale behind disposal outside Fukushima Prefecture and were dissatisfied by the lack of information disclosure and transparency. While the government's efforts to disseminate information about the current status and future of Fukushima have been effective to a certain extent, they are insufficient to achieve widespread public understanding of the policy. Our results indicate that attention needs to be paid to procedural fairness and explanations of risks.

Factors influencing acceptability of final disposal of incinerated ash and decontaminated soil from TEPCO's Fukushima Daiichi nuclear power plant accident.

TEPCO's Fukushima Daiichi nuclear power plant accident prompted extensive decontamination work. The decontaminated soil and incinerated ash generated by the process are scheduled for final disposal by March 2045 outside Fukushima Prefecture. The final disposal is unprecedented worldwide. Clarifying their acceptability will contribute to the final disposal of decontaminated soil and incinerated ash, as well as add knowledge about the perceived risk of low-concentration radioactive waste. A questionnaire survey was conducted to assess the psychological factors influencing final disposal acceptability. The results of the structural equation modeling demonstrated stable results, with risk perception decreasing acceptability, social benefits increasing acceptability, and personal benefits having limited impact. The initiative for the final disposal of decontaminated soil and incinerated ash can facilitate the reconstruction of Fukushima Prefecture after the disaster. Trust and intergenerational expectations are critical factors influencing the acceptability of this disposal. The responses were classified based on the relevance of moral norms using cluster analysis and moral foundations. The influence of each element on acceptability varied depending on the cluster. Trust was identified as the most influential factor in acceptability, regardless of the level of importance placed on moral norms.

Scientific consensus views are useful, but dangerous, without a code of ethics.

Using the Fukushima accident experience, this letter discusses recent efforts on measuring scientific consensus views-that is, quantifying the agreement among scientists. In the field of radiological protection, the efforts to measure scientific consensus views deserve attention, because hoaxes have been spreading even after the Fukushima nuclear accident. We discussed two points. First, the visualization of the diversity of scientific opinions shatters the diversity illusion caused by the mass media's irresponsible dissemination of pro and con arguments. Second, the use of scientific consensus views without an ethical code is dangerous. Measuring scientific consensus views should be accompanied with the development of ethical guidelines on using it.

Uncertainty among families of patients with cerebrovascular diseases in Japan: association with quality of life and background characteristics.

PURPOSE: To determine the relationship between family uncertainty and family quality of life (QOL) during the recovery period of patients with cerebrovascular disease in Japan, and the factors that influence family uncertainty. METHODS: Data were collected from copies of patient medical files and interviews with family members of 85 patients admitted to two rehabilitation wards in Japan. Family uncertainty was measured using the Japanese version of the Managing Uncertainty in Illness Scale-Family Member form (MUIS-FM) and family QOL using the World Health Organization Five Well-Being Index (WHO-5). Multiple linear regression analysis was applied to investigate associated factors. RESULTS: WHO-5 score was significantly negatively associated with MUIS-FM score (ß = - 0.236, p = 0.03); other factors associated with MUIS-FM score were the Care Shared Decision-Making Questionnaire for care providers score (ß = - 0.384, p < 0.001), Short Intolerance of Uncertainty Scale score (ß = 0.296, p = 0.001), and history of surgical treatment (ß = 0.199, p = 0.032). CONCLUSIONS: Family QOL could be improved by reducing family uncertainty. It is also suggested that promoting shared decision-making between healthcare providers and patients' families may help reduce family uncertainty. It is necessary to take into account not only family intolerance of uncertainty but also uncertainty that varies by type of acute care provided.

The Association Between Fathers' Self-assessment of Their Own Parenting and Mothers' Recognition of Paternal Support: A Municipal-Based Cross-Sectional Study.

BACKGROUND: Discrepancies between parents' reports of paternal parenting have been gaining attention, but epidemiological evidence is scarce in Asia. This study aimed to clarify agreement/discrepancy between paternal and maternal recognition of paternal parenting and the association between actual paternal parenting time and background factors. METHODS: Data from couples whose children attended 4-month child health check-ups in Fukushima City were analyzed (N = 509). Based on paternal recognition of paternal parenting (PRPP) and maternal recognition of paternal support (MRPS), couples were classified into four groups. Each group's paternal household work and parenting time were analyzed. Univariable and multivariable analysis were performed to investigate the association between agreement/discrepancy and background factors of children and parents. RESULTS: Frequency of positive agreement (PRPP+ and MRPS+) was 83.9%, whereas negative agreement (PRPP- and MRPS-) was 2.6%. As for discrepancy, PRPP+ and MRPS- was 8.4% and PRPP- and MRPS+ was 5.1%. Fathers' total median parenting time was 2 (weekdays) and 6 (weekends) hours, and showed significant differences among the four groups. Multivariable analysis revealed that compared to positive agreement, maternal mental health condition and pregnancy intention were significantly associated with the discrepancy PRPP+ and MRPS-, paternal mental health condition and marital satisfaction with the discrepancy PRPP- and MRPS+, and maternal mental health condition with negative agreement. CONCLUSIONS: We identified differences in parenting time and mental health characteristics among couples depending on agreement/discrepancy in recognition of paternal parenting. Assessing both parents' profiles is necessary in clinical practice to promote paternal participation in childcare.

Trajectory and factors of radiation risk perception of students aged 10-12 years at the time of the Fukushima Daiichi Nuclear Power Station accident.

Various studies have investigated radiation risk perceptions after the accident at the Fukushima Daiichi Nuclear Power Station. However, student surveys are limited. This study aimed to investigate the perception of radiation risk among students aged 18-20 years who were in the 5th and 6th grades of elementary school at the time of the accident. We surveyed students in the Fukushima Prefecture and outside the prefecture. Out of all the data, 59% of the respondents were living in the Fukushima Prefecture at the time of the accident and 41% outside the prefecture. Trajectory analysis showed that changes in anxiety levels over time since 2011 could be divided into five classes: (a) the anxiety was the highest, and this tendency persisted. (b) High at the beginning, but decreased more quickly than class 1. (c) High at the beginning, but it diminished quickly. (d) Not high, but did not diminish easily in later years. (e) Low from the beginning, and persisted. Multinomial logistic analysis showed that among students living outside the prefecture at the time of the accident, a significantly higher proportion was in groups 4 and 5 than in group 2. A significant proportion of boys were present in groups 3, 4 and 5. A significant proportion of students whose current educational institutions were inside the prefecture were present in group 3. The level of anxiety was associated with the academic course, but not with subjective knowledge of radiation. In contrast, in the qualitative analysis of the free text, 31% considered 'knowledge about radiation' as the reason for the reduction in anxiety level. At the time of the investigation, most young people were not anxious about radiation. However, approximately 20% still had strong anxiety. We established that continuous risk communication is necessary. Furthermore, that stabilization and support related to life in general is important.

Father-child bonding among Japanese fathers of infants: A municipal-based study at the time of the 4-month child health checkup.

We aimed to clarify the factor structure of a bonding measure among Japanese fathers with infants and the factors associated with the subscales. Among fathers of children attending the 4-month health checkup, the Japanese version of the Mother-to-Infant Bonding Scale had a two-factor structure comprising "anger" and "lack of affection." Anger was associated with fathers' work demands and poor mental condition, and lack of affection with fathers' older age, poor mental condition, and interpersonal problems at home. Paternal parenting support needs to account for not only the fathers themselves, but also interpersonal communication at home and in the work environment.

Nos propusimos clarificar la estructura de factores de una medida de acercamiento afectivo entre los papás japoneses con infantes y los factores asociados con las subescalas. Entre los papás de niños que asistían al chequeo de salud de 4 meses, la versión japonesa de la Escala de Acercamiento Afectivo Madre a Infante tuvo una estructura de dos factores que comprende "ira" y "falta de afecto." La "Ira" se asoció con las responsabilidades del trabajo de los papás y la débil condición mental, y la "falta de afecto" con la más vieja edad de los papás, la débil condición mental y los problemas interpersonales en casa. La crianza paterna apoya las necesidades de dar cuenta no sólo de los padres mismos, sino también de la comunicación interpersonal en casa y el ambiente de trabajo.

Notre but était de clarifier la structure de facteur d'une mesure de lien entre les pères japonais de nourrissons et les facteurs liés aux sous-échelles. Parmi les pères d'enfants présents pour leur visite médicale de 4 mois la version japonaise de l'Echelle de Lien Mère-Nourrisson était une structure de deux facteurs comprenant "la colère" et "le manque d'affection". "La colère" était liée aux exigences du travail des pères et à une condition mentale moins élevée, et "le manque d'attention" était lié à l'âge plus élevés des pères, à une condition mentale moins élevée et à des problèmes relationnels à la maison. Le soutien de parentage paternel a besoin d'être pris en compte non seulement pour ce qui concerne les pères eux-mêmes mais aussi la communication relationnelle à la maison et l'environnement au travail.

Communication between Health Professionals and Community Residents in Fukushima: A Focus on the Feedback Loop.

Interactive communication and the ability to consider feedback are critical for linking health professionals and the community. Goto and colleagues developed and conducted health literacy training workshops for public health nurses after the 2011 nuclear accident in Fukushima to improve their communication skills. The present study aimed to examine the association between past workshop attendance and nurses' attitudes toward feedback from community residents. We conducted a questionnaire survey with 723 public health nurses in Fukushima and analyzed differences in feedback acceptance, work environment, basic characteristics, and health literacy levels between health literacy workshop attendees and non-attendees. Among 582 respondents, 19.4% were past attendees and showed a higher likelihood of accepting feedback from community residents (amount: adjusted odds ratio [aOR] = 1.87, 95% confidence interval [CI]: 1.21-2.88; specificity: aOR = 1.69, 95%CI: 1.09-2.61; satisfaction: aOR = 2.34, 95%CI: 1.50-3.65) than did non-attendees after adjusting for other variables. Furthermore, work engagement was associated with positive feedback acceptance (amount: aOR = 1.43, 95%CI: 1.03-1.98; specificity: aOR = 1.57, 95%CI: 1.12-2.20; satisfaction: aOR = 1.97, 95%CI: 1.38-2.81). We note the importance of creating a better work environment as well as a training system at the organizational level that encourages public health nurses to learn about health literacy and to improve their communication skills. This could improve professional/community relationships, increase the accessibility of health information for the public, and ultimately improve community health.

Usefulness of the whole-body counter for infants and small children (BABYSCAN) as a risk communication tool after the Fukushima Daiichi nuclear power plant incident.

Responding to the radiation-related concerns of parents/guardians with infants/small children is an important public health issue for regional recovery after radioactive contamination. This study summarizes the results of a systematic internal contamination screening of infants/small children, aged 0-6 years, using BABYSCAN and individual counselling sessions with physicians about radiation concerns from 2014 to 2018 in Minamisoma City. Of 3,114 participants, no one was found to have internal contamination with radioactive caesium with a detection limit of 50 Bq/body. The questionnaire survey showed a decreasing trend of concerns about food contamination and playing outside as possible causes of internal contamination over time. Because people's concerns were diverse in counselling sessions, individual responses are required. This study showed that examinations using BABYSCAN provide an opportunity for direct dialogue between the parents/guardians of infants/small children and experts. This can be considered a model case for risk communication conducted by the local government after a radioactive contamination incident.

Low dose of external exposure among returnees to former evacuation areas: a cross-sectional all-municipality joint study following the 2011 Fukushima Daiichi nuclear power plant incident.

There is little information on the radiation dose levels of returnees to areas once designated as legal no-go zones, after evacuation orders were lifted subsequent to the 2011 Fukushima Daiichi nuclear power plant incident. This study used individual radiation dosimeter monitoring and a location history survey to conduct the most recent dose assessment of external exposure among returnees to former no-go zones. We specifically determined correlation and agreement between external doses and the air dose rate in residential areas and quantified both uncertainty and population variability of the observed data using Monte Carlo (MC) simulation methods. A total of 239 voluntary participants across ten municipalities were analysed; their representativeness of all affected municipal populations was confirmed in terms of air dose rate distribution in residential areas. We found that individual doses were statistically significantly correlated with the air dose rate based on government airborne monitoring. This implies that airborne monitoring can provide sufficient information for understanding dose levels among such returnees. The MC simulations demonstrated that the mean of the annual dose in 2019 (including natural background doses) was 0.93 (95% uncertainty interval 0.53-1.76) mSv, with limited variation between municipalities. As of 2019, this implies that doses from external exposure were very low among returnees and would be associated with a very low likelihood of physical effects according to current scientific consensus. However, these results should be taken with caution due to several study limitations, including selection and participation biases. Regardless, its findings will enhance societal debates about how both individual-dose and government airborne monitoring practices should operate in the future and how the government can improve the public outlook for radiation doses in incident-affected areas.

Lower Psychological Distress Levels among Returnees Compared with Evacuees after the Fukushima Nuclear Accident.

Psychological distress has become a serious health risk after the Fukushima nuclear accident. Although, following the lifting of evacuation orders, the affected people have started returning home, their current status of psychological distress has not been reported yet. Here, we report the levels of psychological distress in both returnees and evacuees by using a K6 indicator. In January 2018, questionnaires were randomly distributed among 2,000 people, aged 20 to 79 years old, who were registered on the Basic Resident Register in the evacuation order areas of nine municipalities where residents have now started returning home. The total number of participants was 625. The returnees showed a significantly better psychological distress status than the evacuees. Multivariate-adjusted odds ratios (95% confidence intervals) among the returnees (reference = evacuees), estimated from a logistic analysis by using age, sex, and annual income as covariates, were 0.525 (0.325-0.846) for K6 ≥ 10 and 0.444 (0.216-0.911) for K6 ≥ 13. The prevalence of K6 ≥ 10 in the returnees when adjusted by the age and sex distribution of the whole of Japan was 16.2%, higher than the value (10.3%) at 20 to 79 years old in the whole of Japan. Psychological distress among the evacuees is an urgent problem to be resolved, and social support is still necessary for the returnees. Long term follow-up of returnees, investigations of causality between return and psychological distress and its governing factors in each of the evacuee and returnee groups are required for the implementation of effective countermeasures.

Unreliable Information as a Risk Factor for Worse Mental Fatigue among Residents in Fukushima after the Nuclear Power Station Accident.

After the Fukushima nuclear accident in 2011, there was confusion among the public caused by uncoordinated information about radiation provided by diverse channels. We explored the association between information sources regarding reconstruction progress after the disaster and mental fatigue in Fukushima. We used data from the annual public opinion survey by the Fukushima Prefectural Government on its policies from 2013 to 2015, which contained survey responses from 1,300 community residents randomly selected from the 28 municipalities in the Fukushima Prefecture. The survey contained a question assessing mental fatigue: "How often do you usually feel mentally tired or depressed?" In total, 2,130 participants (758 participants in 2013, 699 participants in 2014, and 673 participants in 2015) were analyzed. The respondents were classified as two categories, "high mental fatigue" and "low mental fatigue," based on their responses to this question. Overall, the proportion of participants with high mental fatigue was 13.2%. There was no association between the year of survey or occupation and high mental fatigue. Cluster analysis was performed to classify information sources. Then, we conducted a cross-sectional analysis of the associations between clusters of information sources and high mental fatigue. We found that unreliable information sources, such as "Internet" and "a combination of TV, radio, and word of mouth," were significantly associated with high mental fatigue, compared with reliable information sources, such as "municipal public relations in addition to major media (newspaper, TV, and radio)." These findings provide important insights into how information sources affect mental fatigue following a disaster.

Worsening Health Status among Evacuees: Analysis of Medical Expenditures after the 2011 Great East Japan Earthquake and Nuclear Disaster in Fukushima.

After Fukushima disaster in 2011, the health status of the region's residents deteriorated. We analyzed the health status, care needs, and access to health services among evacuees and non-evacuees using healthcare expenditure (for self-employed and unemployed individuals aged < 75 years) and long-term care expenditure (mainly for individuals aged ≥ 65 years). Fukushima Prefecture was divided into four areas according to their evacuation status: non-EOAs (municipalities that did not include evacuation order areas (EOAs)); EOAs/non-EOAs (municipalities that included both EOAs and non-EOAs); short-term EOAs (municipalities where the EOA designation was lifted in most areas by fiscal year (FY) 2011); and long-term EOAs (municipalities where most EOA designations remained in place until the end of FY 2015). Increases in expenditure on healthcare and long-term care per capita in short-term and long-term EOAs were greater in FY 2015 than the average values in FYs 2008-2010. The increases in expenditure were higher in short-term and long-term EOAs than those in non-EOAs and EOAs/non-EOAs. The increases in dental health expenditure were attributed to enhanced accessibility to dental health facilities. Furthermore, the evacuations contributed to increases in healthcare and long-term care expenditure, independent of aging and improved accessibly to health facilities. Possible explanations for these increases include the poor health status of the evacuees following the evacuations, reduced availability of informal care provided by family members and neighbors, and reduced patient copayments. The findings highlight the necessity of health promotion among evacuees.

Risk Factors for Problem Drinking among Evacuees in Fukushima following the Great East Japan Earthquake: The Fukushima Health Management Survey.

Many studies have consistently reported the bidirectional relationship between problem drinking and psychological distress following a disaster, but the risk factors of problem drinking following a disaster remain unclear. In this study, we therefore aimed to explore the risk factors associated with the incidence of problem drinking among evacuees after the Great East Japan Earthquake of March 11, 2011. We used the data for evacuees of the Fukushima Daiichi nuclear power plant accident, obtained from the Mental Health and Lifestyle Survey. A total of 12,490 individuals from 13 municipalities, which included the evacuation order areas after the accident, completed surveys between 2012 and 2013. The CAGE (Cutting down, Annoyed by criticism, Guilty feeling, and Eye-opener) questionnaire was used to screen the participants for alcohol dependence, and a score ≥ 2 indicated problem drinking. Logistic regression models were applied to investigate the possible predictors of problem drinking. The results showed that insufficient sleep and heavy drinking (≥ 4 drinks per day) were significant risk factors for the incidence of problem drinking in both men and women. Additional risk factors included family financial issues due to the disaster and trauma symptoms among men and a diagnosed history of mental illness among women. Other remaining variables were not significantly associated with problem drinking. The present study is the first to identify the risk factors for problem drinking following a compound disaster. Our findings could be used to develop a primary intervention program to improve evacuees' health and lives following a disaster.

Radiation doses and decontamination effects in Minamisoma city: airborne and individual monitoring after the Fukushima nuclear accident.

After the Fukushima accident, airborne monitoring was implemented to measure airborne radiation. We examined the relationships between airborne and individual radiation monitoring and clarified the use of airborne monitoring to evaluate the effects of decontamination on residents' received doses. We used the air dose rate data from four airborne monitors conducted between 2013 and 2016, and the dose data from four individual monitors (in which a total of 18 392 adults and 3650 children participated), conducted in Minamisoma City during the same period. We examined the Pearson correlation coefficients between the airborne and individual monitoring data and estimated exposure ratios (ERs; ratios of individual dose to air dose rates) among adults and children. We also estimated the effects of decontamination on residents' doses based on airborne monitoring data, adjusting this for timing and dosing through propensity score matching, which were then compared to individual monitoring data. There were significant correlations between airborne and individual monitoring doses among adults and children, and more than 80% of residents showed a good estimation-observation agreement within a factor of two. The median of ERs was 0.304 and 0.250 among adults and children, respectively. There was a significant difference between the two. Effects of decontamination on residents' doses estimated from airborne monitoring were significantly lower than those estimated from individual monitoring. These findings suggest that airborne monitoring can be used to estimate representative radiation doses within residential areas. It may be a useful tool for enhancing communication among stakeholders and supporting individual and policy decisions; however, it is less sensitive for evaluating individual effects of decontamination than individual monitoring. Combined use of airborne and individual monitoring also showed a lower median of ERs in children than in adults and in a Japanese government's model, possibly due to prioritised decontamination for children and differences between their behavioral patterns.

Impact of decontamination on individual radiation doses from external exposure among residents of Minamisoma City after the 2011 Fukushima Daiichi nuclear power plant incident in Japan: a retrospective observational study.

Following the Fukushima incident, radiation doses from external exposure accounted for the majority of the total doses. Although countermeasures are being implemented, with the aim of reducing radiation exposure, little information is available on the effects of decontamination on individual doses among the residents of radioactively contaminated areas. To evaluate the effectiveness of the decontamination measures in reducing individual doses, and to examine the influence of the timing of decontamination and the district, data were analysed for 18 392 adults and 3 650 children in Minamisoma City, Fukushima, who participated in a voluntary screening programme using individual radiation dosimeters (Glass Badge) between June 2013 and September 2016. The dose reduction rates (DRR) were calculated for one year by comparing the first and last three-month measurement results between areas with and without decontamination. Using a regression approach and Monte Carlo simulation, the dose reduction rate by decontamination eliminating the effect of physical decay (DRRd') was also estimated as a function of the timing of the decontamination and the dose at the time of starting the decontamination. The annual DRR in areas with decontamination for both adults and children were significantly higher than those in areas without decontamination, depending on the timing of decontamination: 31%-36% for 2013-14 for adults in decontamination areas and 33%-35% for children in decontamination areas, compared to 12%-23% and 13%-23% for adults and children in areas without decontamination, respectively. There was a positive correlation between DRRd' and individual doses, and DRRd' was estimated at 30%-40% for adults and children with doses of 3 mSv y-1 in 2013 and 2014. This study demonstrated that decontamination does lower individual doses from external exposure. The higher the dose at the time of starting the decontamination, the greater the dose reduction rate by decontamination, regardless of the timing of the decontamination. Our study confirms that decontamination was useful for high-dose areas in the later phases of the incident.