Verification of the Effectiveness of Risk Communication Materials Using Natural Radiation Levels as a Reference Standard: Results from a Survey of First-Year Health Department Students

Abstract

Even before the Fukushima Daiichi Nuclear Power Plant accident, people were continuously exposed to various naturally occurring radioactive materials, including radon. However, public awareness and understanding of this exposure remain limited. When communicating the risks of radiation exposure from the Fukushima accident, explanatory materials have not typically incorporated data from coastal areas of Fukushima Prefecture collected after the incident to clarify the actual levels of artificial and natural radiation exposure. This study aimed to assess whether presenting radiation dose data from coastal areas of Fukushima Prefecture—using natural radiation as a reference point—could influence risk perception regarding the health effects of radiation exposure and its potential impact on future generations. The study focused on students enrolled in health science-related departments at Hirosaki University. Before being presented with the data, the students had limited understanding of radiation. However, after reviewing the explanatory materials, 89 students (48.4%) demonstrated an improved understanding of its potential impact on future generations, while 87 students (47.3%) showed increased awareness of the effects on their own health. Regarding the reduction in risk perception, many students attributed it to the fact that radiation levels 10 years after the Fukushima nuclear accident were not significantly different from natural background radiation in most areas. These findings suggest that providing actual radiation measurement data from affected areas can significantly influence risk perception and decision-making processes. The results indicate that participants became more aware of the presence of natural background radiation, and the comparison with current radiation levels in Fukushima played a key role in shaping their risk perception.

1. Introduction

On 11 March 2011, at 14:46 JST, a magnitude 9.0 earthquake struck the Tohoku region of Japan, triggering a powerful tsunami along the Pacific coast, including the coastal areas of Tohoku [1]. As a result, the Fukushima Daiichi Nuclear Power Plant (FDNPP) operated by Tokyo Electric Power Company (TEPCO) sustained severe damage, leading to the release of radioactive materials into the environment [2,3]. On the day of the accident, the Japanese government issued an evacuation order for all residents within a 2 km radius of the FDNPP. This evacuation zone was subsequently expanded, and by the following days, areas within a 20 km radius were designated as an “evacuation order area” [1]. By May 2012, approximately 160,000 residents had been displaced. Although some have since returned to areas where evacuation order had been lifted, as of November 2024, around 25,000 remain evacuated [4]. Following the accident, a wide range of information was disseminated through the media and social networking services [5,6,7,8]. However, much of this information remained unclear or inconsistent. The government’s communication regarding the status of the FDNPP, the necessity of evacuation, and the potential health effects of the accident was widely criticized as insufficient and inadequate [9]. Consequently, public concern over the health effects of radioactive materials released during the accident persisted for years after the event [10]. Since the accident, various radiation risk communication activities have been led by national organizations to reduce public anxiety regarding radiation. For example, the Japanese Ministry of Education, Culture, Sports, Science, and Technology supports radiation education in school curriculums, and the Japanese Ministry of the Environment (MoE) creates materials for the general public on the health effects of radiation [11].

Previous studies have used risk comparisons to effectively communicate quantitative risk information [12]. Currently, radiation risks from the FDNPP accident are often contextualized by comparing them to cancer risks associated with smoking, alcohol consumption, and lack of physical exercise, as well as risks from medical radiation exposure and natural background radiation in daily life [13]. Covello et al. [12] proposed guidelines for risk comparisons, ranking the desirability of 14 different types of comparisons. Comparisons between different types of risks are generally considered unacceptable. Therefore, we argue that the materials presented so far have not effectively promoted public understanding or acceptance of the risks associated with the Fukushima nuclear accident. Furthermore, one reason the public rejected these materials is that the radiation data used for comparisons were not based on actual measurements taken in Fukushima Prefecture after the accident, making it difficult to assess the true impact. While natural exposure to radionuclides, including radon, has always existed, the public remains largely unaware of this. Our survey of the general public conducted after the accident indicates that many people perceive artificial radionuclides released during the incident more negatively than natural radionuclides [14]. Similarly, Solvic [15] reports that while nuclear power and nuclear waste are viewed as high risk, naturally occurring radioactive materials like radon gas are considered low risk. In essence, the public tends to view the risks of a nuclear accident as disproportionately high. However, it is important to note that these findings are based solely on perception surveys, rather than on direct measurements and comparisons of artificial versus natural radiation following a nuclear accident.

In addition, Covello et al. [12] suggest that the most effective risk comparisons use a familiar reference. Based on this principle, we considered that recognizing the presence of natural radiation and using it as a benchmark to compare radiation doses from the FDNPP accident could serve as an effective risk communication tool. This approach aims to create public understanding and acceptance of the health risks associated with the accident, including potential effects on future generations. The radiation dose comparison follows specific criteria, ensuring that the data used are both relevant and reliable. Additionally, we believe this approach enhances credibility, as the comparison is based on actual radiation dose measurements—both from the accident and from natural sources—collected in areas affected by the FDNPP accident.

A survey of the general public in Tokyo in 2021 revealed that, although there has been progress in their understanding regarding the recovery of Fukushima Prefecture and the health effects of radiation, even a decade after the accident, approximately 40% of survey respondents continued to believe that radiation exposure would result in adverse health effects for residents of Fukushima Prefecture and cause genetic impacts on the local population [16]. Similarly, a 2022 web-based survey conducted by the MoE on the public perceptions of radiation-related health risks found that around 40% of respondents shared this concern [17]. These findings suggest that a significant portion of the general public still perceives radiation from the accident as a persistent health and genetic risk.

The authors have collaborated with local governments and universities in the coastal areas of Fukushima Prefecture, particularly Namie Town, to measure radiation levels and share the results with residents [18,19]. Interviews with local residents and various surveys [20,21,22,23] have revealed that some people in these regions still hold misconceptions about radiation exposure, which can contribute to harmful rumors. A survey conducted eight years after the accident on the psychological state and return intentions of residents in Tomioka Town, Fukushima Prefecture, found that 29% of those who had returned, 59% of those undecided, and 65% of those who had decided not to return believed that “returning would cause genetic effects in the next generation”. Additionally, 20%, 46%, and 65%, respectively, believed that “returning to Tomioka Town would cause cancer”, while 20%, 46%, and 55% believed that “cancer would occur if they lived in Tomioka Town”. These findings indicate deeply rooted misunderstandings about the health and genetic effects of radiation from the FDNPP accident [24]. More than 13 years have passed since the FDNPP accident, and Fukushima Prefecture is now in the recovery and chronic phases of the disaster cycle. Decontamination efforts have significantly reduced radiation levels compared to the acute phase immediately after the accident, with doses continuing to decrease [25]. In many areas, exposure levels are now comparable to those of natural background radiation [26]. However, due to inadequate public communication about the accident and radiation-related health effects, reputational damage persists. To address this, it is essential to first assess the current radiation levels in coastal areas of Fukushima Prefecture 13 years after the accident and update this information accordingly. Based on these updates, it is necessary to evaluate whether public awareness of radiation risks has changed since the FDNPP accident. Furthermore, understanding the effectiveness of risk communication—particularly in explaining radiation exposure in the context of natural background levels—is crucial. Developing effective communication strategies for those hesitant to return and preventing the spread of harmful rumors should remain key priorities.

The explanatory materials used in this study to compare risks are based on data measured locally after the Fukushima nuclear accident. In addition, the materials incorporate the opinions of local residents and local authorities. This scientific basis and the opinions of local residents and local governments are used in this study. This is the first time that risk perception of health and genetic effects of the Fukushima nuclear accident has been investigated using scientific evidence and data that incorporate the opinions of residents and local governments. Furthermore, if this approach proves effective as a risk communication method during the current chronic phase of recovery, it could help alleviate public anxiety and reduce misinformation surrounding the Fukushima nuclear accident.

In the medical field, knowledge of radiation is required in various situations such as diagnosis and treatment. As future medical professionals, nursing students, and students of radiological technology and science will be in positions to explain the risks of radiation to patients and the general public; consequently, it is necessary for them to have correct knowledge about radiation. It is therefore believed that the verification of materials that facilitate the comprehension and elucidation of the health effects of radiation and its impact on future generations is of considerable significance, not only in the context of public health, but also in the domain of medical practice.

The purpose of this study is to examine whether presenting the results of a dose survey—distinguishing between artificial and natural radiation—based on radiation data measured in the coastal areas of Fukushima Prefecture can improve first-year students’ risk perception regarding the health effects of radiation from the FDNPP accident and its potential impact on future generations.

2. Materials and Methods

2.1. Subjects

Approximately 250 first-year students participated by answering a survey. The students were enrolled in the Department of Nursing, Department of Radiological Technology, Department of Medical Technology, Department of Physical Therapy, Department of Occupational Therapy, and Department of Psychological Support at the Faculty of Health Sciences of Hirosaki University. As a comparison group for the survey, 15 radiological technologists working at medical institutions in Fukushima Prefecture were also included.

2.2. Survey Method

This study employed a self-administered questionnaire survey using Microsoft Forms. Each participant was provided with an explanatory document with a QR code linked to the questionnaire content. The explanatory document also contained a randomly assigned number to link the responses before and after the explanation, and participants were asked to enter the number assigned to them before answering the questionnaire items. The explanatory material using natural radiation levels as a “reference standard” is presented in Figure 1. This material is based on the author’s survey of radiation levels in residents returning to three municipalities in the coastal area of Fukushima Prefecture. The explanatory sheet outlines three specific measurements and results. The first measurement presents the investigation of radon and thoron, key contributors to natural radiation levels in the atmosphere, as well as radiocesium levels in private homes. The second measurement details the analysis of radon and radioactive cesium in the drinking water used by each resident in daily life. The third measurement shows the results of the survey of ambient dose rates in the environment, mapping external exposure doses, and visualizing both natural and artificial radiation components. Detailed data collection methods, conditions, and analytical approaches for these measurements are provided in a separate paper [27]. Based on the results from surveys 1–3, the corresponding doses were calculated and presented at the bottom of the chart. A comparison table of exposure doses from artificial and natural sources is also included and based on the results of surveys 1–3. Additionally, the stacked bar graph on the reverse side illustrates the comparison of radiation doses from these sources, reflecting the survey results from the front page. A stacked bar graph was chosen because, when assessing the health effects of radiation, understanding an individual’s total (cumulative) exposure is crucial, and it is standard practice to express this in terms of annual dose. These data serve as a “reference standard”, enabling residents to easily compare their exposure levels from artificial radiation sources. The histogram was created in response to requests from 70 returning residents and visually represents how their individual doses compare to those of others in the survey.

The survey of students in the Department of Health Sciences was conducted in June 2024, before and after a class attended by students from all majors. The survey of radio-logical technologists was conducted at a July 2024 meeting hosted by the Fukushima Prefecture Radiological Technologists Association. This meeting was for engineers in Fukushima Prefecture who were interested in radiation protection and nuclear power disasters.

The survey procedure was as follows: First, participants completed a questionnaire assessing their basic knowledge of radiation and its health effects. Next, Figure 1 was distributed, and a five-minute explanation was provided using a projector. This presentation compared radiation levels resulting from the FDNPP accident with natural radiation levels prior to the accident. Finally, participants were asked to complete the same questionnaire on the health effects of radiation that they had filled out before receiving the materials and explanation.

2.3. Content of the Questionnaire

The questionnaire asked each respondent’s gender, age, and home prefecture. For students of the Department of Health Sciences, the questionnaire asked their major, whether they had studied radiation outside of lectures and seminars at school, and whether they had taken any radiation-related classes before entering university. Additionally, the radiological technologists were asked about their years of clinical experience. The survey items on basic knowledge of radiation (

Table 1. Questions about basic knowledge of radiation and answers.

Questions About Basic Knowledge of Radiation	Answers	Students (n = 184)	Radiological Technologists (n = 15)
Q1-1: Do you think you are exposed to radiation exceeding 1 mSv in a year?	Yes	71 (38.6%)	14 (93.3%)
	No	24 (13.0%)	1 (6.7%)
	Don’t know	89 (48.4%)	0 (0.0%)
Q2-1: Do you think artificial radiation is different from natural radiation from the viewpoint of the health effect?	Yes	105 (57.1%)	14 (93.3%)
	No	56 (30.4%)	0 (0.0%)
	Don’t know	23 (12.5%)	1 (6.7%)
Q3-1: Do you think the health effect caused by the same dose is different between internal exposure and external exposure?	Yes	128 (69.9%)	8 (53.3%)
	No	12 (6.5%)	7 (46.7%)
	Don’t know	44 (23.9%)	0 (0.0%)
Q4-1: Have you ever heard the word “radon” before?	Yes	94 (51.1%)	15 (100%)
	No	67 (36.4%)	0 (0.0%)
	Don’t remember	23 (12.5%)	0 (0.0%)

) were the same as those used in previous studies by the authors and were specifically designed to test basic knowledge of natural and artificial radiation [14]. Moreover, new questions were posed regarding memories of the FDNPP accident and recognition of the term “radon”, which is a form of natural radiation. Furthermore, the same questions had been asked in a web survey conducted by the Ministry of the Environment in 2022 to determine whether there were any changes in perceptions of the effects of radiation exposure on future generations and on one’s own health before and after an explanation was given [17].

Questions about the health effects of radiation are given in

Table 2. Survey questions on the health effects of radiation.

Question	Answer
Q1: What do you think about the health effects of radiation on the next generation (children to be born in the future) in the areas affected by the accident at TEPCO’s Fukushima Daiichi Nuclear Power Plant?	Very unlikely to occur
	Unlikely to occur
	Likely to occur
	Very likely to occur
Q2: How many health effects (e.g., cancer) due to radiation from the accident at TEPCO’s Fukushima Daiichi Nuclear Power Plant do you think will occur to people in Fukushima?	Very unlikely to occur
	Unlikely to occur
	Likely to occur
	Very likely to occur
Q1 and Q2 Reasons	1. I got that impression from information I heard from people close to me.
	2. I got that impression from information I saw on the internet.
	3. I thought so after looking at information from national and international professional organizations.
	4. I got that impression from information given by the press.
	5. That’s what I thought when I heard the information from government agencies.
	6. The dose from the relevant accident was considered low.
	7. Because I don’t think this is scientifically known.
	8. Because I think radiation is bad for me.
	9. Because I think radiation is something that builds up in the body and has a negative impact on health.
	10. Because I have not seen any information on the observed health effects.
	11. Because there is no difference compared to the original exposure to natural radiation.
Q3: Do you think reconstruction and restoration in Fukushima Prefecture is progressing?	I think so
	Somewhat agree
	Can’t say either way
	Somewhat disagree
	I don’t think so
Q4: Do you think there are cases where people in Fukushima Prefecture are looked at in a special way after the nuclear accident?	I think so
	Somewhat agree
	Can’t say either way
	Somewhat disagree
	I don’t think so

. Regarding Q1 and Q2, the authors added the option “because there is no difference compared to the amount of exposure to natural radiation that already exists” to the 10 options given in the Ministry of the Environment survey and asked respondents to choose from 11 options.

2.4. Analysis Method

The data obtained were subjected to basic statistical analysis using SPSS statistical analysis software (Ver. 24.0). Changes in perceptions of radiation before and after the explanation of the natural radiation data were examined using the chi-square and Fisher’s test. The significance level was set at less than 5%.

2.5. Ethical Considerations

The purpose of the questionnaire was explained verbally and in writing to participants; the survey objectives, methods, and ethical background were explained; and participants were asked to make their own decision as to whether or not to participate in the survey.

3. Results

The number of respondents in this survey was limited to those who answered the questions before and after the explanation of the materials. Furthermore, the analysis was limited to those who entered the number assigned to them in advance to identify them as respondents and whose answers before and after the explanation were judged to be from the same person. The number of students’ respondents in this study was 208 before and 192 after the materials were explained. The number of respondents was 184 (valid response rate 83.0%). In addition, although there were 20 responses to the questionnaire from the meeting of the Radiological Technologists Association, the responses from four students and one nurse with no clinical experience as radiological technologists were excluded. This left 15 valid responses, resulting in an effective response rate of 75%.

3.1. Attributes of Subjects

The attributes of the participants are shown in

Table 3. The demographic and other characteristics of the subjects.

.

The distribution of students’ majors in the Department of Health Sciences was as follows: 65 (35.3%) in the Department of Nursing, 38 (20.7%) in the Department of Radiological Technology, 35 (19.0%) in the Department of Medical Technology, 16 (8.7%) in the Department of Physical Therapy, 19 (10.3%) in the Department of Occupational Therapy, and 11 (6.0%) in the Department of Psychological Support. The mean age of the subjects was 18.4 ± 0.6 years. In terms of gender, 50 (27.2%) students were male, and 132 (71.7%) were female. None of the subjects were from Fukushima Prefecture. Thirty-five (19.0%) of the subjects had previously studied radiation, and 45 (24.5%) had attended a lecture on radiation before entering university. When asked if they were anxious about radiation during the 2011 FDNPP accident, 96 (52.2%) responded that they did not remember. This was followed by 67 students (36.4%) who answered “no” and 13 students (7.1%) who answered “yes”. Thirteen years after the FDNPP accident, 122 students (66.3%) responded that their awareness of radiation had changed, 23 (12.5%) responded that they had not changed, and 33 (17.9%) responded that they could not say either way. When asked how their anxiety about radiation had changed, 47 students (25.5%) answered that it had increased, 39 (21.2%) answered that it had decreased, 67 (36.4%) answered that it had not changed, and 31 (16.8%) answered that they could not say either way.

The 15 radiological technologists were all male, and, with the exception of one, were all from Fukushima Prefecture. The mean age was 50.7 ± 8.2 years, and the mean number of years of clinical experience as a radiology technician was 28.2 ± 9.0 years. At the time of the accident, eight (53.3%) were worried, and five (33.3%) were not worried. The concerns they had at the time included “I thought I might not be able to live in the area anymore”, “radiation exposure”, “I thought it would be okay, but I was worried”, and “Unlike medical exposure, I was worried about where and how much radiation was being released”.

3.2. Awareness and Image of Basic Knowledge of Natural and Artificial Radiation (Table 1)

In response to Question Q1-1, “Do you think you are exposed to radiation exceeding 1 mSv in a year?” 71 students (38.6%) answered “Yes”, 24 students (13.0%) answered “No”, and 89 students (48.4%) answered “Don’t know”. Of the 71 participants who provided a correct response to Q1-1, 56 provided a specific value in response to Question Q1-2, inquiring about their estimated annual exposure to the aforementioned question. The reported values ranged from 0.1 mSv to 100 mSv, demonstrating a considerable degree of variability. Of these, six students (10.7%) replied “2.1 mSv”.

In response to Question Q2-1, “Do you think artificial radiation is different from natural radiation from the viewpoint of the health effect?” a total of 105 participants (57.1%) indicated that they did, 56 (30.4%) provided the correct response of “No”, and 23 (12.5%) stated that they were unsure. Of the 105 people who answered “Yes” to Q2-1 when asked which type of radiation has a greater effect on the human body, 90 students (90.5%) answered “artificial radiation”. When asked to write down what they thought of when they heard the word “artificial radiation”, many people wrote “X-ray” and “CT”. When asked to write down what they thought when they heard the word “natural radiation”, 62 students (33.3%) answered that they did not know.

In the question 3-1 “Do you think the health effect caused by the same dose is different between internal exposure and external exposure?” The correct answer of “No” was selected by 12 students (6.5%), “I don’t know” was selected by 44 (23.7%), and the most common answer was “Yes” with 130 students (69.9%). Among the respondents who provided detailed responses about internal exposures, five cited “thyroid” and “iodine”. However, the remaining responses were diverse, encompassing terms such as “dangerous”, “prone to cancer”, “food and drink”, and others. On the other hand, the most common response to questions about external exposure was “I don’t know” 90 (48.4%). In terms of specific details, 20 students (9.1%) mentioned the Fukushima nuclear accident or the term “nuclear power plant”. There were also nine responses mentioning “X-rays”. It is difficult to understand the concepts of internal and external exposure, and many people are unable to come up with details.

The radiologic technologists’ responses to Q1-1 through Q3-1 were as follows: 14 (93.3%) answered Q1-1 and Q2-1 correctly, and one (6.7%) answered “I don’t know”. For Q3-1, eight (53.3%) answered “yes”, and seven (46.7%) answered “no”. Fifteen respondents provided detailed responses, and the terms most frequently associated with the concept of “internal exposure” were “food” and “iodine”. In contrast, the terms most frequently associated with the concept of “external exposure” were “X-rays” and other responses.

When asked whether they had ever heard the word “radon” (Q4-1), 94 students (51.1%) answered “Yes”, 67 (36.4%) answered “No”, and 23 (12.5%) answered “I don’t remember”. In response to the preceding inquiry, respondents who indicated “Yes “were asked to specify the content in question. Although 15 students (8.1%) indicated that they were unsure where they had heard it, the next most prevalent response was “It came up in chemistry class”, which was provided by 11 students (7.0%). In the radiologic technologists’ responses, all 15 respondents said that they had heard of it, and specific words such as “hot spring” and “natural radiation” were mentioned.

3.3. Changes in Risk Perception Regarding the Effects of Radiation on Future Generations and Health Effects Before and After Presentation of Explanatory Materials

Before the materials were explained, the most common response to Q1 (“What do you think about the health effects of radiation on the next generation (children to be born in the future) in the areas affected by the accident at TEPCO’s Fukushima Daiichi Nuclear Power Plant?”) was “It is unlikely to occur” (97 students, 52.7%). The second most common response was “It is likely to occur” (71 students, 38.6%). On the other hand, after the explanation, 51 students (27.7%) responded that it was very unlikely to occur, and the number of people who responded that it was very likely to occur decreased significantly to 25 (13.4%) (p < 0.001). The most common reason for choosing the answer before receiving the explanation was “Because I think radiation is something that builds up in the body and has a negative impact on health” (41 students, 22.3%) (

Table 4. Changes in students’ risk perception regarding the health effects of radiation before and after explanation of the materials.

		Before Explanation	After Explanation	p Value a
Q1	Very unlikely to occur	10 (5.4%)	51 (27.7%)	<0.001
	Unlikely to occur	97 (52.7%)	104 (56.4%)
	Likely to occur	71 (38.6%)	25 (13.6%)
	Very likely to occur	6 (3.3%)	4 (2.2%)
Q2	Very unlikely to occur	2 (1.1%)	28 (15.2%)	0.023
	Unlikely to occur	74 (40.2%)	101 (54.9%)
	Likely to occur	103 (56.0%)	53 (28.8%)
	Very likely to occur	5 (2.7%)	2 (1.1%)
Q3	I think so	74 (40.2%)	79 (42.9%)	n.s.
	Somewhat agree	86 (46.7%)	83 (45.1%)
	Can’t say either way	14 (7.6%)	11 (5.0%)
	Somewhat disagree	8 (4.3%)	9 (4.9%)
	I don’t think so	2 (1.1%)	1 (0.5%)
	No answer		1 (0.5%)
Q4	I think so	37 (20.1%)	43 (23.4%)	n.s.
	Somewhat agree	89 (48.4%)	91 (49.5%)
	Can’t say either way	22 (12.0%)	22 (12.0%)
	Somewhat disagree	22 (12.0%)	16 (8.7%)
	I don’t think so	14 (7.6%)	11 (6.0%)
	No answer		1 (0.5%)

^a n.s., not statistically significant.

).

This reason was also the most common among those who answered that it was “likely to occur” (31 out of 71 students, 43.7%).

In contrast, the most prevalent response after the explanation was that there is no difference compared to the original exposure to natural radiation (62 students, 33.3%). This was followed by the assertion that the dose from the relevant accident was considered low (32 students, 17.2%; Figure 2).

Q1 and Q2 refer to survey questions on the health effects of radiation from Table 2. The responses to options 1–11 show the background and reasons for the respondents’ perceptions of radiation risk, as shown in Table 2.

Subsequently, a more detailed analysis of the changes in risk perception before and after the explanation showed that 89 (48.4%) students’ risk perception decreased, 83 (45.1%) did not change before or after the explanation, and 12 (6.5%) students’ risk perception increased. Of the 89 in the student subject group whose perception of risk decreased, the most common trend was that a significant proportion changed their answer from a “likely to occur” to “unlikely to occur”. This change in perception was observed among 40 students, representing 44.9% of the total number of student participants (

Table 5. Comparison of changes in risk perceptions regarding the health effects of radiation among students and radiologists before and after the explanation of the materials.

	Students	Radiological Technologists	Before Explanation	After Explanation	Students	Radiological Technologists
Q1
Risk perception decreased	89 (48.4%)	3 (20.0%)	Very likely to occur	Very unlikely to occur	1 (0.5%)
			Very likely to occur	Unlikely to occur	5 (2.7%)	1 (6.7%)
			Likely to occur	Unlikely to occur	40 (44.9%)
			Likely to occur	Very unlikely to occur	7 (3.8%)
			Unlikely to occur	Very unlikely to occur	36(40.4%)	2 (13.3%)
Did not change	83 (45.1%)	12 (80.0%)	Very unlikely to occur		7 (3.8%)	11 (73.3%)
			Unlikely to occur		56 (30.4%)	1 (6.7%)
			Likely to occur		20 (10.9%)
Risk perception increased	12 (6.5%)	0 (0.0%)	Very unlikely to occur	Unlikely to occur	3 (1.6%)
			Unlikely to occur	Likely to occur	5 (2.7%)
			Likely to occur	Very likely to occur	4 (2.2%)
Q2
Risk perception decreased	87 (43.3%)	3 (20.0%)	Very likely to occur	Likely to occur	3 (1.6%)
			Very likely to occur	Unlikely to occur	2 (1.1%)
			Likely to occur	Very unlikely to occur	6 (3.3%)	1 (6.7%)
			Likely to occur	Unlikely to occur	54 (29.3%)
			Unlikely to occur	Very unlikely to occur	22 (12.0%)	2 (13.3%)
Did not change	85 (46.2%)	12 (80.0%)	Very unlikely to occur		0 (0.0%)	10 (66.7%)
			Unlikely to occur		44 (23.9%)	1 (6.7%)
			Likely to occur		41 (22.3%)
Risk perception increased	12 (6.5%)	1 (0.0%)	Very unlikely to occur	Very unlikely to occur		1 (6.7%)
			Very unlikely to occur	Unlikely to occur	1 (0.5%)
			Unlikely to occur	Likely to occur	8 (4.3%)
			Very unlikely to occur	Likely to occur	1 (0.5%)
			Likely to occur	Very likely to occur	2 (1.1%)

).

A comparison of the responses of 40 students before and after providing the explanation revealed a notable shift in the rationale behind their answers. Prior to the explanation, the majority (19 students) indicated that “radiation accumulates in the body and has a negative impact on health”. However, following the provision of the explanation, the majority (16 students) asserted that “there is no difference compared to the natural radiation that already exists”. This was followed by the belief that the dose from the accident was minimal (10 students). The next most common trend in responses was a shift from “unlikely to occur” to “very unlikely to occur”, with 36 (40.4%) students responding that way. A comparison of the reasons for their choices before and after the explanation revealed notable shifts. When asked why before the explanation, seven students selected the reason “because I have not seen any information on the observed health effects”, and six students selected the reason ”because I don’t think this is scientifically known” or “because I think radiation is bad for me”. In contrast, after receiving an explanation, the most common reason given was that “there is no difference compared to the original exposure to natural radiation”, with 19 students choosing this option. The responses of the 83 students who did not change their answers before and after the explanation were most often “unlikely to occur” (56 students, 30.4%). A comparison of the reasons for choosing before and after the explanation is provided below: Before the explanation, 14 students selected the reason “because I have not seen any information on the observed health effects”, 13 selected the reason “because I don’t think this is scientifically known”, and 11 selected the reason “I got that impression from information I saw on the internet”. After the explanation, the most common reason given was that “there is no difference compared to the original exposure to natural radiation” (16 students), and the second most common reason given was that the dose from the relevant accident was considered low (11 students). Twenty students chose the “Very likely to occur” response. Among them, the reasons given most frequently before the explanation were “because I think radiation is something that builds up in the body and has a negative impact on health” (seven students) and “I think radiation is bad for me” (five students). After the explanation, nine gave the reason “because I think radiation is something that builds up in the body and has a negative impact on health”, and six gave the opinion “I think radiation is bad for me”. Twelve students (6.5%) reported increased perceptions of risk. There were five students who moved from “unlikely to occur” to “likely to occur”. The reasons given before and after the explanation were “because I think radiation is something that builds up in the body and has a negative impact on health” and “because I don’t think this is scientifically known.” for two students each before the explanation, and after the explanation, “I think radiation is bad for me” to four. All the students’ responses were divided into three groups based on whether their perception of risk had decreased, remained the same, or increased after reading the materials. Fisher’s test was conducted for each of the following: demographic characteristics, basic knowledge (percentage of respondents who answered Q1-1, Q2-1, Q3-1), and degree of anxiety at the time of the accident and now. However, none of the items showed statistically significant differences. On the other hand, 11 (73.3%) radiological technologists answered that Q1 was “very unlikely to occur”, and their answers did not change after the explanation. Three (20.0%) also decreased their risk perception, and two of them moved from “unlikely to occur” to “very unlikely to occur” (Table 5). The most common reason for choosing the answer before receiving the explanation was “because there is no difference compared to the original exposure to natural radiation” (six radiological technologists, 40.0%). In addition, three (20.0%) chose the reason “I thought so after looking at information from national and international professional organizations”. After the explanation, the most common reason for choosing was that there was “because there is no difference compared to the original exposure to natural radiation” (10 radiological technologists, 66.7%).

Before the materials were explained, the most common response to Q2 (“How many health effects (e.g., cancer) due to radiation from the accident at TEPCO’s Fukushima Daiichi Nuclear Power Plant do you think will occur to people in Fukushima?”) was “likely to occur” (103 students, 56.0%). This was followed by the response “unlikely to occur”, which was selected by 74 students (40.2%). After the explanation, 101 students (54.9%) indicated that the event was “unlikely to occur”, while 53 (28.8%) indicated that it was “likely to occur” Notably, the number who indicated that the event was “unlikely to occur” increased significantly, while the percentage who indicated that it was “likely to occur” decreased significantly (p = 0.023) (Table 4).

The most common reason given for the answer was “I think radiation is bad for the body” (40 students, 21.7%), followed by “Radiation accumulates in the body and has a negative effect on health” (32 students, 17.4%), and “I don’t think it is scientifically known” and “I’ve never seen any information about it being recognized as having a negative effect on health” (22 students each, 12.0%). Following the provision of an explanation, the most frequently selected response was that there was no difference compared to the natural radiation that already existed (50 students, 27.2%). This was followed by a response where the dose from the accident was low (26 students, 14.0%). The third most frequently selected response was that radiation accumulates in the body and negatively impacts health (26 students, 14.1%) (Figure 2).

A detailed analysis of the change in perception before and after the explanation revealed that 87 students (47.3%) had a lower perception of risk regarding the likelihood of an event occurring before and after the explanation. By contrast, 85 students (46.2%) did not change their answers. In addition, 12 students (6.5%) answered that their risk perception had increased. The most common trend among those whose risk perception had decreased was a change in their answers from “likely to occur” to “unlikely to occur”, with 54 students (29.3%) responding in this way (Table 5).

A comparison of the reasons provided by the 54 students who altered their choices before and after the explanation revealed that the most prevalent responses prior to the explanation were “I believe radiation is detrimental to the body” (23 students) and “I believe radiation is harmful” (15 students). However, following the provision of the explanation, the responses shifted to “There is no difference compared to natural radiation that already exists” (19 students) and “I thought the dose from the accident was low” (15 students). Of the 85 students whose responses remained consistent before and after the provision of an explanation, 44 (23.9%) indicated that the event was “unlikely to occur”, while 41 (22.3%) stated that it was “likely to occur”. Of the 44 who answered “unlikely to occur”, 12 chose “There are no reports of any observed health effects” as their reason before the explanation, and 13 chose “because the difference from natural radiation is small to begin with” as their reason after the explanation. The risk perception increased for 12 students, and eight of them changed their perception from “unlikely to occur” to “likely to occur”. The reasons provided by the eight students before and after the explanation were as follows: Before the explanation, three students selected “because I don’t think this is scientifically known”, two students chose “because I did not see any information on the observed health effects”, and each one selected “because I think radiation is bad for me”, “I got that impression from information I saw on the internet “, “because there is no difference compared to the original exposure to natural radiation”.

After the explanation, two students indicated “I thought so after looking at information from national and international professional organizations”, two students selected “I think radiation is bad for the body”, and two selected “I think radiation is something that builds up in the body and has a negative impact on health”. One participant each chose “I got that impression from information I saw on the internet” and “because I don’t think this is scientifically known”.

The student participants were divided into three groups based on whether their perception of risk had “decreased”, “remained the same”, or “increased” after reading the material. Then, Fisher’s test was conducted for each of the following: demographic characteristics, basic knowledge (percentage who answered Q1-1–Q3-1), and level of anxiety at the time of the accident and now. However, there were no items for which a statistically significant difference was found.

Prior to the provision of an explanation, 10 (66.7%) of the radiological technologists indicated that the probability of the event occurring was extremely low, while three (20.0%) responded that the probability was low. Following the provision of an explanation, 13 (86.7%) technicians indicated that the probability of an event occurring was extremely low, while one (6.7%) responded that the probability was low.

The most common reason given before the explanation was that there was no difference compared to natural radiation that already existed (seven technicians, 46.7%). This remained the most prevalent response even after the presentation of an explanation (nine technicians, 60.0%).

3.4. Changes in Risk Perception Regarding the Effects of Radiation on Future Generations and Health Effects Before and After the Presentation of Explanatory Materials—Trends in Responses to Q1 and Q2 Before and After the Explanation

Upon analysis of the results for students in the Department of Health Sciences, 61 (33.2%) had diminished perceptions of the probability of occurrence for both Q1 and Q2. Additionally, 57 students (31.0%) demonstrated no change in perception, a proportion that was significantly higher than that of students who displayed an enhanced likelihood of occurrence (p < 0.001).

In response to the question, “Do you think that recovery and restoration in Fukushima Prefecture is progressing?”, 74 students (39.8%) answered “I think so”, and 88 (47.3%) answered “I somewhat agree” before the explanation. After the explanation, 79 (42.5%) answered “I think so”, and 85 people (45.7%) answered “I somewhat agree”. No significant difference was observed in the change in the percentage of responses before and after the explanation. The responses of the radiology technicians were also the same after the explanation, with eight (53.3%) saying “I somewhat agree” and three (20.0%) saying “I can’t say either way” (Table 4).

When asked whether they thought that people in Fukushima Prefecture were sometimes looked at differently after the nuclear accident, before the explanation, 90 students (48.4%) answered “to some extent”, the most common response, followed by 37 people (19.9%) who answered “yes”. After the explanation, 93 students (50.0%) answered “to some extent”, the most common response, followed by 43 students (23.1%) who answered “yes”. No significant difference was observed in the percentage of responses before and after the explanation. In the responses of the radiological technologist, “somewhat agree” was selected by six (40.0%) and “can’t say either way” by five (33.3%). However, after the explanation, “somewhat agree” increased slightly to nine technicians (60.0%), and “can’t say either way” decreased slightly to four (26.7%) (Table 4).

4. Discussion

It has been reported that radiation anxiety is influenced by gender, age, having children, and being affected by the FDNPP accident [28]. In this study all the students were from outside Fukushima Prefecture, and the majority were female. At the time of the 2011 accident, these students were young children aged 6–7, and 36.4% of them said they had “no anxiety” about the nuclear power plant accident at that time. Yasui et al. [29] investigated the level of anxiety caused by the nuclear accident among college students who were 10 to 12 years old at the time of the earthquake, tsunami, and nuclear accident and found that the level of anxiety was low among students from outside Fukushima Prefecture soon after these events, and the results were the same. The students in this study were younger than those in Yasui et al.’s study, so their memories were unclear, and 52.2% said they did not remember, suggesting that they were not particularly interested in the nuclear accident in the first place. However, only one radiological technologist was not from Fukushima Prefecture, and the average number of years of clinical experience indicated that many had already been working as radiologists at the time of the accident. The majority of them expressed concerns about the situation at that time.

Comparing the trends in the responses of health science students regarding their basic knowledge of natural and artificial radiation with the results of a similar survey conducted by researchers after the accident among residents of Aomori and Fukushima Prefectures [14], the correct response rate for all items was lower than that of the general public, including the annual dose of natural radiation, effects of natural and artificial radiation, and internal and external exposure. This is because the survey was conducted in 2014, only three years after the accident, when public interest was still high, and many of the respondents were directly affected by the Fukushima nuclear disaster. In addition, in the previous survey, answers were limited to yes or no. By adding the “I don’t know” option, the number of ambiguous answers decreased. The authors believe that this was one of the factors that led to a decrease in the correct answer rate. On the other hand, apart from those who answered that they did not understand the first-stage questions, many people answered that they did not understand the numerical values or content of the concept, and few people answered with confidence. In addition, the question of the present survey that had a particularly low correct response rate was Q3, which concerned the effects of internal and external radiation exposure. This question also had a low correct response rate of 10% in a past survey of firefighters [30]. This time, there were many responses that indicated the students had no concept of internal exposure, and there was a lack of knowledge about the reality of internal exposure. However, as a characteristic of the subjects in terms of exposure to natural radiation, the previous survey [14] showed that 100 mSv and other high levels tended to be common. Although there were cases of zero, none of the subjects in this survey answered zero, indicating that they were aware that there was at least some risk.

As the students in question were studying in medical departments, some of them recalled artificial radiation from nuclear power plants, while others recalled medical-related content, such as radiation therapy, X-rays, and CT scans. Radiological technologists had a high rate of correct answers for the effects of exposure to radiation from natural sources and exposure to artificial and natural sources, but the rate of correct answers among the three questions for internal and external exposure was low. In a survey of radiological technologists in Fukushima Prefecture conducted by Ohba et al. [31], it was found that knowledge of internal exposure varied depending on the length of training at the time of the nuclear accident and whether the person had directly experienced the accident, as this type of knowledge was something that radiological technologists rarely came into contact with during their daily work in medical facilities. Ohba et al. also found that practical experience of internal exposure testing using whole-body counters (WBCs) affected knowledge of internal exposure. The subjects of the present study were radiology technicians working in Fukushima Prefecture. Although they were not asked whether or not they had practical experience, it would be assumed that those who were involved in WBC and other examinations immediately after the accident had relevant knowledge.

Half of the students (51.6%) had heard the word “radon”. In 2009, the WHO stated that radon is a risk factor for lung cancer in tobacco smokers, and regulations have been introduced in many countries around the world for residential buildings [32]. In a large-scale survey conducted in Italy, 39% of participants reported being aware of radon gas [33]. In comparison, the awareness among students in this study tended to be higher. However, despite the general familiarity with the term “radon”, it appears that students lacked specific knowledge, as they were unsure of where they had encountered the information or whether they had learned about it in previous classes. Additionally, there was no mention of radon in relation to natural radiation. According to the 2008 UNSCEAR report [34], the average annual effective radiation dose from natural sources is 2.4 mSv worldwide and 2.1 mSv in Japan. Of this, the dose from internal exposure to radon accounted for 50%, but students had almost no knowledge of this. On the other hand, all the radiology technicians said that they had heard of it. Because the content also included the word “natural radiation”, which was not mentioned by the students, it was concluded that the radiology technicians had a higher level of basic knowledge about radiation than the students of the health department, and that their knowledge was more systematic than the students’ knowledge, which was more fragmented.

Regarding the change in risk perception of radiation’s health effects (Q1 and Q2) before and after receiving explanatory materials, there was a significant decrease in the number of respondents who believed these effects were “likely to occur” and a significant increase in those who believed they were “very unlikely to occur”. This trend suggests that providing explanatory materials and explanations helps reduce concerns about the long-term health effects of the FDNPP accident, including its impact on future generations. In a survey of nursing students conducted by Yamaguchi et al. [35], changes in knowledge of radiation and changes in risk perception of genetic effects before and after a lecture on radiation were investigated. In this study, the likelihood of these effects occurring was assessed using a four-point scale, ranging from “very unlikely to occur” to “very likely to occur”. For the analysis, responses were categorized into two groups: the “low likelihood” group, which included those who answered “very unlikely to occur” or “unlikely to occur”, and the “high likelihood” group, which included those who answered “likely to occur” or “very likely to occur”. The percentage of students in each category was then analyzed to assess changes in perception.

The percentage of students who responded that the likelihood of these effects occurring was low was lower than that for effects on future generations (47.1% vs. 97.3%, p < 0.001) and for health problems occurring later in life (before lecture 24.3% vs. 94.7% after lecture, p < 0.001). Yamaguchi et al. [35]. found that there was a significant improvement in radiation risk perception after the lecture compared to before it. In this our study, using the same rating scale for the low and high likelihood groups, the perceived impact on the next generation increased from 58.1% before receiving the materials to 84.1% after, while concerns about late-onset health problems rose from 41.3% to 70.1%. Although the percentage of participants whose risk perception decreased was relatively small, the fact that some reduction was observed through the explanatory materials alone—without the need for a full lecture—demonstrates their effectiveness. In addition, our study also analyzes changes in individual risk perceptions before and after viewing and explaining the materials because the subject response trends are linked before and after the explanations. In total, 48.4% of both subject groups felt that the effects on future generations had decreased, and 43.3% felt that the effects on their own health had decreased. Among those who decreased their risk perception, 44.9% changed from “highly likely” to “unlikely”, and 29.3% changed from “unlikely” to “very unlikely” regarding the impact on the future generation. Similarly, the percentages for the impact on their own health were 40.4% and 12.0%, respectively, indicating a tendency to estimate the risk perception one level lower after the presentation and explanation of the data. These results indicate that the materials used in this study were effective in visually reducing risk. Previous studies have shown that a certain amount of anxiety about the effects of radiation on the human body can be measured by acquiring knowledge through lectures and other means, and a certain amount of risk reduction can be measured [35]. Tomizawa et al. [36] examined the relationship between knowledge of the effects of radiation on the human body and fear of radiation among first- to fourth-year Japanese nursing students and found that knowledge increased and fear decreased with increasing grade. This indicates that increased knowledge decreases risk perception. However, it is worth noting that even when basic knowledge about radiation is limited, as was the case in the background of the student population studied here, materials and simple explanations were sufficient to reduce risk perception in a short period of time. This may be due to the fact that the materials used in this study are easy to understand at a glance and visually comprehensible, with figures comparing radiation doses from natural sources and artificial radiation doses from the FDNPP accident, which we believe may reduce risk perception. In addition, we believe that the use of natural radiation, which is the original standard for considering the effects of radiation from the FDNPP accident, as the basis for comparison made the risk appear less daunting and easier to accept for risk comparisons.

In the subsequent section of this study, an examination will be conducted of the background of individuals who exhibited decreased risk perception. Focusing on the reasons given for choosing the options, those who judged the options to be “likely to occur” and “very likely to occur” before the explanations were most likely to cite “because I think radiation is bad for me” and “because I think radiation is something that builds up in the body and has a negative impact on health” as reasons for their decision. In the survey conducted by the MOE [17], when asked about the impact on the next generation, many respondents who answered that it was very likely or extremely likely to occur selected the same reasons as noted in the present study as their reasons. For this reason, Solvic [15] suggests that the perception of risk is heightened in the case of nuclear accidents due to their rarity and the belief that exposure could have been avoided. Many of the students in this study also cited “nuclear power plants” as the content they associate with man-made radiation, and it is highly likely that their image of radiation as a negative influence led them to select this reason. These findings suggest that, despite being enrolled in health-related departments, students lacked fundamental knowledge of radiation before the explanation. Similar to the general public, they tended to believe that the effects of a nuclear accident would be severe. As a result, many students initially responded that the impact of the FDNPP accident would be significant. In the survey conducted by the MOE, many respondents who chose “unlikely to occur” or “very unlikely to occur” chose “I have not seen any information on the observed health effects” as the reason for their choice, and many of the respondents tended to choose the same reason in this study. However, after the presentation, they shifted to a very low level and also shifted to reasons such as “there is no difference from natural radiation” and “the radiation dose is low”. The participants had no knowledge of natural radiation before the presentation. However, by presenting the material as a comparison, they became aware of natural radiation, and this led to a reduction in risk. The data may have helped them to recognize natural radiation and to judge that the dose of man-made radiation from the Fukushima nuclear power plant accident was lower than they had expected when using natural radiation as a reference point. As a result, seeing evidence-based dosimetry results may have reassured them and led them to reduce their risk. Another reason why they are not worried even if the dose of natural radiation is higher than that of man-made sources is provided by Sandman et al. [37], who note that people tend to have little concern about radon seeping from basements, as it naturally occurs in a familiar environment and is impossible to fully eliminate. Slovic also points out that the intense fear and anxiety associated with radiation do not seem to extend to naturally occurring radioactive materials [15]. In other words, the general public is vaguely aware of their daily exposure to radiation and may not perceive any significant impact on their health or future generations. Furthermore, the absence of visible health problems or noticeable risks from naturally occurring radioactive materials might lead individuals to view it as a low-risk factor. It can be inferred that the explanatory materials, which demonstrated that the current artificial radiation levels from the FDNPP accident were not significantly higher than natural radiation levels, contributed to the shift in perception. As a result, many participants likely classified the risks associated with genetic and health effects as “low” after the explanation. In any case, we believe the explanatory materials played a significant role in altering the risk perception of radiation.

Next, we discuss those who had no change in risk perception. Conversely, those who did not change their risk perception for any of the questions selected “unlikely” or “very unlikely” from the beginning, indicating that they originally had a low-risk perception of radiation. Many participants selected the reasons of “I have not seen any information on the observed health effects” and “I don’t think this is scientifically known”. As reported by Nakayama et al. [38], nine years after the accident, the types of media used for information regarding radiation and the sources of trusted information were found to be associated with concerns about the potential effects on future generations. Additionally, Nakayama et al. noted that individuals who placed trust in government ministries and agencies exhibited lower levels of concern about the potential effects on future generations. This study did not investigate the detailed sources of information that respondents relied on. However, it is conceivable that respondents who perceive risk to be minimal may engage in a systematic and objective analysis of the information they obtain, thereby facilitating an accurate understanding of the risk. Among those who do not alter their perception of risk, one subset acknowledges the high probability of its occurrence. The rationale behind this lack of change in perception is that these individuals recognize the detrimental effects of radiation on the body. Despite explanations regarding natural radiation, their perceptions remain unaltered. Furthermore, a survey conducted by Yamaguchi et al. [35] indicated that a subset of individuals did not alter their risk perceptions after hearing a lecture. It is challenging for these individuals to modify their perceptions of radiation based on the dissemination of materials alone. Consequently, alternative approaches, such as comprehensive risk communication, may be more efficacious. However, after the explanation, the reasons for this were shifted to the fact that there was no difference compared with natural radiation. It can be postulated that this is because the explanatory materials indicated that the current level of artificial radiation resulting from the Fukushima accident is not significantly higher than the current level of natural radiation. This may have contributed to the decision to select a low risk.

However, among those who do not alter their perception of risk, one subset acknowledges the high probability of its occurrence. The rationale behind this lack of change in perception is that these individuals recognize the detrimental effects of radiation on the body. Despite explanations regarding natural radiation, their perceptions remain unaltered. Furthermore, a survey conducted by Yamaguchi et al. [35] indicated that a subset of individuals did not alter their risk perceptions after hearing a lecture. It is challenging for these individuals to modify their perceptions of radiation through the dissemination of materials alone. Consequently, alternative approaches, such as comprehensive risk communication, may be more efficacious. Kusumi et al. [39]. found that citizens with a high level of basic knowledge about radiation and media literacy, who already had a strong sense of risk perception, did not alter their views even when provided with information about both safety and danger of radiation. In other words, individuals who are well informed about radiation risks are less likely to feel reassured, even when presented with information emphasizing safety. Additionally, the media literacy of the students in this study was not specifically assessed, and there were no significant differences in their basic knowledge of radiation. It is believed that one factor contributing to this is that the students already had a clear understanding of the risks, meaning that providing information about natural radiation did not significantly affect their risk perception.

The radiological technologists’ responses indicated that the possibility of an event occurring was deemed extremely low, even prior to the provision of the explanation. Following the explanation, there was no discernible change in their perceptions. Furthermore, a survey on the risk perception of radiation conducted by Perko [40] revealed a difference between experts and the general public. Experts’ perceptions of medical X-rays and natural radiation were significantly higher than those of the general population, whereas their perceptions of nuclear waste and accidents at nuclear facilities were lower than the public’s perceptions. This is because radiological technologists have a solid foundation in fundamental radiation and natural radiation concepts, and they tend to make decisions based on scientific evidence. It can be inferred that they are making well-informed judgments based on this knowledge of the potential effects on future generations and the health implications of the Fukushima nuclear power plant accident. Additionally, the participants in this study had prior experience with radiation measurement as a result of the FDNPP accident. As a result, their perception of risk did not change before or after the explanation of our materials. This is likely because they had already gained an understanding of the concepts presented in our materials through their personal experience with the FDNPP accident. For both Q1 and Q2, 32.8% of the respondents indicated a decrease in awareness of the potential occurrence of the event, while 31.2% reported no change in awareness. This suggests that the responses to Q1 and Q2 were similar for those who reported a decrease in awareness and for those who reported no change in awareness. Furthermore, the authors investigated the impact of variables, such as radiation attributes and knowledge, on perceptual alterations before and after the clarification of Q1 and Q2. However, no relevant items were identified. The students who were the subjects of this survey had only recently commenced their health science studies at the university level. While they aspired to pursue a career in the medical profession, they exhibited a notable deficiency in their fundamental knowledge regarding radiation. The responses to the inquiries regarding their fundamental understanding demonstrated that their knowledge was not particularly robust or, if it existed, it was fragmented. Furthermore, the students demonstrated a notable lack of knowledge regarding natural radiation, particularly in comparison with the expertise of radiological technologists. As there was no relationship among Q3, Q1, and Q2 and the students who were the subjects of this study were from outside Fukushima Prefecture and had almost no memories of the accident, there seems to be no effect on their perception of the risk of health effects or effects on future generations.

5. Conclusions

In this study, by presenting actual radiation measurement data from the coastal areas of Fukushima Prefecture after the FDNPP accident, a tangible impact was observed on the decision-making process for selecting responses to a questionnaire survey. The results of this study suggest that even a group with limited basic knowledge of radiation can visualize and compare radiation doses from the accident using natural radiation as a reference. This ability to make judgments based on visual information can facilitate decisions regarding the evaluation of the impact on future generations and the reduction of risks associated with their own health effects. The data used in this study were collected in Fukushima Prefecture after the accident. We believe that the use of familiar, local data played a significant role in developing an understanding of radiation risk, which is also an important aspect. This was because the participants were able to recognize the existence of natural radiation and to compare it with the current radiation levels in Fukushima Prefecture. Consequently, they were able to gain a sense of security. It was found that information about the dose of natural radiation and visual materials based on this had a significant impact on perceptions of the effects of the nuclear accident on future generations and on health. This suggests that these materials are effective new tools for risk communication. However, it was also found that even if individuals recognized that the effects of the accident were not as serious as those caused by natural radiation, a considerable number of participants still held discriminatory views. This finding indicated that fragmented knowledge could lead to the spread of incorrect information.

6. Limitations

The students in this study, who were from health departments, often lacked a comprehensive understanding of radiation exposure. Many were only six or seven years old at the time of the FDNPP accident, and none were from Fukushima Prefecture, which limited their personal memories of the event. Additionally, various factors contribute to the formation of risk perceptions, including personal experiences and emotions, with one key factor being the understanding of numerical information [41]. The students in this study, having received higher education, were able to immediately grasp the meaning of numerical data, which had a significant impact on their risk perception.

Furthermore, the goal of risk communication is not simply to alleviate public concern or avoid action, but to create an informed and engaged citizenry that is rational, thoughtful, solution-oriented, and cooperative [42]. In terms of influencing perceptions and creating interest, it is likely that the risk of natural radiation was previously unknown to many participants, but learning about it through the study’s materials impacted their risk perception. The radiation data used in this study, which came from the chronic recovery phase several years after the accident, highlighted that artificial radiation was initially higher than natural radiation, which may have caused confusion at that time. The materials used in this study can thus be effective when applied to current exposure situations. Additionally, these materials were created by incorporating feedback from residents who returned to the coastal areas of Fukushima, local government officials, and researchers. However, there is a need to improve how the information is presented, including refining the types of graphs used to make the data more accessible to a larger audience. Future research should also verify the effectiveness of presenting explanatory materials using natural radiation as a benchmark for various groups, taking into account factors such as age and the participants’ geographic origins.