Concern over radiation exposure and psychological distress among rescue workers following the Great East Japan Earthquake Concern over radiation exposure and distress

On March 11, 2011, the magnitude 9.0 Great East Japan Earthquake and tsunami that followed devastated the northeastern coast of Japan and damaged the Fukushima Daiichi nuclear power plant. Members of the Disaster Medical Assistance Team (DMAT) service, established by the Ministry of Health, Labour and Welfare of Japan, were dispatched to the disaster area as a mobile medical team. A previous study with clean-up workers who participated in salvage activities after the Chernobyl nuclear accident revealed that the prevalence of depression, posttraumatic stress disorder (PTSD), and suicidal ideation 18 years after the accident was higher than geographically matched controls and that radiation exposure level was associated with somatic and PTSD symptom severity [1]. However, there is a paucity of evidence available on the impact of subjective concerns over radiation exposure on health. The present study aimed to investigate early psychological distress among DMAT members who provided care to victims of the earthquake in the potentially dangerous situation of radiation exposure, and to ascertain whether an association exists between subjective concern over radiation exposure and psychological distress.

Of the 1,816 DMAT members deployed to the disaster area, 426 agreed to participate in the present study (24% response rate), of whom 424 (65.8% men, 34.2% women; mean age 38.2 (SD = 7.5) years) completed a self-report questionnaire to assess psychological distress. Demographic characteristics are shown in Table 1. Physicians accounted for 24.1% of the sample, nurses 45.8%, and operational coordination staff 30.2%. Most of the women (89%) were nurses, while the occupational distribution was more dispersed for men; 33.7% were physicians, 23.3% were nurses, and 43.0% were operational coordination staff. Among all respondents, 9.2% were concerned over radiation exposure. The prevalence of probable psychological distress as determined by the K6 and CES-D was 4.0% and 21.4%, respectively. Both men and women with such concern showed significantly higher K6, CES-D, PDI, and IES-R scores than in those without concern (Table 2). After controlling for age, occupation, disaster operation experience, duration of time spent watching earthquake news, and past history of psychiatric illness, these associations remained significant in men, but did not remain significant in women for the CES-D and PDI scores. In addition, after excluding those with past history of psychiatric illness, ANOVA results showed no apparent change in the association between concern over radiation and psychological distress in men. In women, however, the association remained significant for the K6 (p = .029) but not for the CES-D, PDI, or IES-R (p = .097, p = .064, p = .064). ANCOVA results for women did not change the association. Moreover, for the ANCOVA, the addition of the two covariates “experience of saving a child during deployment” and “experience of contact with corpses” to the primary analysis of covariance did not change the association in men or women (data not shown).

The present findings suggest that concern over radiation exposure was strongly associated with depressive and posttraumatic stress symptoms. Even among medical workers, who would likely be more knowledgeable than other public service workers about radiation exposure dangers, uncertainty about radiation exposure did have a significant adverse effect on their mental health. Thus, reliable and accurate information on radiation would be helpful for rescue workers, as well as residents, in disaster areas in order to minimize unnecessary psychological distress.

The prevalence of probable severe mental illness as determined by the K6 and depression as determined by the CES-D was 4.0% and 21.4%, respectively, in this study. For reference, the prevalence of depressive disorder was 14.9% among clean-up workers 18 years after the Chernobyl accident [1]. An epidemiological study of a representative sample of community-dwelling Japanese (n = 43,716) using the K6 showed that 6.7% had severe mental illness [15] and a large cohort study among Japanese workers with high and low socioeconomic status showed that 20–27% of men and 30–32% of women met the criteria for depression as determined by the CES-D [16]. Thus, the prevalence of depression in the present study was assumed to be equivalent to that of the general Japanese population or average workforce.

The present study has some limitations. First, 1,390 DMAT members who were invited to participate in the study did not respond, which could limit the external validity of the findings. The lack of response could be attributable to the fact that many rescue workers dedicated themselves to continuing important work at their own hospitals immediately after returning from their deployment and could not find the time to participate in this study. It remains unclear whether similar findings would have been obtained if the full cohort had been recruited successfully. There is the possibility that subjects who responded were more anxious or were more likely to be deployed in areas with high radiation exposure; however, this cannot be confirmed as it is not known if differences in demographic characteristics exist between DMAT members who responded and those who did not. Second, we could not directly examine whether individual personnel were actually exposed to radiation or examine the geographic sites where they were deployed. We also did not assess the exact nature of the disaster work they undertook during their deployment, and this constitutes a weakness in the assessment of the traumatic event. Third, it is important to note that over 70% of participants in the present study were nurses and physicians, which may limit the generalizability of our findings to other rescue worker populations such as the police, local fire departments, and self-defense force, although they all have similar occupational responsibility to the public. Fourth, concern over radiation exposure might be influenced by the level of psychological distress. A longitudinal study is needed to examine the causality. Further research is needed to examine more closely the association between actual exposure level of radiation and psychological distress in individuals at risk from radiation exposure.

In conclusion, the results suggested that concern over radiation exposure was strongly associated with psychological distress among rescue workers.