Assessing the health effects associated with occupational radiation exposure in Korean radiation workers: protocol for a prospective cohort study

Abstract

IntroductionThe cancer risk of radiation exposure in the moderate-to-high dose range has been well established. However, the risk remains unclear at low-dose ranges with protracted low-dose rate exposure, which is typical of occupational exposure. Several epidemiological studies of Korean radiation workers have been conducted, but the data were analysed retrospectively in most cases. Moreover, groups with relatively high exposure, such as industrial radiographers, have been neglected. Therefore, we have launched a prospective cohort study of all Korean radiation workers to assess the health effects associated with occupational radiation exposure.Methods and analysisApproximately 42 000 Korean radiation workers registered with the Nuclear Safety and Security Commission from 2016 to 2017 are the initial target population of this study. Cohort participants are to be enrolled through a nationwide self-administered questionnaire survey between 24 May 2016 and 30 June 2017. As of 31 March 2017, 22 982 workers are enrolled in the study corresponding to a response rate of 75%. This enrolment will be continued at 5-year intervals to update information on existing study participants and recruit newly hired workers. Survey data will be linked with the national dose registry, the national cancer registry, the national vital statistics registry and national health insurance data via personal identification numbers. Age-specific and sex-specific standardised incidence and mortality ratios will be calculated for overall comparisons of cancer risk. For dose–response assessment, excess relative risk (per Gy) and excess absolute risk (per Gy) will be estimated with adjustments for birth year and potential confounders, such as lifestyle factors and socioeconomic status.Ethics and disseminationThis study has received ethical approval from the institutional review board of the Korea Institute of Radiological and Medical Sciences (IRB No. K-1603-002-034). All participants provided written informed consent prior to enrolment. The findings of the study will be disseminated through scientific peer-reviewed journals and be provided to the public, including radiation workers, via the study website (http://www.rhs.kr/) and onsite radiation safety education.

A Cohort Study of Korean Radiation Workers: Baseline Characteristics of Participants

“…Third, the size of our cohort was smaller than cohorts from other countries such as the United Kingdom, the United States, and France [43][44][45][46]. In order to increase the cohort size, enrollment will be continued at five-year intervals, and the development of a strategy to enroll retired workers is now in progress [10]. Lastly, the current occupational classification in the dose registry does not clearly reflect the occupational nature (e.g., profession).…”

“…However, a younger cohort provides some advantages in terms of having fewer uncertainties about information collected such as dosimetry and baseline health status. For instance, older workers with long-term careers may have greater uncertainties about their radiation doses than recently hired workers, due to changes in personal dosimeter types (e.g., film badge or thermoluminescent dosimeters) over long employment periods and deficient or missing dose records (e.g., undocumented dose records) from before 1984, the year from when the national dose registry was available in Korea [10]. In addition, a younger cohort is assumed to be healthy; this is more appropriate for study subjects using a prospective cohort design.…”

“…The design and methods of the KRWS were previously described in its protocol [10]. In summary, a nationwide self-administered survey of demographics, lifestyle factors, and work practices was conducted on 42,607 Korean radiation workers from 24 May, 2016 to 30 June, 2017 at educational institutions where all radiation workers receive radiation safety education every year; among them, 35,789 workers participated in the survey.…”

“…The sources of dosimetry data and cancer incidence data have been described in detail in the study protocol [10]. The radiation doses of the workers collected in this study were personal dose equivalent (H p (10)) from personal badge dosimeters reported to the Central Registry for Radiation Worker Information (CRRWI) from 1984 to the first quarter of 2017.…”

“…In order to overcome the limitations of the previous studies, we launched a national cohort study of radiation workers (aka "the Korean Radiation Worker Study (KRWS)") in various nuclear-related occupations for long-term follow-up, and enrolled study participants to the cohort through a nationwide baseline survey from 2016-2017 [10]. We collected information including demographics, occupational characteristics, and lifestyle factors of the workers, and linked the data with the national dose registry and the national cancer registry.…”