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

Abstract

The Korean Radiation Worker Study investigated the health effects of protracted low-dose radiation among nuclear-related occupations in the Nuclear Safety and Security Commission in Korea. From 2016–2017, 20,608 workers were enrolled (86.5% men and 30.7% nuclear power plant workers). The mean cumulative dose ± standard deviation between 1984 and 2017 (1st quarter) was 11.8 ± 28.8 (range 0–417) mSv. Doses below recording level (≤0.1 mSv) were reported in 7901 (38.3%) cases; 431 (2%) had cumulative doses ≥100 mSv. From 1999–2016, 212 cancers (189 men, 23 women) occurred; thyroid cancer predominated (39.2%, 72 men, 11 women). In men, the standardized incidence ratio (SIR) for all cancers was significantly decreased (SIR = 0.76, 95% CI 0.66–0.88); however, that for thyroid cancer was significantly increased (SIR = 1.94, 95% CI 1.54–2.44). Compared to the non-exposed group (≤0.1 mSv), the relative risk (RR) in the exposed group (>0.1 mSv) after adjusting for sex, attained age, smoking status, and duration of employment was 0.82 (95% CI 0.60–1.12) for all cancers and 0.83 (95% CI 0.49–1.83) for thyroid cancer. The preliminary findings from this baseline study with a shorter follow-up than the latency period for solid cancer cannot exclude possible associations between radiation doses and cancer risk.

Non-cancer disease prevalence and association with occupational radiation exposure among Korean radiation workers

“…However, we observed that the SPRs for thyroid diseases, hyperlipidemia, and hepatitis were increased. The increased SPRs for thyroid diseases can possibly be attributed to thyroid screening, with similar increased thyroid cancer incidence rates observed among radiation workers in several studies 16,[25][26][27][28] . The increased SPR for hyperlipidemia may have been due to improved access to healthcare services for workers through the workers' general health examinations (WGHEs) system, where an examination for hyperlipidemia is included in the second health examination and constitutes a mandatory component of workers' regular health checkups.…”

“…However, considering that selection bias is a common and potentially serious problem particularly in a case-control study 48,49 and nonresponses in voluntary sampling do not seem to necessarily bias the associations among survey items 50 , nonresponses are not likely to have substantially influenced the exposure-disease associations in this study. In addition, the distributions of the number of workers and radiation doses by occupation types in the cohort did not substantially deviate from those of the target population, and the study population was in active service with a mostly healthy status 16 ; therefore, the selection of study subjects would not be highly related to exposure and disease status. Finally, we collected participant demographic and lifestyle data in relation to non-cancer diseases concerning various risk factors; however, we were not able to include other potential risk factors in this study.…”

Bias-corrected <i>H</i>_p(10)-to-Organ-Absorbed Dose Conversion Coefficients for the Epidemiological Study of Korean Radiation Workers

“…Thus, the assessment of the radiation effect on health has become important because of increasing JRPR concerns about protracted exposure. Previous studies generally used the personal dose equivalent Hp (10) to evaluate the health effects associated with occupational exposure. Similar to other countries, the occupational exposure of Korean radiation workers is managed in terms of Hp (10), measured by personal dosimeters such as the thermoluminescent dosimeter (TLD), and the measured Hp (10) values are reported every 3 months to the national dose registry.…”

“…However, to evaluate cancer morbidity and mortality, the International Commission on Radiological Protection (ICRP) strongly recommends the use of an organ-absorbed dose rather than Hp (10) [1]. Unfortunately, it is impossible to directly measure organ-absorbed doses because dosimeters should not be inserted into the human body.…”

“…Unfortunately, it is impossible to directly measure organ-absorbed doses because dosimeters should not be inserted into the human body. For this reason, organ-absorbed doses for radiation workers should be derived from Hp (10) values using dose conversion coefficients. The ICRP has provided the dose conversion coefficients for air kerma-to-Hp (10) and air kerma-to-organ-absorbed doses calculated based on a 30 cm × 30 cm × 15 cm slab phantom (mass composition: 76.2% oxygen, 11.1% carbon, 10.1% hydrogen, and 2.6% nitrogen) and anthropomorphic phantoms coupled with Monte Carlo methods [2,3], respectively.…”