Correction: Data integration of National Dose Registry and survey data using multivariate imputation by chained equations.

[This corrects the article DOI: 10.1371/journal.pone.0261534.].

Data integration of National Dose Registry and survey data using multivariate imputation by chained equations.

INTRODUCTION: Data integration is the process of merging information from multiple datasets generated from different sources, which can obtain more information in comparison to to one data source. All diagnostic medical radiation workers were enrolled in National Dose Registry (NDR) from 1996 to 2011, linked with mortality and cancer registry data. (https://kdca.go.kr/) Survey was conducted during 2012-2013 using self-reported questionnaire on occupational radiation practices among diagnostic medical radiation workers. METHODS: Data integration of NDR and Survey was performed using the multivariate imputation by chained equations (MICE) algorithm. RESULTS: The results were compared by sex and type of job because characteristics of target variables for imputation depend on these variables. There was a difference between the observed and pooled mean for the frequency of interventional therapy for nurses due to different type of medical facility distribution between observed and completed data. Concerning the marital status of males and females, and status of pregnancy for females, there was a difference between observed and pooled mean because the distribution of the year of birth was different between the observed and completed data. For lifetime status of smoking, the percentage of smoking experience was higher in the completed data than in the observed data, which could be due to reasons, such as underreporting among females and the distribution difference in the frequency of drinking between the observed and completed data for males. CONCLUSION: Data integration can allow us to obtain survey information of NDR units without additional surveys, saving us time and costs for the survey.

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

Radiation-induced cancer risks have known stochastic effects; however, regarding non-cancer diseases, evidence of risk at low radiation doses remains unclear. We aimed to identify underlying characteristics concerning non-cancer disease prevalence and determine associations with radiation dose among Korean radiation workers. Using a nationwide baseline survey, 20,608 workers were enrolled. Data concerning participant demographics, occupational characteristics, lifestyle, and lifetime prevalence of non-cancer diseases were linked to a national dose registry. We compared non-cancer disease prevalences in the Korean general population with those in this cohort and undertook a dose-response analysis concerning the cumulative dose. Hyperlipidemia (10.6%), circulatory (9.6%), and respiratory (4.1%) system diseases, followed by thyroid diseases (3.5%), had the highest prevalences, with hyperlipidemia, thyroid diseases, and hepatitis prevalence being higher in the cohort than in the general population. Radiation doses were associated with elevated prevalences of most diseases; however, associations were attenuated and not significant after adjusting for confounders, except for musculoskeletal system diseases (prevalence odds ratio [POR]/10 mSv, 1.03; 95% confidence interval [CI] 1.00-1.07) and cataracts (POR/10 mSv, 1.04; 95% CI 1.00-1.07). Further studies are warranted to investigate the causality of those non-cancer diseases involving more varied confounders such as physical and psychosocial stresses and ultraviolet light.

Cancer Risk After Radioactive Iodine Treatment for Hyperthyroidism: A Systematic Review and Meta-analysis.

Importance: Whether radioactive iodine (RAI) therapy for hyperthyroidism can increase cancer risk remains a controversial issue in medicine and public health. Objectives: To examine site-specific cancer incidence and mortality and to evaluate the radiation dose-response association after RAI treatment for hyperthyroidism. Data Sources: The Medline and Cochrane Library electronic databases, using the Medical Subject Headings terms and text keywords, and Embase, using Emtree, were screened up to October 2020. Study Selection: Study inclusion criteria were as follows: (1) inclusion of patients treated for hyperthyroidism with RAI and followed up until cancer diagnosis or death, (2) inclusion of at least 1 comparison group composed of individuals unexposed to RAI treatment (eg, the general population or patients treated for hyperthyroidism with thyroidectomy or antithyroid drugs) or those exposed to different administered doses of RAI, and (3) inclusion of effect size measures (ie, standardized incidence ratio [SIR], standardized mortality ratio [SMR], hazard ratio [HR], or risk ratio [RR]). Data Extraction and Synthesis: Two independent investigators extracted data according to the Meta-analysis of Observational Studies in Epidemiology (MOOSE) guidelines. Overall quality assessment followed the recommendations of United Nations Scientific Committee on the Effects of Atomic Radiation. The SIR and SMRs and the RRs and HRs were pooled using random-effects meta-analysis. Main Outcomes and Measures: Cancer incidence and mortality for exposure vs nonexposure to RAI therapy and by level of RAI administered activity. Results: Based on data from 12 studies including 479 452 participants, the overall pooled cancer incidence ratio was 1.02 (95% CI, 0.95-1.09) and the pooled cancer mortality ratio was 0.98 (95% CI, 0.92-1.04) for exposure vs nonexposure to RAI therapy. No statistically significant elevations in risk were observed for specific cancers except thyroid cancer incidence (SIR, 1.86; 95% CI, 1.19-2.92) and mortality (SMR, 2.22; 95% CI, 1.37-3.59). However, inability to control for confounding by indication and other sources of bias were important limitations of studies comparing RAI exposure with nonexposure. In dose-response analysis, RAI was significantly associated with breast and solid cancer mortality (breast cancer mortality, per 370 MBq: 1.35; P = .03; solid cancer mortality, per 370 MBq: 1.14; P = .01), based on 2 studies. Conclusions and Relevance: In this meta-analysis, the overall pooled cancer risk after exposure to RAI therapy vs nonexposure was not significant, whereas a linear dose-response association between RAI therapy and solid cancer mortality was observed. These findings suggest that radiation-induced cancer risks following RAI therapy for hyperthyroidism are small and, in observational studies, may only be detectable at higher levels of administered dose.

Increased Incidence of Thyroid Cancer in Occupational Radiation Epidemiology: Attribution to Screening among Radiation Workers.

In most studies on radiation workers, the incidence of thyroid cancer was determined to be higher than among the general population; this is generally assumed to be due to overdiagnosis through thyroid screening. However, there is a lack of evidence on the association between thyroid screening and increased thyroid cancer incidence in most occupational studies. In this study, we compared thyroid cancer screening rates between the general population and radiation workers with various occupations and examined the relationship between these rates and thyroid cancer incidence. We compared thyroid screening rates between radiation workers and the general population with age- and sex-standardized screening ratios (SSRs) using data from two national surveys conducted during 2015-2017 in Korea, and assessed the correlation between these ratios and age- and sex-standardized incidence ratios (SIRs) for thyroid cancer. Screening rates were higher among radiation workers than among the general population, with an overall SSR of 1.58 (95% confidence interval: 1.54-1.62). When various types of occupations were compared, those with an increased SSR also had an increased SIR. SSRs remained high even when the screening period was restricted to the year preceding the survey (the year after the establishment of guidelines for thyroid cancer screening aimed at reducing overdiagnosis). In conclusion, the increased incidence of thyroid cancer among radiation workers compared to that among the general population can be attributed mainly to increased thyroid screening rates. Additional efforts are needed to reduce unnecessary thyroid cancer screening in occupational populations, particularly in those with better access to healthcare, in terms of clinical rationale and for assessing the true increase in thyroid cancer incidence.

Risk of Hematologic Malignant Neoplasms From Abdominopelvic Computed Tomographic Radiation in Patients Who Underwent Appendectomy.

Importance: Whether computed tomography (CT) radiation is truly carcinogenic remains controversial. Large epidemiological studies that purportedly showed an association between CT radiation and carcinogenesis were limited by confounding by indication and reverse causation, because the reasons for CT examination were unknown. Objective: To measure the risk of hematologic malignant neoplasms associated with perioperative abdominopelvic CT radiation among patients who underwent appendectomy for acute appendicitis. Design, Setting, and Participants: This nationwide population-based cohort study used the National Health Insurance Service claims database in South Korea to assess 825 820 patients who underwent appendectomy for appendicitis from January 1, 2005, to December 31, 2015, and had no underlying risk factors for cancer. Patients were divided into CT-exposed (n = 306 727) or CT-unexposed (n = 519 093) groups. The study was terminated on December 31, 2017, and data were analyzed from October 30, 2018, to September 27, 2020. Exposures: Perioperative abdominopelvic CT examination from 7 days before to 7 days after appendectomy. Main Outcomes and Measures: The primary outcome was the incidence rate ratio (IRR) of hematologic malignant neoplasms for both groups. The secondary outcomes were IRR of abdominopelvic organ cancers and IRR of all cancers. The lag period was 2 years for the primary outcome and 5 years for secondary outcomes. The IRRs were calculated using Poisson regression models with adjustment for age and sex. Results: Among the study population of 825 820 patients (52.9% male; median age, 28 [interquartile range, 15-41] years), hematologic malignant neoplasms developed in 323 patients in the CT-exposed group during 1 486 518 person-years and 500 patients in the CT-unexposed group during 3 422 059 person-years. For all hematologic malignant neoplasms, the IRR for the CT-exposed vs CT-unexposed group was 1.26 (95% CI, 1.09-1.45; P = .002). In terms of individual categories of hematologic malignant neoplasms, the CT-exposed group had an elevated risk only for leukemia (IRR, 1.40 [98.75% CI, 1.04-1.87, adjusted by Bonferroni correction]; P = .005). There was no between-group difference in incidence rate of abdominopelvic organ cancers (IRR, 1.07 [95% CI, 1.00-1.15]; P = .06) and that of all cancers (IRR, 1.04 [95% CI, 0.99-1.09]; P = .14). Conclusions and Relevance: This study controlled for reverse causation bias by defining the reasons for CT scan, and findings suggest that abdominopelvic CT radiation is associated with a higher incidence of hematologic malignant neoplasms. Efforts should be continued for judicious use of CT examinations.

Lifetime cancer risks from occupational radiation exposure among workers at interventional radiology departments.

PURPOSE: Interventional medical radiation workers represent an under-studied population worldwide, although they receive relatively high occupational radiation doses. This study aimed to estimate the lifetime cancer risk from occupational radiation exposure among workers at interventional radiology departments. METHODS: A field survey of interventional medical workers in nationwide branches of the Korean Society of Interventional Radiology was conducted in 2017. Organ-specific radiation doses were estimated using national dose registry data and conversion coefficients provided by the International Commission on Radiological Protection. Lifetime attributable risk (LAR) and lifetime fractional risk (LFR) were calculated based on realistic exposure scenarios using a radiation risk assessment tool. RESULTS: LARs from occupational radiation exposure until the age of retirement for all cancers combined were 338 (90.3-796.1), 121 (33.5-288.7), and 156 (41.1-390.6) per 100,000 individuals for male radiologists, male radiologic technologists, and female nurses, respectively. LFR for all cancers combined ranged from 0.22% (0.06-0.53) to 0.63% (0.17-1.47). Regarding the organ site, the highest LAR and LFR among all groups were observed for thyroid cancer. CONCLUSION: This study provides timely evidence of potential cancer burden from the current levels of occupational radiation exposure among workers at interventional radiology departments. The risks varied by occupational groups, and workers, particularly interventional radiologists, need to be carefully monitored for radiation.

Radiation exposure and fluoroscopically-guided interventional procedures among orthopedic surgeons in South Korea.

BACKGROUND: The use of fluoroscopically-guided interventional (FGI) procedures by orthopedic surgeons has been increasing. This study aimed to investigate the occupational radiation exposure among orthopedic surgeons in South Korea. METHODS: A nationwide survey of orthopedic surgeons was conducted in South Korea in October 2017. The dosimetry data of the participants were obtained from the National Dosimetry Registry. The orthopedic surgeons were categorized by job specialty [spine or trauma specialists, other orthopedic specialists, and residents], and descriptive statistics for the demographics and work-related characteristics were presented. Multivariable logistic regression analysis was used to evaluate the risk factors for the orthopedic surgeons who were not linked with the dosimetry data. RESULTS: Among the total participants (n = 513), 40.5% of the orthopedic surgeons spent more than 50% of their time working with the FGI procedures when compared with their overall work. The average frequency of the FGI procedures among the orthopedic surgeons was 12.3 days per month. Less than 30% of the participants were regularly provided with radiation monitoring badges. The proportion of subjects who always wore lead aprons and thyroid shields were 52 and 29%, respectively. The residents group experienced more unfavorable working conditions of radiation exposure than the other specialists. The dosimetry data were not significantly linked among the residents (odds ratio [OR] 2.10, 95% confidence interval [CI] 1.11-3.95) and orthopedic surgeons working at small hospitals (OR 4.76, 95% CI 1.05-21.51). CONCLUSIONS: Although orthopedic surgeons often performed FGI procedures, they wore protective gear less frequently, and a large proportion of orthopedic surgeons were not monitored by the national radiation dosimetry system. As the number of radiation procedures performed by the orthopedic surgeons increases, more intensive approaches are needed to reduce radiation exposure, especially for spine and trauma surgeons.

Occupational radiation exposure and morbidity of circulatory disease among diagnostic medical radiation workers in South Korea.

OBJECTIVES: We investigated the association between low-dose external occupational radiation exposure and circulatory disease morbidity among diagnostic medical radiation workers. METHODS: A cohort of 11 500 diagnostic medical radiation workers was linked with the National Dosimetry Registry data and the National Health Insurance Service data. Relative risks (RRs) were calculated to explore the association between occupational factors and circulatory disease morbidity, and excess relative risks per 100 milligray (ERR/100 mGy) were estimated to quantify the radiation dose-response relationship. RESULTS: Overall, there were 2270 cases of circulatory diseases during 93 696 person-years of observation (average follow-up=8.1 years). RRs for hypertension were significantly increased for individuals who started working before 2000 compared with those who started in 2005 and later. ERR/100 mGy for all circulatory diseases was 0.14 (95% CI -0.57 to 0.99). Radiation risks of cerebrovascular diseases and ischaemic heart disease were non-significantly increased with estimates of individual cumulative doses to the heart (ERR/100 mGy=3.10 (-0.75 to 11.59) and 1.22 (-0.71 to 4.73), respectively). However, ERR estimates were generally more strongly positive for female versus male workers and for younger workers versus more than 50-year-old workers. CONCLUSIONS: This study provides little evidence in support of a positive association between occupational radiation exposure and the overall risk of circulatory disease over a short follow-up period among medical radiation workers in South Korea. However, significantly increased RR with earlier year first worked, elevated ERR in female workers and young workers should be further followed up.

Suicide deaths among diagnostic medical radiation workers in South Korea, 1996-2017.

OBJECTIVES: Suicide is a leading cause of death in the working-age population. We investigated suicide mortality among diagnostic medical radiation workers in relation to their demographic and occupational factors in South Korea. METHODS: The study population consisted of all diagnostic medical radiation workers enrolled in the National Dosimetry Registry from 1996 to 2011. The registry data were linked with mortality data through the end of 2017. We calculated age-standardised suicide rates, standardised mortality ratios (SMRs) and rate ratios (RRs) by demographic and occupational factors. RESULTS: A total of 207 suicides were identified among 94 367 medical radiation workers, exhibiting a suicide rate of 14.0 per 100 000 person-years. Compared with the general population, suicide rates were lower for both male and female workers (SMR 0.49, 95% confidence interval (CI) 0.42 to 0.57; SMR 0.54, 95% CI 0.41 to 0.70, respectively). Similarly, decreased SMRs were observed across job titles and other work-related factors. However, a shorter duration of employment was positively associated with RRs for suicide; risks were 2.74 (95% CI 1.56 to 4.81) and 4.66 (95% CI 1.53 to 14.20) times higher in male and female workers with less than 1 year of employment, respectively, than in those with at least 10 years of employment. CONCLUSIONS: Diagnostic medical radiation workers in South Korea showed lower suicide rates than in the general population. However, a shorter duration of employment was associated with higher risk of suicide. Suicide prevention efforts could target workers engaged in short-term employment.

Quantifying the contributions of age, sex, methods, and urbanicity to the changing suicide rate trends in South Korea, 2001-2016.

PURPOSE: Suicide rates in South Korea have been one of the highest in the world. The aim of this study is to quantify the contributions of age, sex, method, and place of residence to the trends of the suicide rates between 2001 and 2016 in South Korea. METHODS: Using the suicide data obtained from the South Korean National Death Registration data set for the years 2001-2016, a Joinpoint regression analysis was conducted to determine if there was a significant change in the trend of suicide rates. Next, a decomposition analysis method was used to quantify the contributions of age, sex, method, and places of residence to the changes in the suicide rates. RESULTS: Suicide rates increased between 2001 and 2010, and decreased between 2010 and 2016. Among all the age groups, the 65-79 age group contributed most to the rise (18% in men and 7% in women) and fall (- 15% in men and - 14% in women) of suicide rates. Men contributed much more than women to the increasing trend of suicide rate (63.0% vs. 37.0%). Hanging was the key method of suicide, dominating the ups and downs of the suicide rates. The rates of suicide by pesticide poisoning have been decreasing since 2005 and suicide by charcoal burning continued to increase against a decreasing trend of suicide rate during the period of 2010-2016. The gap of the metropolitan-city-rural suicide rates was narrowing during the period under study, although the rural areas remained to have the highest suicide rates. CONCLUSION: The ups and downs of suicide rates in South Korea were not uniform across different sociodemographic groups. Age, sex, method, and place of residence contributed differently to the changes in suicide rates. Suicide prevention measures can be more focused on certain age-sex-method-region subgroups.

OCCUPATIONAL RADIATION PROCEDURES AND DOSES AMONG NURSES IN SOUTH KOREA.

This study investigated occupational radiation procedures and radiation exposures among nurses in South Korea. A total of 530 nurses were surveyed from 2012 to 2013, and the survey data were linked with the dosimetry data. Multiple regression analysis was used to identify the factors associated with radiation dose. The most frequent procedure performed by the nurses was interventional radiology, followed by fluoroscopy and routine X-ray. The average annual effective dose and the cumulative dose were 0.91 mSv and 4.66 mSv, respectively. Characteristics of nurses exposed to high radiation doses were male, completed graduate school or higher, first worked before 2000 and performing interventional procedures, nuclear medicine test and fluoroscopy. Performing nuclear medicine tests and interventional procedures had a significant positive association with high radiation exposure.

Prevalence and clinical aspects of hearing loss among the South Korean adolescent: Data from a population-based study.

OBJECTIVES: Slight/mild hearing loss is detrimental to communication and academic achievements. This study aimed to describe the prevalence of hearing loss, and to investigate the factors related to noise-induced hearing loss among South Korean adolescent. METHODS: As a population-based retrospective study, 1845 South Korean adolescents aged from 12 to 19 years were analyzed using the data from Korea National Health and Nutrition Examination Survey V (KNHANES V, 2010-2012). The prevalence of hearing loss according to the side, severity, and frequency was calculated. For assessing the noise-induced hearing loss in adolescent, the prevalence of hearing loss only in high-frequency (onlyHFHL, defined as 1) thresholds at 0.5 and 1 kHz of ≤15 dB HL, and 2) maximal thresholds at 3, 4, or 6 kHz ≥ 15 dB HL higher than the highest threshold for 0.5 and 1 kHz) was analyzed. Moreover, the relevance of onlyHFHL in context of sociodemographic factors and noise exposure history was evaluated. RESULTS: The prevalence of unilateral and bilateral hearing loss based on the average of six frequencies (0.5, 1, 2, 3, 4, and 6 kHz) in South Korean adolescents were 8.56% and 1.03%, respectively, and most cases were hearing loss with slight/mild degree. The prevalence of unilateral and bilateral onlyHFHL were 32.74% and 5.53%, respectively. Factors found to be associated with onlyHFHL were sex (female) and household income (high). CONCLUSIONS: According to this population-based study, the prevalence of slight/mild hearing loss and onlyHFHL in the South Korean adolescents were considerably high. With knowledge of the factors related with onlyHFHL, paying more attention to slight/mild hearing loss will be helpful in preventing hearing loss in adolescents.

The flipped classroom model for an undergraduate epidemiology course.

PURPOSE: The flipped classroom has been suggested as a method for efficient teaching in medical education. However, its feasibility and effectiveness in the educational environment are often overlooked. The authors redesigned an epidemiology course applying the flipped classroom method under a traditional curriculum consisting of heavily scheduled classroom hours and explored its feasibility and effectiveness. METHODS: In the fall semester of 2017, we flipped the 'practice of epidemiology' course for third-year medical students at Korea University College of Medicine. We provided online lectures and assigned readings as pre-class materials, and substituted group discussions and communicative activities for traditional lectures. We conducted pre- and post-course surveys to review students' perceptions. We also analyzed the pre-test results and final exam scores for quantitative comparison. RESULTS: Ninety-seven students out of 120 completed the course. Most students made use of the online lectures, but not the reading materials. Lack of time was the most frequently cited reason for under-preparedness. We observed improvements in preparedness, participation, and effectiveness at the end of the course, while changes in satisfaction were unclear. Students' perceptions of course relevance and difficulty were predictive of pre-test outcomes, but the effects of preparedness and length of materials were insignificant. The authors found no evidence of differing test scores before and after the course. CONCLUSION: This study supports the feasibility of the flipped classroom model even under a traditional, heavily scheduled medical curriculum. To encourage self-directed learning and achieve better learning outcomes, restructuring pre-existing curricular components should also be considered in parallel with new instructional methods.

Seasonal changes in suicide in South Korea, 1991 to 2015.

Seasonality of suicidal behavior has been widely reported in many epidemiological studies with a well replicated suicide peak in spring followed by a trough in winter season. Research from some regions over the past few decades has shown a diminishing seasonal pattern of suicides and this introduced a new perspective on the suicide study. Data on all suicide deaths from the period 1991 to 2015 was extracted from the South Korean National Death Registration data set which was made available by Statistics Korea. Our findings confirmed a strong seasonal effect of suicides in South Korea throughout the study period and a marked diminishing pattern was observed since the period of 2006-2010. The rhythm of suicides kept changing across the time intervals with a spring peak followed by a second peak in late summer/autumn. The seasonality varied across age groups and the seasonal effect among the Korean elderly suicides was still found to be significant though a diminishing pattern was observed recently.

Trends in pesticide suicide in South Korea, 1983-2014.

AIMS: Self-poisoning using pesticides is among the major methods of suicide worldwide, and accounts for one-fifth of suicides in 2006-2010 in South Korea. We investigated long-term trends in pesticide suicide rates in South Korea and factors related to these trends. METHODS: We calculated age-standardised rates of pesticide suicide in South Korea (1983-2014) using registered death data. We used graphical approach and joinpoint regression analysis to examine secular trends in pesticide suicide by sex, age and area, and a time-series analysis to investigate association of pesticide suicide rate with socioeconomic and agriculture-related factors. Age, period and cohort effects were examined using the intrinsic estimator method. RESULTS: Age-standardised rate of pesticide suicide fluctuated between 1983 and 2000 before it markedly increased in 2000-2003 (annual percent change 29.7%), followed by a gradual fall (annual percent change -6.3%) in 2003-2011. Following the paraquat ban (2011-2012), there was a marked reduction (annual percent change -28.2%) in 2011-2014. Trend in pesticide suicide was associated with divorce rate but not with other factors studied. Declines in pesticide suicide in 2003-2011 were most noticeable in younger groups and metropolises; by contrast, elderly adults aged 70+ living in rural areas showed an upward trend until after the 2011-2012 paraquat ban, when it turned downward. In the age-period-cohort modelling, having been born between 1938 and 1947 was associated with higher pesticide suicide rates. CONCLUSIONS: Pesticide suicide trend changed substantially in South Korea over the last three decades. Effective prevention should include close monitoring of trends and strong regulations of toxic pesticides.

Thyroid cancer risks among medical radiation workers in South Korea, 1996-2015.

BACKGROUND: Thyroid cancer rates, especially among children, are known to be increased by radiation exposure. However, little is known about the impact of chronic low-dose radiation exposure on thyroid cancer risk in adulthood. This study examined radiation effects on thyroid cancer rates as well as an overall evaluation of thyroid cancer risk among medical radiation workers. METHODS: Data on all diagnostic medical radiation workers enrolled in the national dosimetry registry between 1996 and 2011 were linked with the cancer registry data through 2015. Standardized incidence ratios (SIRs) were used to compare the observed cancer incidence rates in this population to those for the general population while internal comparisons were used to estimate relative risks (RRs) for occupational history and excess relative risks (ERRs) were used to quantify the radiation dose-response relationship. RESULTS: Overall, 827 thyroid cancer cases were reported among 93,922 medical radiation workers. Thyroid cancer SIRs were significantly higher than expected for both men (SIR 1.72, 95% confidence interval [CI] 1.53 to 1.91) and women (SIR 1.18, 95% CI 1.08 to 1.28). However, RRs for thyroid cancer by job title and duration of employment showed no particular pattern among diagnostic medical radiation workers. There were no indications of a significant dose effect on thyroid cancer rates for either men (ERR/100 mGy 0.07, 95% CI -0.38 to 0.53) or women (ERR/100 mGy -0.13, 95% CI -0.49 to 0.23). The findings were similar for different job titles or when limited to workers employed for at least one year. CONCLUSIONS: While thyroid cancer incidence rates among Korean medical radiation workers were somewhat higher than those in the general population, there was no significant evidence that this increase was associated with occupational radiation dose. Additional follow-up together with consideration of other risk factors should provide useful information on thyroid cancer rates in this cohort.

Projected lifetime cancer risks from occupational radiation exposure among diagnostic medical radiation workers in South Korea.

BACKGROUND: Timely assessment of cancer risk from current radiation exposure among medical radiation workers can contribute to the development of strategies to prevent excessive occupational radiation exposure. The purpose of the present study is to estimate the lifetime risk of cancers induced by occupational radiation exposure among medical radiation workers. METHODS: Using estimated organ doses and the RadRAT risk assessment tool, the lifetime cancer risk was estimated among medical radiation workers who were enrolled in the Korean National Dose Registry from 1996 to 2011. Median doses were used for estimating the risk because of the skewed distribution of radiation doses. Realistic representative exposure scenarios in the study population based on sex, job start year, and occupational group were created for calculating the lifetime attributable risk (LAR) and lifetime fractional risk (LFR). RESULTS: The mean estimated lifetime cancer risk from occupational radiation exposure varied significantly by sex and occupational group. The highest LAR was observed in male and female radiologic technologists who started work in 1991 (264.4/100,000 and 391.2/100,000, respectively). Female workers had a higher risk of radiation-related excess cancer, although they were exposed to lower radiation doses than male workers. The higher LAR among women was attributable primarily to excess breast and thyroid cancer risks. LARs among men were higher than women in most other cancer sites. With respect to organ sites, LAR of colon cancer (44.3/100,000) was the highest in male radiologic technologists, whereas LAR of thyroid cancer (222.0/100,000) was the highest in female radiologic technologists among workers who started radiologic practice in 1991. Thyroid and bladder cancers had the highest LFR among radiologic technologists. CONCLUSIONS: Our findings provide an assessment of the potential cancer risk from occupational radiation exposure among medical radiation workers, based on current knowledge about radiation risk. Although the radiation-related risk was small in most cases, it varied widely by sex and occupational group, and the risk would be underestimated due to the use of median, rather than mean, doses. Therefore, careful monitoring is necessary to optimize radiation doses and protect medical radiation workers from potential health risks, particularly female radiologic technologists.

The Burden of Acute Pesticide Poisoning and Pesticide Regulation in Korea.

BACKGROUND: This study aimed to estimate the burden of acute pesticide poisoning and to determine its trend with recently implemented pesticide regulations. METHODS: Disability-adjusted life-years (DALYs) were calculated as the sum of years of life lost (YLLs) and years lived with disability (YLDs) due to acute pesticide poisoning using the methods of the Global Burden of Disease Study 2013. The values of YLLs, YLDs, and DALYs were stratified by sex, age groups, intentionality of poisoning, and causative agents. RESULTS: From 2006 to 2014, DALYs decreased by 69% (from 69,550 to 21,742). The decreasing tendency of DALYs was especially marked from 2011. The total burden of acute pesticide poisoning was mainly caused by YLLs and intentional pesticide poisoning. The highest DALYs due to acute pesticide poisoning occurred in those in their 40s and 50s; however, the decreased rates of DALYs were higher in those aged 10-49 years than in those aged more than 50 years. Herbicides including paraquat contributed to the largest proportion of total DALYs. CONCLUSION: As this is the first study to quantify the burden of acute pesticide poisoning using DALYs, our results provide comprehensive evidence of the importance of using strict regulations to prevent public health hazards due to acute pesticide poisoning.