Occupational radiation exposure and cancer incidence in a cohort of diagnostic medical radiation workers in South Korea.

OBJECTIVES: We investigated the association between protracted low-dose ionising radiation and the risk of cancer in medical radiation workers, the largest group of workers with occupational radiation exposures. METHODS: Data of all South Korean diagnostic medical radiation workers enrolled at the National Dose Registry during 1996-2011 were merged with the death and cancer incidence data until 31 December 2017. SIRs, relative risks and excess relative risks (ERRs) for cancer were calculated to quantify the radiation dose-response relationship using Poisson regression models. RESULTS: A total of 3392 first primary cancer cases were identified among 93 920 diagnostic medical radiation workers. The mean cumulative badge dose in the cohort was 7.20 mSv. The ERRs for solid cancer with a 5-year lag and haematopoietic cancers with a 2-year lag for all workers were 0.15 per 100 mGy (95% CI -0.20 to 0.51) and 0.09 per 100 mGy (95% CI -2.02 to 2.20), respectively. The ERRs for cancers did not significantly vary by job title, different lag years or after excluding thyroid and lung cancers. Sensitivity analyses restricted to workers employed for at least 1 year, or who were employed in or after 1996, or who had exposure to a cumulative badge dose of 1 mSv or more showed similar results. CONCLUSIONS: Occupational radiation doses were not significantly associated with cancer incidence among South Korean diagnostic medical radiation workers. However, cautious interpretation of ERRs is needed due to the limitations of short follow-up and low cumulative radiation doses.

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.

Economic burden of acute pesticide poisoning in South Korea.

OBJECTIVES: To investigate the magnitude and characteristics of the economic burden resulting from acute pesticide poisoning (APP) in South Korea. METHODS: The total costs of APP from a societal perspective were estimated by summing the direct medical and non-medical costs together with the indirect costs. Direct medical costs for patients assigned a disease code of pesticide poisoning were extracted from the Korean National Health Insurance Reimbursement Data. Direct non-medical costs were estimated using the average transportation and caregiving costs from the Korea Health Panel Survey. Indirect costs, incurred by pre-mature deaths and work loss, were obtained using 2009 Life Tables for Korea and other relevant literature. RESULTS: In 2009, a total of 11,453 patients were treated for APP and 1311 died, corresponding to an incidence of 23.1 per 100,000 population and a mortality rate of 2.6 per 100,000 population in South Korea. The total costs of APP were estimated at approximately US$ 150 million, 0.3% of the costs of total diseases. Costs due to pre-mature mortality accounted for 90.6% of the total costs, whereas the contribution of direct medical costs was relatively small. CONCLUSION: Costs from APP demonstrate a unique characteristic of a large proportion of the indirect costs originating from pre-mature mortality. This finding suggests policy implications for restrictions on lethal pesticides and safe storage to reduce fatality and cost due to APP.

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.

WORK PROCEDURES AND RADIATION EXPOSURE AMONG RADIOLOGIC TECHNOLOGISTS IN SOUTH KOREA.

This study explored their work characteristics and safety compliance to identify primary factors influencing high occupational radiation exposure among radiologic technologists. A total of 12 387 radiologic technologists were surveyed from 2012 to 2013 in South Korea. Survey data for demographics and work-related characteristics were linked with the National Dose Registry. Multiple regression analysis was used and '% Excess Risk Explained' was calculated to illustrate the degree to which given risk factors explained the relationship of work procedures and radiation exposure. Characteristics of radiologic technologists exposed to higher radiation doses were male, aged <30, working at a general hospital or hospital, and frequently performing routine diagnostic X-ray, CT, portable X-ray and C-arm. Not being completely separated from patients and wearing lead apron was positively associated with higher radiation exposure. Type of facility and safety compliance were the main risk factors for high radiation exposure in performing diagnostic radiologic procedures.

ESTIMATION OF ORGAN DOSES AMONG DIAGNOSTIC MEDICAL RADIATION WORKERS IN SOUTH KOREA.

This study aimed to estimate the radiation organ doses from occupational exposure in 94 396 Korean medical radiation workers. Data on badge doses (i.e. personal dose equivalent at 10 mm) between 1996 and 2011 obtained from a national dosimetry registry, survey data from 2012 to 2013, and organ dose conversion coefficients provided by the International Commission on Radiological Protection (ICRP) were used for the estimation. The highest mean cumulative badge doses (26.87 mSv) were observed in radiologists, followed by radiologic technologists (15.96 mSv). Male workers exhibited higher mean cumulative badge doses, across occupational groups. The estimated organ doses showed similar trends with those of badge doses. Organs located outside the apron's coverage such as the thyroid showed higher mean organ doses than those protected by the apron. Our findings could contribute to future radiation epidemiologic studies to investigate health effects from occupational radiation exposure in Korea.

Gender Differences in the Longitudinal Association between Work-Related Injury and Depression.

Little is known about gender differences in the association between occupational injury and depression. We investigated the bidirectional association and gender differences between work-related injury and depression using the same cohort in the US Medical Expenditure Panel Survey (MEPS). In Analysis 1, the association of occupational injury and subsequent depression was investigated from 35,155 employees without depression. Analysis 2 included 32,355 participants without previous injury and examined the association of depression and work-related injury. The multivariable-adjusted odds ratio was estimated using a discrete time-proportional odds model. Male workers who had experienced workplace injury were more vulnerable to post-injury depression than non-injured male workers (OR = 2.35, 95% CI: 1.52, 3.65). Female workers with depression were more prone to get injured at the workplace than the non-depressed female workers (OR = 1.44, 95% CI: 1.07, 1.96). These results did not hold in the reverse direction for both genders. Workers compensation benefit was positively associated with the risk of post-injury depression among males, whereas anti-depressant medication and duration of depression were related to workplace injury among females. Gender differences in the direction and associated factors of the relationship between occupational injury and depression highlight the need for gender-specific intervention to the vicious cycle of workplace injury and depression.

Reconstruction of Radiation Dose Received by Diagnostic Radiologic Technologists in Korea.

OBJECTIVES: Diagnostic medical radiation workers in Korea have been officially monitored for their occupational radiation doses since 1996. The purpose of this study was to design models for reconstructing unknown individual radiation doses to which diagnostic radiation technologists were exposed before 1996. METHODS: Radiation dose reconstruction models were developed by using cross-sectional survey data and the personal badge doses of 8167 radiologic technologists. The models included calendar year and age as predictors, and the participants were grouped into six categories according to their sex and facility type. The annual doses between 1971 and 1995 for those who were employed before 1996 were estimated using these models. RESULTS: The calendar year and age were inversely related to the estimated radiation doses in the models of all six groups. The annual median estimated doses decreased from 9.45 mSv in 1971 to 1.26 mSv in 1995, and the associated dose variation also decreased with time. The estimated median badge doses from 1996 (1.22 mSv) to 2011 (0.30 mSv) were similar to the measured doses (1.68 mSv to 0.21 mSv) for the same years. Similar results were observed for all six groups. CONCLUSIONS: The reconstruction models developed in this study may be useful for estimating historical occupational radiation doses received by medical radiologic technologists in Korea.

Potential impact of reactive vaccination in controlling cholera outbreaks: an exploratory analysis using a Zimbabwean experience.

BACKGROUND: To contain ongoing cholera outbreaks, the World Health Organization has suggested that reactive vaccination should be considered in addition to its previous control measures. OBJECTIVES: To explore the potential impact of a hypothetical reactive oral cholera vaccination using the example of the recent large-scale cholera outbreak in Zimbabwe. METHODS: This was a retrospective cost-effectiveness analysis calculating the health and economic burden of the cholera outbreak in Zimbabwe with and without reactive vaccination. The primary outcome measure was incremental cost per disability-adjusted life year (DALY) averted. RESULTS: Under the base-case assumptions (assuming 50% coverage among individuals aged ≥2 years), reactive vaccination could have averted 1 320 deaths and 23 650 DALYs. Considering herd immunity, the corresponding values would have been 2 920 deaths and 52 360 DALYs averted. The total vaccination costs would have been ~$74 million and ~$21 million, respectively, with per-dose vaccine price of US$5 and $1. The incremental costs per DALY averted of reactive vaccination were $2 770 and $370, respectively, for vaccine price set at $5 and $1. Assuming herd immunity, the corresponding cost was $980 with vaccine price of $5, and the programme was cost-saving with a vaccine price of $1. Results were most sensitive to case-fatality rate, per-dose vaccine price, and the size of the outbreak. CONCLUSIONS: Reactive vaccination has the potential to be a cost-effective measure to contain cholera outbreaks in countries at high risk. However, the feasibility of implementation should be further evaluated, and caution is warranted in extrapolating the findings to different settings in the absence of other in-depth studies.