• Journal of Radiation Protection and Research
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• v.46 no.3
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• pp.83-97
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• 2021

Background: The lifetime risk of lung cancer incidence due to radiation for nonsmokers is overestimated because of the use of the average cancer baseline risk among a mixed population, including smokers. In recent years, the generalized multiplicative (GM)-excess relative risk (ERR) model has been developed in the life span study of atomic bomb survivors to consider the joint effect of radiation and smoking. Based on this background, this paper discusses the issues of radiation risk assessment considering smoking in two parts. Materials and Methods: In Part 1, we proposed a simple method of estimating the baseline risk for nonsmokers using current smoking data. We performed sensitivity analysis on baseline risk estimation to discuss the birth cohort effects. In Part 2, we applied the GM-ERR model for Japanese smokers to calculate lifetime attributable risk (LAR). We also performed a sensitivity analysis using other ERR models (e.g., simple additive (SA)-ERR model). Results and Discussion: In Part 1, the lifetime baseline risk from mixed population including smokers to nonsmokers decreased by 54% (44%-60%) for males and 24% (18%-29%) for females. In Part 2, comparison of LAR between SA- and GM-ERR models showed that if the radiation dose was ≤200 mGy or less, the difference between these ERR models was within the standard deviation of LAR due to the uncertainty of smoking information. Conclusion: The use of mixed population for baseline risk assessment overestimates the risk for lung cancer due to low-dose radiation exposure in Japanese males.

• Journal of Radiation Protection and Research
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• v.24 no.3
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• pp.131-142
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• 1999

By using the Korean demographic data and the modified relative risk projection model given in the Committee on the Biological Effect of Ionizing Radiation (BEIR) report-V under the U.S. National Academy of Science, the radiogenic excess risk in Korean population has been evaluated. On the basis of this risk, a safety goal for the safe operation of domestic nuclear power plants has been further derived in terms of personal dose. The baseline risk of death due to all causes in Korea and the trivial risk level, which the society considers safe, were estimated to be $5.2{\times}10^{-3}$ and $5.2{\times}10^{-6}$, respectively. The radiogenic excess cancer risk in Korea has been estimated to be $5.2{\times}10^{-3}$ for tie case of acute exposure to 0.1 Gy and $3.7{\times}10^{-3}$ for the case of chronic lifetime exposure to 1.0 mGy/y. On the basis of these risks estimate, the resulting safety goal for one year opeation of a reactor was 0.05 mSv, which is quite identical with the ALARA guideline prescribed by the USNRC in the Appendix I, 10CFR50.

• Communications for Statistical Applications and Methods
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• v.29 no.3
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• pp.287-299
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• 2022

In radiation epidemiology, the excess relative risk (ERR) model is used to determine the dose-response relationship. In general, the dose-response relationship for the ERR model is assumed to be linear, linear-quadratic, linear-threshold, quadratic, and so on. However, since none of these functions dominate other functions for expressing the dose-response relationship, a Bayesian semiparametric method using splines has recently been proposed. Thus, we improve the Bayesian semiparametric method for the selection of the tuning parameters for splines as the number and location of knots using a Bayesian knot selection method. Equally spaced knots cannot capture the characteristic of radiation exposed dose distribution which is highly skewed in general. Therefore, we propose a nonparametric Bayesian knot selection method based on a Dirichlet process mixture model. Inference of the spline coefficients after obtaining the number and location of knots is performed in the Bayesian framework. We apply this approach to the life span study cohort data from the radiation effects research foundation in Japan, and the results illustrate that the proposed method provides competitive curve estimates for the dose-response curve and relatively stable credible intervals for the curve.

• Journal of Radiation Protection and Research
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• v.17 no.1
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• pp.57-70
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• 1992

An excess risk of lung cancer mortality among Koreans, attributable to indoor $^{222}Rn$ daughters exposure, were quantitatively evaluated by applying a stochastic health risk projection model on the radiation exposure. The lung cancer rate in Korean males and females, based on the 1989 demographic data, were estimated to be $22.4/10^5-y\;and\;9.5/10^5-y$, respectively The lifetime baseline lung cancer risks, deduced from these rates, appeared to be 0.047 and 0.019 for males and females, respectively, and were lower than the corresponding 1984 values of 0.067 and 0.025 in the U.S.A. The excess risk coefficients, derived by modified relative risk projection model of the BEIR-IV Committee under the US National Academy of Science, per annual 1.0 WLM of exposure to indoor radon daughters were estimated to be 0.022/WLM for males, 0.009/WLM for females, and 0.017/WLM for both sexes. The resulting annual frequency of excess lung cancer mortality for the life expectancy in the Korean population appeared to be 230/10^6-WLM, which was an approximate median of $120{\sim}450/10^6-WLM$ reported so far in the world.

• Environmental Analysis Health and Toxicology
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• v.31
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• pp.1.1-1.13
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• 2016

Objectives To investigate the accuracy and scientific validity of the current very low risk factor for hereditary diseases in humans following exposures to ionizing radiation adopted by the United Nations Scientific Committee on the Effects of Atomic Radiation and the International Commission on Radiological Protection. The value is based on experiments on mice due to reportedly absent effects in the Japanese atomic bomb (A-bomb) survivors. Methods To review the published evidence for heritable effects after ionising radiation exposures particularly, but not restricted to, populations exposed to contamination from the Chernobyl accident and from atmospheric nuclear test fallout. To make a compilation of findings about early deaths, congenital malformations, Down's syndrome, cancer and other genetic effects observed in humans after the exposure of the parents. To also examine more closely the evidence from the Japanese A-bomb epidemiology and discuss its scientific validity. Results Nearly all types of hereditary defects were found at doses as low as one to 10 mSv. We discuss the clash between the current risk model and these observations on the basis of biological mechanism and assumptions about linear relationships between dose and effect in neonatal and foetal epidemiology. The evidence supports a dose response relationship which is non-linear and is either biphasic or supralinear (hogs-back) and largely either saturates or falls above 10 mSv. Conclusions We conclude that the current risk model for heritable effects of radiation is unsafe. The dose response relationship is non-linear with the greatest effects at the lowest doses. Using Chernobyl data we derive an excess relative risk for all malformations of 1.0 per 10 mSv cumulative dose. The safety of the Japanese A-bomb epidemiology is argued to be both scientifically and philosophically questionable owing to errors in the choice of control groups, omission of internal exposure effects and assumptions about linear dose response.

• Journal of Korean Society for Atmospheric Environment
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• v.8 no.4
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• pp.247-256
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• 1992

Airborne suspended particulates were collected at Shinchon by a high volume cascade impactor from Sep. 1990 to Aug. 1991. Organic matter was extracted from particulates and fractionated by liquid-liquid extraction and thin layer chromatography. Substances in the PAHs and nitroarenes'subfraction of neutral fraction were determined by capillary gas chromatography. Based on unit risk estimates by multi-stage model of benzo[a]pyrene and the results of exposure estimates, cancer risk was assessed. The annual average concentration of total suspended particulates was 201.77g/$m^3$. The percentage of fine particulates was 57.40. The concentration of total suspended particulates showed seasonal variations and was high in winter and spring. The average concentration of extractable organic matter was 8.12g/$m^3$. In all, 21 PAHs were identified and quantified. The annual concentration of fluoranthene was 2.38ng/$m^3$, and that was the highest value of all PAHs. A carcinogenic compound, benzo[a]pyrene, was at a concentration of 1.84ng/$m^3$. All the 10 nitroarenes were also identified and quantified. The major nitroarene in the Shinchon area was 2,7-dinitrofluorene. The annual concentration of 1-nitropyrene was 1.56ng/$m^3$. Concentrations of PAHs and nitroarenes were high in winter and low in summer. The life time excess risk estimates of benzo[a]pyrene was calculated as 0.96 persons/a million population in this experiment. In the rank of relative potenties, carcinogenic effects of the other PAHs were calculated as 0.004-0.108 persons/a million population.

• Asian Pacific Journal of Cancer Prevention
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• v.14 no.4
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• pp.2643-2647
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• 2013

Background: Despite anti-smoking campaigns, smoking prevalence among Thai males aged 30 or older is high, at around 50%. The purpose of this study was to determine the relationship between smoking and mortality in a rural Thai community. Materials and Methods: Subjects enrolled into the Khon Kaen cohort study between 1990 and 2001 were followed up for their vital status until $16^{th}$ March 2012. The death resource was from the Bureau of Policy and Strategy, Ministry of Interior, Thailand. A Cox proportional hazards model was used to analyse the association between smoking and death, controlling for age, education level and alcohol drinking, and confidence intervals were calculated using the floating risk method. Results: The study recruited 5,962 male subjects, of whom 1,396 died during a median 13.5 years of follow-up. Current smokers were more likely to die than never smokers after controlling for age, education level and alcohol drinking (HR, 95%CI: 1.41, 1.32-1.51), and the excess mortality was greatest for lung cancer (HR, 95%CI: 3.51, 2.65-4.66). However, there was no increased risk with increasing dose of tobacco, and no difference in risk between smokers of yamuan (hand-rolled cigarettes) and manufactured tobacco. Conclusion: Mortality from cancer, particularly lung cancer, and from all causes combined is dependent on smoking status among men in rural Thailand, but the relative risks are lower than have been reported from studies in high income countries, where the tobacco epidemic is more established.

• Clinical and Experimental Pediatrics
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• v.65 no.2
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• pp.85-89
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• 2022

Background: There is evidence of a relationship between prenatal excess androgen exposure and central nervous developmental problems and attention-deficit/hyperactivity disorder (ADHD) in the offspring of mothers with polycystic ovary syndrome (PCOS). Purpose: Here we aimed to use a meta-analysis to investigate whether the offspring of mothers with PCOS are at an increased chance of developing ADHD. Methods: Three main English databases were searched for articles published through December 2020. The Newcastle-Ottawa Scale was used to assess study quality. Study heterogeneity was determined using I² statistics and publication bias was assessed using Begg and Egger tests. The results are presented as odds ratio (OR) and relative ratio (RR) estimates with 95% confidence intervals (CIs) using a random-effects model. Results: Six articles (3 cohort and 3 case-control studies; 401,413 total ADHD cases) met the study criteria. Maternal PCOS was associated with an increased risk of ADHD in the offspring based on OR and RR (OR, 1.42; 95% CI, 1.27-1.57) and (RR, 1.43; 95% CI, 1.35-1.51), respectively. There was no heterogeneity among the included articles based on OR (I²=0.0%, P=0.588) and RR (I²=0.0%, P=0.878). Conclusion: Our study showed that maternal PCOS is a risk factor for ADHD. Therefore, screening their offspring for ADHD should be considered part of the comprehensive clinical care of women with PCOS.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.85-85
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• 2020

South Korea experiences few large scale erosion and sedimentation problems, however, there are numerous local sedimentation problems. A reliable and consistent approach to modelling and management for sediment processes are desirable in the country. In this study, field measurements of sediment concentration from 34 alluvial river basins in South Korea were used with the Modified Einstein Procedure (MEP) to determine the total sediment load at the sampling locations. And then the Flow Duration-Sediment Rating Curve (FD-SRC) method was used to estimate the specific degradation for all gauging stations. The specific degradation of most rivers were found to be typically 50-300 tons/㎢·yr. A model tree data mining technique was applied to develop a model for the specific degradation based on various watershed characteristics of each watershed from GIS analysis. The meaningful parameters are: 1) elevation at the middle relative area of the hypsometric curve [m], 2) percentage of wetland and water [%], 3) percentage of urbanized area [%], and 4) Main stream length [km]. The Root Mean Square Error (RMSE) of existing models is in excess of 1,250 tons/㎢·yr and the RMSE of the proposed model with 6 additional validations decreased to 65 tons/㎢·yr. Erosion loss maps from the Revised Universal Soil Loss Equation (RUSLE), satellite images, and aerial photographs were used to delineate the geospatial features affecting erosion and sedimentation. The results of the geospatial analysis clearly shows that the high risk erosion area (hill slopes and construction sites at urbanized area) and sedimentation features (wetlands and agricultural reservoirs). The result of physiographical analysis also indicates that the watershed morphometric characteristic well explain the sediment transport. Sustainable management with the data mining methodologies and geospatial analysis could be helpful to solve various erosion and sedimentation problems under different conditions.

• Journal of Korean Society for Atmospheric Environment
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• v.23 no.5
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• pp.563-574
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• 2007

There seems to be a consensus among most people that visibility impairment is the most obvious indicator of air pollution. While considerable evidence on the association between air pollution and health outcomes including death and disease have been established, based on industrial complex areas or huge urban cities, time-series, case-crossover and cohort studies, scarce literature exists on the direct evidence for the association between visibility and adverse health outcomes. Our study is assessed the effect of air pollution measured by visibility impairment on respiratory mortality over a period of six years. Relative risks in respiratory deaths were estimated by a Poisson regression model of daily deaths between $1999{\sim}2004$. Daily counts of respiratory deaths as dependent variable was modelled with daily 24-hr mean visibility measurements (kilometers) as independent variable by means of Poisson regression. This model is controlled for confounding factors such as day of weeks, weather variables, seasonal variables and $PM_{10}$. The results in this study is observed the statistically significant association between an inverse health effect and visibility during the study period for respiratory mortality (percentage change in the relative risk for all aged -0.57%, 95% Cl, $-1.01%{\sim}-0.12%$; for $0{\sim}15$ aged -7.12%, 95% Cl, $-13.29%{\sim}-0.51%$; for 65+ aged -0.43%, 95% Cl, $-0.93%{\sim}-0.06%$ per 1 km increased in visibility). The effect size was much reduced during warm season. Visibility impairment resulting from air pollution is strongly associated with respiratory mortality, especially for children may be spent at outdoor. Our result provides a quick and useful indicator for eliciting the contribution of air pollution to the excess risk of respiratory mortality in Seoul, Korea.