The linear no-threshold (LNT) model is an assumption that explains the dose-response relationship for health risks, allowing for linear extrapolation from high doses to low doses without a threshold. The selection of an appropriate model for low-dose risk evaluation is a critical component in the risk assessment process for hazardous agents. This paper reviews the LNT model in light of epidemiological evidence from major international consortia studying ionizing radiation. From a scientific perspective, substantial evidence supporting the LNT model has been observed in epidemiological studies of low-dose ionizing radiation exposure, although some findings suggest non-linear dose relationships for certain cancer sites and variations across populations. From a practical standpoint, the LNT remains the most useful model for radiation protection purposes, with no alternative dose-response relationship proving more appropriate. It is important to note that the LNT model does not directly reflect the magnitude of risk at the population level, and this distinction should be clearly communicated to the public. While applying the LNT model as the principal basis for radiation protection, continuous research into various dose-response relationships is crucial for advancing our understanding.

Background: Human health and environment exposure assessments of chemicals are essential part for REACH and BPR as well as K-REACH and K-BPR. Several useful exposure assessment tools have been developed and updated to become extensively used during more than fifteen years of chemical registrations under REACH and their updates are still going on. Objectives: Evolution of regulatory tools for environment, workers and consumers exposure assessments under REACH is investigated focusing on why and how tools have been developed and updated for the future regulatory tools in Korea. Methods: REACH regulatory tools including EUSES, ECETOC TRA and CHESAR as well as built-in models SimpleTreat and SimpleBox were chosen with other frequently used Tier 1 and 2 tools. Available resources such as homepage information, background documents, related scientific reports, relevant journal publications, up-to-date lists of new version publications, release notes and user guides were reviewed extensively and summarized using easy-readable Tables and Figures. Results: SimpleTreat and SimpleBox are built-in models both for EUSES and ECETOC TRA (Environment). ECHA's CHESAR contains ECETOC TRA (Workers) and ECETOC TRA (Consumers) as well as EUSES and ECETOC TRA (Environment) for environment exposure assessment while results of Tier 2 Stoffenmanager and ConsExpoWeb can be imported. Evolution of CHESAR from version 1 (2010) to 3.8 (2023) has focused on the compatibility of frequent updates of IUCLID, importing functionality, editability, updated use maps, harmonised conditions of use as well as updates of the built-in tools evolved according to scientific development, refinements of the tool, increased conservatism and user-friendliness. CHESAR Platform 1.0 will soon be published to serve both for REACH and BPR. Conclusions: Updates of the tools can be successfully continued by transparency of the tools, participation of industry sectors for tool refinements and tool developers'/authorities' encouragements of partners/users to jointly innovate tools through scientific researches, tool validations and user feedback.

Background: Exposure to fine particulate matter (PM_2.5) and ozone (O₃) poses potential health risks. The Indoor-to-Outdoor ratio (I/O ratio) is a valuable tool for understanding indoor air quality and identifying potential indoor sources. Objectives: The objective of this study was to determine I/O ratios of PM_2.5 and O₃ by different microenvironments and seasons in Korea. Methods: From December 2021 to November 2023, indoor concentrations of PM_2.5 and O₃ were monitored every hour in 13 microenvironments (residential indoor, office, school, restaurant, pub, café, study café, private educational institute, PC room, billiard room, screen golf center, supermarket, and shopping mall) in Korea. Hourly outdoor concentrations of PM_2.5 and O₃ were obtained from local air quality monitoring stations, provided by airkorea.or.kr. The hourly I/O ratio was calculated by the indoor and outdoor concentrations. Results: At the pub, billiard room, and PC room, the median PM_2.5 I/O ratio exceeded 1 in all seasons, except in spring at the PC room (0.9), suggesting indoor smoking as a potential cause. The median PM_2.5 I/O ratio at the restaurant exceeded 1 in winter, autumn, and summer, except for spring (0.9), indicating significant PM_2.5 emission sources in the restaurant. The median O₃ I/O ratio was below 0.5 in all seasons and microenvironments. Conclusions: This study provided useful data on relationships between indoor and outdoor pollution in various microenvironments by seasons. These I/O ratios could be applied for more accurate exposure assessment to protect health of human.

Background: During the coronavirus pandemic, masks played a critical role in preventing respiratory infections. While the performance of masks such as KF-certified masks and N95 masks was evaluated and managed by the authorities, the performance of common masks was not. Objectives: This study aimed to evaluate the performance of uncertified masks in four Asian countries against certification standards (Korean KF80, KF94, and US N95). Methods: Thirty uncertified mask products from Indonesia, 20 from South Korea, 26 from Taiwan, and 30 from Thailand were purchased to perform performance evaluations. The uncertified masks included disposable dental masks, cloth masks, and children's masks. Filtration efficiency and inhalation airflow resistance tests were conducted according to Korean KF80, KF94, and US N95 protocols. Results: None of the 106 identified masks complied with the KF94 standard. A few complied with the KF80 standard: four from Indonesia, four from South Korea, 13 from Taiwan, and 16 from Thailand. Some of the masks met the N95 standard: one from Indonesia, three from South Korea, two from Taiwan, and one from Thailand. Conclusions: Since many uncertified masks did not comply with performance standards, wearing them might not have provided sufficient protection. Performance of uncertified masks could provide critical information for next pandemic management.

Background: One of the major causes of pathogenic E. coli is the feces of infected livestock, and the management of the livestock environment is necessary to prevent pathogenic E. coli. Objectives: The prevalence of pathogenic E. coli was identified from livestock environments, and the molecular characteristics and antibiotic resistance profiles of the isolated pathogenic E. coli strains were analyzed. Methods: In 2022 and 2023, nine points of livestock houses at sites in Chungcheongnam-do Province were selected, and 100 cow feces or soil samples around the livestock houses were collected once per month. Pathogenic E. coli was isolated by selective culture and identified using multiplex PCR. Antibiotic resistance was tested on the isolated strains by using VITEK-2, and candidate strains were selected to perform 16s rRNA sequencing and phylogenetic analysis. Results: A total of 100 samples were tested, and 60 pathogenic E. coli strains were isolated. Of these, 45 and 15 isolates were determined to be single and hybrid pathogenic E. coli , respectively. Among the 15 hybrid pathogenic E. coli strains, eight, five, and two strains were respectively identified as EHEC/ETEC, EHEC/EPEC, and EHEC/ETEC/EPEC hybrids. All 45 isolates showed resistance to at least one antibiotic, and they were susceptible to cefotaxime, amikacin, nalidixic acid, and ciprofloxacin. The highest resistance was against cefalotin, tetracyclin, and ampicillin (20.0%~58.3%). The 16s rRNA sequences of candidate isolates revealed nucleotide sequence identities of 99.1% to 100%. Conclusions: In order to manage pathogenic E. coli from the One Health animal environment perspective, the characteristics of the occurrence of pathogenic E. coli from the livestock environment and molecular biology and antibiotic resistance to isolated strains were analyzed. In order to prevent and manage the occurrence of pathogenic E. coli, these monitoring studies must be continuously conducted.

Background: In order to evaluate the national effort to improve air quality through the Act on Air Quality Management Regions, an investigation of the current status of air quality in respective regions and the health impact of air pollution should be undertaken. Objectives: This study is a preliminary study on the status of PM_2.5 in the central region of South Korea and its health effects. It can be applied to the evaluation of the effectiveness of the Act on Air Quality Management Regions. Methods: Time series variation of PM_2.5 concentrations in the air quality management region (hereafter referred to as AQMR) and in the non-AQMR area in the central region of South Korea were created. Odds ratios (OR) were calculated based on the survey results of whether the residents of Jeollabuk-do were feeling anxiety caused by air pollution by sex, region, and regional characteristics. Relative risk (RR) values of lung cancer deaths in each city in the AQMR for the central region of South Korea were calculated. Results: During the period from Dec. 2018 to Dec. 2021, the average concentration of PM_2.5 was higher in the AQMR at 26.0 ㎍/m³ compared to 19.5 ㎍/m³ in the non-AQMR. The odds ratio (OR) calculated using data from the Jeonbuk Research Institute (2020) suggested that women were more uncomfortable or anxious about their lives due to air pollutants than were men. The OR evaluation results also showed that in terms of PM_2.5 sensitivity, residents in the non-AQMR were relatively more sensitive than those in the AQMR. The relative risk (RR) was calculated to evaluate the relationship between health hazards (PM_2.5) and diseases (lung cancer). As a result, for super-aged people over 80 years old, compared to the non-AQMR (Muju-gun and Jangsu-gun), the residents in the AQMR (Jeonju, Gunsan, and Iksan) have about twice the relative risk of lung cancer. Conclusions: It is necessary to make efforts to improve residents' health and extend their healthy lives through efforts to reduce air pollutants such as PM_2.5 in areas specially selected as an AQMR.

Background: Based on rapid industrial development, environmental pollution has emerged as a social problem and exposure to environmental diseases is increasing. The number of patients suffering environmental diseases in Daejeon Metropolitan City is also steadily increasing, and the prevalence of atopic dermatitis there is the highest in the country. Objectives: In order to minimize exposure to harmful factors for the prevention and management of environmental diseases, an environmental disease management system suitable for the environmental characteristics of each region is needed. Basic preliminary research should be conducted to identify environmental hazards in Daejeon Metropolitan City and establish a management system. Methods: Among the households (about 50 people) participating in the 2022 Indoor Environment Remote Measurement (IoT) program, households (children aged 5 or older and adults) with insufficient results for indoor air quality measurement and symptoms related to environmental diseases were selected. The subjects were tested for living conditions, blood tests, biomarker analysis (immunoglobulin E, Eosinophil count, histamine) and multiple allergy antigen tests (MAST, 93 types). Results: Participants were 53.7% female and 46.3% male, and the average age showed an even age distribution. IgE and eosinophil count were positively correlated, and significant results were found for atopic dermatitis and IgE (p<0.05). Typical risk factors observed in the survey was the amount of indoor ventilation, chemical exposure, heredity, house dust mites, fungi, and food. Conclusions: The purpose of this study was to help establish a regional management system for environmental diseases, research and diagnosis of environmental diseases. This study is meaningful in that it is a study with customized consulting suitable for the environment of Daejeon Metropolitan City. If the limitations are addressed and continuous research is conducted, it will be helpful for the management, diagnosis, and research of environmental diseases.

Background: The prevalence of allergic rhinitis in South Korean adolescents is increasing. Adolescents in South Korea currently use liquid electronic cigarettes more than heated tobacco products. Objectives: The purpose of this study was to assess the association between the use of liquid electronic cigarettes and allergic rhinitis diagnoses among South Korean adolescents. Methods: This study used data from the 17th Korea Youth Risk Behavior Survey in 2021. Out of a total of 59,066 students, data from 18,869 students who had experience with liquid electronic cigarettes were used in the final analyses. Diagnoses of allergic rhinitis by medical doctors were self-reported as outcome variables. Results: For females, when comparing 'daily users' and 'current users' with 'never users', the adjusted odds ratios (ORs) for 'allergic rhinitis' were 2.20 (95% confidence interval (CI), 1.00~4.84) and 1.49 (95% CI, 1.07~2.09), respectively. For males, when comparing 'daily users' and 'current users' with 'never users', the adjusted ORs for 'allergic rhinitis' were 1.42 (95% confidence interval (CI), 0.91~2.22) and 1.41 (95% CI, 1.08~1.84), respectively. Conclusions: The use of liquid electronic cigarettes was statistically significantly associated with increased odds of allergic rhinitis, especially for females. The results of this study will provide a useful scientific basis for establishing public health policy and using the educational data related to the use of liquid electronic cigarettes in the future.