Authors :Dirga Kumar Lamichhane ^{a b}, Eunhee Ha ^c, Yun-Chul Hong ^d, Dong-Wook Lee ^a, Myung-Sook Park ^d, Sanghwan Song ^e, Suejin Kim ^e, Woo Jin Kim^f, Jisuk Bae ^g, Hwan-Cheol Kim ^a, Ko-CHENS Study Group
 
Author Affiliations
a. Department of Occupational and Environmental Medicine, Inha University School of Medicine, Incheon, Republic of Korea
b. Department of Psychiatry, Huntsman Mental Health Institute, University of Utah School of Medicine, Salt Lake City, UT, USA
c. Department of Occupational and Environmental Medicine, Ewha Womans University School of Medicine, Seoul, Republic of Korea
d. Institute of Environmental Medicine, Seoul National University Medical Research Center, Seoul, Republic of Korea
e. Environmental Health Research Division, Department of Environmental Health Research, National Institute of Environmental Research, Ministry of Environment, Incheon, Republic of Korea
f. Department of Internal Medicine and Environmental Health Center, Kangwon National University, Chuncheon, Republic of Korea
g. Department of Preventive Medicine, Daegu Catholic University School of Medicine, Daegu, Republic of Korea
 
Keyword : Environment, Ambient particulate matter, Pregnant women, Surrounding greenness, Sleep quality
 
Abstract
Background Particulate air pollution and residential greenness are associated with sleep quality in the general population; however, their influence on maternal sleep quality during pregnancy has not been assessed. Objective This cross-sectional study investigated the individual and interactive effects of exposure to particulate matter (PM) air pollution and residential greenness on sleep quality in pregnant women. Methods Pregnant women (n = 4933) enrolled in the Korean Children's Environmental Health Study with sleep quality information and residential address were included. Sleep quality was assessed using the Pittsburgh Sleep Quality Index (PSQI). The average concentrations of PM (PM2.5 and PM10) during pregnancy were estimated through land use regression, and residential greenness in a 1000 m buffer area around participants' residences was estimated using the Normalized Difference Vegetation Index (NDVI1000-m). Modified Poisson regression models were used to estimate the associations between PM and NDVI and poor sleep quality (PSQI >5) after controlling for a range of covariates. A four-way mediation analysis was conducted to examine the mediating effects of PM. Results After adjusting for confounders, each 10 μg/m3 increase in PM2.5 and PM10 exposure was associated with a higher risk of poor sleep quality (relative risk [RR]: 1.06; 95% confidence interval [CI]: 1.01, 1.11; and RR: 1.09; 95% CI: 1.06, 1.13, respectively), and each 0.1-unit increase in NDVI1000-m was associated with a lower risk of poor sleep quality (RR: 0.97; 95% CI: 0.95, 0.99). Mediation analysis showed that PM mediated approximately 37%–56% of the association between residential greenness and poor sleep quality. Conclusions This study identified a positive association between residential greenness and sleep quality. Furthermore, these associations are mediated by a reduction in exposure to particulate air pollution and highlight the link between green areas, air pollution control, and human health.

Authors :Sooyeon Hong , Ok-Jin Kim , Hye Li Jeon , Suejin Kim, Jihyon Kil
 
Author Affiliations
Environmental Health Research Department, National Institute of Environmental Research, Ministry of Environment, Incheon 22689, Republic of Korea
 
Keyword : Korean National Environmental Health Survey (KoNEHS), environmental chemicals, human biomonitoring
 
Abstract
In South Korea, a Human Biomonitoring (HBM) program, known as the Korean National Environmental Health Survey (KoNEHS), was launched in 2009. This study aims to provide an overview of environmental chemical exposures in South Korea based on data from the KoNEHS cycle 4 (2018-2020). To ensure population representativeness, Koreans aged 3 years and older were recruited from 426 sites across the country. A total of 6381 participants joined in the collection of biospecimens, which were subsequently analyzed for 33 environmental chemicals or their metabolites, including nine that were not included in the previous cycle. The five most common PFASs were detected in more than 99.7% of the participants. The GM of serum PFOS was the highest in adults at 15.1 ug/L (13.9, 16.4) and in adolescents at 7.97 ug/L (7.42, 8.56). In adults, there was a gradual decrease in the detection rate and concentration of some heavy metals and phthalate metabolites. In children and adolescents, the detection rate of BPA in urine decreased, while the rate of its substitutes BPF and BPS increased, and the rate of propyl paraben in urine decreased significantly. The results of the KoNEHS cycle 4 indicate that exposure levels to certain environmental chemicals are still high, highlighting further monitoring and on-going surveys to determine their trends, especially for newly investigated substances, such as PFASs.

Authors :Byoungcheun Lee ^{a 1} , Eun Ki Min¹ , Geunbae Kim^a , Gilsang Hong^a, Jungkwan Seo^a, Jin Soo Choi^c, Jin Soo Choi^d, Ki-Tae Kim^b
 
Author Affiliations
a. Risk Assessment Division, National Institute of Environmental Research, Incheon 22689, Republic of Korea
b. Department of Environmental Engineering, Seoul National University of Science and Technology, Seoul 01811, Republic of Korea
c. Environmental Exposure & Toxicology Research Center, Korea Institute of Toxicology, 17, Jegok-gil, Jinju 52834, Republic of Korea
d. Gyeongnam Branch Institute, Korea Institute of Toxicology, 17, Jegok-gil, Jinju 52834, Republic of Korea
 
Keyword : Microplastic, PET fiber, Toxicity, Endocrine disruption, NOM, Zebrafish
 
Abstract
Although polyethylene terephthalate (PET) fibers are a representative form of plastic pollutants, studies on their toxicity are currently limited compared to other plastic types. Moreover, the effect of natural organic matter (NOM) on their toxicity has not been investigated. In this study, female and male adult zebrafish were exposed to synthesized PET fibers at concentrations of 0.1, 1, 10, and 100 mg/L in the presence and absence of 10 mg/L of NOM for 10 d. Bioaccumulation of PET fibers in zebrafish intestine, liver, and gills was identified and expression levels of reactive oxygen species (ROS) generation, sex hormones, and oxidative stress and sex hormone-related genes were measured. In addition, the developmental stages of gonadal cells were examined through histological analysis. We found that PET fibers bioaccumulated in the intestine and liver of zebrafish. ROS generation significantly increased at 100 mg/L of PET fibers, the expression of oxidative stress-related genes decreased in female and increased in male zebrafish. Exposure to 100 mg/L of PET fibers did not affect 17-beta estradiol, but significantly decreased the testosterone levels in male zebrafish. Sex hormone-related genes significantly decreased in both female and male zebrafish, except for androgen receptor in female zebrafish. However, these changes were exacerbated by the removal of NOM, suggesting a protective effect of NOM against PET fibers toxicity. We demonstrated that the accumulated PET fibers may lead to oxidative stress and sex hormone alteration, and disrupt the development of gonadal cells. Additionally, the NOM coating did not alter bioaccumulation considerably, but mitigated the adverse effects at the hormone level in PET fiber-exposed zebrafish. Thus, this study provides a basis for further research on the toxicity assessment of PET fibers and interactions between NOM and PET fiber-related toxicity.

Authors : Rishikesh Bajagain, Seam Noh, Young-hee Kim, Hyuk Kim, Kwang-seol Seok, Mark Xavier Bailon & Yongseok Hong
 
Author Affiliations
1. Rishikesh Bajagain : Department of Environmental Engineering, Korea University Sejong Campus, 30019, Sejong, Republic of Korea
2. Seam Noh : Chemicals Research Division, National Institute of Environmental Research, 22689, Incheon, Republic of Korea
3. Young-hee Kim : Chemicals Research Division, National Institute of Environmental Research, 22689, Incheon, Republic of Korea
4. Hyuk Kim : Chemicals Research Division, National Institute of Environmental Research, 22689, Incheon, Republic of Korea
5. Kwang-seol Seok : Chemicals Research Division, National Institute of Environmental Research, 22689, Incheon, Republic of Korea
6. Mark Xavier Bailon & Yongseok Hong : Department of Environmental Engineering, Korea University Sejong Campus, 30019, Sejong, Republic of Korea
 
Keyword : Methylmercury, Diffusive gradient in thin films technique, Long-term monitoring, Lakes, Rivers
 
Abstract
This study aimed to optimize the methods for sampling and analyzing methylmercury (MeHg) concentrated within diffusive gradients in thin films (DGT) and its application to different water bodies. We explored the elution solution for MeHg, comprised of 1.13 mM thiourea and 0.1M HCl, optimizing its volume to 50 mL. In addition, we found that it is necessary to analyze the entire extraction solution after adjusting its pH, to ensure completion of the ethylation reaction. The DGT samplers were deployed in two distinct aquatic environments (i.e., Okjeong Lake and Nakdong River) for up to 6 weeks, and this study demonstrated to predict the time-weighted average concentration with a diffusion coefficient of 7.65 × 10−6 cm2 s−1 for MeHg in the diffusive gel. To assess the diffusive boundary layer (DBL) effects, the DGT samplers with different agarose diffusive gel thickness were deployed. The mass of MeHg accumulated in the DGT resin at a given time decreased with increasing diffusive gel thickness, because of creating longer diffusion pathways within thicker gels. The labile MeHg concentration estimated by the DGT in Okjeong Lake and Nakdong River are found in the range of 61–111 and 55–105 pg L−1, respectively, which were found to be similar to the grab sampling data. Additionally, this study evaluated depth-dependent MeHg in Okjeong Lake. The vertical profile results showed that the concentration of MeHg at the depth of 2.3 and 15.7 m are about 1.5 and 4.6 times of the DGT installed at 0.3 m of the surface layer, respectively, suggesting potential mercury methylation in deep waters. These findings have practical implications for predicting bioavailability, assessing risks, and formulating strategies for water body management and contamination remediation.

Authors :Sohee Jeong^a , Hyeonjung Ryu^a , Hyeokjin Shin^a , Min Gyu Lee^a, Hyunwook Kim^b, Jung-Taek Kwon^c, Jaewoong Lee^c, Younghun Kim^a
 
Author Affiliations
a. Department of Chemical Engineering, Kwangwoon University, Seoul 01897, South Korea
b. Department of Environmental Engineering, University of Seoul, Seoul 02504, South Korea
c. Risk Assessment Division, Environmental Health Research Department, National Institute of Environmental Research, Incheon 22733, South Korea
 
Keyword : Road dust, Tire-wear particle, Pyrolysis-gas chromatography-mass spectrometry, Styrene-butadiene rubber, Natural rubber, Euro-7
 
Abstract
Increase in road traffic leads to increased concentrations of tire-wear particles (TWPs), a prominent source of microplastics from vehicles, in road dust. These particles can re-enter the atmosphere or move into aquatic ecosystems via runoff, impacting the environment. Consequently, accurately assessing and managing TWP levels in road dust is crucial. However, the ISO method (ISO/TS 20593 and 21396) uses a constant ratio of styrene-butadiene rubber (SBR) to natural rubber (NR) for all tires, disregarding the variability in tire composition across different types and brands. Our study found substantial SBR content (15.7 %) in heavyweight truck tires, traditionally believed to be predominantly NR. We evaluated the SBR/NR content in 15 tire types and proposed a method to more accurately evaluate TWP concentrations in road dust from five different locations. Our findings suggest that the conventional ISO method may underestimate the concentrations of TWP due to its reliance on a static ratio of SBR/NR. This study underscores the necessity for a more flexible approach that can adapt to the variability in SBR and NR content across different tire types. By delineating the limitations inherent in current assessment methods, our research contributes to a more adaptable understanding of TWP concentrations in road dust. This advancement prompts the development of a revised methodology that more accurately reflects the diverse compositions of tire rubber in environmental samples.

Authors :Hyeokjin Shin^{a 1} , Minseung Hyun^{a 1} , Sohee Jeong^a , Hyeonjung Ryu^a, Hyunwook Kim^b, Min Gyu Lee^a, Woosuk Chung^a, Jaehwan Hong^a, Jung-Taek Kwon^b Younghun Kim^a
 
Author Affiliations
a. Department of Chemical Engineering, Kwangwoon University, Seoul, 01897, South Korea
b. Risk Assessment Division, Environmental Health Research Department, National Institute of Environmental Research, Incheon, 22733, South Korea
 
Keyword : Urban pollution monitoring, Road dust, Tire-wear particle, Carbon black, Heavy metals
 
Abstract
The interdependence of traffic dynamics and air quality on the concentrations of tire wear particles (TWP), heavy metals, and carbon black (CB) in road dust collected from 15 locations in Seoul, South Korea, was assessed. Pearson correlation, principal component analysis, and network analysis were employed to evaluate the correlations among traffic volume, vehicle speed, air quality parameters (PM10, PM2.5, NOx, and CO), and the concentrations of TWP (5934 to 16,253 mg/kg, average 9581 ± 4086 mg/kg), CB (371–22,287 mg/kg, average 4291 ± 6096 mg/kg), and heavy metals (Cr, Mn, Fe, Ni, Cu, Zn, As, Cd, and Pb) in road dust. The enrichment factors for heavy metals and the pollution index of TWP and CB were also calculated to evaluate the contribution of vehicle-derived particulate substances to road dust contamination. It was found that Cluster B, characterized by traffic-related variables such as traffic volume, vehicle speed, and heavy metals (Zn, Cd, and Pb), was significantly correlated with these pollutants, with correlation coefficients reaching up to 0.933. TWP was identified as a significant mediator in the increase of Zn, Pb, and Cd concentrations linked to traffic activities, contributing to pollution levels that were 2–16 times higher than the geochemical background. The presence of TWP and CB in road dust was identified as an indicator of contamination from traffic-related activities, highlighting the importance of Zn, Pb, and Cd as emerging pollutants that require targeted management strategies.

Authors :Donghyun Kim^a , Yusun Shin^a , Jong-In Park^a , Donghyeon Lim^a, Hyunjoon Choi^a, Seongwon Choi^a, Yong-Wook Baek^b, Jungyun Lim^b, Younghee Kim^b Ha Ryong Kim^c Kyu Hyuck Chung^d Ok-Nam Bae^a
 
Author Affiliations
a. College of Pharmacy Institute of Pharmaceutical Science and Technology, Hanyang University ERICA Campus, Ansan, South Korea
b. Humidifier Disinfectant Health Center, Environmental Health Research, National Institute of Envrironmental Research, Incheon, 22689, South Korea
c. College of Pharmacy, Korea University, Sejong, South Korea
d. College of Pharmacy, Kyungsung University, Busan, South Korea
 
Keyword : Humidifier disinfectant (HD), In vitro benchmark dose (BMD), New approach methodologies (NAMs), Systematic review, Adverse outcome pathway (AOP), Polyhexamethylene guanidine (PHMG), Mixture of chloromethylisothiazolinone and methylisothiazolinone (CMIT/MIT)
 
Abstract
Dosimetry modeling and point of departure (POD) estimation using in vitro data are essential for mechanism-based hazard identification and risk assessment. This study aimed to develop a putative adverse outcome pathway (AOP) for humidifier disinfectant (HD) substances used in South Korea through a systematic review and benchmark dose (BMD) modeling. We collected in vitro toxicological studies on HD substances, including polyhexamethylene guanidine hydrochloride (PHMG-HCl), PHMG phosphate (PHMG-p), a mixture of 5-chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-4-isothiazolin-3-one (CMIT/MIT), CMIT, and MIT from scientific databases. A total of 193 sets of dose-response data were extracted from 34 articles reporting in vitro experimental results of HD toxicity. The risk of bias (RoB) in each study was assessed following the office of health assessment and translation (OHAT) guideline. The BMD of each HD substance at different toxicity endpoints was estimated using the US Environmental Protection Agency (EPA) BMD software (BMDS). Interspecies- or interorgan differences or most critical effects in the toxicity of the HD substances were analyzed using a 95% lower confidence limit of the BMD (BMDL). We found a critical molecular event and cells susceptible to each HD substance and constructed an AOP of PHMG-p- or CMIT/MIT-induced damage. Notably, PHMG-p induced ATP depletion at the lowest in vitro concentration, endoplasmic reticulum (ER) stress, epithelial-to-mesenchymal transition (EMT), inflammation, leading to fibrosis. CMIT/MIT enhanced mitochondrial reactive oxygen species (ROS) production, oxidative stress, mitochondrial dysfunction, resulting in cell death. Our approach will increase the current understanding of the effects of HD substances on human health and contribute to evidence-based risk assessment of these compounds.

Authors : Yong Joo Park^{a 1} , Ha Ryong Kim^{b 2} , Jun Woo Kim^{c 3} , Jong-Hyun Lee^{d 4}, Younghee Kim^{e 5}, Jungyun Lim^{e 6}, Yong-Wook Baek^{e 7}, Kyu Hyuck Chung^{b a 8}
 
Author Affiliations
a. College of Pharmacy, Kyungsung University, Busan, South Korea
b. School of Pharmacy, Korea University, Sejong, South Korea
c. Inhalation Toxicology Center, Jeonbuk Department of Non-Human Primate, Korea Institute of Toxicology, Jeongeup, South Korea
d. EH R&C Co., Incheon, South Korea
e. Humidifier Disinfectant Health Center, Environmental Health Research Department, National Institute of Environmental Research, Incheon, South Korea
f. School of Pharmacy, Sungkyunkwan University, Suwon, South Korea
 
Keyword : PHMG-p, Lung cancer, Adverse outcome pathway, Non-genotoxic, Carcinogenicity assessment
 
Abstract
In this study, we investigated the potential mechanisms by which polyhexamethylene guanidine phosphate (PHMG-p), a known respiratory irritant, may contribute to lung cancer development. Using the adverse outcome pathway (AOP) framework, we analyzed established databases (such as AOP-Wiki) and employed AI tools (AOP-helpFinder) to identify key events (KEs) associated with lung carcinogenesis. Our analysis indicates that chronic inhalation of PHMG-p triggers a non-genotoxic pathway, characterized by cell membrane disruption, inflammation, and oxidative stress, with a point of departure (POD) of 0.0018 mg/m³, suggesting carcinogenic potential. Additionally, a human exposure assessment revealed that most claimants were exposed to PHMG-p levels exceeding the estimated inhalation reference concentration (RfC) of 0.018 µg/m³. While downstream KEs, such as DNA damage, mutation, and cell proliferation, require further investigation, our findings, supported by the AOP framework and potency and exposure assessments, strongly suggest that PHMG-p exposure could induce lung cancer in individuals affected by humidifier disinfectants. These results underscore the importance of a comprehensive risk assessment approach for evaluating the carcinogenicity of PHMG-p.

Authors : Hong Lee^a1 , Sang Hoon Jeong^a1 , Yong-Wook Baek^b1 , Hyejin Lee^a, Jason K. Sa^c, Ji Yoon Lee^c, Yu-Seon Lee^a, Yoon Jeong Nam^a, Jaeyoung Kim^a , Jonghoon Kim^d, Jin Young Choi^a, Su A. Park^a, Je Hyeong Kim^e, Yoon Hee Park^b, Jungyun Lim^b, Young-Hee Kim^b, Younghee Kim^e, Eun-Kee Park^f, Cherry Kim^g, Ju-Han Lee^h
 
Author Affiliations
a. Medical Science Research Center, Korea University Ansan Hospital, Korea University College of Medicine, Ansan, Gyeonggi, 15355, Republic of Korea
b. Humidifier Disinfectant Health Center, National Institute of Environmental Research, Incheon, 22689, Republic of Korea
c. Department of Biomedical Sciences, Korea University College of Medicine, Seoul, 02841, Republic of Korea
d. Department of Health Sciences and Technology, Samsung Advanced Institute for Health Sciences and Technology, Sungkyunkwan University, Seoul, 06531, Republic of Korea
e. Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Korea University Ansan Hospital, Korea University College of Medicine, Ansan, Gyeonggi, 15355, Republic of Korea
f. Department of Medical Humanities and Social Medicine, College of Medicine, Kosin University, Busan, 49267, Republic of Korea
g. Department of Radiology, Korea University Ansan Hospital, Korea University College of Medicine, Ansan, Gyeonggi, 15355, Republic of Korea
h. Department of Pathology, Korea University Ansan Hospital, Korea University College of Medicine, Ansan, Gyeonggi, 15355, Republic of Korea
 
Keyword : Lung carcinogenesis, PHMG-p, TAK1, Necroptosis, MAPK signaling, Somatic mutation
 
Abstract
Polyhexamethylene guanidine (PHMG) is widely utilized in personal hygiene products due to its bactericidal, non-volatile, and hydrophilic properties. However, the long-term toxic effects and underlying mechanisms associated with respiratory exposure to the commonly used form, PHMG phosphate (PHMG-p), are still insufficiently understood. This study aims to elucidate the types of pulmonary lesions and the incidence of lung cancer associated with varying concentrations of PHMG-p and observation periods, along with the molecular mechanisms underlying this relationship. To assess these effects, CT scans and pathological analyses were conducted for up to 54 weeks following initial exposure to PHMG-p. Furthermore, to investigate the underlying causes of pulmonary toxicity, TGF-beta-activated kinase 1 was identified as a PHMG-p-binding protein, and its associated signaling pathways, including necroptosis, apoptosis, and MKK7, were explored. Somatic mutational signature, and gene ontology (GO) analyses were performed to investigate the genetic characteristics of PHMG-p-induced lung carcinogenesis. PHMG-p exposure led to somatic mutations in lung cancer-related genes, including TP53, SOS1, KMT2D, MDM2, ERBB2, SETD2, MET, ARID1A, RBM10, and CDKN2A as well as in genes such as RAB31, WASHC1, DDX11, ECD, STAB2, MUC2, and MUC5AC. The mutated genes were primarily associated with impaired DNA repair mechanisms. GO analysis highlighted the activation of pathways related to cell cycle checkpoints, necroptosis, MAPK, and idiopathic pulmonary fibrosis, while also revealing the suppression of signaling pathways associated with natural killer cells, GADD45, LXR/RXR activation, and IL-15 production. Gain-of-function experiments confirmed the oncogenic roles of PLAU and HMGA2, as well as the tumor-suppressive functions of TBX4 and GPX3. These findings suggest that PHMG-p activates necroptosis and MAPK signaling, increases the frequency of somatic mutations, and inhibits apoptosis, thus fostering an environment conducive to carcinogenesis. This underscores the importance of understanding the potential health risks associated with PHMG-p exposure and provides insights for future research and regulatory considerations regarding the safety of personal hygiene products.

Authors : Sang Hoon Jeong, Hong Lee, Yoon Jeong Nam, Ja Young Kang, Hyejin Lee, Jin Young Choi, Yu-Seon Lee, Jaeyoung Kim, Yoon Hee Park, Su A. Park, Hangseok Choi, Eun-Kee Park, Yong-Wook Baek, Jungyun Lim, Suejin Kim, Cherry Kim & Ju-Han Lee,
 
Author Affiliations
a. Medical Science Research Center, Ansan Hospital, Korea University College of Medicine, 123, Jeokgeum-ro, Danwon-gu, Ansan-si, Gyeonggi, 15355, South Korea
b. Medical Science Research Center, Korea University College of Medicine, 73, Goryeodae-ro, Seongbuk-gu, Seoul, 02841, South Korea
c. Department of Medical Humanities and Social Medicine, College of Medicine, Kosin University, Busan, 49267, South Korea
d. Humidifier disinfectant Health Center, National Institute of Environmental Research, Incheon, 22689, South Korea
 
Keyword : Rat model, Polyhexamethylene guanidine phosphate, Chest CT, Lung cancer, Lung fibrosis
 
Abstract
Polyhexamethylene guanidine phosphate (PHMG-p) is a major component in humidifier disinfectants, which cause life-threatening lung injuries. However, to our knowledge, no published studies have investigated associations between PHMG-p dose and lung damage severity with long-term follow-up. Therefore, we evaluated longitudinal dose-dependent changes in lung injuries using repeated chest computed tomography (CT). Rats were exposed to low (0.2 mg/kg, n = 10), intermediate (1.0 mg/kg, n = 10), and high (5.0 mg/kg, n = 10) doses of PHMG-p. All rats underwent repeated CT scans after 10 and 40 weeks following the first exposure. All CT images were quantitatively analyzed using commercial software. Inflammation/fibrosis and tumor counts underwent histopathological evaluation. In both radiological and histopathologic results, the lung damage severity increased as the PHMG-p dose increased. Moreover, the number, size, and malignancy of the lung tumors increased as the dose increased. Bronchiolar–alveolar hyperplasia developed in all groups. During follow-up, there was intergroup variation in bronchiolar–alveolar hyperplasia progression, although bronchiolar–alveolar adenomas or carcinomas usually increase in size over time. Thirty-three carcinomas were detected in the high-dose group in two rats. Overall, lung damage from PHMG-p and the number and malignancy of lung tumors were shown to be dose-dependent in a rat model using repeated chest CT scans during a long-term follow-up.