BACKGROUND AND OBJECTIVES: Although mass transit systems are convenient and efficient for urban people, little attention has been paid to the potential hearing hazard from their noise. The purpose of the current study was to measure and analyze levels of subway interior noise at peak commuter times and to provide information about commuters' daily dose of noise exposure. MATERIALS AND METHODS: To measure the subway interior noise, nine subway lines inside Seoul (i.e., lines 1-9) and six lines surrounding the capital city area (i.e., Central, Bundang, Sinbundang, Incheon, Gyeongui, and Gyeongchun) were chosen. The noise was measured and recorded by a sound level meter for two-hour periods in the morning and evening. RESULTS: 1) In the LZeq analysis, the average noise level of all 15 lines was 72.78 dB; the maximum and minimum noise levels were 78.34 and 62.46 dB, respectively. The average noise level of the nine lines inside Seoul was 73.45 dB, which was 1.68-dB louder than that of the six lines surrounding the capital city area. 2) Based on the LZeq analysis of 33 measured frequencies, 12.5 Hz was the highest frequency and 20,000 Hz was the lowest. 3) There was no remarkable difference in the level of subway interior noise between morning and evening peak commuter times. CONCLUSIONS: We concluded that the level of subway interior noise was not loud enough for commuters to incur noise-induced hearing loss. Regardless, environmental noise control efforts in the subway system might be needed for commuters who take a subway every day.
Hearing ; Hearing Loss, Noise-Induced ; Incheon ; Noise* ; Railroads* ; Seoul

Background and Objectives: Although thyroid hormones affect human cancer progression, the regulatory mechanism of thyroid hormone receptors in carcinogenesis has not been elucidated. This study aimed to evaluate the expression pattern of the thyroid hormone receptor (TR) and its corepressors, and to investigate the clinical and biological functions of TR. Materials and Methods: Transcriptomic and clinical data for thyroid cancer were downloaded from The Cancer Genome Atlas. Paraffin-embedded tissue sections from patients who underwent thyroidectomy were used for immunohistochemistry. BCPAP cells were treated with T3 to investigate the thyroid hormone target genes. Thyroid hormone receptor alpha (THRA) and Thyroid hormone receptor beta (THRB) were knocked down by transient siRNA transfection. Results: THRA and THRB expression was lower in thyroid cancer tissues than in normal tissues. However, strong focal staining of TRβ was observed in the invasive front. High THRB expression was associated with high Silencing Mediator for Retinoid or Thyroid hormone receptor (SMRT) expression, older age, a high MACIS (distant Metastasis, patient Age, Completeness of resection, local Invasion, and tumor Size) score, more aggressive histological subtypes, more frequent extra-thyroidal extension, and advanced TNM stage. THRB expression was positively correlated with Hypoxia Inducible Factor 1 Subunit Alpha (HIF1A), L1 Cell Adhesion Molecule (L1CAM), and Lysyl Oxidase (LOX) expression. Thyroid hormone-induced HIF1A, L1CAM, and LOX upregulation was abolished by siTHRB but not siTHRA in BCPAP cells. High SMRT and high THRB groups (SMRT/THRB) presented more aggressive clinical features and showed an upregulation of HIF1A, L1CAM, and LOX, as well as of epithelial-mesenchymal transition (EMT)-related genes, causing changes in the tumor microenvironment. Conclusion Cooperative subtype switching from NCOR1/THRA to SMRT/THRB was thus related to aggressive clinical and molecular features, possibly related to EMT and EMT-related tumor microenvironment.