Yo Ishigaki

Radioactive contamination in residential areas of Bangka Island, Indonesia, a major tin- and rare earth-producing region, has rarely been studied, although material stored near mineral-processing workshops may pose a long-term health risk. We collected 46 soil samples around 9 mineral-processing workshops in the Selindung District, Pangkal Pinang City: residential soils from 20 locations at two depths ( n = 40) and 6 workshop-related sediments. High-purity germanium detector analysis showed that 13 of the 40 residential soil samples exceeded the screening criteria of the IAEA Safety Standards Series No. RS-G-1.7 for naturally occurring radioactive material. Residential contamination was highly heterogeneous and was not explained by a simple monotonic distance relationship (Spearman’s ρ = −0.12, p = 0.61). Two upper outliers occurred at 5 and 10 m from the nearest workshops, including the maximum residential activity of 12,992 Bq/kg detected at 5 m, in areas frequently accessed by local residents. Five of 17 locations with quantifiable paired measurements (including 1 tied pair; n = 16 for the Wilcoxon signed-rank test) showed higher activity at 20 cm than at 10 cm, and the paired depth difference was not statistically significant (Wilcoxon p = 0.079), indicating an irregular rather than consistently surface-dominated vertical distribution. Screening-level outdoor annual effective doses for the quantifiable residential samples ranged from 0.051 to 8.46 mSv/y (median 0.42 mSv/y), with the maximum obtained 5 m from a workshop. Nuclide composition analysis further revealed that the activity concentrations of the ²³⁸ U and ²³² Th series increased with total radioactivity, whereas ⁴⁰ K showed only a weak correlation. Maximum activities of ²³⁸ U and ²³² Th approached levels reported by the IAEA for high-purity monazite sand (6,000–20,000 Bq/kg). These findings demonstrate spatial and vertical heterogeneity of technologically enhanced naturally occurring radioactive material in residential zones, indicating a need for site-specific assessment and long-term monitoring.

During the COVID-19 pandemic, taxis were used to transport patients with mild symptoms; however, quantitative field evidence on ventilation performance and driver-area isolation in modified taxis remains limited. We conducted a field demonstration experiment to evaluate a purpose-modified taxi under real driving conditions: approximately constant-speed driving (55 km/h) and variable-speed driving. Rear-cabin ventilation was assessed using carbon dioxide (CO2) tracer-gas decay, and compartmental isolation was evaluated using particle measurements. Estimated air changes per hour were 33.8 h−1 during constant-speed driving and 44.8 h−1 during variable-speed driving. Rear-cabin CO2 concentrations exceeded 8,000 ppm immediately after tracer release in both runs, while front-cabin CO2 concentrations remained near background levels. Rear-cabin particle counts exceeded 12,000 counts per minute (cpm) in both runs, while front-cabin counts remained ≤15 cpm, corresponding to ≤0.12% of rear-cabin peak levels. Under the tested configuration, the modified taxi achieved high rear-cabin ventilation while maintaining strong driver-area isolation. This paired field-verification approach may support practical evaluation of exposure-control measures in purpose-modified passenger transport vehicles.

Airborne transmission of severe acute respiratory syndrome coronavirus 2 in enclosed, mechanically ventilated hospital wards remains poorly characterized. In February 2025, a coronavirus disease cluster involving 17 individuals occurred across multiple rooms in a sealed Japanese hospital ward. Several infected individuals had no documented close contact with the index patient, raising concerns about ventilation-related airflow-induced inter-room aerosol transmission. A multimodal environmental investigation was conducted via (1) CO ₂ decay experiments to quantify air change rates (ACHs), (2) particulate matter (PM) _2.5 aerosol dispersion measurements using fog as a surrogate tracer, and (3) computational fluid dynamics (CFD) simulations to visualize airflow and scalar transport. Measurements were taken in the index room (Room A), corridor, and adjacent Rooms B–D under closed- and open-door conditions. Opening the patient room door significantly increased indoor ACHs (3.29/h → 4.01/h, p = 0.030) and allowed CO ₂ tracer gas to escape into the corridor. In the PM _2.5 dispersion experiment, aerosols released in Room A were detected within the room, corridor, and neighboring rooms, with the highest out-of-room aerosol burden observed at the corridor sensor (area under the curve = 2.6 × 10 ⁵ μg·s/m ³ ). PM _2.5 and PM ₁₀ concentrations were strongly correlated (r = 0.9997), revealing intermediate-sized particles capable of longer-range transport. CFD simulations reproduced key qualitative features of the experiments, including tracer accumulation within curtain-enclosed compartments, delayed leakage through the doorway, and downstream transport toward the corridor. Inter-room aerosol transport can occur in sealed, mechanically ventilated wards without natural ventilation or structural openings between rooms. Opening doors improves in-room ventilation and promotes aerosol leakage, revealing a trade-off between the dilution and contamination of shared spaces. Architectural elements such as privacy curtains contribute to airflow stagnation and uneven aerosol removal. Effective infection control strategies must incorporate airflow pathway management and localized filtration to prevent unintended aerosol migration in mechanically ventilated healthcare settings.

Although previous studies have reported favorable outcomes of Occlu-tab therapy for anisometropic and strabismic amblyopia, its effectiveness for bilateral ametropic amblyopia has not been well documented. This study evaluated the therapeutic effectiveness of Occlu-tab training applied to both eyes in children with bilateral ametropic amblyopia. This retrospective study included 25 children with bilateral ametropic amblyopia (best-corrected visual acuity ≤0.8 in both eyes) treated at the NAZAR Eye Center (Tashkent, Uzbekistan) between September 2024 and February 2025. The eye with better visual acuity, as assessed at the initial visit, was defined as the better eye and the fellow eye as the worse eye. All patients received refractive correction and initiated Occlu-tab training at the first visit. Occlu-tab training was performed for 10 minutes per eye per day (20 minutes total for both eyes), 10 times per month, for 6 months. Visual acuity was assessed at baseline (0 months; 0 M) and at 1 M, 3 M, and 6 M. Changes in visual acuity over time were analyzed using repeated-measures analysis of variance. The mean patient age was 7.96 ± 1.30 years. In the worse eye, mean visual acuity (LogMAR) was 0.32 ± 0.17 at 0 M, 0.28 ± 0.15 at 1 M, 0.22 ± 0.12 at 3 M, and 0.19 ± 0.11 at 6 M (p < 0.001). In the better eye, mean visual acuity was 0.26 ± 0.15 at 0 M, 0.24 ± 0.14 at 1 M, 0.19 ± 0.13 at 3 M, and 0.15 ± 0.11 at 6 M (p < 0.001). Over the 6-month treatment period, Occlu-tab training applied to both eyes was associated with significant visual acuity improvement in children with bilateral ametropic amblyopia. These findings suggest that Occlu-tab therapy may improve in visual acuity in patients with bilateral ametropic amblyopia.

Background: Postharvest losses of sweet potatoes remain substantial due to microbial spoilage and suboptimal storage conditions, with curing commonly used to enhance wound healing and reduce decay. Aims: This pilot study compared spoilage incidence of sweet potatoes (Ipomoea batatas cv. 'Beniharuka') stored under continuous low-level chlorine dioxide (ClO₂) gas exposure with and without curing treatment. Study Design: A two-by-two treatment arrangement in a single non-replicated pilot trial. ClO₂-exposed and non-exposed sweet potatoes were stored in separate warehouse compartments, with cured and non-cured lots placed within each compartment. Place and Duration of Study: Two agricultural warehouses in Ibaraki Prefecture, Japan, from 12 December 2024 to 24 January 2025. Methodology: A total of 507 tubers (80 kg) were allocated to four groups according to the presence or absence of ClO₂ exposure (mean concentration 0.039 ppm for the first 14 days; reduced thereafter due to equipment malfunction) and curing (40 °C, 100% RH, 90 h). Temperature, relative humidity, and ClO₂ concentration were monitored continuously. Spoilage was assessed weekly by visual inspection and palpation, and risk ratios (RR) with 95% confidence intervals were calculated using Fisher's exact test. Results: During weeks 3–6, spoilage incidence was lower in the ClO₂ exposure group than in the non-exposure group (12/236 vs 58/235; RR = 0.206, 95% CI 0.114–0.373, P < .001), whereas curing was associated with higher spoilage incidence (48/253 vs 22/218; RR = 1.88, 95% CI 1.17–3.01, P = .009). However, the ClO₂ compartment was operated at lower temperature (−1.9 °C) and relative humidity (−18.5 percentage points) than the control; therefore, the observed reduction cannot be attributed to ClO₂ exposure alone. Conclusion: In this single pilot warehouse trial, continuous low-level ClO₂ exposure at concentrations below the OSHA occupational exposure limit (TWA 0.10 ppm) was associated with reduced sweet potato spoilage. Because environmental conditions differed between compartments, further trials under controlled conditions are needed to isolate the effect of ClO₂ from that of temperature and humidity.

We evaluated the accuracy and reliability of 12 low-cost CO₂ sensors that are commercially available and promoted for infection control in indoor settings, considering their potential use in clinical environments. A stepwise CO₂ injection protocol and alcohol exposure tests were conducted in a controlled acrylic chamber. Our results showed that only 3 out of 12 sensors (25%) responded reliably to actual CO₂ concentrations and could be calibrated with acceptable accuracy, whereas 67% failed to detect CO₂ but falsely responded to alcohol vapors, frequently present in health care environments. These findings highlight the need for staff development educators to promote accurate sensor selection and propose a practical 3-step screening method that clinical engineers can use without specialized equipment.

Background: Subjective well-being (SWB) is an essential indicator of successful aging. Although social connections enhance SWB among older adults, few interventions have integrated community-based approaches with information and communication technology (ICT). This study evaluated the Chofu–Digital–Choju (CDC) project, a multi-component community intervention fostering in-person and online social connections among community-dwelling older adults in urban Japan. Methods: This quasi-experimental study (January 2022 to March 2024) included community-dwelling older adults aged 65–84 years in Chofu City, Tokyo, Japan. The intervention consisted of online classes, community hubs as local third places, and community events. Baseline and follow-up data were collected using self-administered questionnaires. Propensity score matching (1:1) was used to reduce selection bias, and generalized estimating equations were applied to evaluate the intervention effects. The primary outcome was SWB (Cantril Ladder). The secondary outcomes included social isolation, neighborhood relationships, social participation, health literacy, psychological health, physical activity, and ICT use. Results: Among the 1599 participants who completed both surveys, 209 (13.1%) participated in at least one CDC intervention component. After propensity score matching, 195 pairs were analyzed. No significant interaction effect was observed for SWB (β = 0.08, 95% confidence interval [CI]: −0.20, 0.37; p = 0.565). However, a significant interaction effect favored the intervention group for Internet usage frequency (odds ratio = 1.53, 95% CI: 1.08, 2.16; p = 0.016). A significant borderline interaction was also observed in health literacy (β = 0.13, 95% CI: −0.00, 0.26; p = 0.056), which reached significance in covariate-adjusted sensitivity analysis (p = 0.044). Subgroup analyses revealed that community hub participants showed significant interaction effects in health literacy (p = 0.021) and a trend toward reduced depressive symptoms (p = 0.084). Conclusions: The CDC intervention did not improve SWB over 2 years but enhanced Internet use and supported health literacy and depressive symptoms, particularly among hub participants. Community-based, multi-component interventions that integrate online and in-person activities may foster digital inclusion and specific health behaviors. Although SWB did not change in this study, these proximal gains may serve as foundational steps for long-term improvement. The study protocol was preregistered in the UMIN Clinical Trials Registry (UMIN000051393; Registered on 21 June 2023).

This study assessed the radiation exposure risks from Technologically Enhanced Naturally Occurring Radioactive Materials (TENORM) generated during small-scale tin ore processing on Bangka Island, Indonesia. Twenty individuals, including workers and nearby residents, were evaluated. Workers experienced significant occupational exposure, with mean annual doses of 6.87 mGy/y and some exceeding 26.49 mGy/y. Notably, 71% of residents exceeded the International Commission on Radiological Protection (ICRP) public dose limit of 1 mSv/y at their desk locations, indicating elevated environmental contamination risks. For comparison with the mSv-based dose limits, effective dose was approximated from the measured air kerma using ICRP 116 conversion coefficients (1 mGy ≈ 1 mSv for the relevant gamma energies). A significant correlation (R² = 0.6612) was observed between the distance from the workshops and resident exposure, indicating elevated external doses for workers and nearby residents around small-scale tin workshops. Significant differences in exposure were observed between ore workers and non-ore workers, highlighting both direct occupational exposure and indirect residential exposure (body: p = 0.021, r = 0.52; desk: p = 0.010, r = 0.57). Urinary uranium in the ore worker was 14.3 ng/L, while the two controls showed 7.5–8.8 ng/L. These values are reported descriptively because the sample size was too small for statistical comparison. This study demonstrates significant occupational and environmental radiation exposure risks associated with small-scale tin ore processing. These findings point to the need for strengthened radiation protection measures and improved contamination control around small-scale tin workshops.

The association between patterns of internet use for older adults’ well-being is unclear. We examined the association between the frequency and purpose of internet use and subjective well-being in older Japanese adults. We analyzed cross-sectional data from 2343 community-dwelling older adults (aged 65–84 years). Subjective well-being was measured using the World Health Organization Well-Being Index as a continuous score, and internet use was categorized by frequency and purpose. Hierarchical linear regression analysis was controlled for sociodemographic and health-related covariates. After full adjustment, only daily (B = 1.04, 95% CI [0.53, 1.56]) and dual-purpose use (i.e., for both practical and social communication purposes; B = 0.80, 95% CI [0.28, 1.31]) were independently associated with higher well-being. The analysis of the combined patterns further suggested that daily use was the primary factor. For older adults, regularity of internet use was more strongly associated with well-being than diversity of purpose. Daily integration appears to be a key factor for realizing benefits, suggesting that sustained practice is the foundational step in building the digital capital necessary for a flourishing later life. Longitudinal studies are needed to confirm these findings and untangle the causal relationship between sustained internet use and improved well-being among older adults.

エアロゾル感染対策のためのチェックリストを提案し，126ヵ所の医療福祉施設，全3,337居室を対象に立ち入り調査を行った結果，機械換気の問題が発見された居室が全体の28％と顕著であり，その主要因は掃除不足（39％）とスイッチオフ（24％）であった．機械換気量不足が判明した3施設36居室で清掃による介入実験を行ったところ，換気扇の分解清掃だけでは顕著な改善効果は見られなかったものの，屋外排気ガラリの防虫メッシュ清掃により風量が有意に改善し（p＜0.001），設計風量に対する測定風量の割合が平均37％pt増加した．公共建築物の室内空気質管理において，実測換気量のモニタリングや屋外ガラリの定期点検の必要性が示唆された．