Ambulances are enclosed environments that carry a high risk of airborne and surface microbial transmission, yet effective disinfection technologies remain limited. This study evaluated four photocatalytic oxidation (PCO) configurations-O₃+UVA + TiO₂, UVA + TiO₂, O₃+UVC + ZnO, and UVC + ZnO-against B. subtilis spores. The testing employed a prototype air purification system for ambulance applications, where the photocatalyst TiO2 or ZnO was integrated into a filter medium. This system operated in combination with its corresponding UV light source (UVA or UVC) and an optional ozone generator; all housed within a laboratory-simulated ambulance cabin. (8.998m³), where spores at 1.5 × 10⁸ CFU/mL (8 mL) were spray misted using a nebulizer and sampled using an Andersen Impactor, following the NIOSH method. Disinfection efficacy was quantified as the percentage reduction of B. subtilis spores in the air and on surfaces. Among the tested systems, efficacy ranked as UVA + TiO₂ > O₃+UVA + TiO₂ > O₃+UVC + ZnO > UVC + ZnO. UVA + TIO2 achieved the most rapid and stable disinfection among the tested systems under controlled conditions, reducing airborne spores by > 80% within 15min, achieving complete removal within 90min, and reducing surface contamination by 96.77% at 120min. In contrast, ZnO- and UVC-based systems exhibited lower or inconsistent performance. These findings identify UVA + TiO₂ photocatalysis as a safe, ozone-free, and highly effective strategy for ambulance air purification. Its rapid and durable antimicrobial action demonstrates clear advantages over approaches based on ozone or UVC, offering practical benefits for infection control in emergency medical services and providing a foundation for further optimization of photocatalytic technologies in healthcare settings.

Exhaled CO2 and aerosol dispersion on a cruise ship: Airflow and infection risk insights.

Smog, a hazardous combination of fog and fine particulate matter (PM 2.5), poses a significant threat to cardiovascular health, particularly for patients with preexisting heart conditions. Containing harmful pollutants such as ozone, sulfur dioxide, and nitrogen oxides, smog exacerbates cardiovascular risks by triggering inflammation, oxidative stress, endothelial dysfunction, and vasoconstriction. Exposure to high levels of air pollution has been linked to acute cardiovascular events, including unstable angina and ischemic heart attacks, while chronic exposure accelerates degenerative cardiovascular processes. Individuals with hypertension or compromised cardiac function face heightened vulnerability during smog episodes, with increased risks of adverse cardiac outcomes. Preventive measures such as staying indoors, using air purifiers and protective masks, and minimizing exposure to outdoor pollutants are crucial for mitigating health risks. Additionally, policy-driven interventions, including stricter environmental regulations and the promotion of clean energy, are essential for long-term air quality improvement. Healthcare professionals play a vital role in educating patients on preventive strategies and ensuring adherence to treatment regimens. Given the recurrent nature of smog episodes, a collaborative approach involving governments, healthcare providers, and communities is necessary to address this growing environmental health crisis and safeguard the well-being of vulnerable populations.

Wildland and wildland–urban-interface (WUI) fires substantially elevate fine particulate matter (PM2.5) concentrations in surrounding communities. Portable high-efficiency particulate air (HEPA) purifiers are widely recommended to reduce indoor PM2.5 exposure during such events, yet this guidance largely derives from studies of traffic exhaust, secondhand smoke, or indoor sources, rather than real-world WUI fire episodes. To address this gap, we leveraged data from ongoing randomized crossover trials of long-term use of portable HEPA purifiers in Los Angeles residences. During the Eaton Fire (January 2025), 11 homes were under HEPA intervention and 16 under non-HEPA control. Continuous indoor and outdoor PM2.5 monitoring before, during, and after the Eaton Fire (over 6 weeks) showed outdoor PM2.5 levels rose 148% (19 to 47 µg/m3) and indoor levels 91% (10 to 19 µg/m3) during the fire. HEPA homes had indoor PM2.5 levels 3 µg/m³ (15%, p = 0.01) lower than non-HEPA homes, while outdoor concentrations were comparable. Indoor PM2.5 reductions were unaffected by pre-filter use or clean air delivery rate (CADR)-to-room-volume ratio (0.8–4.9). These findings indicate that portable HEPA purifiers provided statistically significant but modest reductions in PM2.5 levels during WUI fire events. Complementary building-level and behavioral interventions remain critical to reduce indoor exposure in fire-affected communities.

Light-free degradation of hydrogen sulfide via a Cu+ /Cu2+ redox cycle on a titanium dioxide supported copper hydroxide nitrate catalytic adsorbent.

On-Site Test on Fine Dust Reduction in Subway Station Using Electrostatic Type Air Purifier

Photocatalytic mineralization of gaseous formaldehyde over silver-doped metal oxide/MOF heterostructure with a mediator-assisted hybridized step (MAH-S)-scheme charge configuration.

Asthma continues to affect millions of adults in the United States, with indoor environmental exposures playing a major role in symptom burden and control. Limited research has examined the combined influence of multiple household and environmental determinants on adult asthma morbidity, particularly in diverse states such as Texas. We analyzed pooled data from 1596 Texas adults with asthma who completed the Asthma Call-Back Survey between 2019 and 2022. Multivariable logistic regression models, adjusted for survey design and demographic covariates, were used to examine associations between household and environmental determinants and four morbidity outcomes: asthma attacks, recent symptoms, sleep difficulty, and limited activity due to asthma. Current smoking, lack of bathroom or kitchen ventilation, and absence of air purifier use were consistently associated with higher odds of morbidity. Protective associations were observed for homes without mold, rodents, or furry pets. Disparities were also evident, with older adults, women, and non-Hispanic Black respondents reporting greater morbidity. These findings highlight the importance of addressing modifiable exposures such as indoor smoking, ventilation, and allergen control within comprehensive asthma management strategies. Targeted interventions that combine environmental modifications with health education may help reduce asthma disparities and improve the quality of life for adults with asthma.

Effects of inflammatory markers and sleep quality in stroke patients by reducing residential PM2.5 levels: A case-crossover intervention study.

Citizen science with particulate matter sensors at home increases awareness of pollution exposures and can inform health-protective actions, yet little research explores the emotional dimensions of sensing, especially across economic divides. This study shows that participatory air quality sensing is not emotionally neutral. We included 26 parents of asthmatic children in 10 weeks of participatory sensing with indoor and outdoor sensors to understand their exposure experiences. Drawing from weekly surveys and postproject interviews, we found that sensors often generated positive emotions (e.g., empowered, happy) across income levels, underscoring their potential as inclusive tools for asthma management. Parents less often reported negative emotions (e.g., stress, worry); when they did, those were spurred from checking outdoor readings (versus indoor) because outdoor exposures were less controllable. Parents managed emotions by creating contingent boundaries between indoor and outdoor spaces. We recommend expanding access to sensors and air purifiers to promote individual-level environmental health benefits.

IntroductionRespiratory infections like influenza and SARS-CoV-2 pose significant global health risks due to their high transmissibility and severity. SARS-CoV-2 has caused over 7 million deaths worldwide, and the Lancet Commission estimates a >20% chance of a similar respiratory virus pandemic within a decade. Schools, often poorly ventilated, are high-risk settings for transmission. While COVID-19 school closures may have reduced transmission, they likely caused learning loss, mental health issues and increased burdens on parents and caregivers. Air purifiers with High Efficiency Particulate Air (HEPA) filters may offer a non-disruptive mitigation strategy, but the evidence to support their effectiveness in reducing viral transmission is weak. This protocol describes a cluster-randomised, parallel, two-arm, group sequential superiority trial with an interim analysis—to allow early stopping for efficacy or futility—to estimate the effect of portable air purifiers with HEPA filters in primary school classrooms on student absenteeism.Methods and analysisThis group sequential trial will randomise schools (clusters) 1:1 to intervention or control arms in two stages: winter 2025/2026 (N=32 schools; ~736 students) and winter 2026/2027 (N=30 schools; ~690 students). The study setting is Norway. Eligible schools must have classrooms suitable for portable air purifiers, >10 students in grades 5–7 (typically aged 10–13 years) and principal consent. Intervention and control classrooms will each receive two portable air purifiers with HEPA filters operating at a performance equivalent to 3.0 and 0.3 air changes per hour, respectively, with control purifiers acting as shams. Outcomes will be measured during and at the end of a 12-week period. The primary outcome is student absenteeism, measured as full child days of absence aggregated at the class level. An interim analysis is planned at the end of the first stage, with error-spending O’Brien-Fleming stopping boundaries that are binding for efficacy and non-binding for futility. The primary estimand is the marginal incidence rate ratio of student absences, estimated using generalised estimating equations with a negative binomial model to account for overdispersion. Prespecified stopping boundaries will determine stopping, with efficacy boundaries being binding. Treatment effects will be estimated using cluster-bootstrapped CIs adjusted to provide strong control on overall type I and II error probabilities, and a bias correction will be applied if the trial is stopped early for efficacy. All analyses will follow the intention-to-treat principle. The primary question is whether installing and operating air purifiers with HEPA filters (intervention) reduces student absenteeism due to sickness (primary outcome) compared with sham air purifiers (control). Secondary questions examine whether the intervention reduces teacher absenteeism due to respiratory infections, rate and 12-week risk of self-reported respiratory infections among teachers, and teachers’ perceptions of air quality, compared with sham air purifiers. If the trial estimates a statistically significant effect for the primary outcome, a cost-consequence analysis will evaluate the direct and indirect costs associated with operating air purifiers against the potential benefits of reduced student and teacher absenteeism. A process evaluation will explore mechanisms of effect.Ethics and disseminationThe trial has been approved by the Regional Committees for Medical and Health Research Ethics and the National Research Ethics Committee (ref. 737650). Absence data, routinely collected and fully anonymised at the class level, will serve as the primary outcome and does not require informed consent. Informed consent will be obtained from teachers participating in weekly surveys or interviews. Results will be disseminated to stakeholders, participants and the public through peer-reviewed journals, scientific meetings and social media.Trial registration numberNCT07119333.

Behavioral intentions toward air purifier adoption in Thai municipal offices for sustainable indoor air quality

Background: Secondary polycythemia involves elevated red blood cell mass due to increased erythropoietin (EPO) production in response to tissue hypoxia or other stimuli, distinct from primary forms driven by intrinsic myeloproliferative defects. Air pollution, a major global health hazard affecting 4.2 million deaths annually, impairs oxygen delivery via carbon monoxide (CO) and fine particulate matter (PM2.5), potentially triggering pathological erythrocytosis through hypoxia-mediated EPO upregulation. Objective: To synthesize evidence linking air pollution exposure to secondary polycythemia, encompassing mechanistic pathways, epidemiological data, clinical risks, and prevention strategies. Methods: Systematic narrative review of PubMed, Scopus, and Web of Science databases (2005–2025) using keywords: "air pollution," "PM2.5," "CO," "secondary polycythemia," "erythrocytosis," "hypoxia," "EPO," "thrombosis," and related terms. Thematic synthesis organized findings into pathophysiology, epidemiology, clinical outcomes, and preventive strategies. Results: PM2.5 exposure associates with erythrocytosis and thrombocytosis . CO-induced carboxyhemoglobin formation (200-fold affinity to hemoglobin) reduces functional oxygen delivery, mimicking chronic hypoxia and triggering HIF-2α-mediated EPO upregulation. Secondary inorganic aerosol constituents (ammonium, nitrate, sulfate) are primary drivers of PM2.5-associated polycythemia. Clinical complications include hyperviscosity (hematocrit >45%), thrombotic events (43% increased venous thromboembolism risk with PM2.5. Preventive interventions range from source-level emission controls to individual-level personal protective equipment (facemasks, HEPA air purifiers) and clinical phlebotomy. Conclusion: Air pollution drives secondary polycythemia via hypoxia-EPO pathways integrated with oxidative stress and systemic inflammation. Evidence supports urgent clinical vigilance in high-exposure populations and multisectoral public health action targeting emission reduction, population surveillance, and individual protection.

Wildland–urbaninterface (WUI) fires pose unique environmentalpollution challenges due to the combustion of both natural vegetationand synthetic building materials. Following the 2025 Palisades andEaton wildfires in Los Angeles, we conducted a field study to characterizeindoor air quality and surface contamination in 19 homes before reoccupancy.Indoor PM2.5 and PM10 concentrations averaged3.45 and 31.66 μg/m3, respectively, with severalhomes showing indoor-to-outdoor (I/O) ratios of >1 (particularlyforPM10) compared to typical I/O values of 0.45–0.8in residences, indicating persistent indoor particle reservoirs. Dependingon the air-exchange rate, elevated indoor PM levels in noncleanedhomes may arise from two contrasting mechanisms: low ventilation thattraps resuspended fire residues triggered by movements during samplingand high ventilation that induces turbulence and disturbs heavilycontaminated entry zones. Regression analysis suggested that proximityto the fire, absence of air purifiers, use of non-HEPA vacuums, andopen windows during the fire significantly increased indoor PM levels,explaining 73% (PM10) and 86% (PM2.5) of thevariation across homes. Airborne metal concentrations were below health-basedthresholds; however, surface wipe samples revealed widespread contamination,with potassium, magnesium, aluminum, and iron frequently exceeding1000 μg/ft2, and detectable levels of zinc, copper,and manganese in many homes. Lead concentrations exceeded the EPA’sdust clearance levels in multiple homes, especially on window sillsand entry floors. Our findings highlight that while airborne risksmay subside within weeks after the fire, indoor surfaces can retainfire-related pollutants, presenting ongoing exposure risks even 2months after the fire.

Abstract Effective control of airborne virus transmission is essential for preventing the spread of infection and mitigating health risks. Cruise ships are one of the public indoor spaces where SARS-CoV-2 infections have been significant, leading to extended quarantines. Commercial Air purifiers are available; however, depending on their technology, some are efficient at neutralising viruses, but at the same time, they can induce the production of ultrafine aerosol particles, which could be potentially harmful to health. In contrast, others might be less efficient in neutralising viruses, but do not trigger the formation of ultrafine particles. This pilot field study investigates, in real operational conditions, a commercially available air purifier (Airforte Ltd, Aero Quattro) directly integrated into the air ventilation system on board the cruise ship Viking Grace, which cruises between Turku, Finland, and Stockholm, Sweden, during 2022. The patented Aero Quattro air cleaning technology used in this pilot study comprises an active ionisation, two UV-C lights and two photocatalytic honeycomb-type flow laminar systems. The ultrafine aerosol particle size distribution and total aerosol particle concentration were measured online, allowing the measurement of ultrafine particle formation, if any. A non-pathogenic Phi6 surrogate virus was used to simulate the spread of SARS-CoV-2. Viable Phi6 viruses were nebulised inside the air ventilation system, passed through the Aero Quattro, and finally collected using biosampler, to then be offline analysed in the laboratory back on land. We demonstrate that under realistic operation conditions, the Aero Quattro, 1) does not induce the formation of ultrafine particles, 2) successfully eradicates the live Phi6 surrogate viruses within the detection limit. Although this pilot study was performed on a cruise ship air ventilation system under nominal operating conditions, integrating such an air purification system into various air ventilation systems could help restrain virus propagation in different public areas. Graphical Abstract

N6-methyladenosine-dependent mechanisms in PM2.5 cardiorespiratory impairment: A randomized, double-blind crossover trial of air purifier.

Abstract Background Sleep is essential for health and well-being, particularly among older adults. This study examines the associations between indoor air quality and sleep outcomes in older Chinese adults. Method We analyzed cross-sectional data from the 2018 Chinese Longitudinal Healthy Longevity Survey (CLHLS). Latent class analysis (LCA) identified ventilation patterns based on seasonal indoor air quality variations. Multiple linear and logistic regression models examined associations between ventilation patterns, air purifier use, home proximity to major roads, and sleep outcomes (quality and duration). Interaction effects between rural-urban residence and ventilation patterns were also assessed. Results Among 9,902 adults (≥65 years), three ventilation classes were identified: Moderate with Summer-Selective Ventilation (11.2%), Strong Year-Round Ventilation (70.3%), and Minimal Ventilation (18.7%). Older adults with Strong Year-Round Ventilation (OR = 1.16, p < 0.01) and Moderate with Summer-Selective Ventilation (OR = 1.19, p < 0.05) had significantly better sleep quality. After accounting for interactions, urban residents with Strong Year-Round Ventilation had significantly higher odds of good sleep quality (OR = 1.27, p < 0.05). Additionally, older adults with Strong Year-Round Ventilation slept 0.30 hours longer per day (p < 0.001). After interactions, urban older adults with Moderate with Summer-Selective Ventilation slept 0.46 hours longer per day (p < 0.01). Conclusion Indoor air quality, particularly ventilation patterns, is associated with sleep quality and duration among older adults in China. Improving indoor air quality may be an effective strategy to promote healthier sleep, particularly for older adults in urban settings.

Do-it-yourself air purifiers: Educator attitudes and perceptions in a K-12 public school district

Association between yellow dust, PM2.5, and hay fever: A large-scale crowdsourced observational study using the AllerSearch smartphone application.

In-hospital environmental surface and air contamination by monkeypox virus clade Ib in Germany.