Physiochemical characteristics of aerosol particles in the typical microenvironment of hospital in Shanghai, China

Size distribution and relationship of airborne SARS-CoV-2 RNA to indoor aerosol in hospital ward environments

Aerosol particles proved to play a key role in airborne transmission of SARS-CoV-2 viruses. Therefore, their size-fractionated collection and analysis is invaluable. However, aerosol sampling in COVID departments is not straightforward, especially in the sub-500-nm size range. In this study, particle number concentrations were measured with high temporal resolution using an optical particle counter, and several 8 h daytime sample sets were collected simultaneously on gelatin filters with cascade impactors in two different hospital wards during both alpha and delta variants of concern periods. Due to the large number (152) of size-fractionated samples, SARS-CoV-2 RNA copies could be statistically analyzed over a wide range of aerosol particle diameters (70-10 µm). Our results revealed that SARS-CoV-2 RNA is most likely to exist in particles with 0.5-4 µm aerodynamic diameter, but also in ultrafine particles. Correlation analysis of particulate matter (PM) and RNA copies highlighted the importance of indoor medical activity. It was found that the daily maximum increment of PM mass concentration correlated the most with the number concentration of SARS-CoV-2 RNA in the corresponding size fractions. Our results suggest that particle resuspension from surrounding surfaces is an important source of SARS-CoV-2 RNA present in the air of hospital rooms.

Characteristics, non-carcinogenic risk assessment and prediction by HYSPLIT of bioaerosol released from Hospital and Municipal Sewage, China

Bioaerosol is a new type of pollutant, which is related to the spread of many diseases. In particular, the bioaerosol produced in the hospital sewage treatment process contains many pathogenic bacteria, which will impact patients and surrounding residents. In this study, the biochemical tank (BRT) of the hospital sewage treatment station (HSTS) and municipal wastewater treatment plant (MWTP) were used as sampling points. The results showed that the concentration of bacteria (1843 CFU/m³) in bioaerosol produced by BRT of HSTS was higher than that in the air at BRT of MWTP (1278 CFU/m³). The proportion of small-size bacteria (<3.3 µm) in the air of HSTS and MWTP was similar. However, the abundance of small-size pathogenic bacteria in HSTS was higher than that in MWTP, such as Acinetobacter and Arcobacter. The dominant bacteria in HSTS and MWTP were different under different particle sizes. The dominant bacterial genera of bioaerosol in HSTS under different particle sizes were similar (Acinetobacter, Arcobacter, Comamonas); There were significant differences in the dominant bacterial genera of bioaerosol in MWTP under different particle sizes. The dominant strains with particle sizes ranging from 0 ∼ 0.43 µm were Acinetobacter (23.22%). Kocuria (15.13%) accounted for a relatively high proportion in the aerosol of 0.43 µm ∼ 0.65 µm. The dominant strains with particle sizes of 0.65 µm ∼ 1.1 µm and 1.1 µm ∼ 2.1 µm were relatively single, and Exiguobacterium and Paenibacillus accounted for 51.51% and 60.15%, respectively. Source tracker showed that most of the pathogenic bacteria in bioaerosols came from sewage. One hour later, the concentration of particulate matter in the place 200 m away from BRT of HSTS (1 × 10^-10 mg/m³) was higher than that in MWTP (1 × 10^-11 mg/m³). The hazard quotient (HQ) of people around HSTS (HQ_male: 1.70 × 10^-1; HQ_female: 1.36 × 10^-1) was higher than that of MWTP (HQ_male: 1.18 × 10^-1; HQ_female: 9.40 × 10^-2). Pathogenic bacteria (Acinetobacter, Arcobacter) were detected in HSTS and MWTP and the BugBase phenotype prediction results showed potential pathogenicity. More attention should be paid to the protection of the people. It is suggested to strengthen the air sterilization treatment near HSTS according to the diffusion trajectory of bioaerosol, and the surrounding personnel should wear N95 and other protective masks.

Indoor Air Quality in Healthcare Units—A Systematic Literature Review Focusing Recent Research

The adequate assessment and management of indoor air quality in healthcare facilities is of utmost importance for patient safety and occupational health purposes. This study aims to identify the recent trends of research on the topic through a systematic literature review following the preferred reporting items for systematic reviews and meta-analyses (PRISMA) methodology. A total of 171 articles published in the period 2015–2020 were selected and analyzed. Results show that there is a worldwide growing research interest in this subject, dispersed in a wide variety of scientific journals. A textometric analysis using the IRaMuTeQ software revealed four clusters of topics in the sampled articles: physicochemical pollutants, design and management of infrastructures, environmental control measures, and microbiological contamination. The studies focus mainly on hospital facilities, but there is also research interest in primary care centers and dental clinics. The majority of the analyzed articles (85%) report experimental data, with the most frequently measured parameters being related to environmental quality (temperature and relative humidity), microbiological load, CO2 and particulate matter. Non-compliance with the WHO guidelines for indoor air quality is frequently reported. This study provides an overview of the recent literature on this topic, identifying promising lines of research to improve indoor air quality in healthcare facilities.

Evaluating size-fractioned indoor particulate matter in an urban hospital in Iran

Hospitals host vulnerable people with potentially enhanced sensitivity to air pollutants. We measured particulate matter (PM) including PM₁, PM_2.5, and PM₁₀ with a portable device in a hospital, a nearby reference building, and ambient air in Shiraz, Iran. Indoor/outdoor (I/O) ratio values were calculated to infer on the origin of size-fractioned PM. The mean hospital indoor concentrations of PM_2.5 and PM₁₀ (4.7 and 38.7 μg/m³, respectively) but not PM₁ were higher than in the reference building and lower than in ambient air. The highest hospital PM₁₀ mean concentrations were found in the radiotherapy ward (77.5 μg/m³) and radiology ward (70.4 μg/m³) while the lowest were found in the bone marrow transplantation (BMT) ward (18.5 μg/m³) and cardiac surgery ward (19.8 μg/m³). The highest PM_2.5 concentrations were found in the radiology (8.7 μg/m³) and orthopaedic wards (7.7 μg/m³) while the lowest were found in the BMT ward (2.8 μg/m³) and cardiac surgery ward (2.8 μg/m³). The I/O ratios and the timing of peak concentrations during the day (7 a.m. to 4 p.m.) indicated the main roles of outdoor air and human activity on the indoor levels. These suggest the need for mechanical ventilation with PM control for a better indoor air quality (IAQ) in the hospital.

Assessing the seasonality of occupancy number-associated CO2 level in a Taiwan hospital

This study enabled the assessment of indoor CO₂ levels and evaluated the relationship between occupancy numbers with CO₂ levels in a Taiwan hospital. The measurements were conducted over four seasons for five working days (Monday to Friday), with sampling conducted simultaneously from 09:00 am to 5:00 pm and across six locations (for spatial variability): hall (H), registration and cashier (RC), waiting area (WA), occupational therapy room (OT), physical therapy room (PT), and outdoors (O). Based on the analysis, three of the five indoor sampling sites showed significant differences in seasonal CO₂ concentrations (p < 0.0001). Based on our result, the physical therapy room had the highest level of CO₂ concentration that exceeded the IAQ standard in Taiwan Environmental Protection Agency (EPA) in all seasons, in that the number of occupants contributing to nearly 40% of the variation in CO₂ measured. Our results also showed that the indoor/outdoor (I/O) ratios of CO₂ concentration for all locations and seasons exceeded 1 in ~ 100% of those locations. The median I/O ratio at sites WA and OT was 2.37 and 2.08 during four seasons, respectively. The highest median I/O ratio was found at site PT, with a calculated range of 2.69 in spring to 3.90 in fall. The highest correlation of occupancy number and CO₂ concentration also occurred in PT which correlation coefficients were estimated at 0.47, 0.65, 0.63, and 0.40 in spring, summer, fall, and winter. The findings of the present study can be used to understand occupancy number and its effect on CO₂ levels in a hospital environment, as well as the effect of time of day (Monday to Friday) on the number of patients admitted.

Physiochemical characteristics of aerosol particles collected from the Jokhang Temple indoors and the implication to human exposure

This paper presents a detailed study on the indoor air pollution in the Jokahng Temple at Tibet Plateau, and its implication to human health. The mean concentrations of PM_1.0 and PM_2.5 were 435.0 ± 309.5 and 483.0 ± 284.9 μg/m³, respectively. The PM_2.5 concentration exceeded the National Ambient Air Quality Standard (75 μg/m³) by 6.4 times. The size-segregated aerosols displayed a bimodal distribution. One peak was observed in the fine mode (0.4-2.1 μm) and the other peak appeared in the coarse mode (2.1-9.0 μm). The concentration of the total size-resolved PM was 794.3 ± 84.9 μg/m³. The mass fraction of coarse particles shared by 41.1%, apparently higher than that reported at low altitudes, probably due to incomplete combustion at Tibet Plateau with hypoxic atmospheric environment. The total concentration of polycyclic aromatic hydrocarbons (PAHs) was 331.2 ± 60.3 ng/m³, in which the concentration of benzo(a)pyrene (BaP) was 18.5 ± 4.3 ng/m³, over ten times higher than the maximum permissible risk value of 1 ng/m³ on account of carcinogenic potency of particulate PAHs through inhalation. PAHs exhibited a trimodal distribution, of which two peaks were observed in the fine mode and one peak in the coarse mode. With the aromatic rings increasing, the peak intensity increased in the fine mode. Na, Ca, Al, Mg and K dominated the elemental mass profiles, and metals displayed a bimodal distribution with a dominant peak in the coarse range. The total PAH deposition flux was 123.6 and 53.1 ng/h for adults and children, respectively. Coarse particles contributed most deposition flux in the head region, while fine particles contribute most deposition flux in the alveolar region. The increment lifetime cancer risk (ILCR) of PAHs ranaged at 10^-5-10^-4, indicating potential cancer risk to human health. The total deposition flux of metals was estimated at 1.4-13.2 ng/h. With the size increasing, deposition flux increased in the head region while decreased in the alveolar region. The highest ILCR of Cr and Ni were 4.9 × 10^-5 and 1.5 × 10^-6, respectively, exceeding the permissible risk of 10^-6. The hazard quotient (HQ) of Fe (10^-5-10^-4) and Zn (10^-6-10^-5) were much lower than the safe level of 1.0, and thus they were not considered as a health concern.