Indoor Airborne Research Articles

A comparative Study on Mycoflora of Different Care Units in Suez Canal University Hospital, Egypt

Air contains a large number of bacteria and fungi. Their assessment is critical as an indicator of contaminations for any particular environment. Inhalation of air fungal spores is considered a source of different fungal diseases, especially in immunocompromised patients. Therefore, this study aimed to compare concentrations and types of fungal species in both indoor and outdoor air of different intensive care units in a Suez Canal University Hospital. Samples were assessed twice monthly during one year from 2017-2018. Four units were investigated, Cardiothoracic Care Unit, Cardio Care Unit( CCU), Intensive Care Unit (ICU), and the Liver Intensive Care Unit. The results revealed that about 4097.26& 4534.75 colony forming units ( CFU ) were isolated from indoor and outdoor air respectively throughout the study, with a percentage of 20.2%, 27.5% from Cardiothoracic Care Unit, 31.9%, 17.1% from CCU, 17.9 %, 17.1% from ICU, and finally 29.7%, 38.20% from the Liver Intensive Care Unitfrom indoor and outdoor air respectively. The total airborne indoor and outdoor fungal load of the Cardiothoracic Care Unit was high 170.29CFU/m3 &249.11CFU/m3 during December and February respectively. The CCU isolated total fungal flora peaked high 274.8CFU/m3 and 209CFU/m3 indoor and outdoor respectively during November. Also, the total airborne indoor and outdoor fungal load of the ICU showed high counts of 170.5CFU/m3 & 209.8CFU/m3 during December and Novemberrespectively. The liver Intensive Care Unitindoor showed high counts during February 288 CFU/m3. Whereas, outdoor showed high counts during November 419 CFU/m3.

Study of the neurotoxicity of indoor airborne nanoparticles based on a 3D human blood-brain barrier chip

BackgroundThere is growing public awareness regarding the health effects of indoor nanoscale particulate matter (INPM) since people spend the majority of their time indoors. INPM could have a direct entry route into the brain via the axons of the olfactory nerve and migrating across the blood-brain barrier (BBB). Using animals to explore this possibility is not a reliable method to fully demonstrate human physiological responses. We, therefore, set out to develop a human 3D functional blood-brain barrier model to examine the potential effects of INPM on the cerebral nervous system. MethodsHuman astrocytes were co-cultured and human umbilical vein endothelial cells in 3D within a microfluidic chip to simulate the micro-complex physiological structure of the human BBB. This 3D human organotypic model has then been made to investigate any INPM-induced BBB dysfunction linked to potential cellular responses. ResultsA 3D human functional blood-brain barrier was constructed in this study. We observed the translocation of INPM across the blood-brain barrier. The 3D human organotypic chip initially reflected damage to the nervous system with abnormal astrocyte proliferation and a decline in cell viability. We also looked at the behavior of oxidative stress-related biomarkers (ROS, GSH-Px, and MDA). INPM was implicated in aggravating inflammation via reactive oxygen species (ROS). The Keap1-Nrf2-ARE pathway is a key mechanism in cellular resistance to oxidative stress by mediating and activating a variety of antioxidant and detoxification enzymes. Following ROS accumulation, INPM induced abnormal expression of nuclear transcription factor Nrf2. This behavior disturbed the expression of, γ-glutamate synthase (γ-GCS) and heme oxygenase (HO-1), which further exacerbated the imbalance of the antioxidant system. ConclusionsThis functional 3D human organotypic chip effectively mimics the physiological response of the human BBB. The chip provides a micro-complex structure to simulate the internal environment of the human blood-brain barrier, and partially simulates the physiological responses of the BBB to INPM exposure. Based on this model, INPM was shown to affect the blood-brain barrier biofunction by disrupting the Keap1-Nrf2-ARE pathways.

Management of Indoor Airborne Aspergillus flavus by Traditional Air Purifiers Commonly used in India

Management of Indoor Airborne Aspergillus flavus by Traditional Air Purifiers Commonly used in India

Indoor air filtration could lead to increased airborne endotoxin levels

Stand-alone portable air purifiers (APs) have become an increasingly popular method of controlling individual inhalation exposure. Exposure to bacterial endotoxins has a causative role in respiratory inhalation health. Here, we studied the changes in endotoxin levels in indoor air before and after purification by a portable AP equipped with HEPA (high-efficiency particulate air) filters. An increase in endotoxins was observed when a previously used AP was turned on to clean the air. Replacing the HEPA filters in the AP helped to mitigate the increase in endotoxins of larger sizes but not endotoxins of smaller sizes. Consequently, the use of APs could lead to increased endotoxin deposition in airways, especially in the alveolar region. The endotoxin concentrations on the HEPA filters were well correlated with the free DNA concentrations on the HEPA filters. This correlation indicates that the disrupted bacteria, which released free DNA, could also release endotoxins, thus making HEPA filters a source of indoor airborne endotoxins. Our results illustrate a potential endotoxin inhalation risk associated with HEPA-APs as an air cleaning strategy and highlight the importance of composition-specific air cleaning while reducing the particle number/mass.

Optimized determination of airborne tetracycline resistance genes in laboratory atmosphere

Antibiotic resistance genes (ARGs) have been detected in various atmospheric environments. Airborne ARGs transmission presents the public health threat. However, it is very difficult to quantify airborne ARGs because of the limited availability of collectable airborne particulate matter and the low biological content of samples. In this study, an optimized protocol for collecting and detecting airborne ARGs was presented. Experimental results showed that recovery efficiency tended to increase initially and then declined over time, and a range of 550–780 copies/mm2 of capture loading was recommended to ensure that the recovery efficiency is greater than 75%. As the cell walls were mechanically disrupted and nucleic acids were released, the buffer wash protects ARGs dissolution. Three ratios of buffer volume to membrane area in buffer wash were compared. The highest concentrations of airborne ARGs were detected with 1.4 µL/mm2 buffer wash. Furthermore, the majority of the cells were disrupted by an ultrasonication pretreatment (5 min), allowing the efficiency ARGs detection of airborne samples. While, extending the ultrasonication can disrupt cell structures and gene sequence was broken down into fragments. Therefore, this study could provide a theoretical basis for the efficient filter collection of airborne ARGs in different environments. An optimized sampling method was proposed that the buffer wash was 1.4 µL/mm2 and the ultrasonication duration was 5 min. The indoor airborne ARGs were examined in accordance with the improved protocol in two laboratories. The result demonstrated that airborne ARGs in an indoor laboratory atmosphere could pose the considerable health risk to inhabitants and we should pay attention to some complicated indoor air environment.

Indoor airborne phthalates in university campuses and exposure assessment

Phthalates are widely used as plasticizers in consumer products and are ubiquitous in indoor environments. Undergraduates spend a high amount of time indoors, however, little is known on the pollution characteristics and exposure to phthalates in indoor air in a university setting. In this study, passive air samplers measured the concentrations of phthalates in air from dormitories, classrooms, computer rooms, laboratories, and offices of a university in Beijing, China. A Monte-Carlo simulation was used to estimate the undergraduates’ exposure via inhalation based on air concentrations. Six phthalates were detected, including Dimethyl phthalate(DMP), Di (isobutyl) phthalate(DiBP), Di (n-butyl) phthalate(DnBP), Di (2-Methoxyethyl) phthalate(DMEP), Di (2-n-Butoxyethyl) phthalate(DBEP), and Di (2-ethylhexyl) phthalate(DEHP). Sampling rates of polyurethane foam (PUF) were obtained from a calibration study by co-deploying passive and active air samplers in offices and laboratories, and the average sampling rate was 0.62 ± 0.33 m3/day. DnBP and DMEP were the most abundant phthalates in total investigated environments at the university. DMP, DnBP, and DMEP air concentrations showed significant differences in different indoor environments (p < 0.05). All phthalate concentrations were not significantly different between the sunny sides and shadowy sides of rooms (p > 0.05). DMP concentrations were significantly different between male and female dormitories (p < 0.05). Correlation analysis suggests that DiBP, DnBP, and DMEP may originate from the same sources, while DBEP and DEHP may originate from a separate common source. The daily intake of phthalates via inhalation in dormitories is greater than in classrooms, except for DMP, which may lead to higher carcinogenic risks for undergraduates.

Assessing the relationship between surface levels of PM2.5 and PM10 particulate matter impact on COVID-19 in Milan, Italy

The novel coronavirus disease (COVID-19) is a highly pathogenic, transmittable and invasive pneumococcal disease caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), which emerged in December 2019 and January 2020 in Wuhan city, Hubei province, China and fast spread later on the middle of February 2020 in the Northern part of Italy and Europe.This study investigates the correlation between the degree of accelerated diffusion and lethality of COVID-19 and the surface air pollution in Milan metropolitan area, Lombardy region, Italy. Daily average concentrations of inhalable particulate matter (PM) in two size fractions PM2.5, PM10 and maxima PM10 ground level atmospheric pollutants together air quality and climate variables (daily average temperature, relative humidity, wind speed, atmospheric pressure field and Planetary Boundary Layer-PBL height) collected during 1 January–30 April 2020 were analyzed. In spite of being considered primarily transmitted by indoor bioaerosols droplets and infected surfaces, or direct human-to-human personal contacts, it seems that high levels of urban air pollution, weather and specific climate conditions have a significant impact on the increased rates of confirmed COVID-19 Total number, Daily New and Total Deaths cases, possible attributed not only to indoor but also to outdoor airborne bioaerosols distribution. Our analysis demonstrates the strong influence of daily averaged ground levels of particulate matter concentrations, positively associated with average surface air temperature and inversely related to air relative humidity on COVID-19 cases outbreak in Milan. Being a novel pandemic coronavirus (SARS-CoV-2) version, COVID-19 might be ongoing during summer conditions associated with higher temperatures and low humidity levels. Presently is not clear if this protein “spike” of the new coronavirus COVID-19 is involved through attachment mechanisms on indoor or outdoor airborne aerosols in the infectious agent transmission from a reservoir to a susceptible host in some agglomerated urban areas like Milan is.

Solutions to mitigate the impact of measurement noise on the air pollution source strength estimation in a multi-zone building

Indoor contaminants jeopardize people’s health and may even cause serious consequences under extreme conditions. Therefore, the prompt and accurate identification of indoor airborne contaminant characteristics is significant for indoor health and safety. In this paper, we used an inverse Markov chain model, combined with the regularization proposed in our previous research, to identify periodic source strength under steady airflow in a multi-zone building. The impact of different measurement noise (0.05%, 0.1%, 0.2%) on the inverse results was investigated. The results showed that the greater the noise, the greater the oscillation of the inverse result. Furthermore, we also investigated the effect of adjusting the calculation time step (5 s, 10 s, 20 s, 30 s) and adding digital filters (Sliding window filter and Butterworth low pass filter) on the inverse source release rate. The results showed that properly increasing the calculation time step can reduce the impact of measurement noise. The root mean square error (RMSE) of the inverse source strength with 0.1% noise decreased from 22.89 under a 5-s time step to 0.9793 under a 30-s time step. It was also found that adding digital filters could reduce the oscillation of the inverse source results, and the performance of the filters also depends on the calculation time steps.

Key parameters influencing the uptake of m-xylene on photocatalytic paints

Given the toxic nature of many volatile organic compounds (VOCs) present within indoor environments, it is necessary to develop new materials to eliminate them. Photocatalytic paints represent a promising technology to remove the indoor pollutants but they are not optimised yet. Here we evaluate the capacities of one conventional white-wall paint, three photocatalytic paints containing 3.5, 5.25 and 7% of nano-TiO2 PC 500, and two photocatalytic paints with a hybrid cellulose nanocrystals-nano-TiO2 (CNC-nano-TiO2) to eliminate m-xylene from the indoor environment. In particular, we assess the impact of nano-TiO2 content, light intensity, relative humidity (RH), surface temperature (288–320 K) and pigment volume concentration (PVC) on uptake of m-xylene. Uptake coefficients of m-xylene increase by a factor 3, 5 and 3, respectively, as a function of nano-TiO2 content, irradiance and PVC. In contrast, uptakes of m-xylene decrease for a factor of 2 and 3, as a function of RH, and surface, suppressing the photocatalytic activity. The addition of CNC-nano-TiO2 in the binder induces limited binder degradation. These are very promising results which may help to improve the performances of indoor photocatalytic paints aimed to eliminate indoor airborne pollutants.

Particle size, morphology and characterization of indoor and outdoor airborne particulate matter for toxic metals in Karachi

Rapid growth in industrialization and urbanization in Karachi draws attention toward increasing rate of air pollution and its health effects. So, the main objective of the present study was to determine the root cause of daily morbidity associated with airborne particulate matter (PM) exposure in Karachi. Other goal was to highlight those areas which are severely at the risk of particulate matter hazards. For this, high volume air sampler was used to collect PM from both indoor and outdoor air at commercial, residential and educational environments of Karachi. Effect of meteorological parameters on PM was also investigated. Heavy metals (Cd, Pb and Cu) concentrations in PM were determined by atomic absorption spectroscopy, while other elemental composition, morphology and size of PM were analyzed by scanning electron microscopy–energy-dispersive X-ray spectroscopy. The results revealed that PM particles consisted of O, Si, Ca, Cl, S, Na, C, Fe, Cd, Pb, Cu, Mg, Al, Zn, K and Ba. The morphologies of PM were spheroidal, irregular, fractal, narrow elongated, crystalline tabular and fiber like. The indoor and outdoor air at commercial sites (e.g., open markets) was not found suitable from health perspective. Especially, the area of Manghopir road has almost four times higher Pb concentration (1.879 µg/m3) than the WHO standard (0.5 µg/m3). The size range of particles in both outdoor (0.119–1.63 µm) and indoor (0.13–1.02 µm) settings existed in the category of PM2.5. Therefore, these fine particles with hazardous chemical composition and morphology are liable for daily morbidity of exposed population.

Assessment of Air Quality in School Environments in Hanoi, Vietnam: A Focus on Mass-Size Distribution and Elemental Composition of Indoor-Outdoor Ultrafine/Fine/Coarse Particles

Indoor and outdoor ultrafine, accumulation mode, and coarse fractions collected at two preschools (S1 and S2) in Hanoi capital, Vietnam were characterized in terms of mass-size distribution and elemental composition to identify major emission sources. The sampling campaigns were performed simultaneously indoors and outdoors over four consecutive weeks at each school. Indoor average concentrations of CO2 and CO at both schools were below the limit values recommended by American Society of Heating, Refrigerating and Air-Conditioning Engineers (1000 ppm for CO2) and World Health Organization (7 mg/m3 for CO). Indoor concentrations of PM2.5 and PM10 at S1 and S2 were strongly influenced by the presence of children and their activities indoors. The indoor average concentrations of PM2.5 and PM10 were 49.4 µg/m3 and 59.7 µg/m3 at S1, while those values at S2 were 7.9 and 10.8 µg/m3, respectively. Mass-size distribution of indoor and outdoor particles presented similar patterns, in which ultrafine particles accounted for around 15–20% wt/wt while fine particles (PM2.5) made up almost 80% wt/wt of PM10. PM2.5–10 did not display regular shapes while smaller factions tended to aggregate to form clusters with fine structures. Oxygen (O) was the most abundant element in all fractions, followed by carbon (C) for indoor and outdoor particles. O accounted for 36.2% (PM0.5–1) to 42.4% wt/wt (PM0.1) of indoor particles, while those figures for C were in the range of 14.5% (for PM0.1) to 18.1% (for PM1–2.5). Apart from O and C, mass proportion of other major and minor elements (Al, Ca, Cr, Fe , K, Mg, Si, Ti) could make up to 50%, whereas trace elements (As, Bi, Cd, Co, Cr, Cu, La, Mn, Mo, Ni, Pb, Rb, Sb, Se, Sn, Sr, and Zn) accounted for less than 0.5% of indoor and outdoor airborne particles. There were no significant indoor emission sources of trace and minor elements. Traffic significantly contributed to major and trace elements at S1 and S2.

Challenges on detection, identification and monitoring of indoor airborne chemical-biological agents

Potential chemical and biological (CB) attacks in indoor spaces pose specific challenges for prevention and preparedness. This paper summarises the conclusions obtained from the work conducted in the framework of the ERNCIP11The European Reference Network for Critical Infrastructure Protection (ERNCIP) is the Commission co-financed project coordinated by Joint Research Centre aiming at providing a framework within which experimental facilities and laboratories will share knowledge and expertise in order to harmonize test protocols throughout Europe, leading to better protection of critical infrastructures against all type of threats and hazards and to the creation of a single market for security solutions. Three of the working groups deal with CBRN threats: chemical and biological risks to drinking water; detection of indoor airborne chemical-biological agents and radiological and nuclear threats to critical infrastructure.. A thorough review of the existing and emerging technologies for CB detection, coupled with simulations of CB airborne dispersion in (critical) infrastructures to investigate the implementation of such sensors is presented. The conclusions include: (a) limitations of current sensor technology, (b) the effect of spatial variability of contamination within a building envelop on the effectiveness of such technology (c) the importance of early identification of both CB compounds for post-event mitigation.

Decreasing inhaled contaminant dose of a factory worker through a hybrid Emergency Ventilation System: Performance evaluation in worst-case scenario

Air pollution is detrimental to human health, causing several human illnesses. The industrial microenvironment generates high levels of indoor airborne pollutants, becoming a pervasive issue for workers. It is essential to improve the indoor air quality in this workplace by applying enhanced ventilation systems to minimize inhalation risk. Displacement ventilation is used in industrial buildings because of its stratified air distribution and low cost. However, in case of accidental pollutant release, an enhancement is needed to minimize inhalation exposure. This study proposes a hybrid emergency ventilation system using localized push-pull ventilation to improve the installed displacement ventilation system of a representative workshop. Computational fluid dynamics was applied to calculate steady-state indoor air flow and volume-averaged pollutant concentration. System performance was evaluated in terms of source position; a computer simulated person was integrated to the building to confirm effectiveness against personal inhalation. Results showed marked improvement in performance when push-pull technique was used: room-averaged concentration diminished up to 91% while ventilation rate only increased 4%. Inhaled pollutant mitigation was achieved but performance dependence against leakage source and personal position was confirmed.

Particle-induced oxidative damage by indoor size-segregated particulate matter from coal-burning homes in the Xuanwei lung cancer epidemic area, Yunnan Province, China

Size-segregated samples of airborne particulate matter were collected at the coal-burning homes of the Hutou high lung cancer epidemic village and a comparison site Xize village of the Xuanwei County, Yuanan Province, by an Anderson Cascade Impact Sampler in winter and spring to study the toxicological characteristics of different-sized particles. The DNA damage caused by the water-soluble fractions of these size-segregated particles was analyzed by the plasmid scission assay, and the trace element compositions were determined by Inductively Coupled Plasma Mass Spectrometry. The DNA damage rate from the airborne particles in the high lung cancer incidence area was higher than that in Xize village. The different-sized particles have highly varying DNA damage rates, with the values being greater in the small size range than in the large size range. The particle-induced DNA damage rates had a significantly positive correlation with total water-soluble trace elements. Further analysis of the individual elements indicated that the water-soluble heavy metals Zn, Cu, Cd, Rb, Cs, and Sb had a positive correlation with the particle-induced DNA damage, implying that these water-soluble heavy metals played an important role in the DNA damage. The Sr had a negative correlation with the particle-induced DNA damage, suggesting that the water-soluble Sr might counter DNA damage. The mass concentrations of the total and individual water-soluble trace elements were mostly enriched in the small particle size ranges, thus implying the indoor airborne particles in the small size ranges would have a higher health risk.

Morphological Characterization of Indoor Airborne Particles in Seven Primary Schools.

This paper focuses on a study of fine (less than 2.5 µm) airborne particles collected inside seven primary schools located on a coastal Mediterranean area which has a significant industrial hub for the processing of clays and other minerals as raw materials. Of the seven schools, three are located in an urban area 20 km away from the main industrial hub, three are in a town located next to the industrial estate, and one is in a rural location, 30 km from the industrial area. The objective of this study is to identify the main types of particles found in the three examined environments. The particle matter identified in the fine particle samples is grouped into three main groups: mineral compounds, particles from combustion processes and phases emitted in high-temperature industrial processes. The mineral particles, which can come from natural or anthropogenic emissions, have been classified depending on their morphology as isometric allotriomorphs or subidiomorphs, with a tabular habit; acicular forms; or pure crystalline forms. Compounds from combustion processes have two types of morphologies: spheroid and dendritic soot particles. Additionally, in smaller quantities, spherical particles associated with high-temperature industrial processes, such as the emissions of ceramic tile-firing and frit-melting processes, are identified. A summary table is shown, which lists the characteristics, as well as the most significant origin of the main particles identified in the fine (<2.5 μm) airborne particles collected inside primary schools located in three different environments (urban, industrial and rural). A visual scale has been established based on the number of particles observed in the samples of the atmospheric particulate fraction between the sizes of 2.5 and 10 µm collected inside the schools. The ratios Ca/Si, S/Si, S/Ca and (Si+Ca)/S have been established. Results obtained may be useful in epidemiological studies in the ceramic cluster area in order to estimate children’s exposure to different indoor primary school microenvironments. Effective policies and mitigation measurements for the protection of children’s health should be carried out in this highly industrialized area.

Characteristics of airborne bacterial communities in indoor and outdoor environments during continuous haze events in Beijing: Implications for health care

There is solid evidence that haze pollution threatens human health owing to the abiotic pollutants it contains. However, the characteristics of airborne bacterial communities in indoor and outdoor environments exhibiting haze occurrence are still unknown. Thus, we examined variations in both indoor and outdoor airborne bacterial communities in Beijing from December 9–27, 2016, a period which included three haze events. The outdoor airborne bacterial communities were clustered into two main groups (Groups I and II), and they shifted between two typical bacterial communities regardless of the haze event. The Chao1, Shannon, and phylogenetic diversity indexes and abundance of dominant classes changed significantly, as did airborne bacterial community type. The indoor airborne bacterial community closely tracked the outdoor bacterial community type, forming two obvious groups supported by Adonis analysis, changes in dominant classes, and bacterial diversity compared to the outdoor group. Furthermore, we found that the airborne bacterial community type could affect the morbidity of respiratory diseases. Daily pneumonia cases were significantly higher in Group I (p = 0.035), whereas daily amygdalitis cases were significantly higher in Group II (p = 0.025). Interestingly, the enriched classes in the indoor environment were quite different from those in the typical airborne bacterial community environment, except for Clostridia, which had significantly higher abundance in both indoor environments. In conclusion, we found that the two indoor and outdoor airborne bacterial community types changed independently of haze events, and the special airborne bacterial community type was closely related to the incidence of pneumonia in the heavy haze season.

Airborne phthalates in indoor environment: Partition state and influential built environmental conditions

Exposure to phthalates has recently become a major public health concern. The information of indoor airborne phthalates and their air-particle partition in real indoor environmental condition is still limited. In this study, the gas- and PM2.5-concentrations of 7 phthalates in 40 residences were concurrently measured in summer and winter. The major phthalates (median concentration in the summer and winter, respectively) in indoor air were DMP (2442.3 and 2403.4 ng/m3), DiBP (801.0 and 640.0 ng/m3) and DnBP (5173.2 and 1379.6 ng/m3), whereas the major phthalates in PM2.5 were DiBP (1055.1 and 585.9 ng/m3) and DnBP (1658.5 and 1517.0 ng/m3) and DEHP (215.1 and 344.9 ng/m3). Air-PM2.5 partition coefficients (Kp) of DiBP, DnBP and DEHP were calculated: the summer and winter median values (m3/μg) were 0.053 and 0.011 for DiBP, 0.010 and 0.004 for DnBP, 0.021 and 0.025 for DEHP, respectively. Air-PM2.5 partition of DiBP and DnBP approached equilibrium, while that of DEHP did not reach equilibrium in either season. The impacts of built environmental conditions on phthalate concentrations were characterized. Elevated temperature resulted in accumulation of airborne phthalates. Higher air humidity led to more water absorption of aerosols in summer, facilitated mass transfer of phthalates from air to PM2.5, and resulted in greater Kp of DiBP and DnBP in the summer. Any factors such as proximity to local traffic highway and indoor smoking activities, which can increase indoor PM2.5 concentrations, resulted in significantly higher airborne phthalate concentrations. Improving ventilation was not an effective measure to reduce indoor airborne phthalate concentrations.

Coronavirus and Environmental Engineering Science

Coronavirus and Environmental Engineering Science

Application of exogenous indole-3-acetic acid on shoots of Zamioculcas zamiifolia for enhancing toluene and formaldehyde removal

Indoor air pollution is of increasing concern for human health. Amongst the volatile organic compounds (VOCs) found indoors, formaldehyde and toluene are two toxic compounds. Indoor plants have an innate capability to remediate indoor airborne pollutants. Zamioculcas zamiifolia is an ornamental plant local to Thailand reported to be very efficient for VOC removal. Indole acetic acid (IAA) was applied to shoots and roots of Z. zamiifolia to enhance the capability for removing a toluene and formaldehyde mixture. We found that 5 μM of exogenous IAA can enhance Z. zamiifolia efficiency about 20% and 40% for toluene and formaldehyde, respectively, after plant was exposed to initial toluene-formaldehyde mixture concentration 20 ppm (1:1) for 3 cycles (156 h). We found that 5 μM of exogenous IAA had a positive effect on the stomatal aperture opening and stomatal conductance. However, 10 μM of exogenous IAA had a negative effect on the opening of stomatal aperture, and thus initially decreased that remediating ability of Z. zamiifolia for formaldehyde and toluene. We investigated the formaldehyde dehydrogenase activity in shoots of Z. zamiifolia and found significantly enhanced FDH activity in plants supplied with exogenous IAA. We concluded that exogenous IAA in optimum amounts could enhance the mitigating ability of indoor plants for airborne air pollutants. However, our research indicated that the application of IAA to roots could have a negative effect on the remediating ability of Z. zamiifolia.

CORRELATION ANALYSIS BETWEEN INDOOR AIRBORNE BACTERIAL LOAD AND OCCUPANT DENSITY IN HOSPITAL INDOOR AIR

A study of the quantity and types of airborne bacteria and its correlation with human presence was conducted. Air samples were collected from different units for three days and three sessions (morning, afternoon and evening) for the enumeration and identification of bacterial isolates. Walk-through exercise was also conducted prior to every sampling to gather information on the number of occupants present, activities going on, and room characteristics. Isolation study revealed higher bacterial load in the afternoon and evening sessions; with Male Ward and Operating Theatre recording the highest and lowest bacterial loads respectively, as compared to the morning session that was done immediately after cleaning and before influx of people. The Spearman’s Correlation Coefficient showed a positively direct linear correlation between the bacterial load and occupant population irrespective of the three sessions (r = 0.84, 0.88 and 0.93). Identification study showed that the isolates are representatives of normal microflora of the skin, respiratory and gastro-intestinal tracts which includes the following; Staphylococcus aureus, Staphylococcus epidermidis, Micrococcus roseus, Klebsiella pneumoniae, Proteus mirabilis, Bacillus subtilis, Aspergillus, Penicillium, Mucor, Candida and Fusarium species. The study presents evidence of increased concentration of indoor airborne bacteria due to human presence, movement and activities.