Submitted by Orman Language School team:

Sarah Adel Razek
Mohamed Badr Abdel Mohsen
Walaa Mahmoud Abdelmonem

Sponsor and Research Supervisor:

Dr. Abdel Hameed A. Awad
Researcher
Air Pollution Dept.
National Research Center
Dokki, Egypt

Abstract

Airborne dust, bacteria and fungi levels were determined inside four classrooms at Orman School building, Maadi, Cairo. Airborne dust was found at a mean value of 196 mg / m³ indoors whereas it was detected at a mean value of 361 mg / m³ outdoors. Airborne bacteria was recorded at a mean value of 3.51x10³ colony forming units (cfu) / m³. Gram positive bacteria were predominant indoors. These types indicate the need of more adequate ventilation. Fungi levels were recorded at a mean value of 3.03x10² cfu / m³ inside classrooms. Pencillium, Cladasporium, Aspergillus and Yeasts were dominant isolates.

Introduction

Many people spend more than 90% of their time indoors in tightly sealed, poorly ventilated places, schools and public buildings (Reijula 1996). Insufficient ventilation, dust and microorganisms are the main indoor problems (Husman 1996). Many studies on microbial contaminants in indoor air have been recorded by several investigators, in different environments such as hospitals (Gundermann 1974), schools (Camman et al 1980) and slaughter houses (Abdel Hameed 1996).

The inhalation of bioaerosols and dust disseminated from people and animal activities is a primary mechanism in respiratory infection. The exposure to airborne bacteria, fungi, mycotoxins and viruses causes potential biological hazard (Clark et al 1991).

The objective of the present study is to measure the quantities of airborne bacteria, fungi and suspended dust at the Orman School building, and to detect the types, percentages and aerodynamic diameter of bacterial and fungal isolate.

Materials and Methods

The school was investigated during spring season. Four classrooms were selected for the survey. Two classrooms were empty of students. In contrast, one class was the computer laboratory and the other was Kindergarten class.

Slit Sampler

Microbial Sampling

Air samples were collected using a Slit Sampler (Model TV P 818 N^o5587, CAEPAHO B CCCP), (Fig 1) at a flow rate of 25 L / m. The sampling periods ranged between 2 and 3 min. Tripticase soya agar and 3% malt extract agar (Dfco, Detroit, MI) media were used for the counting of total viable bacteria and fungi respectively. Bacteria plates were incubated at 35-37 ^oC. Fungi plates were incubated at 28 ^oC for 7 days.

Bacterial isolates were identified using Gram stain whereas fungi isolates were identified microscopically. The aerodynamic diameter (ad) of the bacterial and fungal species was calculated from density, shape and physical diameter (physical diameter measured microscopically).

Dust Sampling

The mass concentration of airborne dust in indoor and outdoor of the classrooms were collected on conditioned pre-weighed cellulose nitrate filter membrane (pore size 0.45 mm, diameter 25 mm), using an open face holder and sampling pump calibrated to draw 7 L m^-1. The filters were conditioned in a desiccator before weighing and the concentrations of airborne dust was calculated in mg m^-3. The filters were eluted in 5 ml phosphate buffer containing 0.01 v/v Tween 80 and shaken at room temperature for about 30 minutes. Total viable bacteria and fungi counts were measured as previously described.

Results and Discussion

Total viable bacterial counts ranged between 3.6x10³ to 7.14x10³ cfu / m³ with a mean value of 5.51x10³ cfu / m³ (Table 1). The higher bacterial count was detected in class 2 ( Kindergarten class) at a mean value of 6.9x10³ cfu / m³. This indicated that viable bacterial counts related to human activities. The results in the present study are in agreement with Austwick et al (1989) who found total viable bacteria at a mean value of 10³ cfu / m³ in office buildings.

Gram Positive bacteria (cocci and bacilli) were dominant indoors (Table 2). Tetrads, Bacilli, Micrococci and Staphylococci were detected in percentages of 33.3%, 16.7%, 16.7% and 13.9% respectively. Most bacteria indoors are shed from skin and oral activities. Staphylococcus epidermidis is abundant in indoor air (Flannigan 1992). Also, Gram Positive bacteria indicates overcrowding and inadequate ventilation (ACGIH 1989). In the present study, the total viable bacterial counted average in the range of 3.4x10³ to 10⁴ cfu / m³recommended for indoor environments. (Nevalainen 1989).

Fungi levels ranged between 2.20x10² to 4.65x10² cfu / m³ with a mean value of 3.03x10² cfu / m³ inside classrooms, (Table 1). The highest fungal level was recorded in a poorly ventilated classroom (classroom 3) at a mean value of 4.32x"0² cfu / m³. These results are in agreement with Abdel Hameed (1999) who found mold in the range of 4.5x10² and 8.20x10 ² cfu / m³ in homes. The mycological examination of 51 isolates is recorded in table 2. Penicillium, Aspergillus, Cadosporium and Yeasts were the predominant isolates. Alternaria, Rhizopus and Gunninghomella were also isolated. Aspergillus and Penicillium are normal indoors whereas Cladosporium and Alternaria are of outdoor origin (Miller 1992). Also, Penicillium, Aspergillus and Cladosporium are common in non problem houses (Ledford 1994).

Table 2 shows the aerodynamic diameter of the fungal and bacterial isolates. The aerodynamic size is a critical factor for evaluating respiratory exposure to fungal spores. Penicillium, Aspergillus and Cladosporium have aerodynamic diameters of less than 5mm (Table 2) and can enter the gas exchange tissue of the lung. In contrast, Alternaria, Rhizapus, and Gunninghamella have aerodynamic diameters greater than 5mm and may be deposited in the nasal region. Alveolitis is caused by any biological dust of a size smaller than 5mm (Husman 1996) as well as Aspergillus and Penicillium are toxigenic (Okudaira et al 1977).

Airborne dust levels ranged between 178 and 214 mg m^-3 indoor and varied between 357 and 365 mg m^-3 outdoor (Table 3). The bacterial laden dust was recorded at a mean value of 3.6x10⁷ cfu gm^-1 whereas fungi was detected at a mean value of 1.65x10⁶ cfu gm^-1. So, suspended dust is a nuisance to human health due to its carrying of large counts of b oindicators.

In the present study, low bioaerosols density does not mean a clean and healthful environment. The concentrations of less than 100 cfu m^-3 may be unhealthy to immunosuppressed people (ACGIH 1989). Gram Positive bacteria are predominant and indicated in overcrowding and inadequate ventilation. Cladosporium, Penicillium are aeroallergens and may elicit health effects in sensitive individuals, especially children.

Acknowledgment

We would like to express our deep thanks, sincere appreciation and gratitude to Dr. Abdelhameed A. Awad, Researcher, Air Pollution Dept., National Research Centre, Dokki, Egypt, for suggesting and planning the program of the work, sound supervision and viable advice.

References

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The Project Reviewers

Bernd Eggen, Amelia Irion, John Lovell, Brad Roscoe , Hossam El Badawy