IDENTIFICATION AND ASSESMENT OF AIRBORNE BACTERIA IN SELECTED SCHOOL ENVIRONMENTS IN VISAKHAPATNAM, INDIA

Transcription

1 IDENTIFICATION AND ASSESMENT OF AIRBORNE BACTERIA IN SELECTED SCHOOL ENVIRONMENTS IN VISAKHAPATNAM, INDIA * K. Nirmala Kumari, Ch. M. Shravanthi and T. Byragi Reddy Department of Environmental Sciences, AUCST, Andhra University, Visakhapatnam, India *Author for Correspondence ABSTRACT Exposure to bioaerosols in indoor & outdoor environments has been linked to various adverse health effects such as airway disorders and upper respiratory tract symptoms. Schools are one of the critical social infrastructures in a society, and children are particularly at risk of lung damage and infection caused by poor air quality. Maintaining a healthy environment and, therefore, reducing disease transmission risk should inarguably be one of the key agendas in school operation. It is important to understand the microbial community within public areas and, in particular, in schools as poor health in children impacts on wider society. Outbreaks of infection can lead to closure of schools and parents taking time off work to care for them, thus impacting on the economy (Cauchemez et al., 2009). The air in almost all indoor locations contains microorganisms due to their ubiquity in the environment on and in human beings. The aim of this study was to assess exposure levels of bacterial aerosols in the school environment in Visakhapatnam, Andhra Pradesh. In this paper, we highlight the importance of airborne transmission of microorganisms in schools and the impact on children s health and wider economic and social implications. We propose the concept of air hygiene; measuring and assessing the level of bio aerosols emitted from human sources (primarily respiratory) can serve as a guide to indicate overall air quality, associated with airborne infections.the concentrations of bacterial aerosols were measured at four different schools in Visakhapatnam which includes two government schools & two private schools. The results from the present work indicated that Bacillus spp., Micrococcus spp., and Staphylococcus spp were the dominant bacterial genera. The paper summarizes and explores the peer-reviewed literature on bacterial air quality in schools, a field that is of increasing interest to the research community, educators and school facilities managers, and the public at large. The study also reveals the comparison of air borne bacterial concentrations among the four schools. We also observed specific allergens in classrooms at levels sufficient to affect sensitive occupants. Studies of health symptom associated with bacteriology in the classrooms are very rare, but taken with more general knowledge of IAQ, suggest that improved ventilation and targeted indoor pollutant source reductions could reduce certain occupant symptoms and improve the standard of health of the occupants. Key Words: Bioaerosols, Bacteria, Anderson s Sampler, Biochemical Test, Schools and CFU INTRODUCTION Bioaerosols are ubiquitous in the environment and include viruses, bacteria, fungi, pollen, plant or animal debris, as well as fragments and products of these organisms. Today, people spend almost 90% of their time indoors in variety of enclosed micro-environments (Klepeis et al., 2001; Leech et al., 1996). Children on a per-body-weight basis tend to inhale relatively more air than adults and elderly persons are more likely to have weak body defense systems. In addition, people with less immunity or with existing respiratory conditions, such as allergies and asthma are at increased risk of exposure to bioaerosols and their derivatives. Bioaerosols indoors are mainly of outdoor origin (Burge, 1990; Levetin et al., 1995). They enter through a range of avenues: heating ventilation and air conditioning system, doors, windows, cracks in the walls, attached to people and objects etc. Once in the indoor environment, a range of abiotic factors (water, humidity, temperature, nutrients, oxygen, and light) determines their growth. Among bacteria, Staphylococcus aureus the most important in terms of human health effects (Mentese et al. 2009). Bioaerosols can be found both outdoors and indoors (Mentese et al., 2012a). Therefore, it is important to study bioaerosols both indoors and outdoors. Factors such as human activities, geographic conditions, seasonal changes, meteorological parameters, type and extent of vegetation, and air pollution affect the composition and concentration of outdoor bioaerosols (Abdel Hameed et al., 2009; Nasir et al., 2012). On the other hand, air conditioning systems, ventilation, vegetation, resuspension of dust, indoor sources (the presence of people, kitchen, and bathroom), temperature and humidity are among the factors affecting the composition and concentration of indoor bioaerosols (Mentese et al., 2009, 2012b; Nasir et al., 2012; Ruzer and Harley 2012). Bioaerosols studies have been reported at office building, hospital, cave, calf house, public places, lake, recreation facilities, island, food stuff, school, flood sites and home etc. Some studies report the effect of meteorological parameters viz. temperature, humidity, wind velocity and wind direction on bioaerosols (Giorgio et al., 1995; Wang 21

2 et al., 2010). Though bioaerosols is an important area of research, it has not been very well attempted in India. Considering the importance of bioaerosols, this short-time study has been carried out which is first of its kind report from Visakhapatnam. The study was aimed to find out the concentration of culturable bacteria in air along with their Gram characterization. An attempt has also been made to correlate the concentration of bacteria with meteorological parameters. Total Airborne Bacteria Eight papers were found in scientific journals and conference proceedings in which measurements of airbornebacteria were reported (Bates and Mahaffy, 1996; Black and Worthan, 1995; Cousins and Collett, 1989; Gallup et al., 1993; Maroni et al., 1993; Meklin et al., 1996; Mouilleseaux et al., 1993; and Thorne, 1993). Typically, only one or afew schools were investigated often with no identification of bacterial species. The reported range varies over two orders of magnitude, from 7 colony forming units (CFU)/m3 to 19,500 CFU/m3. Occupant density and ventilation rates, strong determinants of total levels of airborne bacteria, were not reported in these studies. Morey (1984) suggested that concentrations above 1000 CFU/m3 indicate possible microbial contamination warranting further investigation. Health impacts The presence of airborne particles and microorganisms, their occurrence and behaviour in relation to each other with respect to size (μm [fungi, bacteria and actinomycetes] and nm [cellular fragments] scales) and aerodynamic properties allow them to be released at high numbers on site, but also potentially travel away from site, downwind. Bioaerosols are generally less than 10 μm in size and are therefore not filtered out by the hairs and specialized cells that line the nose. They can therefore penetrate deep into the lungs, causing both respiratory and gastro-intestinal symptoms (CIWM, 2002). Exposure to bioaerosols has been associated with human health effects and symptoms usually manifest inflammation of the respiratory system, coughs and fever and inhalation of bioaerosol may cause or exacerbate respiratory diseases. They have been also known to cause gastrointestinal illness, eye irritation and dermatitis. Organic Dust Toxic Syndrome (ODTS) is an acute disease, which results in symptoms resembling those of influenza, such as shivering, an increase in body temperature, dry cough, and muscle and joint pains (Rylander, 1997). Particularly relevant to waste management facilities are infections caused by Aspergillus fumigatus. Invasive aspergillosis is a particularly severe infection, which may be fatal and is primarily a concern with at risk and immuno-suppressed patients MATERIALS AND METHODS Sampling site Four schools were selected for the study, with different environmental status. Among them two schools are government schools (A.U school & Government primary school) and the other two schools are private schools (Kotak school & Pollocks school). A.U school &Kotak school were located at Chinna Waltair area & are very near (<500m) to the Beach of Visakhapatnam city,which are on the coastline of Bay of Bengal Government primary school &Pollocks school were located at Isukathota area little away( <2km) from beach area. Sampling was done at the locations of School entrance, Corridor, Assemblyhall and in class rooms at morning and afternoon hours (i.e in b/w a.m& p.m).each school is sampled twice in a month at alternate weeks and their average bacterial concentrations are represented seasonally. Collection and characterization of culturable airborne bacteria The sampling was carried out with an Andersen 6 stage viable impactor (Graseby-Andersen, Atlanta, USA). The samples were taken from living rooms and outdoors. The Andersen six stage viable particle sampler is a multiorifice cascade impactor, which collects and aerodynamically sizes all the particles regardless of their physical size, shape or density and can be related to human lung deposition. The sampler operates at a flow rate of 28.3 l/min with suction provided by a calibrated vacuum pump. The sampled air enters the inlet cone and cascades through the succeeding orifice stages with successively higher orifice velocities from stage 1 to stage 6. The particles were inertially impacted, according to their size, onto agar plates. The aerodynamic sizes of particles collected on each stage are: stage 1 (7μm & above), stage 2 (4.7μm - 7μm), stage 3 (3.3μm - 4.7μm), stage 4 (2.1μm - 3.3μm), stage 5 (1.1μm - 2.1μm) and stage 6 (0.65μm - 1.1μm). The six stages Andersen viable impactor has been widely used for the investigation of indoor and outdoor bioaerosols over many years due to its high collection efficiency and ability to preserve culturability during sampling (Reponen et al., 1994; Pastuszka et al., 2000; Hyvarinen et al., 2001; Meklin et al., 2002; Kim and Kim 2007). The impactor is designed so that all particles collected, regardless of physical size, shape, or density, are aerodynamically sized and can be directly related to human lung deposition. 22

3 The impactor was loaded with six Petri dishes containing Mannitol Salt Agar, Endo Agar, MacConkeyAgar, Pseudomonas Agar, EMB Agar, Bacillus Cereus Agar and Nutrient Agar prior to sampling. The Nutrient Agar was used for the total bacterial counts while, cultivation and enumeration of gram negative bacteria was carried out on the MacConkey agar. One sample was taken at each location and sampling was always carried out around noon at each location at the height of 1 meter. The sampling duration was 15 minutes and after collection the agar plates were incubated at 37ºC for hours for bacterial colony forming units. The number of colonies from each plate was enumerated and the total numbers of culturable colony forming units per cubic meter (CFU/m3) for all the stages made were calculated. After incubation, distinct individual colonies were picked up which were different in size, shape, colour, transparency, surface and elevation and further sub cultured on different agar plates to ensure that it was not contaminated with other colony. Gram staining was done by standard Gram staining protocol using Crystal violet, Iodine and Safran in for all sub cultured colonies. The bacterial genera were identified according to Bergey s Manualand biochemical tests (Kim et al. 2009, 2011).The measurements were carried out at each sampling location, for a minimum of half an hour in conjunction with bioaerosol sampling. The mean temperature and relative humidity was calculated for each site for both indoors and outdoors. RESULTS AND DISCUSSION In summer the airborne bacterial concentrations among the selected four schools ranged from cfu/m3 in School 1 ( lowest) cfu/m3 in School 3(highest). All the three schools ( cfu/m3, cfu/m3, cfu/m3) except school-4 (685.51cfu/m3) have shown higher outdoor bacterial levels during summer than their indoor bacterial concentrations. School-4 exceptionally showed higher indoor bacterial levels being cfu/m3. In rainy season the airborne bacterial concentrations ranged from cfu/m3 in school-3 (lowest) cfu/m3 in school-2 (highest). The outdoor the airborne bacterial concentrations of School-1, School-2, School-4 were cfu/m3, cfu/m3 & cfu/m3 which were comparatively very high than indoors cfu/m3, cfu/m3 & cfu/m3. Only school-3 exhibited higher indoor (826.85) cfu levels than outdoors (434.62). In winter season the airborne bacterial concentrations ranged from cfu/m3 in school-2 (lowest) in school-4 (highest). School 1 and School-2 showed higher indoor levels (i.e cfu/m3, cfu/m3) than outdoors ( cfu/m3, cfu/m3). While School-3 & School-4 were higher in terms of outdoor airborne bacterial levels cfu/m3, cfu/m3 than indoor levels cfu/m3 & cfu/m3 respectively. Sampling results of school 1 is presented in Table 1 and 2. Table 1: Sampling results of School 1 (Summer; March), Sampling Time 10Minutes, Flow rate 28.3 l/min Average number of Colonies CFU/m 3 S. No Media Used Indoor Outdoor Indoor Outdoor Dominant Genera 1 MSA S. aureus S. epidermis 2 Blood Agar Staphylococcus Streptococcus 3 Pseudomonas Pseudomonas sps 4 Mac-conkey Klebsiella 5 EMB Agar P.aureginosa 6 Nutrient Agar All bacteria Table 2: Sampling results of School - II (Summer; April),Sampling Time 10Minutes, Flow rate 28.3 l/min Average number of Colonies CFU/m 3 S. No. Media Used Indoor Outdoor Indoor Outdoor Dominant Genera 1 MSA Staphylococcus 2 Blood Agar S. aureus Streptococcus 3 Pseudomonas Pseudomonas sps 4 Mac-conkey Klebsiella 5 EMB Aga Enterobacter 6 Nutrient Agar All bacteria 23

4 The recommended maximum limits are: 1000 CFUs/m3 for the total number of bio-aerosol particles set by the National Institute of Occupational Safety and Health (NIOSH); The recommended indoor airborne bacterial levels set by American Conference of Governmental Industrial Hygienists (ACGIH) is (> 500 cfu/m3) and outdoor air level are 1000 CFUs/m3. On an average, we observed relatively higher values of bacteria (CFU/m3) in summer as compared to rainy and winter seasons. It could be due to suitable climatic conditions of tropical region as well as the local activities which can give rise to airborne bacteria. Humans on campus may be significant contributor of bacteria. Apart from these, warm weather of tropics, open waste disposal, cafeteria and vegetation etc. may also contribute bacteria in air. Another additional factor of contribution could be the soil dust coming out from construction of buildings in the surroundings of the site. The presence of suspended soil dust in air supports microbes. During rainy season the higher outdoor air borne bacteria levels may be higher due to open drainage networks present adjacent to the school buildings, geographical location and climatic conditions. The study also showed higher concentration of airborne bacteria during summer & monsoon season than in winter season. On an average, the percentage of Gram +ve bacteria was found higher than Gram ve bacteria during both the seasons. Among Gram +ve bacteria, mainly cocci dominate over rod shape bacteria. CONCLUSION The present work was among the very few studies evaluating bioaerosols both indoors and outdoors of four different school locations of Visakhapatnam city. It is advisable that strict measures should be put in place to check the increasing microbial load in the school environment. This is necessary, because school is a place where children go to promote their life, may serves as an avenue to contact diseases and diminish the children health. Due to higher concentration of viable counts of bacteria and lack of standard guidelines of those indoor contaminants in schools with respect to Indian conditions, it is strongly recommended that comprehensive exposure assessment program in schools is required in order to determine whether exposure of indoor air is able to cause risks in children; to set up standards/guidelines and permissible limits for the concentration of microbial community for schools environment. Since, assessment of airborne dust carrying both culturable and nonculturable microbial communities serve as a better indicator for managing and abating the contemporary health risks and also quality of indoor air. These preliminary results suggested carrying out further comprehensive studies on airborne bacteria at more number of sites and longer duration REFERENCES Abdel H & Awad A (2002). Environmental Study in Subway Metro Stations in Cairo, Egypt. Journal of Occupational Health, Bates JM & Mahaffy DJ (1996). Relationships of reported allergy symptoms, relative humidity and airborne biologicals in thirteen Florida classrooms. Proceedings of Indoor Air 96: The 7th International Conference on Indoor Air Quality and Climate, Nagoya, Japan Black MS & Worthan A (1995). Development of a school reoccupancy plan following evacuation due to IAQ complaints - A case study. Proceeding of the ASHRAE IAQ 95 Conference, Burge HA (1995). Bioaerosol investigations, In: Bioaerosols. Burge HA, Editions, Boca Raton, CRC Press, USA 123. Cauchemez S, Ferguson NM, Wachtel C, Tegnell A, Saour G, Duncan B & Nicoll A (2009). Closure of schools during an influenza pandemic. The Lancet Infectious Diseases, 9(8) CIWM (2002). Biological Techniques in Solid Waste Management and Land Remediation. Chartered Institution of Wastes Management, Northampton 69. Cousins DM & Collett CW (1989). Indoor air quality in 12 schools: A case study. Proceedings of ASHRAE Conference IAQ 87, The Human Equation: Health and Comfort, Gallup JM, Zanolli J & Olson L (1993). Airborne bacterial exposure: preliminary results of volumetric studies performed in office buildings, schools and homes in California. In: Proceedings of Indoor Air '93: The 6 th International Conference on Indoor Air Quality and Climate, Helsinki, Finland Giorgio CD, Krempff A, Guiraud H, Binder P, Tiret C & Dumenil G (1996). Atmospheric pollution by airborne microorganisms in the city of Marseilles. Atmospheric Environment, 30(1) Hyvarinen A, Vahteristo M, Meklin T, Jantunen M, Nevalainen A & Moschandreas D (2001). Temporal and spatial variation of fungal concentrations in indoor air. Aerosol 461 Science and Technology, Kim KY & Kim CN (2007). Airborne microbiological characteristics in public buildings of Korea. Building and Environment,

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