Normal and dusty days comparison of culturable indoor airborne bacteria in Ahvaz, Iran

Abstract

Important sources of chemical and biological indoor pollutants include outdoor air, the human body and human activities, emission from materials, furnishings, appliances and use of commodities. The main purpose of this study was to identify culturable indoor airborne bacteria in normal and dust event days in indoor environments of a school, a hospital and a university in Ahvaz city, which individuals such as children, teenagers, adolescences and old people had activity there. Samples were collected using the biostage sampler, an Andersen-based method, with a flow rate of 28.3 l/min, from July 2010 to March 2011. Temperature and humidity were measured and registered in each time of sampling. The identification of bacteria was performed to genus level by using appropriate methods and standard biochemical tests. Gram-positive bacteria in both normal and dust event days with more than 90 % had the highest concentration and frequency. Predominant bacteria in normal and dust event days were Staphylococcus spp. (72.9, 87.9 %), Streptomyces spp. (60.9, 62.1 %), Bacillus spp. (94, 89 %) and Micrococcus spp. (65.4, 71.2 %), respectively. The highest concentrations of bacteria in normal and dust event days were in winter. The range of bacteria in normal and dust event days were 0–4,800 and 210–10,000 cfu/m3, respectively. There was a significant difference between the concentration of bacteria in normal and dust event days (p = 0.001) and also a significant association was found between the concentration of total bacteria with temperature and humidity (p < 0.05). The concentration of bacteria in dust event days was 1.8 times higher than normal days. Consequently, the concentrations of bacteria in all three sampling sites were higher in dust event days than normal days indicating the impact of dust storms on increased bacterial concentration in indoor environment.