Airborne Bacteria in an Urban Environment

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Abstract
Samples were taken at random intervals over a 2 yr period from urban air and tested for viable bacteria. The number of bacteria in each sample was determined, and each organism isolated was identified by its morphological and biochemical characteristics. The number of bacteria found ranged from 0.013-1.88 organisms/l of air sampled. Representatives of 19 different genera were found in 21 samples. The most frequently isolated organisms and their percent of occurrence were Micrococcus (41%), Staphylococcus (11%) and Aerococcus (8%). The bacteria isolated were correlated with various weather and air pollution parameters using the Pearson product-moment correlation coefficient method. Statistically significant correlations were found between the number of viable bacteria isolated and the concentrations of NO (-0.45), NO2 (+0.43) and suspended particulate pollutants (+0.56). Calculated individually, the total number of Micrococcus, Aerococcus and Staphylococcus, number of rods and number of cocci isolated showed negative correlations with NO and positive correlations with NO2 and positive correlations with NO2 and particulates. Statistically significant positive correlations were found between the total number of rods isolated and the concentration of NO2 (+0.54) and the percent relative humidity (+0.43). The other parameters tested, SO2, hydrocarbons and temperature, showed no significant correlations.