Abstract
Numerous studies have focused on occupational and indoor environments because people spend more than 90% of their time in them. Nevertheless, air is the main source of bacteria in indoors, and outdoor exposure is also crucial. Worldwide studies have indicated that bacterial concentrations vary among different types of outdoor environments, with considerable seasonal variations as well. Conducting comprehensive monitoring of atmospheric aerosol concentrations is very important not only for environmental management but also for the assessment of the health impacts of air pollution. To our knowledge, this is the first study to present outdoor and seasonal changes of bioaerosol data regarding an urban area of Poland. This study aimed to characterize culturable bacteria populations present in outdoor air in Gliwice, Upper Silesia Region, Poland, over the course of four seasons (spring, summer, autumn and winter) through quantification and identification procedures. In this study, the samples of bioaerosol were collected using a six-stage Andersen cascade impactor (with aerodynamic cut-off diameters of 7.0, 4.7, 3.3, 2.1, 1.1 and 0.65 μm). Results showed that the concentration of airborne bacteria ranged from 4 CFU m−3, measured on one winter day, to a maximum equal to 669 CFU m−3 on a spring day. The average size of culturable bacterial aerosol over the study period was 199 CFU m−3. The maximal seasonally averaged concentration was found in the spring season and reached 306 CFU m−3, and the minimal seasonally averaged concentration was found in the winter 49 CFU m−3. The most prevalent bacteria found outdoors were gram-positive rods that form endospores. Statistically, the most important meteorological factors related to the viability of airborne bacteria were temperature and UV radiation. These results may contribute to the promotion and implementation of preventative public health programmes and the formulation of recommendations aimed at providing healthier outdoor environments.
Highlights
Conducting comprehensive monitoring of atmospheric aerosol concentrations is very important for environmental management and for the assessment of the health impacts of air pollution
We focused on culturable bacteria only because these micro-organisms are very sensitive to interaction with other air pollutants and seem to be highly influenced by various meteorological factors, including air temperature, relative humidity (RH) and wind speed, as well as UV radiation
The average concentration of the total bacterial aerosol collected in the outdoor air in Gliwice, over four seasons differed significantly
Summary
Conducting comprehensive monitoring of atmospheric aerosol concentrations is very important for environmental management and for the assessment of the health impacts of air pollution. An aerosol may be defined as a relatively time-stable twophase system consisting of finely divided particles (that can be solid or liquids) suspended in a gas (which is air). Biological particles suspended in the air may consist of bacteria, fungi, viruses and/or pollen, fragments of the above or their metabolic products (e.g. mycotoxins) and endotoxins (part of the outer membrane of the cell wall of gram-negative bacteria). Such particles may be suspended in the air either as individual organisms or attached to dust particles or tiny droplets of water (Adhikari et al 2006; Lighthart 1997). Bacteria and microscopic fungi cells are 0.3 to 100 lm and pollen, and other biological particles range from 10 lm up to even hundreds of micrometres (Haas et al 2010; Kołwzan et al 2005; Libudzisz et al 2008; Nevalainen et al 1993)
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