Atmospheric pollution by airborne microorganisms in the city of Marseilles

Outdoor airborne microflora was investigated in urban and natural areas, the city of Marseilles and the natural reserve of Porquerolles Island, respectively. In Marseilles, concentrations of airborne viable microorganisms averaged 791 ± 598 bacteria m−3 (with a geometric mean of 536 ± 103 bacteria m−3) and 92 ± 92 fungi m−3 (with a geometric mean of 63 ± 15 fungi m−3). In Porquerolles Island, concentrations of airborne microorganisms reached 42 ± 70 bacteria m−3 (with a geometric mean of 26 ± 7 bacteria m−3) and 46 + 55 fungi m−3 (with a geometric mean of 33 ± 8 fungi m−3). Airborne microflora, which increased a log-normal distribution in Marseilles, was shown to have a large variability. Airborne bacteria increased with temperature and wind velocity whereas airborne fungi increased with temperature and varied with wind direction in urban and natural areas. Partial identification of bacteria in Marseilles and Porquerolles Island showed that geographical location had qualitative as well as quantitative influence on airborne microflora, this was illustrated by an increase of global airborne microorganisms, and more particularly Gram negative bacteria, in the urban area.