Backgrounds and aim: Ambient particulate matter (PM) is considered to be an important indicator of outdoor air quality. Many adverse health effects are associated with high concentration of particulate matter in ambient air. Exposure to pollution due to bioaerosols is an almost inescapable feature of urban living throughout the world. Exposure to ambient air microorganisms is associated with wide range of adverse health effects. The aim of the present study was to determine the concentration of particulate matter and airborne bacteria in Ahvaz ambient air and investigation of the environmental parameters effects on airborne bacteria concentration.

Materials and Methods: Air sampling for presence of bacteria was conducted using a microbial air sampler (Quick Take-30, SKC, USA). Tryptic Soy Agar which is a specific media for bacterial culture was used as a media. The number of cultivable bacteria on TSA media was counted using colony counter apparatus and was expressed as colony forming units per cubic meter (CFU m-3).

Results: The mean concentration of PM10, PM2.5, PM1 and airborne bacteria at four sampling sites were 149.35, 46.58, 25.6 µg/m3 and 446.67 CFU /m3, respectively. The highest concentration was observed in the Day month (21 December to 21 June). The lowest concentration was detected in Bahman (21 June to 21 February) month.

Conclusion: It was found that the more the human activities, the denser the urban environment, the lower vegetations, the higher the bacterial concentration, which bacterial concentrations have reverse relation with temperature and UV index.