Four Seasons Monitoring of Microbial Quality of the Sofia Urban Air

The microbiological quality of air in cities is crucial for the citizens’ health. The aim of present study was to assess the air’s microbiological quality in the capital of Bulgaria - Sofia for a period of nine months covering all four seasons. Five densely urbanized and of intensive car traffic points were monitored. The study started in September 2018 and ended in July 2019. Gravitation method using Nutrient agar and Sab¬ouraud dextrose agar was applied, and counting was performed using the Koch method. The results showed that the total number of microorganisms ranged between 1x1.8x102 - 3.6x104 CFU/m3. The total number of yeasts and molds was between 0-1.8x104 CFU/m3. The highest number of microorganisms was registered in winter and summer, due to the high humidity and dust particles content as carriers of bacteria, fungi, molds, and their spores in winter and favorable for the microbial growth temperatures in the summer, respective¬ly. Among the five monitored sampling points, according the total number of microorganisms, the most polluted were Eagles’ Bridge and BulBank, and for the yeasts and molds number - Borisova Garden and BulBank. Seasonally, the sampling point BulBank demonstrated highest microbial content in the air – at winter and summer while the lowest bacteria content was observed at New Bulgarian University sampling point - the very beginning of the autumn, at spring and in summer. Compared with results published by other researchers Sofia air is moderately contaminated with microorganisms. High microbial amount in the air is particularly dangerous for people suffering from chronic respiratory diseases, immunocompromised citizens, pregnant women, and children.