Concentrations of Aerosol Numbers and Airborne Bacteria, and Temperature and Relative Humidity, and Their Interrelationships in a Tie-Stall Dairy Barn

SIMPLE SUMMARY: Aerosol particles are important elements of atmospheric pollution. Livestock barns are some of the most crucial anthropogenic sources of generation and emission of aerosol particles to the surrounding environment. Along with environmental pollution, these particles can cause numerous diseases in humans and animals. Besides causing diseases, these particles are said to have a significant role in the transmission of infectious diseases. Microorganisms that bind to aerosol particles are known as bioaerosols, which ultimately spread diseases in and between farms. Environmental factors such as temperatures (temp.) and relative humidity (RH) may have significant effects on aerosol particles and airborne bacteria. The present study was undertaken to find out which factors have more significant effects on the regulation of aerosol particles and airborne bacteria in the dairy environment. In the present study, we found that temperatures have profound effects on the regulation of aerosol numbers and various airborne bacteria. This temperature-dependent emission inventory of aerosol particles and various airborne bacteria will play a crucial factor in the mitigation of aerosol particles and various airborne bacteria in the dairy environment. ABSTRACT: Aerosol particles and airborne microorganisms are crucial factors of indoor air quality. The purpose of the present study was to evaluate the interrelationships among aerosol numbers, various types of airborne bacteria, temperature, and relative humidity (RH) to decide which parameters have more significant relationships among them. The concentrations of aerosol numbers, airborne total aerobic bacteria, Staphylococcus aureus (S. aureus), and Escherichia coli (E. coli) in the indoor air, as well as indoor and outdoor temperatures and RH, were assessed each week for a total of 20 days in a tie-stall dairy barn during the summer season in Tochigi, Japan. The mean concentrations of the fine aerosol numbers (0.3–2.0 µm) were greater than the mean concentrations of coarse aerosol numbers (5.0–10.0 µm). Among the airborne total aerobic bacteria, the mean concentration of airborne S. aureus was higher compared with airborne E. coli. More significant positive associations were found between outdoor environmental temperatures and aerosol numbers rather than indoor temperatures and aerosol numbers. All three types of airborne bacteria were associated with both outdoor and indoor environmental temperatures. These findings are crucial in the mitigation of aerosol numbers and airborne bacteria in the indoor air of dairy barns.