Influence of temperature and humidity on the dynamics of aerosol numbers and airborne bacteria in a dairy calf house

Aerosols are essential indicators of indoor air quality in livestock houses. An investigation was conducted in a dairy calf house into the relationships between the concentration of aerosol number and the concentrations of the airborne aerobic bacteria, Staphylococcus aureus (S. aureus), Escherichia coli (E. coli), and Salmonella spp. examining their dependence on air temperature and relative humidity (RH). The aerosol number concentration and the concentrations of airborne aerobic bacteria, S. aureus, E. coli, and Salmonella spp. in the indoor air were monitored over 19 weeks, in Tochigi, Japan. A significant positive relationship was found between the concentration of airborne aerobic bacteria with aerosol sizes 0.3-5.0 um and 0.5-1.0 mu m and Salmonella spp. No relationship was found among the different sizes of aerosol concentration with airborne S. aureus or E. coli concentrations. The most significant positive relationships with temperature and RH were found with the 0.3-5.0 mu m aerosol size range. Aerosol sizes 5.0-10.0 mu m showed no associations with either air temperature or RH. Both airborne aerobic bacteria and S. aureus were strongly positively related to temperature. These findings will play a crucial role in elucidating the role of aerosols in the transmission of different types of airborne bacteria, and ultimately this could play an essential part in mitigating the influence of aerosols in the transmission of airborne bacteria in dairy houses. (C) 2020 IAgrE. Published by Elsevier Ltd. All rights reserved.