Abstract

Introduction: Bioaerosol researches have broad potential to increase scientific understanding in various disciplines from climate change to our health. One example related to the health problem, tuberculosis is known as an airborne pathogen, which still causes early mortalities in many countries. In Japan, the number of patients with tuberculosis has been decreasing; however, the patients diagnosed with non tuberculous mycobacteriosis (NTM) tend to be increasing in Japan. The previous study indicated the highly polluted industrial region, the number of patients infected with Mycobacterium kansasii tends to be higher (Mimura, 2002; Yoshida et al., 2011); however, the detailed mechanism is not fully understood. In this study, we hypothesised that particulate matters might have an influencing factor for the bioaerosols to evade degradation process and survive in the atmosphere. This investigation tries to understand the influencing factor for the viability of bioaerosols together with different particulate matters in a laboratory setup. Methods: For the examination of the survival of bacterial bioaerosols, two chamber systems were employed. Figure 1 indicates a 128 L Teflon chamber system, which has an internal separator to divide two equal size compartments for the preparation of two different aerosolised materials before mixing them together. For the model bioaerosols, E. coli (DH5α) and Mycobacterium smegmatis (M. Smeg) were used as model bacteria to simulate the survival of bioaerosol under the different conditions. E. coli solution was prepared in phosphate buffer solution (PBS); the titre was adjusted to 108 to 109 colony forming unit (CFU) per ml. Similarly, M. smeg. titre was adjusted to 107 to 108 CFU was used together with PBS. The 128 L chamber was used for the E. coli bioaerosols experiments, and 17 L chamber was used for M. smegmatis experiments. For the particulate matters, we have examined the dust from coastal sludge, Gobi desert dust, and soot as environmental aerosols. Dryness and ultraviolet (UV) ray were used as stress factors to mimic the real environmental stresses. Conclusions: The result indicated that the co-existence of DH5α with desert dust from Mongolia significantly decreased the viability and with the coastal sludge dust from Japan significantly increased the viability of the airborne DH5α compare to the control PBS dust (p<0.05) under the dry stress condition. Furthermore, experiment with soot as a model air pollutant with M. Smeg indicated a possible evading effect from UV stress to increase the survival rate. Co-existing of different types of airborne particulate matter influenced the viability of airborne bacteria as bioaerosol in the laboratory measurements. This result indicated the possible mechanism of the bacterial bioaerosol to survive in the atmosphere for an extended period, which may have an important implication for the environmental health aspect of atmospheric science.