Kosa (Asian duststorm) is a well-known phenomenon where particles are transported from Mongolia and northwestern China via Eastern Asia to the American continent. Kosa bioaerosols (airborne microorganisms within Kosa) were frequently found during Kosa event, and there is concern that they may affect human health. For biological observation and evaluation of Kosa events, we made sampling of aerosols in Kosa events on May 2 (KOSA1) and May 13 (KOSA2), 2011, at Kanazawa, Japan. From the data of lidar from Toyama, SPRINTARS simulation model and the backward trajectories of air masses, both events were originated in desert area of Mongolia. KOSA episode 1 was stronger than KOSA episode 2 above the surface boundary layer, and KOSA episode 2 contained the particles from the local source such as soil, sea salt, and various particles formed in the polluted atmosphere. The DNA to total suspended particle matter (SPM) ratios in KOSA1 and KOSA2 were 0.012 and 0.00978, respectively. Bacterial species compositions were identified qualitatively. Many Gammaproteobacteria were cloned and identified from both KOSA. Quantitative toxicity observations to assess the risk of food poisoning were performed by real-time PCR of food poisoning bacteria, Bacillus and Staphylococcus spp. The ratios of the concentrations of Bacillus and Staphylococcus spp. relative to SPM in KOSA1 and KOSA2 were 33.1 and 43.1 copies mu g-SPM-1, respectively. The results of toxicity evaluations by the mathematical simulations suggested that compared with KOSA1, KOSA2 had a 1.35 times higher risk of causing food poisoning.