Objective To investigate the concentration levels and particle size distribution characteristics of microorganisms in the air in large and medium-sized supermarkets in Wanzhou District, Chongqing, China, and to provide data support for normalized prevention and control of coronavirus disease 2019.
Methods According to Examination method for Public Places: Parts 1, 2, 3, and 6, we carried out site setting, sampling, field and laboratory testing.
Results The mass concentrations of PM10 and PM2.5 were significantly higher in winter than those in summer (P < 0.05). The mass concentrations of PM10 and PM2.5 in one of supermarkets both exceeded the standards in winter. The median of total number of bacteria in the air in summer was significantly higher than that in winter (458 CFU/m3 vs 147 CFU/m3, P < 0.05). The median of total number of fungi in the air was significantly higher in winter than that in summer (368 CFU/m3 vs 130 CFU/m3, P < 0.05). The particle size of microbial aerosols in the air was concentrated in the third to sixth grades of 0.65-4.7 μm, with the peak at the fifth grade. The concentration of bacterial aerosols in the air was positively correlated with temperature (correlation coefficient = 0.551, P < 0.05), and negatively correlated with PM10 and PM2.5 (correlation coefficient = -0.414, -0.413, P < 0.05). The fungal aerosol concentration in the air was negatively correlated with temperature (correlation coefficient = -0.301, P < 0.05), and positively correlated with PM10 and PM2.5 mass concentrations (correlation coefficient = 0.401, 0.398, P < 0.05).
Conclusion The microbial aerosol concentrations of large and medium-sized commercial supermarkets in the air in Wanzhou District are at a relatively clean level in summer and winter. The particle size of the microbial aerosols in the air is relatively small, with a possibility of causing lower respiratory tract diseases, which should be paid attention to.
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