An evidential example of airborne bacteria in a crowded, underground public concourse in Tokyo

Abstract

Abstract We examined airborne bacteria in an underground concourse in Tokyo and investigated conditions that influenced bacterial counts. Airborne bacteria were collected by using an impactor sampler. Colonies on plate count agar (PCA) and Columbia colistin–nalidixic acid agar with 5% sheep blood (CNA agar) were enumerated. The range, geometric mean, and 95% CI of the bacterial counts (CFU m−3) on PCA and CNA agar were 150–1380, 456, 382–550 and 50–990, 237, 182–309, respectively. Bacterial counts on PCA significantly correlated with number of the pedestrians (r=0.89), relative humidity (r=0.70) and airborne dust (PM5.0) (r=0.73). Results of a multiple regression indicated independent positive association between the number of pedestrians and bacterial counts on PCA (p