Bioaerosols in public and tourist buses

Public bus system worldwide transports daily more than 34 million people; therefore, air quality inside buses is an important urban air pollution issue. Airborne microbiological composition and abundance was examined inside five different fuel type buses (diesel (EURO IV and EURO V), hybrid diesel (HD), compressed natural gas (CNG), hybrid natural gas (HCNG) and electric vehicle (EV)) from Barcelona bus system, inside and outside the tourist bus and different periods of campaigns (summer: May–September and winter: November–March). Quantitative PCR was used to quantify total bacteria, Penicillium/Aspergillus and Cladosporium sp. and Kinetic Chromogenic Limulus Amebocyte Lysate (LAL) Assay for endotoxins. The targeted 16S rRNA genes were amplified and sequenced to asses bacterial community composition and biodiversity. Regarding the targeted microorganisms, the results showed low bioaerosol concentrations, being fungi and endotoxins below the detection limit, although bacterial airborne has a geometric average of 10 3 equivalent E. Coli genomes/m 3 . Airborne bacterial community biodiversity showed that Actinobacteria and Proteobacteria were the most abundant Phylum in the different sampled buses and in the two seasons (summer: May–September and winter: November–March). While regarding to genera taxonomic category, the different fuel type buses presented a high overlap degree, being Cutibacterium the most abundant and Paracoccus the one only detected inside. The different seasons showed that the different taxonomic genera decrease from summer: May–September to winter: November–March and in this case Paracoccus was the most abundant. Overall, biodiversity inside buses is greatly affected by the presence of humans inside, but also by the outdoor sources at the moment of the sampling, and the seasonal period, more than the type of bus.