Indoor air quality assessment with respect to culturable airborne bacteria, total volatile organic compounds, formaldehyde, PM10, CO2, NO2, and O3 in underground subway stations and parking lots

We measured the concentrations of indoor pollutants (fine particulate matter (PM10)), culturable airborne bacteria (CAB), total volatile organic compounds (TVOCs), formaldehyde (HCHO), CO2, NO2, and O3 in subway stations and public parking lots at a national scale in South Korea in order to determine their possible relationships with other underground environmental factors and facility characteristics. Indoor pollutants were sampled at 59 underground facilities with a total of 187 samples in subway stations and parking lots. Kruskal–Wallis and Mann–Whitney analyses were used to examine the relationships between atmospheric pollutants at underground facilities and indoor/outdoor differences in PM10 and O3 concentrations. Underground PM10 concentrations were higher than outdoor concentrations at all underground facilities (p < 0.001), while underground O3 concentrations were lower than outdoor O3 concentrations at all underground facilities (p < 0.001).