Traffic-related PM2.5 aerosol in residential houses located near major highways: Indoor versus outdoor concentrations

PM2.5 mass concentration and its elemental composition were measured inside and outside of six houses located at a distance of approximately 30–300 m from major highways. To investigate the amount of traffic particles penetrating from indoor to the outdoor (I/O) environment, the data were analyzed by three-way factor method PARAFAC. The PM2.5 I/O ratio ranged from 0.5 ± 0.2 to 2.9 ± 1.2 in spring and from 0.7 ± 0.1 to 4.7 ± 6.9 in fall. The traffic component was very pronounced in the ambient air of the six houses. Although the distance from the highway and traffic intensity are generally important for assessing the indoor concentration of traffic-related aerosols, the data collected in this study suggest that – specifically for houses located in a close proximity to major highways – these two factors may not necessarily play the most important role in differentiating exposure levels between houses.