Ambient air particulate total lung deposited surface area (LDSA) levels in urban Europe.

This study aims to picture the phenomenology of urban ambient total lung deposited surface area (LDSA) (including head/throat (HA), tracheobronchial (TB), and alveolar (ALV) regions) based on multiple path particle dosimetry (MPPD) model during 2017-2019 period collected from urban background (UB, n = 15), traffic (TR, n = 6), suburban background (SUB, n = 4), and regional background (RB, n = 1) monitoring sites in Europe (25) and USA (1). Briefly, the spatial-temporal distribution characteristics of the deposition of LDSA, including diel, weekly, and seasonal patterns, were analyzed. Then, the relationship between LDSA and other air quality metrics at each monitoring site was investigated. The result showed that the peak concentrations of LDSA at UB and TR sites are commonly observed in the morning (06:00-8:00 UTC) and late evening (19:00-22:00 UTC), coinciding with traffic rush hours, biomass burning, and atmospheric stagnation periods. The only LDSA night-time peaks are observed on weekends. Due to the variability of emission sources and meteorology, the seasonal variability of the LDSA concentration revealed significant differences (p = 0.01) between the four seasons at all monitoring sites. Meanwhile, the correlations of LDSA with other pollutant metrics suggested that Aitken and accumulation mode particles play a significant role in the total LDSA concentration. The results also indicated that the main proportion of total LDSA is attributed to the ALV fraction (50 %), followed by the TB (34 %) and HA (16 %). Overall, this study provides valuable information of LDSA as a predictor in epidemiological studies and for the first time presenting total LDSA in a variety of European urban environments.

Effects of hygroscopic growth of ambient urban aerosol particles on their modelled regional and local deposition in healthy and COPD-compromised human respiratory system.

Total, regional and local deposition fractions of urban-type aerosol particles with diameters of 50, 75, 110 and 145 nm were modelled and studied in their dry state and after their hygroscopic growth using a Stochastic Lung Model and a Computational Fluid and Particle Dynamics method. Healthy subjects and patients with severe chronic obstructive pulmonary disease (COPD) were considered. The hygroscopic growth factors (HGFs) adopted were determined experimentally and represent a real urban-type environment. The hygroscopic growth of particles resulted in decrease of the deposition fractions in all major parts of the healthy respiratory system and the extent of the deposited fractions was rising monotonically with particle size. In the extrathoracic (ET) region, the relative decrease was between 7% and 13%. In the lungs the deposition decreased by 11-16%. The decrease of deposition fraction due to hygroscopic growth was more accentuated in the conductive airways (up to 25%) and less pronounced towards the terminal airways. The spatial distribution of the deposited particles remained highly inhomogeneous with some areas containing thousands times more particles than the average number of particles per unit surface area. For COPD patients, the hygroscopic growth produced similar deposition alterations in the ET region than for healthy subjects. In the conductive airways, however, the particle growth caused a substantial relative decrease in the deposition fractions. In contrast, the relative depositions of hygroscopic particles increased in the acinar region.