Size distribution of protein aerosols in a megacity in Northwest China and their in silico deposition characteristics in the human respiratory tract

Abstract

Proteins in atmospheric aerosols are the major components causing allergic reactions in the human respiratory tract and they are an increasing concern for public health. However, the deposition characteristics of proteins in the respiratory tract remain unclear, which hinders a comprehensive understanding of their threat to human health. In this study, size-segregated aerosol samples were collected in Xi 'an, and the protein concentration was then determined using the bicinchoninic acid (BCA) assay. Concurrently, the total and regional deposition doses of proteins in different age groups (infants, children, adolescents and adults) were estimated using a multi-path particle dosimetry (MPPD, v.3.04) model. The results showed that the total deposition dose varied seasonally, and it was significantly higher in autumn and winter than in spring and summer. Moreover, across all seasons, the highest deposition doses were recorded in adults (10.82 × 10^–3, 9.35 × 10^–3, 17.98 × 10^–3, and 20.33 × 10⁻³ μg/min), while infants (1.84 × 10^–3, 1.58 × 10^–3, 3.14 × 10^–3 and 3.68 × 10⁻³ μg/min) had the lowest doses. For different regions of the respiratory tract, the deposition dose in the extra-thoracic (ET) region consistently exceeded that in the tracheobronchial (TB) and pulmonary (PUL) regions, and it increased with age. Especially during summer, the deposition dose in the ET region of adults was 9.8 times higher than that of infants. Notably, the proteins deposited in the TB region are rapidly removed, while half of proteins deposited in the PUL region would persist for more than 1 year. The findings of this study contribute to a better understanding of the health risks associated with ambient proteins.

Graphical abstract