A Model of Deposition of Hygroscopic Particles in the Human Lung

Exposure to airborne particulate matter is associated with a number of negative health effects ranging from respiratory diseases to systemic effects and cancer. One important factor for understanding the health effects is the individual variation in the respiratory tract deposition of inhaled particles. In this study, we describe an experimental set-up for size-resolved measurements of the lung deposited fraction of airborne particles, covering the diameter range from 15 to 5000 nm. The set-up includes a system for generating a stable aerosol with a sufficiently broad size distribution. We used a scanning mobility particle sizer and an aerodynamic particle sizer to determine particle number and size. The set-up was used to investigate individual differences in the deposition fraction (DF) of particles in the respiratory tract for a group of 67 subjects of both sexes aged 7-70 years. The measured DF was applied to two model aerosols, one representing an urban environment and one a rural environment, and the particle deposition rates were derived (i.e., the deposited amount of particles per unit time). Furthermore, the deposition rates were normalized to lung surface area and body mass -two dose measures that are considered relevant for the health effects of airborne particles. In addition to validation of the set-up, we show that there is a large individual variation in DF, with some subjects having a DF that is more than twice as high as that of others. Although we observe differences in the DF between different subgroups, most individual variation was explained neither by age nor by gender. When normalizing the deposition rates to lung surface area or body mass, the deposition rates of children become significantly higher than those of adults. Furthermore, the individual variability is larger for the lung surface area or body mass normalized deposition rates than for DF.

Section: Discussionsupporting

confidence: 48%

A Set-up for Respiratory Tract Deposition Efficiency Measurements (15-5000 nm) and First Results for a Group of Children and Adults

Rissler

Nicklasson

Gudmundsson³

et al. 2017

“…However, hygroscopic particles are typically dominant in the ambient environment (Asgharian, 2004;Montoya et al, 2004;Löndahl et al, 2009). To address this problem, we adjusted the ICRP curve for both hydrophobic and hygroscopic particles based on an assumption that particles generated from combustion sources (i.e., traffic emission or biomass burning) are nearly hydrophobic and inorganic/organic secondary aerosols are a mixture of less hygroscopic and more hygroscopic particles (Weingartner et al, 1997;Cruz and Pandis, 2000;Väkevä et al, 2002;Massling et al, 2005;Varutbangkul et al, 2006;Löndahl et al, 2009;Tritscher et al, 2011).…”

Section: Icrp Modelmentioning

confidence: 99%

Source Apportionment of the Lung Dose of Ambient Submicrometre Particulate Matter

Beddows

Delgado-Saborit

et al. 2016

Urban ambient aerosols have been of much concern in recent decades due to their effects upon both atmospheric processes and human health. This study aimed to apportion the sources of submicron particles measured at an urban background area in London and to identify which sources are most responsible for particles deposited in the human lung. Particle number size distributions (PNSD) measured by a Scanning Mobility Particle Sizer (TSI, USA), covering the size range of 16.5-604 nm at the London North Kensington background sampling site during 2012 were used in a Positive Matrix Factorization (PMF) model to apportion to six dominant sources of particles. These included local traffic emissions (26.6% by number), aged traffic emissions (29.9%), urban accumulation mode (28.3%), nucleation (6.5%), inorganic secondary aerosol (1.7%) and mixed secondary aerosol (6.9%). Based on the ICRP model, the total deposition efficiencies of submicron particles for the aforementioned sources in the human respiratory tract were 0.57, 0.41, 0.24, 0.62, 0.24 and 0.24, respectively. In terms of source apportionment of particles deposited in the lung, traffic emissions represent the main source of particles deposited by number in both the regional and total lung, accounting for 59 to 71% of total deposited particles, followed by regional accumulation mode (17%) and nucleation (10%) particles. Secondary aerosols only account for 5.1% of total deposited particles by number, but they represent the main source of particles deposited in the lung expressed as surface area (44.6%) and volume (72.3%) of total deposition. The urban accumulation mode contributes 27.3% and 17.3% of total deposited particles by surface area and volume, while traffic emissions contribute 26.6% and 9.7%, respectively. Nucleation contributes only 1.6% and 0.7% of total deposited particles by surface area and volume.

“…This growth may directly impact the site of deposition in the respiratory tract and the overall deposition in the airways. The model for hygroscopic growth was used in MPPD to include the effect of hygroscopic growth on deposition (Asgharian, 2004).…”

Section: Respiratory Tract Deposition Modelmentioning

confidence: 99%

Particle Size Distribution of Mainstream and Exhaled Cigarette Smoke and Predictive Deposition in Human Respiratory Tract

Sahu

Tiwari

Bhangare

et al. 2013

102

The particle size distribution of cigarette smoke is an important factor in predicting the deposition fraction of the inhaled particles in various regions of the respiratory tract. Mainstream cigarette smoke is a direct concern for smokers, while the exhaled and side stream smoke contribute to passive (second hand) smoking. The particle size distribution of tobacco smoke for mainstream and exhaled smoke has been studied in this work. This study investigates how smoking behavior, including puff volume and number of puffs, affect the particle size distribution of mainstream cigarette smoke. Scanning Mobility Particle Sizer (SMPS) was used to measure the particle size distribution of mainstream and exhaled cigarette smoke. The values of count median diameter (CMD) mobility size for the first four consecutive puffs were found to be 193 nm, 198 nm, 194 nm and 186 nm. As the volume of a puff increases from 35 mL to 85 mL, the CMD shifted slightly towards the higher particle size ranges, because of increased probability of coagulation and other combination processes. For the exhaled cigarette smoke, the growth factor was found to be 1.5 ± 0.3 with respect to mainstream cigarette smoke. The experimental results of particle size distributions were used in a Multiple Path Particle Dosimetry (MPPD) model to predict deposition patterns in the human respiratory tract. The MPPD model results show the deposition fractions for mainstream cigarette smoke were 0.163, 0.152 and 0.298 for the head, trachea and bronchi (TB) and pulmonary region, and those for exhaled cigarette smoke were 0.273, 0.064 and 0.134 respectively. The total calculated deposition fraction for mainstream and exhaled cigarette smoke was found to be 0.613 and 0.471, respectively.