Modeling regional deposited dose of submicron aerosol particles Tareq Hussein a, b, ⁎, Jakob Löndahl c , Pauli Paasonen a, d , Antti Joonas Koivisto e , Tuukka Petäjä a , Kaarle Hämeri b, e , Markku Kulmala a a University of Helsinki, Department of Physics, P. O. Box 48, FI-00014 UHEL, Helsinki, Finland b The University of Jordan, Department of Physics, Amman 11942, Jordan c Lund University, Department of Design Sciences, PO Box 118, SE-221 00 Lund, Sweden d International Institute for Applied Systems Analysis, Schlossplatz 1, Laxenburg, A-2361, Austria e Finnish Institute of Occupational Health, Nanosafety Research Centre, Topeliuksenkatu 41a A, FI-00250 Helsinki, Finland HIGHLIGHTS • Modeling can accurately estimate deposited dose of aerosol particles in the respiratory system. • Hygroscopicity of inhaled particles is an important factor in calculations of deposited dose. • Most likely, adult males receive higher deposited dose than adult females. • The pulmonary/alveolar region received the largest fraction of the deposited dose. • The deposited dose received on workdays is high because the exposure level is high. abstract article info Article history: Received 22 January 2013 Received in revised form 4 April 2013 Accepted 8 April 2013 Available online xxxx Keywords: Activity pattern Hygroscopicity Particle number size distribution Particle number Particle mass Particle surface area We developed a simple model to calculate the regional deposited dose of submicron aerosol particles in the respiratory system. This model incorporates measured outdoor and modeled indoor particle number size distributions, detailed activity patterns of three age groups (teens, adults, and the elderly), semi-empirical estimation of the regional deposition fraction, hygroscopic properties of urban aerosols, and reported breathing minute volumes. We calculated the total and regional deposited dose based on three concentration metrics: particle number (PN), mass (PM), and surface area (PSA). The 24-h total deposited dose of fine particles in adult males was around 40 μg (57 × 109 particles, 8 × 102 mm 2 ) and 41 μg (40 × 109 particles, 8 × 102 mm 2 ) on workdays and weekends, respectively. The total and regional 24-h deposited dose based on any of the metrics was at most 1.5 times higher in males than in females. The deposited dose values in the other age groups were slightly different than in adults. Regardless of the particle size fraction or the deposited dose metric, the pulmonary/alveolar region received the largest fraction of the deposited dose. These values represent the lowest estimate of the deposited dose and they are expected to be higher in real-life conditions after considering indoor sources of aerosol particles and spatial variability of outdoor aerosols. This model can be extended to youngsters (b 12 years old) after gaining accurate information about the deposition fraction inside their respiratory system and their breathing pattern. This investigation is foreseen to bridge the gap between exposure and response in epidemiological studies. © 2013 Elsevier B.V. All rights reserved. 1. Introduction Air pollution can be in the form of gas phase or particulate matter that exists with sufficient amounts in the atmosphere leading to envi- ronmental impacts and health effects, which have been directly linked to the so called “deposited dose” (e.g. Anderson, 2009; Dockery et al., 2005; Lohmann and Feichter, 2005; Pope et al., 2002; Haywood and Boucher, 2000; Künzli et al., 2000; Jones, 1999). The deposited dose can be measured by monitoring the inhaled and exhaled particle concentrations. This method can be also extended to get an empirical estimation for the deposition patterns of aerosol particles in the respiratory system. In practice, the regional dose in the respiratory system is very difficult to be addressed experimentally. Therefore, the regional dose is typically estimated by means of mathe- matical models; the most widely available are the International Com- mission on Radiological Protection model (ICRP) and the multiple path particle dosimetry model (MPPD). To calculate the deposited dose with such models requires the exposure time and level, breathing characteristics, respiratory parameters, anatomy of the lungs, and physical–chemical properties of inhaled particles. Typically, the Science of the Total Environment 458-460 (2013) 140–149 ⁎ Corresponding author at: University of Helsinki, Department of Physics, P. O. Box 48, FI-00014 UHEL, Helsinki, Finland. Tel.: +358 9 19150709; fax: +358 9 19150860. E-mail address: tareq.hussein@helsinki.fi (T. Hussein). 0048-9697/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.scitotenv.2013.04.022 Contents lists available at SciVerse ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv