Estimation of Respiratory Deposited Doses for Metals in Submicron Aerosol Using Mobile Aerosol Lung Deposition Apparatus (MALDA)

JINHO LEE, Inkyu Han, Masoud Afshar, Wei-Chung Su, University of Texas Health Science Center at Houston

     Abstract Number: 21
     Working Group: Health-Related Aerosols

Abstract
Submicron aerosol inevitably could be inhaled in human respiratory and the consequent deposition of submicron aerosol in the human’s lower airways could lead to adverse health effects. Hence, the exposure to submicron aerosol has been and continues to be an essential occupational and environmental health issue. To correctly estimate health risks caused by the exposure to submicron aerosol in the workplace and the environment, it is important to acquire aerosol respiratory deposition data and aerosol chemical composition in various environments. This study used a special approach that combines several aerosol characterization methods to estimate the respiratory deposited dose of selected metals contained in the submicron aerosol.

The aerosol particle size distribution was measured by NanoScan SMPS, the aerosol samples were collected by MOUDI, and the aerosol size-dependent metal composition was analyzed by ICP/MS. The critical aerosol respiratory deposition data were acquired by a newly developed human lung respiratory tract model, Mobile Aerosol Lung Deposition Apparatus (MALDA). The MALDA has 3D-printed human respiratory tracts (Head airway, Tracheobronchial airway, and Alveolar region) and can measure the deposition fraction of ultrafine particles in the human lung in a short time.

Based on the 1) size-dependent metal composition of particulate matter in the ambient air obtained from MOUDI and 2) size-dependent aerosol respiratory deposition fraction in head to TB airway and alveoli region obtained from MALDA, the respiratory deposited dose of aerosol was estimated. The experiment was carried out at an outdoor industrial section in Houston, Texas.

Results obtained showed that the hourly respiratory deposited dose of harmful metals contained in ambient submicron aerosol could be ideally estimated in the human head-to-TB airways and alveolar region. Over the half of the ultrafine particles of seven target metals (Cr, Ni, V, Mn, Cu, Pb, and Fe) were deposited in the alveolar region of MALDA (from 52.3% to 53.1%), and the hourly deposited dose was varied from 474.5 to 41,409.0 ng/hr. The deposited dose of metal was highest at the aerosol diameter of around 100 nm.

The deposited dose acquired in this study can be used to calculate the cumulative deposited dose due to prolonged aerosol exposure and then be further applied to estimate the associated health risks.