A fully replicated human airway system is a new experimental tool that is overcoming limitations in studying aerosol deposition in lungs at UTHealth Houston School of Public Health.

The Mobile Aerosol Deposition Apparatus (MALDA), designed and 3D-printed by Wei-Chung Su, PhD, assistant professor of epidemiology, human genetics, and environmental sciences, consists of a head airway, tracheobronchial airways, and a representative section of the alveoli. The system is paired with two particle sizers that measure the particle size distribution of the aerosol of concern in human airways to study lung depositions of the harmful aerosol present in the community or workplace air.

“By further understanding the chemical composition of the aerosol, we will be able to estimate the inhalation dose of some toxic substances contained in the aerosol, then assess health risks for people who have occupational or environmental exposure,” says Su in a release.

Aerosol is solid or liquid particles that vary in size ranging from nanometers to micrometers and can suspend in the air for a long period of time. Those with a diameter of 10 microns or less (PM10), can come from the dust of construction sites, stone cutting, and spray painting, for example; while those with a diameter of 0.1 microns and less (ultrafine particles) can occur in the combustion of gasoline, diesel, or jet fuel. 

The inhalation and deposition of harmful aerosol in the respiratory tract can lead to various adverse health effects such as chronic obstructive pulmonary disease, pulmonary impairment, cardiovascular disease, and even lung cancer.

By placing the airway system and particle sizers on a lab trolley with a battery-powered vacuum pump, MALDA is fully mobile and capable of carrying out aerosol respiratory deposition experiments in any real-life environmental and occupational setting. MALDA can be used as a solution for aerosol-related health studies to gather on-site data where it may be impossible to collect human data.

“MALDA can provide useful experimental data for health research, especially for lung problems caused by aerosol exposure,” says Su in the release.

The comprehensive replicated human airways allow passage of air into the lung section called tracheobronchial airways which are identified by numerous airway bifurcations. The MALDA airways reach all the way to the 11th airway bifurcation, farther than many previous models that only extended as far as the fourth or fifth airway bifurcation. The extension in airway bifurcations allows Su and his research team to study aerosol respiratory deposition more accurately.

During his earlier research into occupational aerosol exposure, Su faced many critical limitations and began thinking about ways to improve aerosol respiratory deposition data acquisition. When he began working at the School of Public Health in 2016, he received a pilot research project award from the National Institute for Occupational Safety and Health that gave him the funds to design and 3D-print the MALDA in the UTHealth Houston 3D Printing Service Center. MALDA took nearly two years to build—from designing blueprints to performance evaluation to full assembly.

MALDA has already been applied to several environmental and occupational aerosol exposure studies to estimate aerosol respiratory depositions, including research on welding fumes, e-cigarette aerosol, community ultrafine particles, and aerosol generated from dental cleanings.

Su and his team are currently working on developing an upgraded MALDA experimental approach to efficiently obtain the deposited mass of aerosol in the human airways to estimate associated health risks.

Photo caption: Wei-Chung Su, PhD, center, works with Minjung Kim, left, a visiting student from National Seoul University, and Jinho Lee, right, PhD student at UTHealth Houston School of Public Health, to test MALDA in an industrial setting. 

Photo credit: UTHealth Houston