Southwest Center for Occupational and Environmental Health

SWCOEH’s Wei-Chung Su, PhD, CIH, designs Mobile Aerosol Lung Deposition Apparatus (MALDA)

Houston (March 30, 2023) – Wei-Chung Su, PhD, CIH, the Interim Program Director of Industrial Hygiene for the Southwest Center for Occupational and Environmental Health (SWCOEH), has developed the Mobile Aerosol Lung Deposition Apparatus (MALDA), an experimental tool for the efficient and systematic study of aerosol respiratory deposition.

MALDA contains two systems: a human airway system (including a set of 3D-printed realistic human airway replicas) and an aerosol measurement system (with two units of aerosol particle sizer). By installing the two systems on a lab trolley with a vacuum pump, MALDA becomes mobile and can conduct aerosol respiratory deposition experiments in real-life settings outside the laboratory. MALDA is used to study occupational and environmental health exposures, including welding fumes, 3D printing emissions, and e-cigarette aerosols.

Dr. Su first thought of MALDA in 2016 after he joined the SWCOEH. He started to develop MALDA in 2017 after obtaining a research training award through the SWCOEH Pilot Projects Research Training Program. Currently, an NIEHS research grant supports the MALDA project.

“I learned from my past research experience that the traditional lung deposition experimental method requires significant time, and the experiment could only be carried out in the laboratory,” Dr. Su said. “To overcome this limitation, I believed it was possible to achieve efficient data acquisition by employing direct-reading aerosol. So, I built MALDA with realistic human airway replicas and portable aerosol particle sizers with battery-powered air pumps to enable automatic and efficient aerosol respiratory deposition measurements. MALDA allows conducting experiments in real-life settings.”

Su was joined by UTHealth Houston School of Public Health doctoral student Jinnho Lee, MPH, and Minjung Kim, MPH, a visiting student from Seoul National University, South Korea, to set up and calibrate the MALDA system for aerosol respiratory deposition studies on community exposure to ambient ultrafine particles. The experiment was conducted at an industrial area around east Houston in a Houston Health Department (HHD) air quality monitoring site.

“We know that different monitoring sites collect information on the air quality that populations in nearby communities are exposed to,” Dr. Su said. “Our initial data showed that ultrafine particles collected from the site close to the Houston Ship Channel and the industrial area contain relatively more heavy metals than other sites.”

Dr. Su is currently working to improve MALDA’s lung deposition data.

“I am currently in the process of developing a miniaturized temperature and humidity conditioner to be installed at the inlet of MALDA to adjust the air status of the air inhaled into the MALDA to 88 F and 99% RH. In this way, we could mimic the real condition in the human airways, which will improve further the accuracy of the MALDA’s lung deposition data.”

The collaboration between Dr. Su and Minjung Kim provided a unique addition to the testing materials.

“Minjung brought some mosquito incense from South Korea for conducting lung deposition studies using MADLA,” Dr. Su said. “Mosquito incense is a popular product in South Korea and in other Asian countries to repel mosquitos. But aerosol respiratory deposition caused by incense burning could induce potential respiratory effects such as irritation. Minjung’s study will inform us of the potential health risks for the population using those products.”

Research with MALDA continues with a new project in the Rio Grande Valley of Texas where Dr. Su’s team is studying indoor aerosol exposure for residents living in underserved neighborhoods. 

The SWCOEH provides graduate-level training opportunities for occupational and environmental health professionals through our industrial hygiene, occupational and environmental medicine, occupational epidemiology, and Total Worker Health^®.