Chang Geun Lee, a PhD candidate in the Purdue University School of Health Sciences, holds a 3-D-printed head that wears a silicone face mask, which is used to “capture” heavy metal particles from welding fumes. (Tim Brouk)
Written by: Tim Brouk, tbrouk@purdue.edu mini welder
About the size of a standard kitchen oven, a shiny, cherry red steel box is the newest piece of equipment in the lab of Jae Hong Park, Purdue University School of Health Sciences associate professor. Numerous hoses and wires extend from the curious construction.
In recent years, the Aerosol Research Lab has focused on toxic particles found in the air at job sites where welding is done. Using samplers of his own design, Park and his students would take air samples from construction sites, factories and other facilities where the welding occurred. The researchers would usually find varying amounts of particles containing heavy metals such as manganese, chromium and iron, which are harmful to humans if inhaled.
Now, instead of taking the samplers, respirators and other pieces of equipment to manufacturing facilities to show the importance of wearing respirators to avoid breathing in toxic particles, the red steel box in Park’s lab does the job. Built by his PhD candidate Chang Geun Lee, he and Park can safely create their own toxic particles from fumes generated from welding inside the box. A glass window allows the researchers to see what they’re doing.
Fitted with thick protective leather gloves, the steel box contains a real welder’s gun and pieces of scrap metal. Wearing eye protection, the researchers must only weld for five minutes to generate enough fumes and particles to analyze using a chain of equipment attached to the box. Of course, welders are working for eight to 10 hours straight, often in a confined area.
“Most of the welders just wear (face) shields, not respirators,” said Lee, who had previously studied mechanical engineering before his time at Purdue. “We are testing a lot of different types of commercially available respirators to see how effectively they can reduce the exposure.”
The work so far has found that even wearing some face protection does not fully block out the potentially health-affecting particles. For example, exposure to manganese can lead to manganese toxicity, which can result in permanent neurological damage that includes tremors, difficulty walking and facial muscle spasms.
Before the researchers spark the welding gun, they place a 3D-printed human head into an adjacent, clear plastic box that captures the fumes blown in via a centrifugal fan from the welding box. The head is connected to equipment that can count and separate the particles by size, which reveals what heavy metal particles are made during a welding job and inhaled by the welder. Depending on what the researchers need, the head is fitted with various personal protective equipment (PPE), such as respirators and welding helmets, to evaluate their effectiveness in protecting the welder from breathing in harmful particles.
“We created this actual head model using the NIOSH (National Institute for Occupational Safety and Health) Anthropometric Digital Headforms so that it is an average size of the American workers’,” Lee explained. “The head has the actual nose and nostrils. So basically, he can breathe. He can inhale the welding fumes we generated here. In that way, we can compare the outside welding fume concentration and the amount deposited in the body. We can also test welding helmets or respirators. We can evaluate how much they can decrease the exposure to welding fumes.”
Lee has been testing not only inhalation exposure but also dermal exposure using the head replica. To simulate dermal exposure, he created thin artificial skin using silicone, which was designed to fit the faces of the 3D-printed heads. This allows him to analyze how particles stick to the artificial skin, closely replicating how particles adhere to human skin, especially around the nose and mouth. After particles are deposited onto the artificial skin, heavy metals are analyzed using an X-ray fluorescence machine in the lab.
“As you can imagine, the smaller size particles can be inhaled much easier,” Lee said. “Nanoparticles can be much more hazardous than other respirable particles because larger particles can still get out from your lungs by coughing.”
With the work funded by two NIOSH grants, Park and Lee found some top-of-the-line respirators do a good job in protecting workers from toxic fumes. However, some companies don’t invest in such equipment, opting for cheaper and less effective protection. The researchers also found most older welders prefer to not wear any kind of breathing protection while many younger welders do.
PPE manufacturers offer a wide variety of respirators. For example, 3M produces dozens of different respirators — ranging from a half-face respirator priced as low as $10 to hooded, heavy-industrial respirators that reach $2,000 or more. The respirators that feature built-in fans, known as powered air-purifying respirators, are considered the safest option. However, both workers and companies are often hesitant to use them because of their high cost and heavy weight.
“That is one of the hard, hard things when we are communicating with welders — those who have been welding for years typically resist wearing any respirators,” Lee said. “But we show them the actual welding fumes we collected on the (respirator) filter: ‘Hey, this can go into your lungs. You have to wear it.’
“Young welders, actually, are really happy to wear (respirators). We found out some have started to use advanced respirators with purifiers.”
The researchers recommend welders wear a combination of welding helmets and respirators.
Lee is set to graduate with his PhD in May after spending years in Park’s lab. A huge fan of heavy metal bands like Megadeth, Metallica and Slayer and performing in multiple bands in his native South Korea, he laughed at the irony of working with toxic heavy metals like nickel, copper and zinc. He expects to submit six papers from his toxic particles and aerosols research to journals for publication. Lee is especially proud of the many hours he’s put into improving the health of welders, even taking the time to learn how to weld properly. The work can inform companies on how to better protect their welders, both through personal protective equipment and ventilation systems within their facilities.
“We know of companies that are already working to improve their ventilation systems because of our reports,” Lee said. “They can also recommend or mandate their welders to wear a respirator because we proved the respirator is effective in reducing the welding fume exposure.”
Park said Lee’s impactful work proved high-end respirators improve the health of welders. Welding inside the box while testing numerous combinations of PPE, including welding helmets, masks and respirators, without leaving the lab was crucial in this work.
“What we are doing in our program, we are studying and applying the knowledge for protecting actual welders and other workers,” Park said. “He’s doing outstanding work because he’s like a principal investigator of these pilot projects. So, as a PhD student, he did an excellent job.”
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