WEST LAFAYETTE, Ind. — Do you know what’s in your carpet or on your floors? It might be frightening to think about. But consider this: During their first year of life, babies are crawling through not just the dirt down there, but also what scientists call “bio-gunk,” a new study finds.
These churning little bodies end up inhaling biological bits in their lungs at a rate that is, in relation to their body mass, four times what a walking adult would breathe in the same room. Researchers at Purdue University, however, say it could actually be a good thing. It seems counterintuitive, but moving through these clouds of bio-gunk — typically dirt, skin cells, bacteria, pollen, and fungal spores — may help babies develop stronger immune systems that resist asthma and allergies.
“We are interested in the biological material an infant inhales, especially during their first year of life when they are crawling. Many studies have shown that inhalation exposure to microbes and allergen-carrying particles in that portion of life plays a significant role in both the development of, and protection from, asthma and allergic diseases,” says Brandon Boor, an assistant professor of civil engineering and environmental and ecological engineering at Purdue, in a release. “There are studies that have shown that being exposed to a high diversity and concentration of biological materials may reduce the prevalence of asthma and allergies later in life.”
Scientists have previously studied how much dirt and biological material is stirred up into the air when adults walk through rooms, but this study is the first to consider the amount of dirt and debris babies agitate as they roll, slide and crawl their way from place to place. Although they cover shorter distances, their faces are much closer to the floor where the dirt and bio-gunk come in higher concentrations.
To figure out just how much gunk infants are mired in, the researchers built a robot with the likeness of crawling baby and tested it on carpet samples that had been used in homes. They measured and analyzed the particulates in the air of the crawling zone.
“We used state-of-the-art aerosol instrumentation to track the biological particles floating in the air around the infant in real-time, second-by-second. The instrument uses lasers to cause biological material to fluoresce. Most bacterial cells, fungal spores, and pollen particles are fluorescent, so they can be reliably distinguished from non-biological material in the air,” explains Boor. “We also worked with a microbiology group at Finland’s National Institute for Health and Welfare, which conducted DNA-based analysis of the microbes we collected onto filters.”
Researchers discovered that the storm cloud of dirt and bio-gunk hanging over the robotic babies is sometimes 20 times more concentrated than the air several feet up from the floor where walking adults would be breathing. Add to that, researchers say, the fact that infants do not have the same respiratory capabilities as adults to protect themselves against the dust storm.
“For an adult, a significant portion of the biological particles are removed in the upper respiratory system, in the nostrils and throat,” says Boor. “But for very young children, they more often breathe through their mouths, and a significant fraction is deposited in the lower airways—the tracheobronchial and pulmonary regions. The particles make it to the deepest regions of their lungs.”
Researchers say that as ominous as this sounds, it may be exactly the way nature intended. Since the late 1980s, the “hygiene hypothesis” has gained traction, which basically says that an overly sterile environment means an unchallenged and underdeveloped immune system.
“Exposure to certain bacterial and fungal species can result in the development of asthma,” adds Boor. “But numerous studies have shown that when an infant is exposed to a very high diversity of microbes, at a high concentration, they can have a lower rate of asthma later in life. Such exposures act to stimulate and challenge your immune system.”
Because most children in Western societies spend the bulk of their time indoors, breathing the air near the floor, there is ample opportunity for their respiratory systems to be tested by dust and bio-gunk. Researchers say this study provides new information, but there is more to be learned about the relationship between these early crawling exposures to microbes and respiratory health.
The study results were published Nov. 16, 2017, in the journal Environmental Science & Technology.
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