Steam Disinfecting Baby Bottle Nipples Releases Micro-, Nanoplastics: Study

Some parents steam the silicon-rubber nipples of baby bottles to disinfect them, but the process can actually release micro- and nanoplastics, a team of researchers has found.

"Babies are the most sensitive group for any contaminants, not only microplastics (< 5 mm by definition)," the co-corresponding author of the study, Baoshan Xing, said in the news release from the University of Massachusetts Amherst (UMass Amherst). "Conventional techniques are unable to detect these small particles, and the smaller the particles, the larger the physiological effect."

The university noted that traditional techniques can't detect particles that are smaller than 20 micrometers, or about half the thickness of a human hair. For the study, published in the journal Nature Nanotechnology, the researchers collaborated with colleagues in China to have a closer look at the baby bottle teats using a "new and emerging technique" known as optical photothermal infrared (O-PTIR).

They used this technique to look at the surface of the silicone teats as well as the wash waters after steam disinfection. Sure enough, the process revealed "flake- or oil-film-shaped" micro- and nanoplastics that are as small as 0.6 micrometers in the wash waters of steam-disinfected nipples. Furthermore, they also found "submicrometre-resolved steam etching on and chemical modification of the teat surface."

"Silicone rubber was considered to be a thermally stable polymeric material in the past, but we noticed that it undergoes aging after repeated moist heat disinfection," study lead author, Yu su, said as per the news release.

"The results indicated that by the age of one   year, a baby could ingest >0.66 million elastomer-derived micro-sized plastics (MPs) (roughly 81% in 1.5 – 10  μ m)," the researchers wrote.

According to the researchers, the results highlight a new "entry route" for micro- and nanoplastics into the environment as well as in people's bodies. Although the full environmental and health risks of these small particles are unknown, there is "growing concern" over their possible impacts.

In 2020, for instance, a study found that bottle-fed babies consume "millions" of microplastics each day. Similarly, in a study published in September this year, researchers tested adults' and babies' feces and found that they all contained "at least one type of microplastic," with babies having 10 times higher PET concentrations on average compared to adults.

"Some plastics go into the sewer systems. They get into the water and landfills," Xing said, as per the news release. "They have such a long lifetime in the environment because they don't decompose readily."

The researchers noted that apart from the nipples of baby bottles, other products with such silicone-rubber material also "likely" produce micro- and nanoplastics when they're heated to above 100 degrees Celsius. This includes items such as bakeware and cooking appliances.

"The behaviors of these silicon rubber-derived micro- and nanoplastics in the environment are unclear," study corresponding-author, Rong Ji of Nanjing University said in the news release. "Further research is needed to clarify their potential risks to both humans and the environment."