Scientists Find High Concentrations of Something Foul in Baby Poop: Microplastics

According to the journal Nature, scientists have found microplastics “everywhere they have looked,” from the bottom of the ocean to the bottom of your beer, from drinking water to rainwater, and from Arctic snow to Antarctic ice. Now, researchers at New York University’s Grossman School of Medicine have found them somewhere else that might surprise you: in baby poop.

In a study that appears this month in the journal Environmental Science & Technology Letters, published by the American Chemical Society (ACS), researchers say microplastics are prevalent in both adult and infant feces, but that the latter contain at least one type of microplastic in substantially higher concentrations.

Specifically, researchers analyzed fecal samples from six infants and 10 adults, as well as three samples of meconium (i.e., a newborn’s first stool). Using mass spectrometry, they determined in each sample the concentrations of polyethylene terephthalate (PET) and polycarbonate (PC)—two of the most common types of microplastics. While PC levels were similar in adult and infant feces, there was 10 to 20 times as much PET in the stools of infants compared to the stools of adults. Every single sample, including the three meconium samples, contained at least one type of microplastic.

“We were surprised to find higher levels in infants than adults, but later tried to understand various sources of exposure in infants,” the study’s lead author, Grossman School of Medicine professor Kurunthachalam Kannan, told British newspaper The Guardian. “We found that infants’ mouthing behavior, such as crawling on carpets and chewing on textiles, as well as various products used for children, including teethers, plastic toys, feeding bottles, utensils such as spoons … can all contribute to such exposure.”

Microplastics are tiny plastic fragments—less than 5 millimeters in length, or about a fifth of an inch—that result from the breakdown of larger plastics. While babies ingest them from things like toys, bottles, and teethers, adults commonly ingest them from products like water bottles and plastic food trays. In fact, last year a Nature Foods study found plastic baby bottles secreted large quantities of microplastics: bottle-fed infants were estimated to consume 1.5 million particles a day.

Whatever the source, scientists generally have assumed that microplastics exit the body after passing harmlessly through the digestive system. According to ACS, however, recent research suggests that the smallest microplastics can penetrate cell membranes and enter the bloodstream. In studies of cells and laboratory animals, that have been linked to cell death, inflammation, and metabolic disorders. In humans, however, ACS reports that “health effects, if any, are uncertain.”

Even if the human impacts of microplastics are uncertain, the environmental impacts are quite clear: In a December 2020 explainer on the topic, environmental health expert Leigh Shemitz and green chemist Paul Anastas—both of Yale University—said microplastics can injure wildlife.

“When a fish or invertebrate absorbs … microplastics by eating them, they can experience health problems such as a severe interference to or an abrasion with their digestive tracts, which can be fatal,” Shemitz said.

In a 2020 study in the journal Environmental Pollution, scientists estimate there could be as many as 125 trillion microplastic particles in the world’s oceans alone.

Back on land, Kannan acknowledges that little is known about the human impacts of microplastics, but advocates a conservative approach to microplastics in children’s products—just in case. He told The Guardian: “We need to make efforts to reduce exposure in children. Children’s products should be made free of plastics.”