Infants have more microplastics in their faeces than adults, a study has found. Microplastics are plastic particles smaller than 5mm in size that have been released into the environment from the breakage of bigger plastic objects. They are a threat to the environment because they do not easily biodegrade, and recent research has found them in dust, food, fruit, bottled water and, as a result, animal and human faeces. Human exposure to microplastics is a possible health concern, but little is known about its extent. In a small study, researchers from New York University School of Medicine discovered that infants have 10 to 20 times higher microplastic concentrations in their stool than adults, specifically when it comes to PET (polyethylene terephthalate) microplastics. These are used mainly in the production of textile fibres, water bottles and mobile phone cases, for example. “Human exposure to microplastics is a health concern,” said Kurunthachalam Kannan, a professor in the paediatrics department at NYU Grossman School of Medicine and the lead researcher on the study. “We need to make efforts to reduce exposure in children. Children’s products should be made free of plastics.” The research is published in the American Chemical Society’s Environmental Science and Technology Letters. It has been estimated that the average person can ingest up to 5 grams of microplastic a week. Some of the microplastics pass seamlessly through the digestive system and are expelled in faeces, some microplastics are accumulated within bodily organs, and recent research has shown that some pieces cross cell membranes and enter the bloodstream. Other studies have shown generational transmission of microplastics from pregnant mothers to their baby’s placenta. Not much is known about how microplastics affect and possibly damage the human body, but some tests on laboratory animals have shown inflammation, cell shutdown and metabolic issues. By analysing the faeces of six infants and 10 adults, and three newborns’ first stool, through a method called mass spectrometry, Kannan and his team looked into human exposure to two common microplastics – PET and polycarbonate (PC). Every sample had at least one type of microplastic in it. The level of PC microplastics were roughly the same in adults and infants, but infants had 10 to 20 times higher levels of PET microplastics. “We were surprised to find higher levels in infants than adults, but later tried to understand various sources of exposure in infants,” Kannan said. “We found that infants’ mouthing behaviour, 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.” These findings are in line with those of other studies, albeit few, that have looked into microplastic contamination in human stools, said Scott Coffin, a research scientist at the California State Water Resources Control Board who was not involved in the research. If anything, these results suggest that current estimates of exposure to microplastics are likely underrepresentative, Coffin said, quoting the study he believes to be the most rigorous assessment to date, conducted by researchers at the Wageningen University and Research. “A component that is not accounted for in this study is the accumulation of microplastics into organs following exposure,” said Coffin. Excretion of all microplastics ingested is unlikely in humans, Coffin said, so the levels overall might be even higher. This, among many other details, is still to be ironed out in future studies. For example, there is a possibility of contamination during the experiment when dealing with faeces and microplastics (contamination from diapers, for example, or from the scientific equipment itself). Plus, the analytical method used to calculate the mass of microplastics in faeces is relatively uncommon, according to Coffin, and has not yet to his knowledge undergone robust validation. Overall, the exposure to and hazards of microplastics to humans are poorly understood, but Coffin said the study provided much-needed preliminary data.