Microplastics aren't on the USDA's food pyramid, but maybe they should be. We're certainly consuming enough of them to merit a mention.
Research led by Kieran Cox at the University of Victoria in Canada found that, on average, we're consuming 50,000 particles of microplastic a year and breathing in a similar amount. She and her colleagues looked at the number of particles found in common foods and then looked at the recommended daily intake of those foods. They also looked at inhalation rates and drinking water sources, with bottled water winning the prize for best possible way to add more plastic to your diet. According to their work, those who get the majority of their water through bottled water consume as much as 90,000 more microplastic particles annually than those who drink tap water.
Their work, called Human Consumption of Microplastics, was an analysis of 26 studies that was published in the journal Environmental Science & Technology. And though the researchers know that such an analysis leaves room for a lot of variation, they think their numbers are "likely underestimates."
The sources of this plastic are plentiful. Take dust, for example. Most of us have probably heard that much of the dust in our homes is made up of the dead skin we shed, but that's actually a myth. Dust is made up of dander, insect waste, dirt — and a surprising number of chemicals and fungi.
We can add a new ingredient to the dust recipe, and that's microplastics, small fibers that have broken down from larger plastic objects. While we've been worrying about how much plastic marine life ingests because of pollution, we haven't been paying attention to how much plastic we ingest ourselves.
According to a June 2018 study, each time we sit down to eat a meal, more than 100 pieces of microplastic fall onto our plates with the rest of the dust from the air. IFL Science says the study, originally published in Environmental Pollution, was intended to compare the number of plastic fibers found in a mussel to the number eaten in the average household.
Researchers found the average mussel contains less than two plastic fibers. It seems we're far more likely to ingest microplastics floating around the air than we are to ingest them from the seafood we eat.
The researchers determined the amount of microplastics that fall on our plates by placing petri dishes with sticky dust traps on tables in three homes during meal times. After 20 minutes, as many as 14 pieces of plastic fell into the dishes. When researchers took into account how much larger a dinner plate is than a petri dish, they estimated "114 plastic fibers probably fall on your plate at each meal, totaling between 13,713 and 68,415 each year." The toll to human health is not completely understood yet, but some plastics contain chemicals that are believed to contribute to health problems like obesity and diabetes.
The findings in this research are sobering, but perhaps they can be used to inspire us to severely cut back on the plastics we consume.
Editor update: This story has been updated with new information since it was first published in April 2018.