This is according to Canadian researchers, who – writing in Environmental Science & Technology – have reviewed 26 studies analyzing the number of microplastics found in fish, shellfish, added sugars, salts, alcohol, tap or bottled water, and air. (Some foods were not included simply due to a lack of data.) The aim: to find out how much of the stuff we are, on average, consuming, using the recommended American dietary guidelines as a basis.
So, first things first. What is microplastic?
Microplastics are micro-sized pieces of plastic derived from the degradation of larger plastic products, among other sources. Their ubiquity is so widespread, they have been found everywhere from the remote plains of Antarctica to the deepest ocean trenches, not to mention in the guts of countless sea creatures. A previous study suggests seafood eaters may be unwittingly eating 11,000 microplastics a year. While another says we could be eating more than 100 pieces of plastic per meal.
This time around, the researchers found that the number of microplastics in your diet will vary, depending on factors like age, sex, and, of course, personal food preferences and restrictions. But the general outcomes seemed to be somewhere in the region of 74,000 and 121,000 particles a year – plus an additional 90,000 if you like to drink all your water bottled.
Between 39,000 and 52,000 of this total is consumed through the food we eat. The rest via inhalation. What’s more, these figures are likely conservative estimates, the researchers say, accounting for just 15 percent of Americans' calorific intake.
What this news means for our health, however, is less clear. Some microplastics are small enough to break into human tissue, which could potentially lead to the release of toxic substances and/or trigger an immune response but no negative health effects have been demonstrated as of yet.
"This report provides an alarming indication of the wider impacts of plastic pollution. It’s a crisis that is not only blighting our landscapes and oceans but affecting the food we eat and the water we drink," Thavamani Palanisami, a senior research fellow at the Global Centre for Environmental Remediation (GCER) at the University of Newcastle, said in a statement.
But others point to some limitations to the study – specifically, the lack of studies examining the prevalence of microplastics in the human food chain and the impact of microplastics on human health.
"It is important to understand that the particle exposure numbers presented are a current best guess based on a narrow number of studies," Kevin Thomas, director of the Queensland Alliance for Environmental Health Sciences (QAEHS) at the University of Queensland, added.
"Plastics in the environment are a serious environmental issue. Wildlife is killed by ingesting plastic, usually due to (macro)plastic causing blockages in their stomachs," said Lauren Roman, a CSIRO postdoctoral researcher at CSIRO Oceans and Atmosphere.
"Regarding human health effects, to the best of my knowledge in the scientific literature, there is currently no credible scientific evidence linking human dietary exposure to microplastics in their diet (shellfish, plastic bottles etc) to negative health effects."
"This doesn't mean that there are no negative health effects, it's possible there are and they just haven't been found, but imminent danger is very unlikely."