This update looks at two new studies that draw attention to possible everyday sources of microplastics in our homes that may be putting these pollutants directly into our food and bodies.
Despite the small size of microplastics (anything less than 5 mm long), they remain a massive problem. Each year, over 3 million metric tons enter the environment—and hundreds of thousands of grams may be entering each of us. This is an ongoing issue, and one that chemists and environmental scientists continue to revisit as they race to find solutions for preventing new fragments and cleaning up existing contamination.
Previous work has shown there are microplastics entering our drinking water from plastic bottles and teabags, but how many of us have considered the impact of the utensils we use in our homes? Plastics degrade and fray over time, and some kitchen items undergo considerable wear and abrasion—take, for example, your cutting board. Those of us with plastic cutting boards in the home will know they become scarred with use, resulting in a roughened surface and many score lines from repeated slicing and dicing. But the reality is, this wear and tear results in fragments coming loose each and every time we use the board. Some of this may come down to how you use a knife, or what you are cutting – and some materials represent an inherently greater risk than others.
New research from teams working across the US, Canada, and Europe showed that the microplastics released from polypropylene chopping boards was greater than polyethylene—both by mass (5–60% greater) and number of fragments (14–71% greater). The study, published in Environmental Science & Technology, estimated that each of us could be ingesting as much as 50 grams of microplastics every year directly from our home chopping boards. These findings are lower than a previous study that reported a loss of 875 grams from a polyethylene board within 40 days of commercial use, but they join a host of other staggering numbers for microplastic burdens in our everyday lives. This includes the incredible idea that just one plastic teabag used at brewing temperature can release 3.1 billion nanoplastics into a single cup of tea. Many of us moved to plastic utensils in the kitchen over concerns that traditional wooden boards and spoons might harbor bacteria—but perhaps some of this science needs a rethink, and a move back to more natural and sustainable materials. If this study is correct, we could avoid up to one-third of our annual plastic consumption by simply replacing our chopping boards.
Another overlooked route for microplastics into the human body is leaching from contact lenses. A team in China found that over 90,000 microplastic particles could be released from a pair of contact lenses over the course of a year. Leaching in sunlight has often been cited as a risk for plastic bottles, but until now it has been hard to measure this phenomenon for polymer contact lenses. To address this, the researchers used a high-content screening system to rapidly capture and count microplastics. For lenses subjected to longer irradiation, more and larger microplastics were released. Evaluating the impact of this on eye health will be important. The authors point out that microplastics can act as carriers for microorganisms and have also been shown to accumulate chemicals on their surfaces, which could be an issue if these fragments are retained in the eye.
Unlike many other reports on microplastics, one striking point here is that these two studies both uncover products that we are using that are having a direct effect on us as individuals. Perhaps it is just this kind of science that will finally convince some of us to take microplastics seriously and make those small-scale individual changes whose impacts may hit much closer to home.