Many of us have become accustomed to seeing newspaper headlines about the alarming presence of microplastics – small particles of plastic with a dimension less than 100 microns – in our environment. First microplastics were being reported in the water, fresh and salt, then soil, then even in the rain and snow. Microplastics (or more likely aerosolized nanoplastics) have been found in the air, they have been found at the top of mountains, in deserts, and on all continents. Industrial agriculture, automobile tires, improperly dumped garbage, and laundry (fiber shedding into the water) are all sources of microplastic. It is thought that much of this material ends up at the bottom of the ocean as it circulates through the environment.
Of course, if all this plastic is around us, then how are we interacting with this relatively new contaminant? Microplastics have been found in fish and other animals, and more recently in us. Recent studies show microplastics in breastmilk and in newborn feces for example. Older studies have identified microplastics in lungs and other organs of human cadavers. It is probably safe to say that most of us contain some amount of microplastic. A popular estimate says that we are all consuming an average of a credit card’s worth of plastic (~5g) every week. In our diets, microplastics likely primarily come from packaging, plastic cups and bottles, etc., and to a lesser extent food sources such as fish or milk/dairy that likely contain some amount of microplastics. Studies have also found detectable levels of microplastics in some sources of tap water.
These studies are alarming. What are the potential side effects of this? What precautions should we be taking? For example, the breastmilk study came from Italian researchers who suggested that pregnant women avoid any food or drink in plastic packaging, a difficult ask in our modern world. The International Journal of Environmental Research and Public Health recently had a special issue devoted to these topics;
https://www.mdpi.com/journal/ijerph/special_issues/microplastics
There is still much for us to learn about potential harms caused by these particles. Potential concerns include inflammation or other immune responses to the presence of these foreign objects. Another potential reason for concern is that those particles that have circulated through the environment may also accumulate other pollutants. Some food packaging still contains bisphenol A (BPA), which is a known endocrine disruptor. Small molecule pollutants such as pesticides are likely to concentrate on microplastics in an aqueous environment. A 2019 the World Health Organization concluded that it could not find evidence of a threat to human health from microplastics in drinking water, but that this should be studied further.
https://www.who.int/news/item/22-08-2019-who-calls-for-more-research-into-microplastics-and-a-crackdown-on-plastic-pollution