The Effects of Microplastics on Human Health
Plastic contamination of the natural environment has now reached epidemic levels, with particular concern surrounding tiny ‘microplastic’ particles. How do microplastics affect human health?The amount of plastic in the world’s oceans has long been cause for deep concern. Plastic pollution is a major cause of marine animal deaths and habitat destruction.
In recent times, tiny plastic microbeads used in cosmetics began hitting world headlines. They were subsequently banned as a result of their potentially damaging effects in some parts of the world.
Now, a new concern has reached public awareness: microplastics.
It's difficult to parse whether microplastics affect us as individual consumers of seafood, because we’re steeped in this material—from the air we breathe to both the tap and bottled water we drink, the food we eat, and the clothing we wear. Moreover, plastic isn’t one thing. It comes in many forms and contains a wide range of additives—pigments, ultraviolet stabilizers, water repellents, flame retardants, stiffeners such as bisphenol A (BPA), and softeners called phthalates—that can leach into their surroundings.
Some of these chemicals are considered endocrine disruptors—chemicals that interfere with normal hormone function, even contributing to weight gain. Flame retardants may interfere with brain development in fetuses and children; other compounds that cling to plastics can cause cancer or birth defects. A basic tenet of toxicology holds that the dose makes the poison, but many of these chemicals—BPA and its close relatives, for example—appear to impair lab animals at levels some governments consider safe for humans.
Studying the impacts of marine microplastics on human health is challenging because people can’t be asked to eat plastics for experiments, because plastics and their additives act differently depending on physical and chemical contexts, and because their characteristics may change as creatures along the food chain consume, metabolize, or excrete them. We know virtually nothing about how food processing or cooking affects the toxicity of plastics in aquatic organisms or what level of contamination might hurt us.
The good news is that most microplastics studied by scientists seem to remain in the guts of fish and do not move into muscle tissue, which is what we eat. The United Nations Food and Agriculture Organization, in a thick report on this subject, concludes that people likely consume only negligible amounts of microplastics—even those who eat a lot of mussels and oysters, which are eaten whole. The agency reminds us, also, that eating fish is good for us: It reduces the risk of cardiovascular disease, and fish contain high levels of nutrients uncommon in other foods.
That said, scientists remain concerned about the human-health impacts of marine plastics because, again, they are ubiquitous and they eventually will degrade and fragment into nanoplastics, which measure less than 100 billionths of a meter—in other words, they are invisible. Alarmingly these tiny plastics can penetrate cells and move into tissues and organs. But because researchers lack analytical methods to identify nanoplastics in food, they don’t have any data on their occurrence or absorption by humans.