Plastics are polymers, meaning they are made up of repeated units of a smaller molecule — for example, many ethylene molecules strung together make polyethylene. Microplastics are small pieces and fragments of plastic less than five millimeters (three-sixteenths of an inch) in diameter. They come from multiple sources and have been accumulating in the environment for at least 70 years, since plastics came into our lives.
In the environment, larger pieces, such as plastic water bottles, Styrofoam plates, or plastic wrap, break up into smaller and smaller pieces. Microplastics now are found everywhere, from the deepest oceans to the highest mountains. Being so tiny, they cannot effectively be removed from the environment.
Where do they come from? Here are some of the other major sources.
Textiles: Microfibers derived from textile shedding account for one of the largest sources of microplastics in air, soil, food, and water. Most shedding occurs during washing and drying, but clothing also sheds when being made, worn, and disposed of. Washing a typical load of laundry can generate over nine million microfibers; dryers release similar amounts. Released to the air, they are transported to remote locations. While wastewater treatment plants capture most microfibers from washing machines, the numbers are so high that the amounts entering the receiving water (rivers, estuaries) are astronomical.
Furthermore, sewage plants move most of them into the biosolids or sludge, which is often subsequently applied to fields, thereby converting microfibers into soil pollutants.
Tires are the second largest source, shedding microplastics during driving, thus polluting air, soil, and waterways, with the highest levels measured in roadsides and urban areas. Tires contain a complex mixture of hundreds of chemicals, such as metals, antioxidants, and PAHs (oil-related). In fact, chemical leachate from tires is responsible for the deaths of thousands of salmon on the West Coast because of the chemical 6PPD-quinone.
Human exposure to tire-wear particles and associated chemicals near roadways is high. Larger tire particles (like crumb rubber) are often put underneath artificial turf to make it spongy. They and the artificial turf itself release microplastics when walked, run, or crawled on. (Artificial turf also contains PFAS — “forever chemicals” — a class of chemicals linked to cancer, nervous-system toxicity, immune dysfunction, and thyroid and cardiovascular disease.)
Paint: Plastics such as epoxy resins, polyacrylates, and latex are a large component of paints. These polymers are often coated with chemicals that are color additives and antifouling agents, some of which may be toxic. They can enter the environment during painting, as flakes from the degradation of paint on buildings, ships, piers, etc., or during scraping of old paint from boats.
Personal care products: Microbeads are spherical microplastics intentionally used in cosmetic products, serving as exfoliants in facial cleansers and scrubs. Several countries have banned them in these products. The U.S. passed the Microbead-Free Waters Act in 2015.
Preproduction pellets: Pellets (or “nurdles”) are the building blocks for nearly every plastic product. About three to five millimeters in size, they enter the environment via spills at production sites or during handling and shipping. They remain in the environment for many years, fragmenting into smaller plastics that float and move long distances. They absorb contaminants from the water and can be mistaken for food by marine animals and birds. Eating pellets can damage the digestive tract and impair behavior. Additionally, the toxic chemicals in the plastics can have many harmful effects, including endocrine, reproductive, or immunological effects.
Agriculture and fisheries: Plastics are used on farms, and plastic mulch releases microplastics. Each year 7.4 million tons of plastics are used in agriculture, most of it for less than one year, releasing microplastics in the soils. Fishing nets and fishing line, now made of plastic, similarly release them. There are many lost (“derelict”) fishing nets throughout the ocean that continue to release microplastics into the water for many decades.
What harm do they do? Microplastics are complex, consisting of the basic polymers, purposely added chemicals and contaminating chemicals that they pick up from the surrounding environment (such as metals or PCBs). Their effects can be due to their physical characteristics, e.g., size, shape, density, and structure, which can damage tissues. Other damage can arise from toxic effects of the additive chemicals, which can cause cancer, reproductive toxicity, endocrine (hormone) disruption, immune toxicity, metabolic changes, and more.
Additive chemicals almost always include phthalates and bisphenols, which are known to damage the endocrine system. In addition to the standard additives in plastics, microfibers from textiles contain an assortment of dyes, anti-wrinkle chemicals, water-repellent chemicals, and other unique toxic chemicals.
There have been thousands of studies on the effects of microplastics on aquatic animals, and harmful effects have been noted on reproduction, development, behavior, enzyme changes, and many other functions in a great variety of invertebrates and fishes. Regarding human impacts, we cannot do experiments on humans, but studies have demonstrated the presence of microplastics in just about all of our organs — liver, kidney, lungs, heart, placenta, breast, testes, and others. Their presence doesn’t prove that they cause damage, but it is discomforting.
There are some indications that higher concentrations in plaque in the heart may be associated with increased risk of heart attack, and that higher concentrations in the uterus may be associated with reduced fertility. There have also been numerous experiments on mice and rats demonstrating the toxic effects.
Is there anything we can do? There is one major source of microplastics that our individual actions can affect. Consumers can reduce their input of microfibers to the environment by changing their clothing purchases and laundry practices. Buying fewer clothes and keeping them a longer time helps. Buying more natural fabrics such as cotton rather than synthetics will also help.
When doing the laundry, washing full loads, using cold water, not using fabric softeners, using front loaders rather than top-loading machines, and drying on a clothesline rather than a dryer will all reduce the release of microfibers. There are now special filters that can be put onto washing machines that will capture about 90 percent of the fibers. They cost around $150. Washing machine companies are also manufacturing new machines with built-in filters.
Other activities, such as using fewer (or no) single-use plastics such as cups, straws, utensils, and bottles can make a difference in reducing the planetary plague of plastics. Recycling has been touted for decades, but in the U.S. only about 5 percent of the plastics put in recycle bins ever get recycled.
There are international negotiations ongoing for a plastics treaty that should be completed in 2025. I am part of the Scientists Coalition for an Effective Plastics Treaty, which is working hard to have the treaty include reductions in plastics manufacture (which is increasing at an alarming rate). However, more than 200 lobbyists from the plastics industry were present at the last meeting.
Judith S. Weis, who lives part time in Springs, is a professor emerita of biological sciences at Rutgers University. She will speak at the East Hampton Library on Sept. 28 at 2 p.m. about her book “Marine Pollution: What Everyone Needs to Know,” a second edition of which is just out from Oxford University Press.