Linda Crampton is a science writer who is interested in environmental issues. She is very concerned about the harmful effects of pollution.
Plastic and Microplastic Pollution
Plastics are very useful and popular materials. They may be dangerous for animals when they are discarded, however, especially when they enter the ocean. Marine animals can become trapped in large pieces of plastic debris. Both large and small pieces of plastic may enter their bodies, injuring or killing them. The material also leaches potentially dangerous chemicals in seawater and perhaps inside an animal's body as well.
People who refuse to buy plastic or who reuse items made from the material should certainly be encouraged. They may be shocked to learn that they are probably still releasing plastic debris into the environment, however.
Plastic degrades to produce tiny microplastic particles. This degradation happens in the home as well as in nature. Clothes made of synthetic fibres release microplastic threads when we wash them. Tiny beads made of microplastic are present in some cosmetics and toiletries and are flushed down the drain when we wash our bodies or brush our teeth. Microplastic pellets are produced for some industrial uses and can also pollute the environment. Researchers are worried that the tiny particles of plastic collecting in the ocean may be harming living things.
The Nature of Plastic
Plastic is a synthetic or semi-synthetic material that is molded and shaped when soft and then solidified. It's made of organic polymers. A polymer is a long molecule made of repeating units. In chemistry, the term “organic” means that the units contain carbon.
Plastics can be made from a wide range of chemicals, including polystyrene, polyvinyl chloride (PVC), polyamide (nylon), polyethylene, polyethylene glycol (PEG), polypropylene, and polycarbonate. One form of acrylic is poly(methyl methacrylate), or PMMA. Its name is spelled in various ways. Acrylics and polyesters are families of plastics.
Plastics are so ubiquitous in our environment that it's hard for someone to avoid absolutely all sources, even with the best intent. It's important to recycle or repurpose the material wherever possible and—if appropriate—to lobby companies to use environmentally safer materials.
Degradation of the Material in the Environment
It’s often said that plastics don’t degrade. They do, in fact, break down, though this is generally a very slow process. (There are some degradable plastics that may break up faster than normal ones.) The long polymers that make up the structure of a plastic gradually break up into shorter polymers. The degradation products may be dangerous for living things
Additives used to make the plastic are released as the material breaks down. These additives include potentially harmful substances such as bisphenol A (or BPA) and phthalates. BPA is used to make polycarbonate plastics and epoxy resins. Phthalates are added to certain plastics to make them pliable and are also present in some cosmetics. BPA and phthalates can be endocrine (hormone) disruptors, but whether or not low levels of the chemicals harm adult humans is a controversial topic. Many researchers agree that the chemicals are dangerous for a fetus, young children, and some animals, however.
A piece of plastic usually contains other chemicals as well, including pigments, flame retardants, and light stabilizers. The stabilizers slow or prevent the degradation of the material when it's struck by the ultraviolet component of sunlight. This is useful when a plastic is being used but is a hindrance to degradation when the material is discarded.
What Are Microplastics?
Plastics are classified according to their size. Microplastics are particles less than 5 mm in size (or less than 1 mm in size in some classification schemes). Nanoplastic particles are even smaller. As is the case for microplastics, the effects of the nano form on humans and animals need to be explored. A common method of classifying the material is shown in the table below.
|Plastic Classification||Particle Size|
> 100 mm
100 mm to 5 mm
5 mm to 0.330 mm
< 0.330 mm
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The word “bioturbation” in the illustration above refers to the disturbance or transport of sediments by living things. Burrowing and its consequences or ingestion followed by defecation are methods by which the sediments may be disturbed or transported.
Primary Sources of Microplastics
Two general classes of microplastics exist. Primary ones are those that are deliberately created by humans for a specific purpose. Secondary ones are produced by the natural breakdown of larger pieces of plastic in the environment.
Some examples of primary microplastics include the following. The first source is often classified as a primary type even though the material arises due to degradation. The degradation is caused by human activity instead of occurring in nature.
- Polyester, acrylic, and nylon are examples of plastics used to make clothing. Research suggests that one load of laundry can release as many as 1,900 plastic microfibres.
- Cosmetics designed to exfoliate skin sometimes contain microbeads made of plastic. These enter the environment after we wash, shower, or take a bath.
- Microbeads are also present in some toothpastes and enter the environment after we have brushed our teeth.
- Microplastic pellets are used in industrial processes. They may escape into the environment accidentally or be deliberately dumped.
Microplastic particles released into the environment often reach the ocean, since many wastewater treatment plants are unable to remove them.
Up until relatively recently, there has been a widespread tendency to treat the ocean as a convenient place to dispose of all sorts of unwanted material, either deliberately or unwittingly.
— The GESAMP Organization
Secondary Sources of the Particles
Plastic Garbage and Debris
Plastic that produces secondary microplastics arises from many sources. Accidental release of the material into the ocean is bad, but deliberate release is even more frustrating. Even today, when people are becoming more aware of pollution, some ships still throw their garbage overboard. Dumping of plastic garbage by communities, individuals, and industries, especially near or in the sea, is a big contributor to the debris in the ocean. Natural disasters like floods and storms can also transfer plastic to the ocean.
Another problem is the degradation of nylon fishing lines in seawater, which releases microplastic particles. Microplastic dust is released from plastic ropes and other items made of the material on land as a result of wear and tear. The dust may eventually enter water.
Disposable Contact Lenses
The degradation of contact lenses may be an additional source of microplastics. A research team at Arizona State University recently carried out a national survey. They found that 15 to 20 percent of disposable contact lens wearers get rid of the lenses by flushing them down a toilet or a sink instead of putting them in the garbage.
The lenses are often made of poly(methyl methacrylate), fluoropolymers, and silicones. The combination creates relatively soft lenses whose chemical bonds are weakened by the microbes in wastewater treatment plants. The researchers say that the lenses are broken into fragments that collect in the sludge of the plants and can eventually form microplastics. The sludge is often spread on land. From here, some escapes into rivers and the ocean as runoff when it rains. Sludge also escapes into waterways due to overflows at treatment plants.
Potential Dangers of Microplastic Pollution
The harm caused by large pieces of plastic debris that enter the ocean is well known. Animals may become entangled in the material or may mistake it for food. The swallowed material may block the animals' intestines, starve them, or suffocate them. It may fill their stomachs and take the place of real food. The effects of microplastics on living things are uncertain, but researchers are concerned about their potential influence on the health of marine organisms and perhaps even on us.
Scientists know that microplastics are accumulating in oceans around the world and in ocean sediments, that they take a long time to degrade completely, and that they are being ingested by marine animals at the bottom of the food chain. They have also discovered that microplastic is present in the bodies of at least some fish. In addition, scientists know that chemical pollutants stick to tiny pieces of plastic and enter the bodies of animals that ingest them. These pollutants include dioxins, DDT, and PCB molecules (polychlorinated biphenyls).
In lab experiments on isolated tissue, microplastic particles have entered cells and caused cell damage. This doesn't necessarily mean that they will do the same thing in an intact body, where normal body processes may neutralize the particles.
Microplastic might be harmful to marine animals and to us if we eat contaminated seafood, but investigators need to demonstrate this in their research. This research is very important. If the particles are found to be harmful, perhaps more stringent and better-monitored regulations with respect to plastic waste will be established.
So much microplastic material is accumulating in the ocean and it's made of such tiny particles that we will probably never be able to remove it. The best that we can do is to prevent the formation of any new microplastic. Reducing the amount of megaplastic pollution should be a big help in this process.
Potential Dangers for Large Filter Feeders
Three filter-feeding sharks exist today: the whale shark, basking shark, and megamouth shark. The fish swim through the ocean with their mouths wide open. Tiny organisms known collectively as plankton—and probably bits of microplastic as well—enter the mouth and are trapped on projections from the gills known as gill rakers. Filter-feeding whales feed in a similar way, but they trap the plankton on plates of baleen hanging from their upper jaw instead of on gill rakers. Since they are mammals like us, they have lungs instead of gills.
A study performed by researchers in multiple countries and published in early 2018 made a depressing discovery. The researchers reported that large filter feeders in the ocean may be swallowing hundreds or even thousands of microplastic particles every day. Potential problems from the particle ingestion include nutritional deficits, injuries to the digestive system, and toxin absorption. Some of the animals are already endangered due to other reasons. It's important that we discover whether the microplastic is affecting them.
Nature of the Great Pacific Garbage Patch
Any discussion of plastic debris in the ocean really needs to mention the Great Pacific Garbage Patch. This patch is a huge, swirling mass of plastic and microplastic material trapped in a gyre in the North Pacific Ocean. It's sometimes referred to as the largest landfill in the world. It's actually made of two areas called the Western Garbage Patch and the Eastern Garbage Patch. The latter area is larger. Its name is sometimes used as a synonym for "Great Pacific Garbage Patch".
The Eastern Garbage patch is very large, but its size is hard to measure and seems to vary. It's been described as being equal to the size of Texas, equal to twice the size of Texas, or even equal to the size of Europe. The large pieces of plastic debris in the region are very obvious, although they don't form a continuous cover over the water as some people imagine. This is why the garbage patch can't be seen in satellite photos. Most people are unaware that there is a large quantity of hidden microplastic material in the area. The Great Pacific Garbage Patch is shameful evidence of our love of plastic and our carelessness about its fate and its effect on other creatures when it's no longer useful.
The video below refers to the Plastiki. The boat is a cataraman made of recycled plastic bottles. It was created to draw attention to the world's problem with the material.
Microplastics in Arctic Sea Ice
The garbage patches are not the only ocean sites containing concentrated microplastic. Plastic is becoming a problem in some parts of the Arctic. Large pieces of plastic debris are being found on shores in the Norwegian Arctic, most of it in the form of discarded fishing gear. Scientists in Svalbard say that in the late 1970s the bird known as the northern fulmar had very little plastic in its stomach. In 2013, a survey found that some northern fulmars contained as many as 200 pieces of the material. Another sad observation in Svalbard is that some reindeer die every year after getting their antlers tangled in discarded fishing nets on beaches.
Norwegian scientists have found concentrated collections of microplastic particles in Arctic sea ice. The particles are produced from larger pieces of debris. The scientists have discovered that one litre of melted sea ice in the area holds up to 234 microplastic particles, which is a much higher concentration than is found in the open ocean. Seawater freezes from the top to the bottom. Since microplastics are most concentrated in the surface water, they become trapped in the ice as it forms.
The Norwegian fishing industry has become more careful about discarding plastic debris in recent years. People involved in the industry are also collecting debris that they find. These are excellent developments. Nevertheless, plastic is still being found on shores. Another problem is that the ice in the Arctic is currently shrinking. Scientists are concerned about what will happen when contaminated ice melts.
Cleaning plastic from beaches is important work. It's a shame that it needs to be done. The material needs to be disposed of safely, preferably by the person discarding it.
Deposits on the Sea Floor
In 2020, a group of researchers from multiple institutions reported the highest concentration of microplastic ever discovered on the sea floor. The scientists found 1.9 million pieces in a "thin layer" of sediment with an area of one square metre. It's believed that currents in the deep ocean transported the pieces to that location. Local deposits of plastic on the ocean floor may be equivalent to surface accumulations in the garbage patches. The sea floor is the home and/or feeding ground of many creatures, so the accumulation of waste could be harmful. This is another topic that needs to be investigated.
Vital Questions That Need to Be Answered
Studying microplastic is a relatively new endeavour for researchers. There's much that scientists don't yet know about the material as well as some important questions that need to be answered.
- Do microplastic particles hurt living things?
- Do the pollutants that they carry harm animals?
- Do the plastic particles and the pollutants become more concentrated as they move up the food chain?
- Do they affect us when we eat marine animals?
Since the answers to the above questions aren't yet available, we need to address the plastic problem now in order to stop or at least reduce the damage that may already be occurring. It would be very sad if evidence that microplastics are harmful accumulates and we discover that it's too late to help many forms of marine life and perhaps even some humans.
- A PDF Microplastic Report from GESAMP (Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection)
- Plastic pollution and ocean giants from the BBC (British Broadcasting Corporation)
- Don't throw contact lenses down the drain from Arizona State University
- Microplastic fragments in sea ice from the BBC
- Microplastics on the sea floor from the phys.org news service
This content reflects the personal opinions of the author. It is accurate and true to the best of the author’s knowledge and should not be substituted for impartial fact or advice in legal, political, or personal matters.
© 2012 Linda Crampton