Microplastics, Plastic Pollution and Effects on Marine Life
Plastic and Microplastic Pollution
Plastics are very useful and popular materials. They may be dangerous to animals when they are discarded, however, especially when they enter the ocean. Marine animals can become trapped in large pieces of plastic garbage. Both large and small pieces of plastic may enter their bodies, injuring or killing them. Plastics also leach dangerous chemicals in seawater and perhaps inside an animal's body as well.
People who refuse to buy plastic or who reuse plastic items if they do enter their home should certainly be encouraged, but they may be shocked to learn that they are probably still releasing plastic debris into the environment.
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 particles when we wash them. Microplastic particles are present in some cosmetics and toiletries and are flushed down the drain when we wash or brush our teeth. The microplastic may eventually reach the ocean, since water treatment plants are unable to remove it. Microplastics are produced deliberately for some industrial uses and can also pollute the environment.
The Growing Problem of Microplastic Pollution
What is Plastic?
Plastic is a synthetic or semi-synthetic material which is molded and shaped when soft and then solidified. Plastics are 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. 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 plastic wherever possible and - if appropriate - to lobby companies to use environmentally safer materials.
It’s often said that plastics don’t degrade. They do in fact break down, although generally very slowly. (There are some degradable plastics that break up faster than normal plastics.) The long polymers that make up the structure of a plastic gradually break up into shorter and shorter polymers. These degradation products may still be dangerous to living things, however.
Additives used to make the plastic are released as the plastic degrades. These additives include potentially harmful substances such as bisphenol A (or BPA), which is used to make polycarbonate plastics and epoxy resins, and phthalates, which are added to certain plastics to make them pliable and are also present in some cosmetics. Both of these substances are endocrine (hormone) disruptors, but whether or not low levels of the chemicals harm adult humans is a controversial topic. However, many researchers agree that the chemicals are dangerous for a fetus, young children and some animals.
How Do Microplastics Differ From Plastics?
Plastics are classified according to their size. Microplastics are plastic particles less than 5 mm in size (or less than 1 mm in size in some classification schemes). Nanoplastic particles are even smaller. Like microplastics, their effects on humans and animals need to be explored. A common method of classifying plastics is shown in the table below.
> 100 mm
100 mm to 5 mm
5 mm to 0.330 mm
< 0.330 mm
Microplastics in the Ocean
Primary Sources of Microplastic
There are two general classes of microplastics. Primary microplastics are those that are deliberately created by humans for a specific purpose. Secondary microplastics 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 microplastic even though it arises due to degradation. The degradation arises due to human activity instead of occuring 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. Microplastic dust can also be released from plastic ropes and other plastic items as a result of wear and tear.
- Cosmetics designed to exfoliate skin often contain "microbeads" made of plastic. These enter the environment after we wash, shower or take a bath.
- Plastic 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 accidently or be deliberately dumped.
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 Microplastic
Plastic that produces secondary microplastics arises from many sources. Accidental release of plastic 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 plastic debris in the ocean. Naturals disasters like floods and storms can also transfer plastic to the ocean. Another problem is that nylon fishing lines are degraded in seawater, releasing microplastic particles.
Potential Dangers of Microplastics
The harm caused by large pieces of plastic debris that enter the ocean is well known. Animals may become entangled in the plastic or may mistake it for food. The swallowed plastic 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 the pieces of microplastic and are ingested along with the plastic particles. 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 particles might be harmful to marine animals and to us if we eat contaminated sea food, but investigators need to demonstrate this in their research. This research is very important. If microplastic is found to be harmful, hopefully 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 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.
The Great Pacific Garbage Patch
Any discussion of plastic and microplastic 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 Eastern Garbage Patch 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 Eastern Garbage Patch and The Plastiki Expedition
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 this form of plastic. Do the plastic 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? These are important questions which still need to be answered.
A PDF Microplastic report from GESAMP (Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection)
© 2012 Linda Crampton