Nine things to know about microplastics
Picking up a plastic bag from the beach makes a bigger difference than you might imagine.
1. What are microplastics?
Microplastics come in all sizes, shapes and colours. Some particles are so small that they’re invisible without a microscope, while others are perceptible as grains or fibres of different sizes.
Microplastics are defined as plastic pieces that are between 1 micrometre (one millionth of a metre) and 5 millimetres in size. Nanoplastics are particles that are smaller than 1 micrometre.
All plastics are manufactured industrially. There is no such thing as “natural” plastic. Plastic consists mainly of carbon and hydrogen, which are bound together in long chains called polymers. The length of the chains, how they’re woven together and what other substances are included (e.g. chlorine) determine the properties of different plastic types.
Plastics also contain chemical additives that give the plastic certain properties. Phthalates are a chemical that make hard plastic soft and pliable in products like garden hoses and vinyl floor coverings, for example.
2. Where do microplastics come from?
Scientists distinguish between primary and secondary microplastics. Primary microplastics are small plastic particles that are intentionally manufactured in this size for use in cosmetic products or as abrasives. Secondary microplastics result when larger plastic products – such as plastic bags, bottles or fishing nets – break down into smaller plastic pieces.
Microplastics originate from a variety of sources. Car tire treads, made of a mixture of rubber and plastic, are a major land source. Studies have shown that an average car tire loses about 1.5 kilos over its lifetime from normal wear and tear, dispersing millions of microplastic particles into the environment.
Paint from buildings, roads and ships, and fibres from synthetic fabrics are additional sources of microplastics. Sportswear and fleece clothing release large amounts of fibre when washed and end up being flushed out with the wastewater. In modern water treatment plants, a lot of this material is filtered out and discharged into the collected sludge, but some still gets through. When the sludge from wastewater treatment plants is used as agricultural fertilizer, farmland becomes the recipient of large quantities of plastic fibres.
About 75 per cent of all plastics that wind up in the ocean originate on land and are transported via rivers. Insufficient garbage handling makes rivers in Asia and Africa particularly vulnerable. Trash from ocean vessels – either lost or tossed from ships – accounts for the rest of the plastic debris in the ocean. Rubbish, and especially plastic, is piling up in five huge ocean gyres. The effects of the sun, wind and waves, coupled with abrasion from sand and stone, break down the plastics into smaller fragments and create huge amounts of microplastics and nanoplastics.
3. Why should we be concerned about microplastics?
Three attributes of microplastics in particular give cause for concern:
- a) Plastics are difficult or impossible to get rid of.
- b) Microplastics can harm aquatic organisms and animals.
- c) We don’t know enough about how microplastics can affect people.
Plastic is designed to be highly durable. This means that plastic breaks down very slowly or not at all in nature. The result is that plastic accumulates rapidly, especially in the ocean. It may be possible to remove larger plastic particles from the ocean, but microplastics already there are impossible to get rid of.
Animals that ingest larger plastic particles are adversely affected. A good example is the dying whale found last year with 30 plastic bags in its stomach in Western Norway. Plastic debris blocked its intestines so the whale was no longer able to digest food.
Lab experiments show that microplastics can also be harmful to animals like copepods, which are small crustaceans. When they fill up their stomachs with microplastics they are less able to take in other nutrients, slowing down their growth and development.
As larger animals consume smaller organisms, the microplastics can work their way up the food chain. In other words, people also become susceptible to ingesting microplastics when we eat fish and seafood.
4. Which is more dangerous – the plastic itself or the chemicals in the plastic?
The plastic itself is often less worrisome than the chemical additives found in plastic. In many plastic products, added fillers and chemicals comprise more than 80 per cent of the overall weight.
These substances are added to give the plastic the desired characteristics, such as hard plastics that hold their form versus others that are soft and flexible. Flame retardants are added to some types of plastics like power cords that need to be heat and fire resistant.
Pollutants such as industrial chemicals, pesticides and metals can in some cases adhere to the plastics that end up in the ocean or in rivers and other waterways. And when living organisms ingest the plastic, the chemicals follow and can subsequently move up the food chain. The additives or contaminants that may be released from the plastic are then taken up into the body.
5. How do microplastics get into us?
Ingesting microplastics through foods that we consume, such as fish or other seafood, has already been mentioned. We also breathe in and swallow microplastic particles from artificial turf, in airborne dust from roads or from house dust in our homes. We can absorb them via products like cosmetics and toothpaste, or through particles from plastic kitchen utensils or food packaging. Microplastics have also been detected in drinking water, albeit in small quantities.
We still don’t know for sure whether microplastics or plastic chemicals are found in vegetables and fruits from plants that have been fertilized with sludge from water treatment plants.
6. What effects do microplastics have on people?
Scientists still know very little about how microplastics affect people. But experiments carried out with marine organisms such as copepods and algae can give us some indications.
Experiments with copepods, oysters, scampi and crabs show that marine animals consume less food when they ingest microplastics. This reduces their energy levels, which in turn can lead to a lower immune response, less growth and fewer offspring.
Chemicals leached from plastics can cause hormonal disturbances that result in fewer offspring, abnormal development and disease.
7. What is being researched about microplastics?
One aspect of microplastics that NTNU and SINTEF researchers are studying is their effect on microalgae and copepods. How long do plastics remain in animals? Are they there long enough to release chemicals that have harmful effects on the animals? The researchers are also investigating the transfer of microplastics through the food chain and the leaching of microplastic chemicals.
8. How can we know what products contain microplastics?
Creams and hygiene products that list polyethylene among the ingredients probably contain microplastics. Cosmetics may contain plastic in a gel form, such as polyethylene terephthalate (PET) or polymethyl methacrylate (PMMA).
9. How can I help reduce microplastic pollution?
Help keep the environment free of plastic waste. By picking up one discarded plastic bag you remove millions of potential microplastic particles.
Make conscious choices as a consumer. Consider alternative products if the packaging tells you that the product contains microplastics. Can you wash clothes made from plastic fibres a little less often? Bring cloth shopping bags along instead of using plastic bags. Avoid buying single-use plastic products. Sort your waste and recycling.
We can do a lot as individuals. The most important thing is to be aware of the challenges so that we can make conscious choices.
Iurgi Salaverria studies marine pollution and works at NTNU’s Department of Biology.