The world is filled with billions of particles of plastic. As small as dust, they are almost invisible - but they cause huge problems. What are microplastics, and where do they come from?

What are microplastics?

When it comes to plastic pollution, we usually think of shopping bags floating around in the sea, or marine animals getting caught in old fishing nets. But microplastics are just as widespread - and they cause a different set of problems.

As the name suggests, they are tiny pieces of plastic less than 5mm long. As small as a grain of sand, microplastics are almost impossible to spot and difficult to remove once they have infiltrated a system. They can end up all over the world and have been discovered in Arctic ice and on deep ocean floors. A recent study looking at sedimentSolid material, such as stones and sand, that settles at the bottom of a river, lake or ocean. in the Great Australian BightA bight is an open bay. The Great Australian Bight is a large oceanic bight off the central and western portions of the southern coastline of Australia. found around 14 particles per gram. Scaled up, this could mean the world's ocean floors contain around 16 million tonnes of microplastic.

Are there different types?

Yes: primary and secondary. Primary microplastics are designed to be small for commercial use. MicrobeadsExtremely small materials made deliberately to enhance cosmetic and cleaning products. They were originally used as a polishing agent in toothpaste. are placed in cosmetics to assist cleaning; they also act as thickening agents in detergentsSubstances that clean.. MicrofibresExtremely light artificial fibres used to make cloth. They are made of polyester, a kind of plastic. shed from clothing and textiles such as fishing nets also count as primary microplastics.

Secondary microplastics do not start out small. They result from the breakdown of larger plastic items such as water bottles. This breakdown is caused by exposure to environmental factors such as the sun's radiationEnergy given off when radioactive material decays. It can be extremely harmful and sometimes fatal, causing vomiting, skin damage, hair loss and cancer. and ocean waves.

How do they get into the oceans?

In several ways. Some of it is simply from littering. Some comes from the microbeads put in cleaning and cosmetic products as they are flushed down drains and pass through water systems to the sea.

But most of the environmental pollution is the result of storms, water run-off and wind which carry plastic rubbish and microbeads into oceans. Once there, they are consumed by marine animals.

Aren't they too small to make a difference?

Absolutely not. We may think of plastic as clean and sterile, but it is in essence made up of fossil fuelsFuels made from decomposing plants and animals, including coal, natural gas and oil. These fuels release carbon dioxide, causing global warming.. It does not readily break down into harmless molecules, and it takes thousands of years to decompose fully.

Microplastics are no different. In fact, their size causes problems that larger litter might not. They are so small that they mix with natural sand and sediment, making them practically impossible to remove. And they soak up chemicals, making them harmful and sometimes even toxic to animals that consume them by mistake. Microplastics have been detected in creatures of all size, from plankton to whales.

Is it just a problem for wildlife?

No. Once fish start eating the tiny particles, plastic is in the food chain. And it passes directly back to us. Studies in 2019 found that an average of 33% of the fish we eat contained some kind of plastic.

And it isn't just fish. Microplastics end up in the water we drink - and they are small enough to get caught up in the air like dust, meaning we can even breathe them in. The average American consumes 70,000 particles a year. People who drink bottled water could consume an extra 90,000 on top of that.

What can we do about it?

Scientists are still unsure whether consumed microplastics themesleves are harmful to human or animal health - and what specific dangers they may pose. Even so, many countries are taking action to reduce microplastics in the environment. Some microbeadsMost countries have banned rinse-off microbeads - the tiny pieces of plastic (often coloured) that are added to products such as face scrubs and shower gels. They are designed to be flushed down drains. are now illegal in several countries including Canada, New Zealand, India and the UK. In 2017, a United NationsAn international organisation focused on keeping peace. Its refugee agency, the UNHCR, aims to assist refugees around the world. resolution discussed the need for regulations to reduce them.

Individuals can also make a difference by avoiding microbead products, recycling, drinking tap water and most of all, reducing single-use plastic usage.