Synthetic fabrics and car tires are major source of microplastic pollution

polluted canal in Chennai
CC BY 2.0 McKay Savage -- A canal in Chennai, India, that's choked with garbage. Eventually it will make its way out to sea.

We hear a lot about plastics breaking down at sea, but scientists are discovering that a shocking quantity of plastic enters the ocean already in microscopic form.

The source of ocean plastic pollution is usually assumed to be mismanaged waste -- those plastic bags and containers that get missed by the recycling truck or blown away in the wind. These items end up in waterways, washing out to sea, and breaking down over time into the tiny pieces we know as microplastics.

But what about the plastic that enters the water already in a tiny form, a microplastic even before it's reached the sea? This is a form of pollution scientists know very little about, and yet it appears to represent a much larger chunk of ocean pollution than previously realized.

A new report by the International Union for Conservation of Nature (IUCN) examines the source of these primary microplastics. The report strives to estimate and map where they come from and how many there are worldwide, in hopes of educating consumers who might not realize how widespread the problem is and providing useful information to policymakers.

The report explains the difference between different forms of plastic pollution:

Primary microplastics can be a "voluntary addition to products such as scrubbing agents in toiletries and cosmetics (e.g. shower gels). They can also originate from the abrasion of large plastic objects during manufacturing, use or maintenance such as the erosion of tyres when driving or of the abrasion of synthetic textiles during washing."

Secondary microplastics originate from the "degradation of larger plastic items into smaller plastic fragments once exposed to marine environment. This happens through photodegradation and other weathering processes of mismanaged waste such as discarded plastic bags or from unintentional losses such as fishing nets."

There are a surprising number of sources of primary microplastics. These include

- tires driving on the road
- washing of synthetic textiles
- marine coatings
- road markings
- personal care products (although plastic microbeads are being banned in many countries)
- plastic pellets spilled during transportation
- city dust

primary microplastics© IUCN

The vast majority of these come from land-based activities, with only 2 percent coming from activities at sea. The two biggest land-based sources are laundering synthetic clothing and the abrasion of tires while driving, making up two-thirds of all primary microplastics released. The study estimates that 1.45 million tons of primary microplastics are added to the oceans each year, which is 30 percent of the notorious 'plastic soup'. To put this into perspective:

"This is equivalent to 43 light plastic grocery bags thrown into the world ocean per person or roughly one per week. This number varies however widely across regions. Going from 22 equivalent grocery bags per capita in Africa and the Middle East, this goes up to 150 bags in North America – a seven-fold difference."

What is a person supposed to do about these distressing numbers? In some cases the solution is fairly straightforward, i.e. removing plastic microbeads from personal care products. With others, it requires technological innovation, such as creating fabrics that do not shed when laundered and tires that do not erode while driving, i.e. natural rubber.

It's a real mental shift to start thinking about plastic pollution in terms of involuntary losses, as opposed to an inadequate waste management system; and it's eye-opening that is so extensive. Simply by living our lives, even if we strive to be zero waste, we could still be contributing significantly to the problem.

You can read the full report here (free access).

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