Sunday, 13 January 2019

One third of microplastic in the oceans comes from washing clothes - really?

I recently heard a claim that a third of microplastic in the ocean comes from laundry, as synthetic clothes shed fibres in the wash. (This was on a radio program called New Year Solutions: clothes, on radio 4.) This struck me as unlikely so I checked and I believe I found the source: a report from the IUCN in 2017[1]. They do indeed estimate that a third of primary microplastics come from laundry – averaged over the world. However this varies hugely in different regions. I found estimates specific to the UK in a report by Eunomia for Friends of the Earth [2]. They found that only 8% of UK primary microplastic is from laundry. The bulk is actually from tyre wear from cars and lorries.

Large pieces of plastic can break down into tiny ones but we don't know how long this takes.
Primary microplastic is made of particles that start out tiny. Secondary microplastic comes from large bits of plastic like plastic bags and bottles that degrade into tiny pieces. We have little idea how long this takes or how much large plastic degrades at all. However large pieces of plastic are also harmful. They cause problems to large marine animals that eat them.

Larger plastic items in the sea come mainly from other places where garbage handling is less reliable.
Overall we dump much more large plastic into the ocean than primary microplastic. However most of this is from developing countries where garbage handling is not very reliable. (I wish I could be sure that we have no responsibiility for this, but I fear some of this plastic may come originally from the UK, exported for handling). There is relatively little plastic released directly from Europe and North America. For us, microplastic is a bigger problem.

Quantities of large plastic and microplastic reaching the oceans by region. IUCN [1]

Most microplastic comes from clothing fibres and road wear on tyres.
Over the world, tyres and laundry account for about two thirds of marine microplastic. The largest other sources are plastic from paint on the road (7%), coatings on ships and marine infrastructure (4%) and personal care products (2%) [1].

In the UK, eight times as much microplastic comes from tyres than laundry.
The proportion of microplastic from tyres and laundry varies between regions. In North America there is more than four times as much from tyres as laundry. In India and S. Asia there is 14 times as much from laundry as tyres. According to Eunomia from the UK there is probably eight times as much from tyres as from laundry.

Estimates of marine plastic from the UK [2]. Plastic pellets are from manufacturing, paint is mainly from road markings. The bars show the range of uncertainty for each type.

This suggests tyres are more harmful - but we don't really know.
Although there is much more plastic from tyre wear than laundry, that does not necessarily mean it causes more damage in the environment. The harm caused depends on the size and shape as well as chemical composition. Particles from laundry are mainly long and thin, e.g. 10-20 micron wide but several mm long [3], while tyre wear can be smaller or larger: from 10nm to 300 micron [4]. Shrimp are more likely to eat long thin particles than round ones [5]. Also surface characteristics are important, as plastics can contain toxins or adsorb toxins onto their surface which makes them dangerous to eat [6]. There is a huge amount we don’t know about the impact of microplastic on marine ecosystems.

How can we reduce microplastic from clothes?
There are several products that can collect fibres in your washing machine and reduce the quantity flushed out. For example Cora ball but this only catches about 26% and the guppy friend wash bag  which has been shown to catch around 80%.

Alternatively you can avoid washing your clothes so much, or use clothes with biodegradable fibres. That does not necessarily mean just organics like cotton and wool; some synthetics are also biodegradable such as Tencel, made from cellulose sources, and rayon, also known as viscose.

How can we reduce microplastic released from tyre wear?
It is difficult to imagine a biodegradable tyre though apparently the industry is working on it [2]. Tyres are usually made of a mix of natural and synthetic rubber. Natural rubber does biodegrade but it takes a long time.

In the meantime, the main ways to reduce tyre wear are:
  • Lose weight – use the lightest vehicle you can (a bicycle is good!) and avoid carrying around heavy stuff you don’t need.
  • Drive smoothly – there is more wear when you are accelerating or decelerating.
  • Take the train or tram instead – metal wheels on metal rails do not shed microplastic.

Note that electric vehicles are just as bad as conventional when it comes to tyre wear.

[1] Primary Microplastics in the Oceans: a global evaluation of sources (IUCN) 2017

[2] Reducing Household Contributions to Marine Plastic Pollution (Eunomia) Nov 2018

[3] Microplastic pollution from textiles: A literature review (Beverley Henry, Kirsi Laitala and Ingun Grimstad Klepp) 2018

[4] Wear and Tear of Tyres: A Stealthy Source of Microplastics in the Environment (Pieter Jan Kole, Ansje J. Löhr, Frank G. A. J. Van Belleghem, and Ad M. J. Ragas, Environmental Research and Public Health) Oct 2017

[5] Size- and shape-dependent effects of microplastic particles on adult daggerblade grass shrimp (Gray, A.D.,Weinstein, J.E., Environmental Toxicology and Chemistry) 2017

[6] Do microplastics cause harm in the Marine Environment? (Exeter University) 2014

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