Dr. Anne Marie Mahon:

Today, I am just going to talk about microbeads in the context of plastic litter. It is a big problem. The G7 summit in 2015 highlighted that this is a global challenge directly affecting marine ecosystems and potentially human health. We are all familiar with the sight of littered beaches. Let us look at microplastics in the context of marine litter. They are small fragments of less than 5 mm and greater than 1 µm and by weight, in some of the most polluted areas of the oceans 25% of the total mass of plastics are microplastics.

It sounds like it is a lesser problem. However, the number of particles microplastics produce by comparison with macroplastics is much greater, as can be seen from the circulated graph. This is significant because of the size of the microplastics. They absorb, release and interact with pollutants that already exist in the environment much more than larger plastic particles because of the large surface-volume ratio. Also, they release other chemicals that are inherent to microplastics, be they the monomers that make up the polymer or the additives themselves.

I have circulated among members a graph showing the pathway of microplastics, or plastic litter, in time. As time progresses, the litter breaks down into smaller particles. As it does so, there is an increase in the ability of these particles to absorb and interact with organic contaminants. There is also an increase in the bioavailability of microplastics. I refer to how many compartments of the environment they can penetrate and how many organisms they can penetrate. Going down into the nanometre scale - there is, of course, a continuum - it is a matter of how many compartments of each organism can be penetrated. Can it penetrate the circulatory system? Can it penetrate a cell? These are very different in terms of impact.

Let me refer to the types of microplastics. Litter, such as the litter at beaches, breaks down into fragments. There are plastics generated by machining by industry. It could be a medical devices industry, a recycling industry or another. Such an industry produces a lot of microplastic litter. Synthetic fibres in our clothing are microplastics and they produce over 2,000 per wash. This is a big input. Astroturf pitches and roads are giving off fragments. We are doing some work on this at present to determine the output. The construction industry demands a lot of plastics. There are many different plastics for insulation and piping. This is a more diffuse source but, most likely, a large contributor.

The more primary types of microplastics are the microbeads. Some estimates suggest that 2% to 3% of the total microplastic loading would be due to microplastic beads. It is difficult to say. Also to be considered are the nurdles that are used for microplastics to convert into other plastic products.

What have we been finding in the environment? We have not been finding a lot of microbeads. We are mostly finding fibres. We are finding fragments. The graph on this subject indicates, by way of grey dots, that in our first study we found 96% fibres and 0.2% microbeads. Another large study, outlined in the slide with the red triangle, shows a figure for microbeads or spheres of 4%. Another study, which examined the stomachs of fish, found no microbeads at all. However, there are some freshwater studies that show more microbeads. I refer to the Rhine and the Manchester basin. It might be that microbeads are more concentrated in freshwater environments near high-urbanisation zones.

Most of the microbeads are plastics are channelled through the wastewater treatment system. We find that most microplastics end up in the sludge, but some of the lighter ones go out into the receiving waters. We know of some impacts on biota, especially in laboratory-based trials.

A range of different polymers make up microbeads. Some are more toxic and hazardous than others. There is a large size range. Included are bulking agents and glitters, which do not sound so necessary in many cases. I have an example of some microbeads from a toothpaste for children aged up to two. I will pass it around to members so they may all see what it is. There are up to 95,000 particles in one tube of the toothpaste. Microbeads are in personal care products and detergents. These contribute 2,000 to 3000 tonnes of microplastics per year. Paints, coatings and abrasives contribute 40,000 to 50,000 tonnes per year. This shows the volume produced by personal care products by comparison with more industrial sources. There are alternatives. Some companies are already using alternatives to microbeads to show they are not always completely necessary.