What are microplastics?

Plastic production has led to an explosive rise in tiny, pervasive particles - dubbed microplastics and nanoplastics - which have infiltrated biological and even geological systems across the planet. The worry is that these may lead to serious health harms, and last week two papers looking at this subject piqued our interest; one considered baby birds eating diets polluted with plastic, the other looked at the health and productivity of plants upon which we all depend to feed us. So we thought we should explore the topic in more detail, investigating microplastics and asking what impact they might be having, and how.

But what exactly are they? Richard Thompson is Professor of Marine Biology at the University of Plymouth. He coined the term “microplastic” over 20 years ago…

Richard - They're small pieces, if you like, of the everyday plastics that we're familiar with in bottles, in crisp packets, parts of cars and aeroplanes that will break down in the environment over time into smaller and smaller pieces and then there are also sources that come from the wear of products while we're using them. So the pieces enter the environment small and they arise, for example, from the abrasion of tyres as you drive a car along the road or of textiles and clothing or even the walking around in them actually. We've shown that millions of particles can be generated in a domestic wash but over an annual cycle you probably generate as many of these microplastic fibres while you're walking around. It is part of a continuum and we've got evidence of harm stretching right away along that continuum where plastic pollution can cause harm. The larger items, the rope and netting, can cause entanglement. Smaller pieces, a few centimetres in length, are readily ingested by seabirds and turtles and can block the digestive tract. Some of the smaller microplastics have the potential, if they're eaten, to pass from the digestive tract into the circulatory system.

Chris - Where are they then? Is it just an ocean problem or if we look at land, sea, air, are they everywhere?

Richard - I can't of course say that they're everywhere. The science can't tell us at the minute because we haven't looked everywhere. What I can tell you is that pretty much everywhere we have looked we found them. They're in the air we breathe, they're in the water we drink and they're in the food we eat. We found them from shorelines right down to the deep sea. We found them from the poles literally to the equator and when we first did some of that work I was astonished to find concentrations of microplastic in arctic sea ice and in deep sea sediments that were greater than some of the concentrations I was finding in local waters near to me in Plymouth which is, compared to the population of the arctic or the deep sea, considerably bigger and considering these particles come from humans I was really surprised how all pervasive they were. I think there's an important point there to recognise pollution from particles as opposed to substances that can dissolve in seawater. I remember my marine pollution lecturer saying the solution to pollution is dilution. If you're dealing with a particle those particles have the potential to disperse and become re-concentrated at distance and if they're harmful that means that they could have potentially harmful effects at a distance because they can become re-concentrated.

Chris - And how might they cause harm and if they're everywhere presumably nothing is immune from potential impact from them because we know that with say asbestos decades ago we thought this was an amazing material and indeed it is structurally fantastic but when it breaks down into tiny particles it gains a much more insidious behaviour. So is this the sort of situation we're now confronted by with plastic? We're going to start finding health harms that we never thought perhaps were out there when we first began using what we regard as an amazing material.

Richard - Well plastics of course are amazing materials and used responsibly they have the potential to reduce our environmental footprint and to bring immense societal and economic value and I think it's about learning to use them more responsibly than we have so far. You're right they are everywhere now. There are a wide range of laboratory studies demonstrating potential for harmful effects on a range of different organisms for example reducing the capacity of small marine worms to gain weight in the normal way to put on weight and you might think well that sounds like some sort of slimming pill but actually over a lifetime that's going to reduce their fecundity, their reproductive output if you like, it's going to reduce their potential for survival and if you're a predator that feeds on one of those worms it could reduce the food intake that's available to you. But that's just one example, there's a wide range of examples of evidence of harm. We're seeing uptake by plants as well. I mean we humans are really just another species and the scientific consensus here is that while we've got reports of plastic in humans and that doesn't surprise me because they're in the air we breathe the water we drink and the food we eat at the moment understanding how those microplastics cause harm in humans is an emerging field. Is this another asbestos? I mean people often ask me that question. It's impossible to say and I certainly don't want to demonise plastics. They've got the potential to bring a wide range of environmental benefits and economic benefits and you know have the potential to help us fix some of the problems on the planet. I think it's about using them more responsibly and making sure they don't escape to the environment in any form because we've now got considerable evidence of the potential for harm. And that's harm to wildlife, it's economic damage and its potential harm to human health and well-being.