Newsletter No 3 September 2010

Plastics - unwrapping a new research topic at IVM


Dr. Heather Leslie

plastic_cb_9_10Plastics have so fantastically revolutionized our lifestyles since their wide-scale introduction in the mid-20th century that we can hardly imagine life without them. Not even for a day! Yet the very properties that make them outstanding materials with which to package our food, design medical devices, reduce aircraft weight, clothe ourselves and create millions upon millions of interesting consumer goods, also contribute to an emerging pollution problem for the environment. And this is why some IVM researchers are focusing their attention on this complex issue – an issue that requires interdisciplinary solutions.

Plastics, an environmental issue?

Plastics are inert polymers that are resistant to degradation. Being resistant to biotransformation by even the most inventive of micro-organisms sounds like a favourable property but this means that plastics are virtually incapable of fully degrading under natural circumstances. In fact, every gram of plastic that has ever been manufactured still exists today, unless it has been incinerated. And that amounts to a lot of grams.
 
In 2008, we Europeans alone produced more than 60 million tonnes of plastic and 24.9 million tonnes of post-consumer plastic waste. A small percentage of that plastic waste gets incinerated, another small percentage gets recycled, up to an estimated 80% is cast into landfills, and the rest? It ends up as litter on land, in rivers, and eventually in oceans, and may get transported by air and water currents to the remotest of areas.

Plastics do weather, meaning they can get brittle and break into smaller pieces. Weathering is often accelerated by the leaching of additives out of the plastic. Indeed, polymers almost always contain large amounts of performance-enhancing additives to such as plasticizers, dyes, lubricants, flame retardants, biocides and many more. Wind action and abrasion on the land, wave action in the sea and UV light can also lead to fragmentation of plastic pieces so small they are invisible to the naked eye. This is known as ‘microplastic’.

And there is another property of plastic polymers – their hydrophobicity – that makes them attractive substrates for binding of thousands of known organic pollutants, which then migrate with the plastics on long range transport routes. Several studies, particularly by Japanese researchers, have shown that plastic pellets sampled from around the world typically contain a million times higher concentrations of hydrophobic and persistent organic pollutants (POPs) than the surrounding water does.

How can this damage an ecological system?

Large pieces of plastics do damage mainly when animals ingest it, mistaking it for food, or when they get tangled in it, resulting in suffocation or starvation (e.g. ghost fishing when nets get lost at sea). But IVM is quite interested in the tinier pieces, in the micrometer range. While they are harder to see, there are more of them and they can potentially cause different kinds of ecological damage. Ingestion of microplastics may facilitate the uptake of POPs bound to the particles, causing toxicological effects at threshold levels. But there are also many other possible ways plastic pollution might cause ecological degradation.

Microplastics can potentially interfere with ecological processes at the sea surface, which they co-inhabit with phytoplankton – the key primary producers of oceans - and zooplankton, which probably represent an entry route of microplastics to lower levels of the food chain. Microplastic particles also must make up a portion of the ‘marine snow’ on which mesopelagic, deep sea organisms and perhaps eel larvae feed on in the Sargasso Sea. While microplastics have be identified in every beach sand sample so far examined from around the world, practically no microplastic data is currently available for sites further inland. In fact almost all of the potential ecological effects of microplastics still remain unstudied. IVM is currently involved in scientific initiatives to change this situation.

What is IVM’s involvement?

Interest in this topic at IVM has been growing for some time. Recently a review paper on the topic of microplastics in the environment was presented by researcher Dr. Heather Leslie (IVM Chemistry and Biology Department) at the annual European conference of the Society of Environmental Toxicology and Chemistry (Setac). For many researchers in the audience, and also for the board of society, this first-ever plastics session peaked interest and put the topic on the scientific agenda. IVM has formed an interdisciplinary research team lead by Prof. dr. Jacob de Boer in which chemists, economists, policy experts, environmental law experts and ecotoxicologists are all involved. The aim is to come to understand the extent of microplastic pollution in the environment and its ecological impact, but also to investigate options and costs of mitigation and devise governance strategies to solve this problem.

On a poster presentation by the task group advising on the Marine Strategy Framework Directive, it was noted that if human beings had as much plastic in their stomachs as a typical Northern fulmar does (a bird of prey now being monitored in the OSPAR program), the way humans view this problem would probably be quite different. For the time being, while we have a hard time finding someone’s blood which does not contain plastics additives (such as bisphenol A and certain flame retardants), our stomachs are typically not full of plastic. However, IVM also understands from food chain studies that contaminants can be transferred by ‘secondary poisoning’. Ingested microplastic particles are known to be absorbed in the gastrointestinal tract in humans and other mammals. When the seafood you eat, such as a mussel, has been filtering microplastics from the water column - which we know from laboratory studies can be absorbed and retained in its tissues - then there might be an exposure risk for us too. Something to think about. And something that IVM will be deliberating too, along with various other research angles of this complex global issue.

Contact information: Dr. Heather Leslie