Inland waterways are just as polluted by plastic debris as the world’s oceans. The fact that plastics evidently do not dissolve and disappear without a trace in either saltwater or freshwater but instead of this disintegrate into tiny pieces under the influence of light and mechanical forces is proving to be problematic. Our Topic of the Month in September 2014 already reported about the impact that microplastic particles have on the marine environment and the organisms that live in it. Up to now, it has only been possible to speculate what long-term consequences the man-made problem of microplastic will have. The scientific community, which has only been studying the issue intensively for a few years, needs more time to be able to make a realistic analysis. The experts are, however, more aware than ever before that action needs to be taken. So does forewarned mean forearmed in this case? In an interview with k-online, Professor Christian Laforsch from Bayreuth University in Germany says that one important step among many others will be to determine the effectiveness and conclusiveness of the various existing methods and processes with which microplastic particles are investigated and to harmonize them.
k-online: Professor Laforsch, where does the microplastic in inland waterways come from?
Professor Laforsch: The sources of primary and secondary microplastic have not been ascertained yet. All we know is that there are various possible sources.
k-online: What is the difference between primary and secondary microplastic?
Professor Laforsch: Primary microplastic particles include the additives incorporated in such articles as household cleaning, cosmetic and personal products in order to give them a desired effect. So it can be assumed that primary microplastic reaches the environment primarily via the sewage system. Primary microplastic also includes the raw material granulates used in plastics manufacturing. How do these granulates get into the water? We can only guess: perhaps accidents, carelessness, negligent handling of raw materials. Secondary microplastic involves plastic particles that are produced when – for example – plastic bottles or plastic bags floating in the water disintegrate under the influence of UV radiation and mechanical forces.
k-online: When is plastic considered to be microplastic?
Prof. Laforsch: At the present time, microplastic is the name given to plastic fragments that are smaller than 5 millimetres (mm). A distinction is in the meantime also made between large microplastic particles (5 to 1 mm) and small microplastic particles (smaller than 1 mm).
Perfekte Täuschung: Wasservögel verwechseln Plastik mit Nahrung.
k-online: What risks do microplastic particles represent?
Professor Laforsch: We have proved that a wide range of different organisms from many different tropical levels ingest microplastic. This has been demonstrated with organisms that obtain their food on the surface of the water, with organisms that obtain food from water below the surface and with organisms that live in the sediment. Water fleas eat microplastic particles too, because they confuse them with natural elements of their food – which is the main reason why animals and other organisms ingest microplastic.
k-online: What are the consequences of this mistake?
Prof. Laforsch: Albatrosses, for example – to use a prominent example – confuse plastic floating in the water with small fish or squid. The birds then feed it to their young. The albatross population has decreased by up to 80 per cent in some regions, because young birds have starved to death. Or: turtles confuse plastic bags floating in the water with jellyfish and die eating them. Most animals eat plastic because they confuse it with proper food, because it sticks to proper food or because it is surrounded by organic material (biofilm). It is, however, important to say that the impact of plastic on organisms has not been investigated really well so far.
k-online: Isn’t the plastic simply excreted by the digestive system?
Professor Laforsch: Some organisms excrete everything they ingest. Little plastic balls were, however, used in the relevant studies. It is potentially possible that minute microplastic particles can be absorbed by cells – including human cells – and can be smuggled into the organism. It probably depends on the surface structure of the microplastic particles whether they can penetrate tissue.
k-online: What consequences can be expected if microplastic is absorbed by tissue?
Professor Laforsch: It has been demonstrated that the ingestion of microplastic by bivalvia can lead to inflammatory reactions in the tissue. One of the other properties of plastic is to augment pollutants in water. Studies have shown that the pollutants can damage the livers of fish if they eat contaminated microplastic particles. Additives used in plastics manufacturing can also have toxic or hormonal effects on the organisms that ingest them.
k-online: What pollutants can adhere to plastic particles?
Professor Laforsch: What are, for example, involved are residues primarily of pesticides used in agriculture or persistent organic pollutants (POP). These are substances that are only degraded or transformed in the environment slowly.
k-online: Can the plastics industry do more to minimise the production of microparticles in the environment? Is there a lack of information about this issue?
Professor Laforsch: We are in the process of trying to develop a dialogue and the plastics industry is doing the same. In the past, the industry was not even aware of how serious the microplastic problem is. In addition to this, plastic has up to now been considered more of a blessing than a curse. It goes without saying that the primary aim is to inform and educate.
k-online: Here in Germany or mainly in developing countries?
Professor Laforsch: The industrialised nations in the west have a great deal of catching up to do as well. Otherwise we would not find any more plastic in the environment in our part of the world. But this is not the case.
k-online: The problem of ocean contamination by plastic has been discussed and investigated scientifically for a long time now. Is the situation there comparable to the problem in inland waterways?
Professor Laforsch: It can in general be said that the problems and effects of plastic in general and microplastic in particular are comparable in saltwater and freshwater. The extent to which the results of the different studies can be compared is questionable, however.
k-online: What exactly do you mean by that?
Professor Laforsch: The different study groups use different methods, e.g. when taking microplastic samples. The effect of using different filters with different pore sizes is that microplastic particles of varying sizes are fished out of the sea. This inevitably leads in turn to results that are difficult to compare with each other, e.g. when water pollution is being investigated. Another problem is apparent when attempts are made to identify a microplastic particle definitely as such. Eyesight is only of limited use here, while microscopes soon reach their limits too. A find can be recognised as plastic by sight, past experience and feel up to a certain particle size. Science should not, however, be based on “feelings”; verified methods need to be applied. This means that we probably have either an over- or underestimate of plastic contamination in studies that have characterised microplastic particles visually in the past.
k-online: Does this mean that the statements made in all the studies completed to date – particularly those relating to saltwater too – must be questioned?
Professor Laforsch: This is possibly the case with studies based on data obtained by using purely visual methods. There are, however, very many study groups that are working with reliable methods. To make sure that nothing is misunderstood here: the basic statements are accurate. The studies that have been made using dependable methods are reliable. There may well be variations from region to region. It is, however, an undisputed fact that the world’s oceans are suffering from serious plastic contamination.
k-online: What do you suggest in order to improve the scientific basis?
Professor Laforsch: What are needed are dependable, reproducible detection methods, such as Raman spectroscopy or FT-IR spectroscopy. These methods exist, but they are often very laborious, because they are not automated. Pyrolysis combined with gas chromatography / mass spectrometry (GC/MS) is also proving to be an extremely helpful instrument to characterise microplastic particles. Up to now, there have not been any binding standards about this, either in Germany or elsewhere. Work should be done on this in future, with the development and establishment of harmonised approaches for solving the problem.
k-online: Professor Laforsch, thank you very much for this interview.
The interview was conducted by Guido Deußing.
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