Microplastics - a Trojan horse for hydrophobic pollutants?

Keskiviikko 14.8.2024 klo 16.22 - Mikko Nikinmaa

I just went through my book Introduction to Aquatic Toxicology, which was written in 2012-2013 and published in 2014. When reading it, one noticed that it did not have anything on microplastics, although today it is a major topic in aquatic toxicology. How on earth could one have missed such an important topic? To understand why it was not included, I checked the Web of Science, searching for articles including the word microplastics, and found that although in the past five years close to 17600 articles were published, there were only 81 published before the end of 2013, approximately half of them in 2013. Thus, the topic was virtually unknown for aquatic toxicologists, when I wrote the book. Since, further, I was not involved in studies in that area, not picking it up as a possibly popular future topic is understandable.

In contrast, nanotoxicology, which started as a study area in early 2000’s, was quite fashionable with the largest number of publications in 2014. I was then worried about the lack of environmental relevance of the studies, because without a link between the environmental exposure and toxic effects, the studies of nanomaterial toxicity lack real importance. I suppose the ecological importance of nanotoxicology has not been established, as the number of articles on nanotoxicology keeps decreasing, being about 60 % of the highest article number last year.

It remains to be seen if microplastics are shown to be an ecologically relevant issue. So far most of the studies have demonstrated that microplastic particles are found everywhere. Thus, they are taken up by organisms, and can also penetrate cells. However, as long as the microplastic is inert material, little toxicity is expected, since small inert particles  such as cellulose has always entered organisms. The situation may change radically, if microplastics are in contact with hydrophobic pollutants. They will preferably attach to the plastics, and when the microplastic particle enters organism, exert toxicity. In this case, the microplastic particle is the Trojan horse in which toxic materials can enter the cells and induce damage. I am expecting to see these kinds of studies: clean microplastic particles showing little toxicity, and particles associated with hydrophobic pollutants being toxic. If and when this prediction is right, we should aim at decreasing microplastic contamination, but especially releasing hydrophobic pollutants to the environment.                                                                                                                                                                                                                                                                                                                                                                                                                                                                   

Nanoparticles and microplastics - real threats or toxicological fashions

Lauantai 13.1.2024 klo 19.21 - Mikko Nikinmaa

In the beginning of 2000s nanotoxicology became very popular. Before 2004 there were no Web of Science articles, in the 5-year period 2004-2009 175, 2010-2014 slightly above 1000 and between 2015 and 2019 about 2100. The results clearly showed that nanomaterials can be toxic. However, virtually all studies were done with nanomaterial levels which far exceeded environmentally relevant levels. Once it was established that nanoparticles can be toxic, it has become clear that their effects in nature must be demonstrated before they can be considered to be an ecotoxicological problem. Luckily it appears not to be the case as the number of nanotoxicological studies has decreased markedly, to about 900, in the last five years.

One can naturally hope that all the studies which demonstrated the possibility of toxic effects were enough to alert the people responsible for the disposal of nanomaterials about the need to consider how the waste is treated. If that were the case, toxicological research had reached a major goal: preventing a potentially significant environmental problem from developing. In worse case, the situation shows that a lot of scientists eagerly follow the fashion and study something that is popular without considering its importance. What the results have shown is that nanoparticles are probably entering the cells of organisms via, e.g., pinocytotic pathways. Thereafter the effects are probably due to the toxicity of the compound(s) which the particle is made of, and environmental impact depends on the probability of nanoparticle concentration reaching a level which causes malfunction of some organisms.

Thus, nanoparticle toxicity is really the toxicity of the material that the particle is made of, the particle itself is only a means of entering the cells. For example, charged compounds are virtually impermeant, but if they are nanoparticle components, they can be taken up via pinocytosis. If the charged compound thus entering the cell is toxic, it will be harmful. So instead of nanotoxicology addressing all nanomaterials, we should evaluate, which toxic materials are used in nanoparticle formulation. If a material is inert, toxic effects are not likely.

About five years after nanotoxicology became in fashion, the same happened to microplastics. Between 2011 and 2015 there were merely 290 studies about them, but during the past five years close to 14000. Most of the studies are concerned with the distribution and uptake of the microplastics. They have now been found everywhere, from Antarctica to glaciers in the Alps and within virtually all organisms, mothers’ milk etc. Their occurrence everywhere is quite clear, but actually very little is known about their toxicity. In contrast, plastic waste, macroplastics has various harmful effects in addition to fouling the environment. Animals get stuck to plastic waste, plastics can clog their lungs, gills or intestine. To everyone watching news reels the sorry sights of seals and birds having died in nets is familiar. But microplastics, their effects are uncertain.  

If microplastics are made of pure polyethene or polyethylene, I have difficult to see that they could be toxic. They are inert materials which can, in my opinion, best be compared to cellulose or starch, which we and all the herbivores eat and digest all the time. However, as with nanoparticles, microplastics can be toxic, if they are associated with toxic materials. This is possible or even probable, if the environment is polluted with hydrophobic toxicants. They get adsorbed to plastics instead of any aqueous material. The toxic particles can then be taken up via pinocytosis and exert cellular toxicity. However, again as with nanoparticles, microplastics in themselves are not toxics, they are just the means by which hydrophobic toxicants can get in the tissues.

As a conclusion, I must stay that many of the studies on nanoparticles and microplastics have been done because the topics are fashionable. Instead of showing over and over again that nanoparticles can be toxic or that microplastics are found everywhere one should start considering, when their presence causes environmental risk because of their association with the pollutants which are the true problem.

From plastic waste to green hydrogen, profitably

Torstai 5.10.2023 klo 14.50 - Mikko Nikinmaa

In recent past, plastics have been only considered as a waste, which one should diminish as much as possible. Most of the everyday plastic is polyethylene, and exciting new avenue for its recycling has recently been reported. Wyss et al. (https://doi.org/10.1002/adma.202306763) have written in Advanced Materials how one can produce hydrogen and graphene by rapid heating of polyethylene without any carbon dioxide emissions. By selling graphene, which is needed in increasing amounts, the production of a major energy source for future, hydrogen, becomes highly profitable.

So, a vision for a hydrogen production emerges which simultaneously nearly abolishes plastic problem. First, consumers are paid a small sum of money per kg of polyethylene returned to recycling stations. This is done, because while environmentally concerned people recycle plastics anyway, many people who are now throwing plastic bags to the environment would probably keep them if they knew that some money is given when the plastic is taken to recycling station. Second, the collected plastic is taken to hydrogen production facility. Hydrogen and graphene are produced, and hydrogen becomes, in fact, an energy source with no cost, as the produced graphene can be sold to any interested party at a price that is below today’s market price.

At the moment, the method for the production of hydrogen and graphene from waste plastics is at the lab scale, so scaling it up to commercial scale needs some time. However, in about five years the vision may become reality. It amounts to combatting climate change and plastic problem simultaneously, and doing it profitably. This shows again, how innovative new solutions can make green shift profitable, opposite to what the conservative, oil-loving populists say.

An Agreement Reached on Protecting High Seas

Maanantai 6.3.2023 klo 19.32 - Mikko Nikinmaa

Worldwide agreement on the protection of open oceans was reached yesterday. In comparison to climate change and biodiversity protection negotiations, reaching an agreement was easy, and nobody expressed serious dissatisfaction. Not surprisingly, though, the negotiations even in this “easy” case took ten years. The reason for reaching an agreement is, however, not that governments would have become environmentally conscious, but because of the following fact. The open seas are ocean areas, which are not under the control of any nation. The maximal “economic zones” where different nations can restrict the use of the sea area are 200 nautical miles (about 370 km) from the coast. Beyond that point anyone from anywhere can use the resources of the sea and sea bottom. Thus, they belong to no nation state, but because more than 70 % of earth’s surface is ocean, form the majority of sea area.

Protecting the oceans is crucial in order to combat climate change and feed world’s people. It is not generally known that oceanic algae consume about half of the carbon dioxide and produce half of the oxygen in the world. Consequently, the well-being of oceans is as important for preventing global temperature rise as preventing the rain forest loss of Amazonas. Because of aquatic pollution, which should now be decreased as the result of the agreement, oceanic photosynthesis has probably decreased by 10-15 %. People have not really cared about what happens to the open oceans before the huge plastic gyres have caught everyone’s eye. It is clear that not only plastic waste but all sorts of chemicals, including oil components are something that sea organisms encounter all the time. To my mind it is probable that the marked decrease in eel stocks, which has occurred in the last 50 years, is to a large extent caused by oceanic pollution. Because of the very strenuous spawning migration, even slight pollution can overstress the eels so that spawning becomes ineffective.

At present, less than 1 % of the oceans is protected. The agreement states that by 2030 30 % of the high seas would be protected. This would enable many overfished species to recover. However, even though the actual protection of the seas is important, it is even more important that the pollutant discharge to oceans is diminished. Only that can help the high seas to stay healthy or recover.

Out of Sight, Out of Mind

Keskiviikko 24.2.2021 klo 16.55 - Mikko Nikinmaa

People throw all kinds of thrash all around the place. As a school boy I did a little survey of  trash in roadsides and swimming strands in South Wales. Already at that time the cigarette ends  were very common. And they are a major source of microplastics. With the tide they are washed to the ocean, and start their long-lasting voyage in the sea.

Similarly, people throw all the wrappings, bags and everything else out of the car windows after they have eaten in the car. The car needs to be tidy, but the roadside doesn't since it is soon out of sight. Similarly, bikes, refridgerators etc are just dumped into rivers and lakes, as they sink to the bottom and are out of sight. All kinds of trash are flowing via short pipes to the ocen as long as they are not visible. When the trash is seen, the length of pipes is increased. Different poison barrels are just sunk from boats to the bottom of lakes and seas - out of sight, out of mind.

Environmental crimes, dumping of toxic material, plastic etc, are hardly ever investigated. It is  commonly considered that environmental contamination is not a crime. This attitude has now resulted in the massive plastic waste gyres in the ocans. What has earlier been out of sight has now become visible. Further, the toxins that have been dumped all around the place, start causing effects on organisms. So, it is not out of sight, out of mind any more, since harmful effects are visible.

What should be done is to start collecting all the trash, and make environmental crimes punishable. If both of those things were done the out of sight, out of mind attitude would soon disappear. That would be important for the sake of the environment. 

Aquatic microplastics, not necessarily a problem

Tiistai 25.8.2020 klo 18.18 - Mikko Nikinmaa

Indigestible fibers are considered to be good for you. Such fibers enter your alimentary canal and pass through it without any changes, nothing is taken up in the gut. However, they help in the motility of the gut, and some materials, which are indigestible to us, can be utilized by gut microbes. Regardless, if material is going through your gut without anything taken up, it is inert and if its dimensions are such that it is easily transferred through the gut, cannot be considered harmful. The same is true for all animals.

So, fibers are good for you. If I changed the word fiber to microplastic, then people would start screaming about terrible poisons. Headline news almost everywhere in the world feature every once in a while stories about how these terrible microplastics are found in fish and other seafood, and can therefore be transferred to you. But if the dimensions are correct, the microplastics can be just like any other inert material going through the alimentary canal. Many plastics are nowadays made such that they meet foodstuff packaging requirements. If these plastics are broken down or if microbeads are produced from such plastics, they are completely harmless. We have been drinking water and soft drinks in plastic bottles for tens of years without being poisoned by microplastics, although every time we drink, we digest microplastics. So, in principle, microplastics are not a problem, if the material is foodstuff quality.

Microplastics can, however, be a problem. First, there are many types of plastics, some of which contain toxic components. Currently, about half of all the microplastics entering water are particles from tire wear. With the current traffic situation, there is very little one can do to this type of contamination. This is in contrast to microplastics in wastewater treatment plants, where more than 95 % of plastics are retained. The tire plastics have toxic components. Second, most of the toxic compounds are hydrophobic. Therefore, they adsorb on plastic particles, and will easily diffuse to organisms through the hydrophobic lipid gut walls. In this case it is not the microplastics themselves which are toxic, but the toxic compounds that have found their way to the environment. By stopping the release of these toxicants also the toxicity of microplastics would disappear.

The problem is that by focusing on microplastics in the aquatic environment, one is not addressing the real questions: decreasing road traffic (thus decreasing tire wear particles), decreasing toxicant release (thus decreasing toxicant adsorption and transfer into organisms) and completely stopping the use of toxic compounds in plastics.     

Plastics in the Environment

Sunnuntai 14.4.2019 klo 14.51 - Mikko Nikinmaa

When one thinks about durable, light, easy-to-use and mouldable material, plastics certainly come to mind. It is hard to image that the plastic age is only 50-60 years old. One can hardly image life without plastic containers, plastic-insulated wires, plastic parts in household appliances and cars, and artificial fibres in clothing. This plastics era has produced and is producing so much of the useful materials that the world is choking to them. A very useful, detailed review about plastics, their use and environmental problems generated is written by CJ Rhodes in Scientific Progress 101: 207-260 (https://journals.sagepub.com/toc/scia/101/3).

In a way, lumping many different materials under one common name, plastics is wrong, because the foam used in insulation, fibres of clothing, and plastic packaging of food are very different. However, two things are common: First, most of the plastics are oil-based – more than 90 % of plastics are made of oil. In addition to oil-based products, plastic-like materials can be tree- or other plant material-based. However, these materials are exactly as problematic as oil-based ones except for not being fossil fuel-based. Second, the materials degrade slowly. The average life length of plastics is tens to hundreds of years. This means that virtually all plastics ever produced can still be present. The persistence is the major reason for the environmental problems generated by plastics.

Of the different plastics only less than ten percent are recycled, a little more than ten percent are burned and 80 % are currently ending up in the environment or in garbage dumps. This distribution of the fate of used plastics is the second major reason for the environmental problems. The most visible plastic pollution is that of the oceans, especially the Pacific Garbage Gyre in North Pacific, but virtually all major seas and beaches have significant amounts of trash. The waste problem is most pronounced in Asia, as all of the countries with most environmental plastic waste are there: China, Indonesia, Philippines, Vietnam and Sri Lanka. These countries contribute more than 55 % of world’s total waste. Because recycling is so limited, factories, which would use recycled plastics in their production, have an eternal material supply problem.

About 40 % of all the plastics is used in packaging. This has also the shortest half-life of use, less than a year. Thus, packaging is by far the most extreme case of single-use attitude. The second most important plastics user is building and construction industry with about 20 % proportion. However, the material is turned over in 35 years, decreasing the yearly amount of waste. A much bigger problem is textile industry, as the proportion is 20 %, and the turnover time is less than 5 years. Much of the rest is used in machines and electronics, and the material is turned over in 5-20 years.

The plastic waste can be macro-, micro- or nanosized. The macro-sized, visible material slowly degrades, but can disturb animal life up to hundreds of years. The materials are especially problematic, when they cause strangulation of animals or block their intestine thus inhibiting normal digestion. In addition, animals may feed on plastic materials, which naturally cannot be digested. Also, plastic trash affects the visibility of water. Micro-sized plastic is characterized as material of less than 5 mm but more than 100 nm in any dimension. Next to nothing is known about its appearance in soils, but an increasing number of studies has demonstrated its presence in water. It is notable that much more than 95 % of micro-sized plastic is removed in wastewater treatment plants. Much of the microplastics is ingested by animals. The lack of digestibility is a problem, and can cause starvation, when the alimentary canal is filled with material that cannot be digested. However, very little is actually known about if and how microplastic particles affect organisms. One of the possibilities is that it is not the particles themselves, but dissolved toxic chemicals initially adsorbed on microplastic particles that cause problems. The role of microplastics would in this case be increasing the surface area whereby all the toxic chemicals adsorbed to plastics can diffuse or otherwise be absorbed into the cells. However, the actual mechanisms by which microplastics affect animal functions are poorly known. In fact, one reviewer recently pointed out that the ingestion and egestion of microplastics have been extensively studied, but next to nothing is known about their toxic effects if any. The same is true for nanoplastics, materials with at the most one dimension 100 nm. Their cellular uptake and effects at environmental level are virtually unknown. This is a general problem in nanotoxicology: one has repeatedly shown that nanomaterials can be toxic at high concentrations, but their effects at environmental or predicted environmental level are unknown. One possibility is that they cause inflammation in any tissue they come in contact with.

Since the most important proportion of plastic waste is packaging, and single-use products largely associated with food and drink, it is were nice to know that the amount of trash can easily be decreased immensely by reducing overpackaging and by recycling. Effective plastic collection would be cheap and could be implemented anywhere in the world. Virtually all plastic material used in packaging needs to be recyclable and most of the plastics can minimally be burned. This would be equivalent to burning the same amount of oil. One can say that the major way of combatting plastic waste is to increase the effectiveness of plastic collection. At the moment, out of all trash found in the environment, more than 3/4 is plastics. Finally, replacing plastics by less “eternal” material where possible is needed. This, as reducing packaging, would be something that the production side needs to do. However, the consumers can affect, what is produced, by choosing the products so that overpackaging does not sell any more. The consumers can, on the other hand, do much on the recycling side.

Solutions to plastics problem - 1 & 2

Sunnuntai 16.9.2018 klo 11.18 - Mikko Nikinmaa

Anything done to the plastics is better than that they litter the environment, so the primary problem is their presently poor collection especially in some countries. That could be very easily solved by giving a small token for any plastic taken to waste collecting units. If they don't exist, their generation could be a primary target of developmental aid. The collected plastic could then be used:

1. Plastics use for energy production. Since plastics are made of oil, they could be used for producing energy instead usiage of oil. In the simplest case, this would just mean burning plastic waste to produce energy for heating instead of burning oil. In a more advanced case, plastic waste is processed so that its molecules can be used as part of car fuels. Such processing is already done by some oil refineries.

2. Use of plastics as part of road paving. If the durable waste plastic is ground, it can be mixed to asphalt and used for paving of roads. The asphalt containing plastic particles can be even more durable than asphalt without them.

Naturally these choices do not decrease the carbon dioxide formed by the use of fossil fuels or the formation of microplastic particles from the wear of asphalt or tyres, but it does not increase it either, since microplastic particles are similarly produced from asphalt without added waste plastics. These problems will be resolved only after complete stop of fossil fuel use for energy production and replacement of asphalt in road paving.

Plastics - use as fuel component

Tiistai 24.7.2018 klo 19.57 - Mikko Nikinmaa

Plastics are made of oil. Thus, they could be utilized as components of fuel instead of generating massive garbage gyres in the oceans. And let's face it -since getting rid of the use of fossil fuels takes time, plastics should be used in energy production rather than just be destroyed by burning (without using the energy generated) which increases our carbon dioxide production.

This simple conclusion has now been advocated by the Finnish national oil company Neste. The company will start collecting plastic, and break it down to fuel components. The aim is to have 10-20 % of all petrol made of plastic garbage. This will mean savings in oil import, reduction in carbon dioxide generation and decrease in plastic garbage.

Although the solution does not make us fossil energy-free, it is a step in right direction. And at the present state of affairs anything done in right direction should be done as soon as possible, because it is getting hot in here, and a dop in the ocean must be done in the middle of plastic trash

The plastics problem - are there any solutions?

Sunnuntai 10.6.2018 klo 11.59 - Mikko Nikinmaa

The news about plastic pollution has more or less completely dwelled on the problem, and not much on solutions apart from one: banning the use of plastics. And, unfortunately, most of the news has reached North Americans and Europeans. I say that this is unfortunate, since even if the plastics in North America and Europe were recycled 100 %, this would have hardly any effect on the total amount of plastic waste entering the oceans. There are ten rivers in the world, which deliver most waste to the oceans: three in China, one in Philippines, one in Indonesia, two in Indian subcontinent, one in Brazil and two in Nigeria. Out of the 40 most plastic-polluting rivers 27 are in Asia,  8 in Latin America, 4 in Africa and 1 in Europe (Rhine).

Thus, the most urgent problem is to get waste treatment in the most polluting areas to function. A solution for this would be, if money could be made out of it. A possible way of doing this would be portable systems, Trashpressos (as named by the inventor, Arthur Huang), which press plastic waste to strong tiles, which could then be used in, for example, building houses. In this way, what is now thrown away would markedly reduce the costs of building material - which would be highly beneficial for developing nations.

A way to decrease plastic pollution everywhere is to use materials other than plastics whenever possible and convenient, diminish unnecessary wrappings (nowadays it is possible that, e.g. candies are in plastic bag, and thereafter individually wrapped in plastic) and stop using single-use plastic materials (instead of plastic single-use knives and forks one could have them made of wood as earlier; plastic cups could easily be replaced by paper cups or glasses) - the European Union ban on single-use plastics will certainly drive production and use also elsewhere.

With regards to microplastics, which is a problem also in Europe, the ways of diminishing plastic waste will help in part. However, much of the microplastics is released in washing clothes. In Europe and North America this waste comes into wastewater treatment plants. If the final effluent were filtered through a tight-mesh filter, all of the microplastic waste would be retained. Since the effluent goes through a narrow pipe in any case, this would not even cause a big expense. Such a simple solution would decrease the problem of microplastics release from clothwashing. Another problem is cigarrette buts, which people throw on the ground all the time. Instead, people should put them in waste boxes. This is already now possible, so it is only a matter of educating people. The only source of microplastics that I have not been able to think a reasonable way of getting rid of is the tyre dust. Presently, much of the tyre material is plastics, and is released in the environment. Such dust cannot easily be collected.

However, most of the plastics problem could easily be handled without needing to stop the use of plastic materials in appliances, where they are needed or much better than alternative materials. 

Getting rid of garbage gyres - its not plastics but people's attitude

Sunnuntai 11.3.2018 klo 11.52 - Mikko Nikinmaa

The waste in the seas and also in the terrestrial environment is without doubt a big problem. In this one has taken plastics as something that is the evil. Plastics are undoubtedly a problem, because they are highly stable and, being light, float and are thus easily seen. However, plastics are not the only stable pieces of trash. Similarly, all the metal-made products last almost to eternity. For plasticts to be an environmental problem, they need to reach the environment. If they did not, they would not be a part of the environmental problem.

Plastics are usually made of oil. We are still currently warming up a lot of houses with oil. If all the plastics were collected as part of the waste and burned to produce energy, no plastic waste would be generated and the need for oil would decrease. Is this done in most parts of the world? No, in the best case the plastic waste is a part of the waste ending up in waste dumps, where it is virtually eternal, and in the worst case barges filled with waste are tugged out to the open sea, where the waste is just dumped to the water. Out of sight out of mind. However, this being the case, it is actually wrong to blame a set of good products for generating a problem, when the problem is in our way of waste handling. Further, if the plastics were effectively collected, most of them could be recycled, obliviaing the need of producing new plastics to be thrown away.

Undoubtedly, there is much unnecessary use of plastic materials, and thus, plastic production can be radically diminished. However, there will always be a need for a light-weight, durable material for various appliances. And different plastics are just that, and they can be either recycled or disposed by burning so that no waste is generated. So the real problem is not the plastics, but our way of treating waste. The environment should not receive any permanent waste. People should stop throwing waste, but instead collect it all and either recycle or burn. In addition to plastics, another big permanent source of waste is metals. If they were not thrown in the environment bt recycled, the need for mining with all its environmental problems would markedly decrease.

Plastic waste in the seas

Tiistai 3.1.2017 klo 17.39 - Mikko Nikinmaa

One of the biggest news items on contamination has been the presence of huge amounts of plastics in many areas of world's oceans. One of the greatest sources of plastics are plastic bags - carelessly handled by people. Eighty to ninety % of plastic contamination in the seas comes from coastal areas. Plastics in the coast float up to several thousand kilometers from the disposal point in sea currents.

Plastics are very stable. That is the major reason, why they have become so intensively used. However, abiotically they are slowly degraded to small plastic particles, microplastics, in sunlight and the presence of oxygen. Biologically, bacteria, which are able to use plastics as food source, have evolved. Plastics are made from oil. Thus, oil-eating bacteria have developed to plastic-eating bacteria. They are much more effective at tropical temperatures than in cold. Thus, both oil and plastic pollution are a longer-lasting problem in the arctic than tropical areas.

Although the toxic compounds of oils are also those of many plastics, the major biological effects of plastics are caused by the influence of plastic particles on digestion. Microplastics are virtually undigestible and often clog the digestive tract of animals which eat them. (And this is what most animals do, as plankton-eating animals do either not recognize the difference between real edible animals and undigestible plastic particles or eat animals with digestive tract filled with plastic particles). As the real food cannot then be digested the animals cannot get energy required for living. Consequently, it is presently estimated that millions of birds and fish die annually because of the disturbances in digestion caused by the plastics, and the number of dead invertebrates is much greater.