Microplastics have attracted a huge amount of attention. People tend to be afraid of the unknown and especially so about things that they cannot see with their own eyes. As a scientist, I decided to review all the science I could find on the topic to see whether or not we have genuine cause for concern. That meant reading a huge amount of material, not just skimming through but also checking how the science was done, to make sure that it was professionally conducted. What I found shocked me – we’ve been misled.
Microplastics are defined as plastic fragments of 5mm or less across. They first came to the public’s attention when articles started showing up about the polyethylene microspheres used in some facial scrubs as a mild exfoliant. There was a huge uproar, as this was perceived as a major problem and now the PE spheres are no longer used. A recent report gives an excellent overview (see Primary Microplastics in the Oceans- a Global Evaluation of Sources IUCN 2017). The report says that the global release of primary microplastics in the oceans is estimated to be about 1.5 Mtons/year. However, this number has since been revised. When researchers actually measured microplastics entering the oceans from rivers and rechecked their calculations, they found that prior estimates had been over 1000x too high. The current best estimate for microplastics entering oceans from rivers is ~6000 tons per year. That’s still more than we would like but it is a far, far lower number. See the study The missing ocean plastic sink: Gone with the rivers or the interview with the scientists here.
So, we know that microplastics are real and the quantities are enough to be concerned about. I looked for the data and it turns out that just 2% of the plastic particles in the sea were from in facial scrubs. I was surprised at how low the amount was, in light of the huge amount of attention the topic received. If not facial scrubs, what is responsible for the microplastics in our oceans?
For a substance to present a danger, it has to be toxic and there has to be an exposure route. For example, a bottle of poison on the moon would not be a threat to people on Earth so there would be no danger. In that example, there is toxicity but no exposure. Conversely, we may be exposed to something but if it turns out to be harmless, then there is no cause for concern.
I looked at many studies and we know for sure that birds and fish do eat plastic. Microplastics can be found in their digestive system.
“Plastic was detected in 49 out of 64 fish (77%), with 2.3 pieces on average and up to 15 pieces per individual” and “Most were polyethylene (52.0%) or polypropylene (43.3%).”
Source: Microplastic fragments and microbeads in digestive tracts of planktivorous fish from urban coastal waters
So, the exposure component is there. What about the toxicity aspect? Are these plastic particles harmful to the marine wildlife?
It is interesting to see that PE and PP are the main plastics. It should not be too surprising, as they are the two most commonly used plastics and they both float on water, making them more visible and more likely to be ingested by fish. PE and PP are also two very safe plastics that we use all the time to package food. PE is used for sealable food bags in the kitchen and PP is used for sealable food containers. Both have been used safely for several decades.
The press has drawn the public’s attention to studies claiming that plastics leach toxins, but when we look at those studies, it turns out that the plastic was shown to be safe and only released toxins after the plastic was intentionally soaked in toxins by the experimenters. These studies are not only misleading but irresponsible. We could soak more or less anything in poison and then show that it released some poison once placed in clean water. Interestingly, other workers showed that plastics absorb toxins from water and hold them tightly so that even when ingested by fish, they are able to protect the fish. Have you ever seen a headline highlighting those studies? I have not. Why is that?
So, it is a myth that microplastics are toxic. You can see details of the various studies in the myths tab in the section below. To summarize, having read many studies, here is what they say:
Careful consideration shows no credible evidence that microplastics are causing harm. Some of the data even points to a protective effect whereby the plastic particles absorb toxins in the sea and shield marine animals from exposure.
There is a shocking amount of bad science whereby the experiments were so poorly designed that they should never have been accepted for publication. I have refereed articles for major publishers and I would not have allowed many of the environmental papers to be released. I would encourage people to take the challenge of doing good quality research so that we can learn more about the facts and take appropriate action.
I made a statement that much of the microplastics works is not credible. Having reviewed many studies, it is some of the worst “science” I have ever seen. Those are bold statements, so now I will explain why I made them by looking at several publications individually and explaining why the science is either invalid or, in some cases, fraudulent.
First comes this warning from scientists who point out that many of the studies are not done under realistic conditions.
Microplastic exposure studies should be environmentally realistic
R. Lenza, K. Endersa, and T. G. Nielsen, Proceedings of the National Academy of Sciences, 113(29), E4121 – E4122 . . DOI: 10.1073/pnas.1606615113
The authors warn that:
“Experimental exposure concentrations tend to be between two to seven orders-of-magnitude higher than environmental levels.”
Meaning that many articles are using 100x and 10 million times more more plastic and toxin than are found in the environment. Dose is very important for toxicity. For example, breathing 20% oxygen keeps us alive where 100% oxygen is lethal. Therefore, they go one to say:
“Microplastic research is an emerging field, and there is a lot of misunderstanding and in some cases over- reaction or misinterpretation of results from MP science in the public. We therefore strongly suggest that future studies of MP impact on marine ecosystems should also include concentrations that have been documented in the environment to yield more realistic estimates of sublethal effects.”
Another article points out that the studies are usually done on the wrong kinds of plastic. Many studies are done on polystyrene when that is not at all common in the ocean. Polystyrene is just 1% of microplastic in the ocean so why focus on that? The reason is that polystyrene particles are easily obtainable making it convenient for the scientists to order them.
“Analysis of the available data revealed that 1) despite their widespread detection in field-based studies, polypropylene, polyester and polyamide particles were under-represented in laboratory studies; 2) fibres and fragments (800–1600 μm) are the most common form of MPs reported in animals collected from the field; 3) to date, most studies have been conducted on fish; knowledge is needed about the effects of MPs on other groups of organisms, especially invertebrates. Furthermore, there are significant mismatches between the types of MP most commonly found in the environment or reported in field studies and those used in laboratory experiments.”
They correctly noted that studies are done on the wrong plastics and on the wrong shapes. In the oceans fibers and fragments are found, whereas all the studies are on perfectly round particles.
Another recent study noted that the newspapers are not accurately reflecting what the scientists are saying. Instead they are making microplastics look far worse than they actually are, presumably to sell more newspapers.
“The results show that most scientiﬁc studies (67%) frame microplastics risks as hypothetical or uncertain, while 24% present them as established. In contrast, most media articles reporting on microplastic impacts (93%) imply that risks of microplastics exist and harmful consequences are highly probable.”
Now let’s look at a couple of studies that make plastics out to be a problem…
The abstract for the article states:
“This work provides evidence that microbeads from personal care products are capable of transferring sorbed pollutants to fish that ingest them.”
Later, the article says:
“The bioavailability of PBDEs sorbed to microbeads that did accumulate in the fish is of concern, considering the large volume of MBs (and other microplastics) entering the aquatic environment and their largely unknown environmental fates. Implications for the food chain, including the human diet, from this very fine fraction of plastic debris demand further investigation.”
That sounds like it could be a problem, so I read the article in detail. First, they showed that polyethylene beads from facial wash had no effect on fish that ate them. Then they soaked the beads in known toxins so that they beads absorbed the poison. They fed the toxin loaded beads to the fish and confirmed that a small proportion of the toxins was transferred to the fish.
What does this mean? Let’s picture what would happen in the ocean. The PE beads (proven to be harmless alone), will absorb toxic chemicals. That means less toxic chemicals in the water that the fish are in. That’s great news. What happens if the fish eat the plastic beads? Just 0-12% of the toxin is released by the beads because the toxic chemicals prefer to stay inside the beads. That’s more good news! The plastic beads are purifying the water and protecting the fish. The title of the article could have been “Microplastics miraculously effective at sequestering toxins and purifying seawater”.
I hope this shows you how desperate the environmentalists are to do studies that are unrealistic, improperly performed and incorrectly interpreted. It’s shocking.
In fact, at least two studies have proven that microplastics are very effective at binding toxins and protecting marine wildlife (polypropylene study, nylon study). Yet another study directly tested the hypothesis that microplastics (MP) would lead to accumulation of toxins in fish. What they found instead was:
“Contaminant concentrations in the muscle tissue were unrelated to the MP levels in fish, suggesting a lack of direct links between the levels of HOCs and MP ingestion. Thus, despite their ubiquity, MP are unlikely to have a measurable impact on food intake or the total body burden of hydrophobic contaminants in Baltic herring.”
Source: Hydrophobic organic contaminants are not linked to microplastic uptake in Baltic Sea herring, M. Ogonowski, V. Wenman, S. Danielsson and E. Gorokhova
Oyster reproduction is affected by exposure to polystyrene microplastics
Sussarellu et al., PNAS March 1, 113 (9) 2430-2435 (2016)
The authors state:
“This study provides evidence that micro-PS cause feeding modifications and reproductive disruption in oysters, with significant impacts on offspring.”
I then noticed this:
“analyses on extracted micro-PS particles detected bibenzyl and 1(2H)naphthalenone,3,4,dihydro4phenyl with >90% correspondences”
This means that the PS spheres they used contained toxins not found in household polystyrene. The beads used contain added surfactant and are cross-linked with divinyl benzene, which explains the toxic extractibles found (see manufacturer’s description).
In conclusion, this experiment cannot be trusted because it was not performed properly. They used polystyrene beads when only 1% of plastics in the ocean is polystyrene. They also used a special type of polystyrene that contains toxic chemicals not found in normal polystyrene.
Next is a study on worms that feed on sediment.
“Biouptake in worms was lower by 76% when PCBs were associated with polypropylene compared to sediment. The presence of microplastics in sediments had an overall impact of reducing bioavailability and transfer of HOCs to sediment-ingesting organisms. Since the vast majority of sediment and suspended particles in the environment are natural organic and inorganic materials, pollutant transfer through particle ingestion will be dominated by these particles and not microplastics. Therefore, these results support the conclusion that in most cases the transfer of organic pollutants to aquatic organisms from microplastic in the diet is likely a small contribution compared to other natural pathways of exposure.”
Another study states the following about microplastics (MP):
“Thus, despite their ubiquity, MP are unlikely to have a measurable impact on food intake or the total body burden of hydrophobic contaminants in Baltic herring.”
Both polyethylene, and polypropylene, by far the most abundant microplastics in the ocean, have been proven to absorb toxins from water and sequester them, thereby protecting marine wildlife. Nylon has been shown to do the same, the PA (polyamide) particles were themselves harmless and reduced the amount of BPA in the water:
“The PA particles themselves did not induce negative effects, while the effects of BPA alone followed a typical dose-dependent manner. Sorption of BPA to PA particles prior to exposure led to a reduction of BPA in the aqueous phase.”
For the next article, I did a search of the title to find a link to share here and Google revealed this hit, which was quite a surprise:
“We wish to report a strong suspicion of research misconduct in the following study by researchers at Uppsala University, published in the journal Science on June 3 2016”
Lönnstedt OM and Eklöv P (2016) Environmentally relevant concentrations of microplastic particles influence larval fish ecology. Science 352: 1213-1216. doi: 10.1126/science.aad8828
“Regarding point #4 above, we have evidence including witness reports, photos of the experimental setup, and email correspondences that the experiments reported in the paper were not performed as described by the authors. To be clear, there is a significant mismatch between what is described in the paper and how the experiments were actually performed. Examples include:
For these and other reasons, we strongly suspect that this study constitutes a case of research misconduct.”
You read that correctly. Apparently, these researchers were so desperate to make plastics look bad that they falsified their results. After an investigation, the article was retracted.
I have many more articles that I will be reading and commenting on here.
There is one meta-analysis on this topic but unfortunately, they did not properly screen the articles they included. I checked with the lead author and she admitted that even the studies where they intentionally soaked the plastic in toxins were included. I hope that they do a new meta-analysis only on articles that have been conducted properly. Even with the inclusion of those suspect studies, the meta-analysis showed surprisingly few adverse effects.
One may wonder whether creatures containing plastic could be eaten by people and whether any harm would result. I found one detailed report on that topic and they concluded:
“As an example, a worst case estimate of exposure to microplastics after consumption of a portion of mussels (225 g) would be 7 μg of plastics. Based on this estimate and considering the highest concentrations of additives or contaminants reported in microplastics, and assuming complete release from microplastics, the microplastics will have a negligible effect on the total dietary exposure to PBTs and plastic additives. These contaminants are estimated to contribute only <0.1 percent of the total dietary exposure to these compounds.”
I have not seen a single credible article showing microplastics to be toxic. When reading such studies we should ignore studies based on polystyrene, ignore studies using 100-10 million fold more particles than are actually present in the ocean and ignore studies where the plastic used was intentionally loaded with poison. Realistic, professionally designed experiments are needed if we are to draw meaningful conclusions and so far those realistic studies show no harmful effects.
Here is a partial list of articles claiming that microplastic is toxic along with the reasons that they are not valid experiments. The main reasons these studies are invalid include: using the wrong polymer type, using particles that are the wrong size, the wrong colour, particles that contain toxins and particles that are made artificially to be fluorescent. Many studies use thousands or millions times more microplastic, compared to actual amounts in the ocean.
Single and combined effects of microplastics and pyrene on juveniles (0+ group) of the common goby Pomatoschistus microps (Teleostei, Gobiidae) They used round, red, fluorescent PE particles that must have had surfactant added. They were much smaller with much higher surface area than found in the ocean. They showed that plastics can help the fish by protecting them from toxins. The correct size of particles to use, i.e. the size of actual ocean microplastics is stated as follows: “The size range 800–1600 μm, the most commonly reported from field samples of biota represents a very small fraction of the sizes used in the laboratory” Source: Studies of the effects of microplastics on aquatic organisms – What do we know and where should we focus our efforts in the future?
Microplastics cause neurotoxicity, oxidative damage and energy-related changes and interact with the bioaccumulation of mercury in the European seabass, Dicentrarchus labrax (Linnaeus, 1758) In this article the scientists state: “Fluorescence red polymer microspheres, 1–5μm diameter (lot number: 4-0906-0661), purchased from Cospheric − Innovations in Microtechnology (USA), were used as microplastics model. According to the manufacturer, the particles are spherical, red opaque, 1.3 g/cc density, and can be detected by spectrofluorimetry (excitation wave- length of 575 nm and emission wavelength of 607 nm).” It is clear that they don’t even know what kind of plastic they used! From the description, we can deduce that they were cross-linked polystyrene which are totally unlike any known ocean microplastics. This invalidates their work.
Evaluation of the impact of polyethylene microbeads ingestion in European sea bass (Dicentrarchus labrax) larvae They used red fluorescent PE (which is not realistic) but found no harm and that the PE passed right through the larvae.
Uptake and Accumulation of Polystyrene Microplastics in Zebrafish (Danio rerio) and Toxic Effects in Liver As mentioned above, polystyrene is not the correct plastic to use. Furthermore, other researchers complained that this study was poorly done and not valid. See the study Comment on “Uptake and Accumulation of Polystyrene Microplastics in zebraDsh (Danio rerio) and Toxic Effects in Liver.
Microplastic ingestion decreases energy reserves in marine worms They claimed reduced energy in the worms due to PVC exposure but all effects were within the error bars of the experiment, meaning no detectable effect.
Early warning signs of endocrine disruption in adult fish from the ingestion of polyethylene with and without sorbed chemical pollutants from the marine environment
This study was done quite well but still has some issues. Firstly, they used a polyethylene that was not characterized in any way. They do not state the grade, the manufacturer or what additives were in it. Furthermore, they did the study by replacing 10% of the fish food with plastic. It is well-known that reducing the food given (10% of the nutritional value was removed) can induce physiological changes by itself.
Altered behavior, physiology, and metabolism in fish exposed to polystyrene nanoparticles This study is meaningless. They used polystyrene, which is not a common plastic in the ocean. They chose nanoparticles, which are far smaller than microplastics in the ocean. Nanoparticles have massively more surface area, so they can interact much more than is realistic. Crucially, they used sulfonated polystyrene, which it utterly unlike real polystyrene used in commercial products.
Size‐dependentproinflam‐ matory effects of ultrafine polystyrene particles- a role for surface area and oxidative stress in the enhanced activity of ultrafines They used polystyrene particles, i.e. the wrong kind of plastic and did not specify exactly which type (no product number was given). The particles were from Polysciences, meaning they are cross-linked, probably coloured and unlike real polystyrene. Another invalid study.
Physical Adsorption of Charged Plastic Nanoparticles Affects Algal Photosynthesis They used nanoparticles which are far too small to be realistic. They used polystyrene particles which were synthesized and unlike the kind found in the oceans. Crucially, they used surface modified particles that had a charge added to their surface in order to make them stick to the algae in a way that real plastic particles do not. They concluded that the plastic particles stick to the algae and affect photosynthesis. Of course, if you modify a plastic to stick to the algae, they will block some light. Not a valid or worthwhile study. They might as well have put the algae in a black box and noted that photosynthesis was affected.
Impact of polystyrene microplastics on Daphnia magna mortality and reproduction in relation to food availability
The workers found no effect on health except at exceptionally high microplastic concentrations far above those found in the ocean. They used “2 μm carboxylate-modified polystyrene, fluorescent yellow-green” particles. Meaning that they used the wrong polymer, with the wrong surface chemistry, the wrong size and the wrong color compared to real plastic microparticles.
Polycarbonate and polystyrene nanoplastic particles act as stressors to the innate immune system of fathead minnow
This study used fluorescent nanoparticles unlike any plastic found in the ocean. Not a relevant piece of work.
Microplastics as Vector for Persistent Organic Pollutants In Urban Effluents: The Role Of Polychlorinated Biphenyls
This study actually isolated polyethylene microparticles from commercial facial scrubs,. They showed that the particles can absorb toxins and implied that they could transport toxins. As shown elsewhere in this page, what actually happens according to several studies, is that the PE absorbs toxins from the ocean and protects fish from exposure.
Toxicity of Microplastics to Aquatic Organisms – Clemson Thesis This study was performed on synthetic fluorescent blue polyethylene microspheres from Cospheric. The spheres are made by a different process than real PE in the environment, are the wrong colour, are fluorescent (real PE is not), they are the wrong density, the wrong shape and surfactant needs to be added to disperse them in water (the potential toxicity of surfactant, if used, was not accounted for). The PP fibers used were taken from a marine PP rope that had been on the ground outdoors for three years. The brand of the rope and additives in it were not analysed. We do not know whether the rope had absorbed toxins while lying on the ground. It is not good science to perform studies on poorly characterized materials.
Biodegradable and Petroleum-Based Microplastics Do Not Differ in Their Ingestion and Excretion but in Their Biological Effects in a Freshwater Invertebrate Gammarus fossarum
This study looks at PMMA and PHB microplastics, neither of which are in ocean water, making the study irrelevant.
Microplastic leachates impair behavioural vigilance and predator avoidance in a temperate intertidal gastropod
This study is quite different to others. They exposed gastropods to commercially available PP pellets and polymer pellets randomly collected from a beach. They found that the plastics were non-toxic but the gasptrods were slower to respond to a threat when they were in water exposed to the plastic pellets. Beached plastics had a larger effect than virgin, clean PP pellets. It seems that somehow the chemicals from the plastic confuse the ability of the gastropod to sense danger. The study was done well but the conclusions were incorrect. To understand the relevance of this, we need to consider the whole picture. In the real ocean situation the gastropods would be in water containing toxins that confuse them. Adding microplastics to that system would absorb those toxins and potentially help the gastropods sense chemical danger. Therefore, this experiment was not designed in a way that tells us what would happen in reality.
Brain damage and behavioural disorders in fish induced by plastic nanoparticles delivered through the food chain This study was done on chemically synthesized and surface modified cross-linked polystyrene nanoparticles, which are totally unlike any kind of plastic pollution. They are the wrong chemistry, wrong size, wrong surface and wrong shape so their behavior has nothing whatever to do with how plastic pollution behaves. Real plastic in the ocean is PE and PP, not cross-linked polystyrene beads like the ones used here. Let me put it this way, if you wanted to study apples, would you do the study on bananas? That’s what these so-called scientists have done.
Plastic leachates impair growth and oxygen production in Prochlorococcus, the ocean’s most abundant photosynthetic bacteria This study is massively flawed and should not have been published. They extracted chemicals from HDPE and PVC. They claim to have extracted about 6000 chemicals from each, which makes no sense because plastic formulations contain just a few additives, i.e. 5-10. They extracted 1kg of plastic in 10 liters of water when the real amount of plastic in the ocean is 1×10-13 kg per liter. I.e. they used about 1000 000 000 000x too much plastic! They also did not follow the standard for extraction which specifies 24 hours extraction time. They changed that to 72 hours for no good reason. These authors have gone out of their way to create a results that makes plastics look bad by using unbelievably unrealistic experimental conditions.
Up and away: ontogenic transference as a pathway for aerial dispersal of microplastics This article is not valid for several reasons. They used cross-linked polystyrene particles 2 microns in diameter. Cross-linked PS particles are not present in the ocean, so that alone invalidates the study. The particles were far too small compared to typical microplastics in the ocean (500 microns is typical). The particles were dyed green and were fluorescent. These factors would be expected to significantly affect the likelihood that the larvae would eat the particles. Furthermore, the particles were chemically modified to have a charged carboxylated surface, which would completely alter their behavior inside the larvae. Lastly, they used a concentration of particles far higher than present in the ocean. This is a deeply flawed study that should not have been published.
Trophic transfer and individual impact of nano-sized polystyrene in a four-species freshwater food chain They used synthetic fluorescent polystyrene particles, which are unlike anything found in the ocean. Therefore, the study tells us nothing meaningful. They also used the wrong size of particles and 100x higher concentration than is realistic.