Microplastic in the ocean - overhyped or a real cause for concern?
Like everyone else, I was appalled by the photo of a dead baby turtle next to 104 pieces of coloured plastic. The contents of its stomach and the probable cause of its death - starvation from not eating enough food.
If this is the impact of visible fragments of macroplastic on turtles, what is the impact of much smaller plastics - microplastics? If there is a significant impact, what can be done about it? Or are we concerned too soon and are the effects of microplastics massively reduced by the dilution effect of the ocean? After all, the earth is approximately two-thirds water, which is a lot of water.
Firstly, what are microplastics? Technically, they are 5mm or less and can be primary microplastics - plastics that are deliberately this size e.g. microbeads in skincare products - or secondary microplastics, plastics that are pieces of larger plastics such as plastic bags. There is a case for further classification of these microplastics into ones that are 1 micron to 1mm in size, and could be misidentified as plankton by marine organisms and potentially mistakenly misidentified as food. And, nanoplastics that are 1 micrometre long and could cross a biological membrane, like the gut lining and blood-brain barrier.
So, where are these microplastics coming from? How did they end up in the ocean?
A problem with plastics is also their key selling point - their durability. It means that once in the environment, plastics are ubiquitous and persist. They take a long time to decompose and fragment through physical action, UV radiation, and other actions.
Most of the plastics in coastal and marine environments, more than 80%, comes from the land. The sources of these plastics are varied and too exhaustive to include them all here. But, they include plastics that have escaped from municipal solid waste systems (garbage collection systems) or never entered it at all. Synthetic textiles fibres in the effluent from the textile factories producing clothing and from the washing machines and dryers cleaning these clothes in the home. Synthetic rubber fragments rubbing off car tires on the road and paint from road markings are then washed into streams and oceans. And, contact lenses that are flushed down the toilet and fragment in wastewater treatment systems. Then they are spread on agricultural land and washed into the waterways and ultimately the ocean, a major sink for microplastics.
Source: World Economic Forum, 2019
Of course, microplastics are everywhere. There are microplastics in the air, soil, land, my body, and your body. You name a place, and I guarantee there are microplastics present. Here I am focusing on the ocean.
What are the impacts of microplastic in the ocean?
It is hard to give a concrete answer to this one. Not enough research has been done and not enough research in the right places. For example, in South East Asia where the main ocean plastic waste polluting countries are located.
Studies in the laboratory tend to focus on one type of microplastic and on one species in order to conduct rigorous scientific research. A lot of this research has focused on high concentrations of bead-shaped microplastics and not on the lower concentrations of fibrous/filament plastics that are more typically found in the ocean. In fact, the ocean has a “soup” of microplastics of different shapes, sizes, and compositions including polyethylene (PE), polyethylene terephthalate (PET), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), and more, whose collective effects on individual species and the ecosystem as a whole is largely unknown.
It is estimated that only 1% of the plastics in the ocean have been tracked. I suspect that this figure refers to larger macroplastics than the microplastics I am referring to here. We don’t know how much plastic has been put in the ocean. Only that global plastic production is projected to increase and consequently, plastic entering the oceans is unlikely to slow down unless there is widespread action.
Within the ocean, microplastics have been found throughout the water column, from the surface to the seabed. They have also been found on the shore and much further out at sea, with their distribution affected by winds, waves, and currents.
The impact of these microplastics is not fully known. It is too soon to say. It could be from particle toxicity, where the actual physical microplastic itself could affect feeding, reproduction and growth and more; chemical toxicity, where chemicals in the plastic or adsorbed (yes this is a “d”, adsorbed is “(of a solid) hold (molecules of a gas or liquid or solute) as a thin film on the outside surface or on internal surfaces within the material”) to the surface can cause toxic effects, basically the microplastic is a vector for other chemicals; or toxicity from biofilms that have adhered to the microplastics e.g. bacteria attached to the surface of the microplastic.
Based on the reading I have done, there appear to be some areas that are more of a cause for concern than others, but I just can’t be sure. There may be more, because like I said there is just not enough research being done.
One cause for concern could be organisms ingesting microplastics with no nutritional content and/or microplastics interfering with digestion. These organisms might not be able to eat enough food if they consume too much microplastic and not enough nutritional food. For example, a 2019 lab study found that Pacific mole crabs exposed to microplastic fibres had a shorter life span. A study on the corpses of post-hatchling Hawaiian hawksbill sea turtles found 42 plastics in their stomachs including microplastics, which could have caused starvation.
It is possible that microplastics could have a significant endocrine effect, i.e. hormonal impact. I do remember when I was studying Toxicology reading about a laboratory study that plasticisers (a chemical that makes plastic “bendy”) cause molluscs to change gender, from female to male. Could microplastics at high enough concentrations have a similar effect in the ocean? There have not been enough studies on the endocrine-disrupting effects of some of the chemicals in plastics.
It is, to my mind, unlikely that microplastics themselves will have significant bioaccumulative effects i.e. concentrate up the food chain. Just as microplastic is ingested, they are egested. However, if they are ingested with certain chemicals absorbed to the surface that bioaccumulate then it could be a problem as direct toxicity if the chemicals were above a no observed effect level (NOEL), for example, Polycyclic Aromatic Hydrocarbons (PAHs), Polychlorinated Biphenyls (PCBs) and heavy metals.
It is still too early to say what the impact is, but, in my mind, there is enough cause for concern here to act. The impact of microplastics in the ocean right now might be minimal. But, given that only 9% of plastic is recycled, the production of plastics is expected to increase and there is a large amount of macroplastic in the ocean right now that will fragment, there could be a significant amount of microplastic in the ocean in the near future. By 2050 there could be more plastic than fish (by weight) in the ocean in a business-as-usual scenario, according to “The New Plastics Economy: Rethinking the future of plastics” report by the Ellen MacArthur Foundation.
This seems like a long time away but changing policy is a slow process and getting people to the table to act takes time. So a precautionary approach should be taken. Even some of the more skeptical scientists estimate that microplastics could have an impact in 15 to 30 years.
Microplastic on a finger
Cleaning up all the macroplastic in the ocean could help. There are robots to clean up plastic pollution. However, these robots are just the tip of the iceberg and they are unlikely to scale.
One thing that does need to be done, and quickly, is the implementation of a global monitoring system for microplastics using sensors coupled with monitoring of potential indicator species e.g. filter feeders like mussels and deposit feeders like Asian clams that could be the “canaries in a coal mine” for the ocean. Just like there is a global air pollution monitoring system that covers major cities and hubs and measures air quality. We need a system to monitor and map out the scale of the global problem, and help target research, and measure impact.
Removing plastics altogether is wishful thinking and does not consider the benefits of plastics in our lives. The world would grind to a slow halt if they were removed altogether. But, reducing their production, consumption and closing the loop so less plastic enters the waterways is going to be key.
So, are microplastics in the ocean hype or a real cause for concern? I am going to say now they probably are not, but they could be and, in my mind, a preventative approach should be taken. There is still time to act and take action.
I am compiling a list of companies that have a product or service that could help reduce the amount and/or impact on microplastics here. This is a dynamic list of companies developing anything from sensors to monitor microplastics to films to reduce microplastics in effluent from textile plants. Feel free to message me to add a company or technology to the list.
Disclaimer: I am not an expert in microplastics. I do have a BSc in Biochemistry and MSc in Toxicology, and did work as an Environmental Analyst, so I am not a complete novice. These are my own thoughts and insights based on the desk-based research I undertook into this topic.
Some of my reading material:
Microplastics: Knowns, Unknowns, and Actions | Sheila Hemami | TEDxBeaconStreet
Plastic Pollution Needs Bigger Solutions | Chris Reeves | TEDxNewport
Microplastics in the freshwater environment – An issue of concern
What do we know about the toxicity of micro-plastics in the marine environment? University of Gothenburg
How we can stop the flow of plastic pollution into our oceans? | Tim Niemier | TEDx Merit Academy
Is there a global plastic toxicity debt?
Unseen: Microplastics Research & Solutions
[Alice Horton] Microplastics - From source to sea
Microplastics in Water, ATL Limited
It’s the Little Things that Count: Quantifying & Characterizing Microplastics, Eurofins
Electric clothes dryers: An underestimated source of microfiber pollution
Microplastic in marine organism: Environmental and toxicological effects
Microplastics in the environment: A critical review of current understanding and identification of future research needs
Microplastics and Human Health
Microplastics and Microfibres. Plastic pollution and aquatic ecosystems. Dr Chelsea Rochman
You’ve Got Microplastics, Gadget Lab: Weekly Tech News, Podcast on Spotify
Microplastics - an environmental threat?
Microplastics in Seafood—Garth Covernton
It’s the Little Things that Count: Quantifying & Characterizing Microplastics
A plastic ocean
