By Ranjula Ranasinghe –
As of 2004, the biggest natural disaster in Sri Lanka took place (the tsunami). Now in 2021, the biggest artificial disaster unleashed after the new X-Press Pearl cargo ship had caught fire off its coast, spilling micro-plastics and other chemicals into the ocean. It is imperative to understand the severity of this disaster therefore this article will attempt to explore the consequences and the science behind the devastating long term effects worldwide.
First of all, let’s see how plastics are made? Plastics are primarily made of Crude oil. This oil is separated into a specific category, cracked and then polymerised to form Poly(ethene). Confused? Don’t be. But remember, that is the main thing we all should know. Here is a summary of how plastics are formed:
Crude oil is a fossil fuel (It will eventually run out one day); it was formed from the remains of dead animals and plants that were buried in mud millions of years ago. Over these years, with high temperature and pressure, those remains gradually converted into crude oil, which can now be drilled up from rocks where it’s found.
According to the chemical science, crude oil is a mixture of many different lengths of hydrocarbons (molecules containing only hydrogen and carbon). These different lengths have different characteristics which ultimately form products. Fractional Distillation is used to separate these different length hydrocarbons. The oil is heated and fed into a fractionating column, where it is separated into categories as shown below:
From these categories, Naphtha is our main product in plastic production. Ethylene is the essential substance in making Plastics, which is made from Naphtha through a process called cracking.
Further to that, Ethene(Ethylene) has two carbon atoms: So it can be extracted from the very top of the column, but the problem is, not that much Ethene can be obtained from the top as most of crude oil contains long-chained hydrocarbons. Hence, we use cracking.
Cracking simply means to split up these long-chain hydrocarbons, which are not as useful, into smaller but more useful hydrocarbons. Short-chain hydrocarbons are in high demand since they are flammable, so they make good fuels. So cracking is a fundamental process that is often used in the industry. After the Naphtha has been cracked, it gives us several different length hydrocarbons that are shorter than the original Naphtha, such as Ethylene, Propylene, Butadiene, etc. But the one we need is Ethylene. Big words right? Don’t worry, it’s just some Chemistry. We should learn a bit of that to understand this process.
Finally, this Poly(ethene) is then processed, and made into Nurdles. These Nurdles can then be heated and moulded into a desirable product which we all use.
What are Nurdles?
Nurdles are just tiny plastics pellets. It is the raw material used as the primary building blocks to make all plastic products such as buckets, water bottles, etc. They are less than 5mm in size, so they are a type of micro-plastic. Over time, they will be broken down into smaller and smaller particles by environmental factors such as Ultraviolet rays from the sun, oxygen, wind and wave action. These factors all contribute to making the plastics more prone to breaking easily and causing discolouring and fragmentation. This results in a bigger problem, which you will soon see why.
Nurdles and other plastics out in the environment are a huge problem as they aren’t biodegradable. That means they will remain in the environment for thousands of years. The reason that plastics don’t decompose is due to the fact that they are artificial, man-made substances, so they are foreign to many micro-organisms; these organisms, such as bacteria “don’t know” how to decompose the plastic, so they freely hang around with us. Hope you understand the situation now.
Moreover, these Nurdles can then be spread further by high winds and oceans currents. Seabirds and other marine animals will be attracted to these Nurdles as their small and transparent look often resembles fish eggs or other small animals. So when these marine animals consume the Nurldes, this will make them fill full and lead them into starvation and then eventually death, since they ingest the plastic but don’t digest it. What a tragedy? Isn’t it?
The effect of these Nurdles have on the food chain is significant. Once the Nurdles enter the food chain, it is a disaster for literally everyone. For example, even tiny sea creature called plankton (the base of our food chain) will eat tiny fragment plastics, then another marine animals would eat the plankton that has the plastic inside it, and then another bigger animal would eat that and so on… all the way up to whales, and even humans, since when consuming fish that have had consumed these pellets, essentially means that we too are consuming the plastic. Once eaten, these tiny plastics will pass straight into an animal’s bloodstreams and then block its tissues. It is quite sad really.
According to scientific research, Micro-plastics can also change the temperature and other characteristics of sand, which will affect eggs being incubated by sea turtles. And if this isn’t bad enough, turtles are already an endangered species.
There is an important thing that we should first be aware of. The primary polymer in the plastic itself, such as Poly(ethene) is not considered harmful; due to their larger molecular size, they are considered to be unreactive. But it’s the other monomers, additives, unintentional chemicals, and impurities from the fossil fuel itself which causes the problem. Polymerisation reactions are rarely complete. So unfortunately, unreacted residual monomers can be found in the polymer.
Now this is really, really important to understand, as this is probably the most problematic issue.
Why are some plastics green, red or blue, etc.? Why are some plastics stronger than one another? This is because of….drum roll please…. ADDITIVES! In plastic manufacturing, these additives are used in order to provide plastics with their own unique characteristics: colour, durability, flammability and prolong their lifespan. They are added to provide us with the desired products that we want.
Additives are used for polymerisation, processing, and enhancing performance. Polymerisation additives are the type of additives added at the very start of the reaction (when the monomers first begin to link) to chain the monomers. Additives for processing include plasticisers, which is important for manipulating the flow behaviour, such as making the material more flexible, decrease its viscosity and to make it softer. For example, 75% of PVC itself is made up of plasticisers that soften the material.
However, the problem is, additives aren’t covalently/chemically bonded to the polymer itself and are often more reactive compared to the plastic polymer, so they are able to leach out of the plastic and into the environment. As the additives begins to gradually leave, this will also affect the polymers fragmentation rate, this fragmentation will then further contribute to the leaching and/or absorption behaviour of plastic. This is due to the surface area. As the plastics get smaller and smaller in size, the larger the surface to volume ratio. Hence, its capacity to release and bind compounds is higher for smaller particles compared to larger ones. For example, why do we use casting sugar when baking cakes? It’s because its particles are smaller and more refined, so more of its surface will be exposed compared to regular sugar cubes, so casting sugar will dissolve faster. Likewise, this would be similar to our case.
Some of the important monomers and additives used are:
Bisphenol A (BPA) – One of the primary monomers that’s combined with another monomer called Carbonyl Chloride to make a rigid, clear plastic called Polycarbonate. This BPA is found in things like DVDs, baby bottles, thermal paper receipts. Again, these polymers themselves are inactive, but the unreacted leftover BPA from the polymerisation reaction is, what is able to leach out, and things like heat will speed up this process as heat transfers energy to these molecules, making them vibrate more and providing them an easier tendency to leach. (Which is why you are advised to not microwave plastics). The problem with BPA is that it is an endocrine-disrupting compound; they disrupt our hormone balance. According to research, exposure to such a chemical is involved with around 80 different diseases; some of these are obesity, reproductive disorders and testicular cancer. The young/unborn are most vulnerable to this as their hormone system are still developing.
Phthalates are used in processing as a plasticiser additive, often used to soften Polyvinyl Chloride (PVC) plastic. Scientists claim that being exposed to this could damage the liver, kidneys, lungs, and reproductive system. Studies have also found that exposure to phthalates during pregnancy or before birth can have detrimental impacts on overall brain development, such as decreasing intelligence, problems with attention and hyperactivity, and hinder social skills.
Other important additives that are used are solvents, initiators, and catalysts. Solvents are also a type of plasticiser; some solvents may be toxic and flammable and may be hard to completely evaporate from the polymer when manufacturing, so they will remain in the polymer as residues. Methanol, cyclohexane and heptane are examples of solvents that are harmful to aquatic life. Initiators are chemicals that start the polymerisation reaction; they start the linking of monomers. Potassium Persulfate and Benzoyl Peroxide are some of the most impactful initiators used. They cause respiratory problems and skin irritation. Catalysts are compounds that speed up chemical reactions and are usually based on different metals, like Zinc Oxide and Copper Chloride; these are also known to be deadly to aquatic life.
Furthermore, Nurdles and other plastics also have the ability to attract and concentrate toxins from the sea onto their surface. This is most likely due to the earlier reason that I mentioned about additives not being chemically bonded to the polymer itself and it being more reactive than the polymer, meaning it can exchange with its surroundings/leach out. Persistent organic pollutants (POPs) – the name given to any man-made toxic chemicals such as Polychlorinated Bisphenyls (PCBs) are attracted on to the Nurdles surface, which means after these are consumed by animals, those chemicals can build up in animal tissue which will lead to long term damage.
All plastics leach and absorb hazardous substances!
Another critical concern about plastics are biofilms (thin, robust layers that stick to solid surfaces which contain communities of micro-organisms) that are able to form on the hard, rough texture of plastics which provide a suitable environment for harmful micro-organisms, such as E-coli, making the plastic even more toxic. Once it’s inside an animal’s stomach, it will damage its health with not only its own toxins (additives) but also the harmful biofilm it has accumulated too.
Well, well, well, now who would have thought that such a tiny and harmless-looking “Nurdle” would have such catastrophic, long-lasting effects on everyone? These effects will now carry on for generations. And remember, this was just one spill, that contributed and added on to all the other plastic waste out there…
*Ranjula Ranasinghe – St. Anselm’s College, Wirral