Plastics: Miracle Material or Growing Threat – Part I

Plastics have revolutionised our life and it has become impossible to envision a life without it. In fact, it has become an essential commodity in several fields. For example, in the present pandemic situation, it would be impossible for the medical community to handle Covid-19 patients without having disposable gloves, masks, Personal Protective Equipment (PPE) kits and other protective gear. Plastics also form an important component of medical equipment and surgical instruments, for example, syringes, medicine containers, tubes, dialysis filters to name a few.

However, the most widespread use of plastics is for packing. Food products ranging from grains and pulses, oils, milk and milk products, powder and spices, biscuits and most food items are now sold in plastic packing. It would be challenging to store and transport these products, without the versatile plastic packing. Vegetables, which were generally sold loose, are now being sold weighed and pre-packed in plastic covers. It has also become very common to see pre-cut vegetables according to the type of dish so that now the customer has to only wash and directly use these products. All these products are marketed as ‘easy’ and ‘convenient’ and it is seen that several customers also prefer such products.  

Plastics have become the most important component of our current ‘throwaway culture’. The term ‘Single Use Plastics’ (SUPs) has been framed to include all such plastic items which are used only once and then thrown away. This includes a variety of plastic items like plastic plates, glasses, and cutlery; plastic food wraps and takeaway food container; plastic bottles and caps; grocery bags and shopping bags; tetra packs, multi-layered packing, and sachets, and so on. At present, these SUP’s form a major portion of worldwide plastic production.

However, the issue is not with the plastics. The problem is with how these plastics are used and disposed. The disposal and handling of these plastics have become a major environmental issue. These plastics deface and pollute our earth be it soil or water and even the air we breathe with its toxic presence. The quantity of wastes that are being generated, and also the duration for which these plastics persist in our environment aggravates the issue of plastic pollution. While plastics are considered to be infinitely recyclable, the truth is that it is not so.

Plastics are consists of long chains of repeating units called ‘monomers. For example, polyethylene is a plastic which consists of repeating units of ethylene (C₂H₄). Each chain is called a polymer and may consist of thousands of these monomer units. The type of plastic and its properties will depend on the type of monomer and also the type of additives that are added to it during its production. Each time that plastic is recycled, the polymer chains are disrupted and shortened due to which the quality of plastic will deteriorate. So, a plastic product can generally be recycled only three to five times. Most of the time, plastics are not collected and sent for recycling. Instead, it is carelessly thrown away, sent to landfills and waste disposal sites, or even more dangerously, burnt off. It is common to see plastics strewn across roadsides and waterways especially in backward or developing countries. These plastics find their way into sewers, canals and drainage systems and clog them, providing breeding grounds for mosquitoes and other insects, and increasing the prevalence of diseases like malaria and dengue. Additionally, it is now seen that a good proportion of the floods in urban areas, popularly referred to as ‘Urban Floods’, are mainly caused by blocked drainage and sewerage systems. Eventually, most of the disposed plastics find their way into seas and oceans.

Microplastics: A growing concern Plastics take several hundred years to decompose and even when it does, it only breaks down into smaller particles. The term ‘microplastics’ has been coined for plastic particles that have a size lesser than 5mm and these microplastics are now present in almost all water bodies. Microplastics can be generated not only from the breakdown of plastic items but also from synthetic fibres. Synthetic fibres like polyester, nylon, viscose etc release microfibres into the water during the washing process. These fibres eventually reach seas and oceans through the sewerage and wastewater systems and finally contribute to microplastic pollution in those water bodies. Unlike natural fibres like cotton or jute, these do not breakdown or decompose in water, instead, they simply break down into further smaller particles which will persist in these aquatic bodies for hundreds of years. These microplastics later find their way into the bodies of fishes and other aquatic organisms and then enter the food chain of humans and animals who consume them. These plastics and the associated chemicals accumulate in the bodies of all such organisms and finally disrupt various systems of the body including the nervous system and reproductive systems.

Did you know? In a study by the University of Kerala (Department of Aquatic Biology and Fisheries), microplastics were seen to be present in 32 fishes out of 123 fishes of the species Piaractus brachypomus. About 69 pieces of microplastics as fibres, foams and fragments were obtained from these fishes. The fibres had an average length of 4.5mm while foams and fragments had an average size of 2.35mm and 2.38mm respectively. This particular fish is new to India and was introduced in India for aquaculture around 2004 and is now gaining popularity in Kerala due to its rich and tasty meat. Figure 5 First report of microplastic ingestion by the alien fish (Piaractus brachypomus) in the Ramsar site Vembanad Lake, south India Devi et al. (2020). Marine Pollution Bulletin 160

Types of Plastics and their Identification

Most plastic items, especially bottles will have a marking at the bottom in the form of a number enclosed within 3 arrows. These numbers can be used to identify the type of plastic material which has been explained below.

• Polyethylene Terephthalate (PET) – This is one of the most commonly used plastics and is used to manufacture mineral water bottles and soft drink bottles.  This material is usually transparent. PET is considered to be relatively safe, however, it is important to keep it away from heat. The material of plastic is slightly porous and tends to absorb flavour and smell. Bacteria may accumulate on its surfaces due to its relatively higher porosity and it is suggested that this plastic is not repeatedly reused. PET is also one of the most commonly recycled plastics. They are generally recycled into new PET bottles. However, recycled plastics can be used only as packing material for non-food grade products. Recycled PET fibres can be used for making textiles like carpets, stuffing for pillows and so on.
• High Density Polyethylene (HDPE) – This kind of plastic is usually opaque and stiff and is considered to be safe. HDPE does not easily wear down and is used for making items that require durability and weather resistance. It is used for making jugs, toys, shampoo and conditioner bottles, soap bottles, outdoor benches and tables, and some kinds of plastic bags. HDPE is commonly recycled.
• Poly Vinyl Chloride (PVC) – PVC is used for plumbing pipes, insulation for electric cables, bottles containing cleaning solutions, certain floorings, and tiles; etc. It is usually tough but is not safe for cooking. PVC contains phthalates which are extremely toxic if consumed and have the potential to interfere with hormonal development in humans. Materials labeled as PVC should never be used for cooking especially in microwaves, as phthalates may leach out from PVC during the cooking process.
• Low Density Polyethylene (LDPE) – LDPE is used for making plastic bags, cling films, squeezable bottles, sandwich bags, grocery bags, etc. It is relatively safe health-wise. However, when it is used for packing food, the plastic often gets contaminated with food, oils, or liquids and become difficult to clean. This plastic though theoretically recyclable does not get recycled because of food contamination and due to the difficulty in collecting and segregating these contaminated plastics. Thus, it forms a major bulk of plastic wastes that are not recycled.

• Polypropylene (PP) – It is used for manufacturing medicine bottles, kitchenware, and cutlery, microwave-safe containers, bottle caps, drinking straws, kettles, etc. PP is relatively heat resistant and is considered safe for use.
• Polystyrene (PS) commonly known by the brand name, Styrofoam – This plastic is lightweight and has insulating properties due to the entrained air in these plastics and so it is widely used is for the manufacture of disposable takeaway food containers. It is also one of the most toxic plastics. PS contains chemicals like styrene and benzene which can enter into the food through contact or if these containers are heated. These chemicals are carcinogenic and affect the respiratory system, nervous system and reproductive system. If burnt, PS also releases furans, dioxins and other toxic gases. PS contains a significant quantity of entrained air within the polymers and so even though these plastics are lightweight, they occupy a lot of space. This makes it difficult to collect, store and transport these plastics to specialised PS recycling factories. PS also absorbs food and liquids due to its porous nature and gets contaminated which makes the recycling of these plastics even more difficult. This plastic is also used for packing different items in the form of thermocol or foam peanuts.

Common ‘Plastics’ posing as recyclable materials

1. Multi-Layer Plastics (MLP) used in packing is a complex material that is environmentally unfriendly. It consists of layers of plastics encased within layers of aluminium. This kind of packing is used for packing a variety of food-grade products including biscuits, potato chips, tea and coffee powder, spices (including turmeric, chilly powder, garam masala, pepper etc), etc. MLPs ensures that the food item is preserved for longer durations without the penetration of moisture, air or other odours into or outside of the package. This is important in a country like India where there is a wide range of temperatures and humidities. MLPs are very difficult to recycle such materials because of their composite nature. Since it is extensively used, especially in the food industry, there is a very strong lobby supporting these packing materials both by the MLP manufacturers and the food industry as well. This makes it very difficult to introduce a complete ban on it.

2. Tetra pack – This is an extremely sterile material and a safe system of packing. The packed product can be stored for up to several months without requiring refrigeration. However, it is a highly problematic material from an environmental point of view. There is a common misconception that tetra packs are made of paper and can be recyclable. This is very far from the truth as this is a composite packing and is difficult to recycle. These tetra packs actually consist of multiple layers of paper, plastic and aluminium. This composite packing must be first sent to specialised units for separation before they can be recycled.

3. Paper cups and plates – These items are not just ‘paper’. They have a wax coating as well as a plastic layer to make it waterproof and to make the material more rigid. Such a composite material cannot be recycled especially if it is contaminated with food. Paper plates often have a thin aluminium layer backing and these plates cannot be recycled unless these layers are separated.