Useful and highly variable material characteristics have made plastic the material of choice for an array of industries. The use of plastic outside of military applications began after World War II, seeing the plastics industry grow faster than that of any other man-made material (1). The plastic industry in South Africa is not exempt from the international growth trend, growing at a faster rate than the local economy in recent years (2). A total of 1.518 million tons of virgin polymer was converted into products in South Africa during 2016 (3).
The United Nations Environment Programme Yearbook 2014 proposed microplastics as one of ten emerging issues and identifies it as an important factor in the loss of biodiversity globally (4). Plastic is found everywhere in the environment from remote mountain lakes, the deep ocean to the air we breathe.
Microplastics are synthetic polymer particles smaller than 5 mm and can be categorised into primary and secondary microplastics (5). Primary microplastics are particles produced to be very small like pellets used in plastic production, or microbeads used in the cosmetic, pharmaceutical and sandblasting sectors. Secondary microplastics are the result of breakdown of larger plastic items, whether fibrous or solid articles that get broken down. This breakdown can happen on land or in water.
Fibres are more prone to become airborne than fragments due to higher wind resistance, hence up to 90% of synthetic particles found in the air are fibres (6). Fibres are released by the weathering of textile products, of which clothes are the greatest culprits (7). A single wash from a laundry washing machine can release up to 1900 fibres into waste water discharge (8).
These particles from the various sources above move around in the air and get deposited on land or in water. An estimated 7% of oceanic microplastics are deposited directly into the ocean by wind transfer (9). Waste water treatment plants can remove up to 97% of microplastics (10) and plastic from that water gets sedimented out and deposited into agricultural land as waste water sludge (11). Rivers carry plastics to the ocean, where most of it will remain and get broken down.
Studies also show that the smaller the particles get, the higher the abundance, as larger fibres break down into smaller pieces (12). These smaller particles also have a higher surface to area ratio and can adsorb more pollutants than their larger counterparts. These pollutants can be released once the particle has entered the body (13). Inhaled particles not removed by natural defence mechanisms become trapped in the respiratory tract can have several effects. Because of the small particle size, many plastic particles are able to cross the cellular membrane (14). When inside the cell they can release adsorbed toxins, plasticisers and other pollutants that have been shown to be associated with microplastics in the environment.
~ Carina Verster from the Unit for Environmental Sciences and Management at North-West University.
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