Microplastics are normally associated with the degradation of larger pieces of plastics, such as macroplastics. However, microplastics can be specifically engineered to be small in size. These are referred to as ‘primary’ microplastics. Primary microplastics are manufactured at a microscopic size such as microbeads and scrubbers which are mainly incorporated in cosmetic and personal care products. Another example of primary microplastics are nurdles.
Nurdles, or ‘pre-production pellets’, are the raw material for manufacturing everyday plastic products. They are used in a number of industries, such as the food and beverage industry for the manufacture of plastic bottles to the automobile industry for the production and assembly of numerous vehicle parts.
Due to their microscopic size, these nurdles are easily caught by the wind when spills occur during transport or handling, they wash or float their way into the sea. Nurdles come in all sorts of colours, and their size and shape make it very easy for marine life to mistake them for food.
‘Secondary’ microplastics are minute plastic fragments derived from the breakdown of larger plastic debris in the marine environment. Plastic debris in the sea is exposed to a number of physical, biological and chemical processes. Such processes include exposure to ultraviolet light, mechanical abrasion caused by the water movement, and reactions with chemicals in the sea. All of these factors will eventually reduce the structural integrity of plastic debris, resulting in fragmentation.
Both primary and secondary microplastics are of great concern to the marine environment, mainly due to their potential impact on the marine life. The decrease in the size of these particular fragments does not only increase the bioavailability of microplastics to thousands of species, but it also increases the likelihood of absorbing and desorbing toxic substances.