Microplastics are small fragments of plastic material, generally defined as smaller than what can be seen by the naked eye. Our increased reliance on plastics for countless applications has negative consequences to the environment. For example, the plastic manufacturing process is associated with air pollution, and volatile organic compounds released over the life of the plastic have deleterious health effects for humans. Plastic waste takes up significant space in landfills. However, microplastics in the aquatic environment has been a newly emerging concern in the public consciousness.
As the name implies, microplastics are very small, generally too small to see although some scientists include pieces up to 5mm in diameter (about a fifth of an inch). They are of various types, including polyethylene (e.g., plastic bags, bottles), polystyrene (e.g., food containers), nylon, or PVC. These plastic items become degraded by heat, UV light, oxidation, mechanical action, and biodegradation by living organisms like bacteria. These processes yield increasingly small particles that eventually can be classified as microplastics.
Microplastics On the Beach
It appears that the beach environment, with its abundant sunlight and very high temperatures at ground level, is where the degradation processes operate fastest. On the hot sand surface, plastic trash fades, becomes brittle, then cracks and breaks down. High tides and wind pick up the tiny plastic particles and eventually add them to the growing great garbage patches found in the oceans. Since beach pollution is a major contributor of microplastic pollution, beach cleanup efforts turn out to be much more than esthetic exercises.
Environmental Effects of Microplastics
- Many persistent organic pollutants (for example, pesticides, PCBs, DDT, and dioxins) float around the oceans at low concentrations, but their hydrophobic nature concentrates them on the surface of plastic particles. Marine animals mistakenly feed on the microplastics, and at the same time ingest the toxic pollutants. The chemicals accumulate in the animal tissues and then increase in concentration as the pollutants are transferred up the food chain.
- As the plastics degrade and become brittle, they leach out monomers like BPA which can then be absorbed by marine life, with relatively little known consequences.
- Besides the associated chemical loads, ingested plastic materials can be damaging for marine organisms, as they can lead to digestive blockage or internal damage from abrasion. There is still much research needed to properly evaluate this issue.
- Being so numerous, microplastics provide abundant surfaces for small organisms to attach. This dramatic increase in colonization opportunities can have population-level consequences. In addition, these plastics are essentially rafts for organisms to travel further than they usually would, making them vectors for spreading invasive marine species.
A more recent source of trash in the oceans is the tiny polyethylene spheres, or microbeads, increasingly found in many consumer products. These microplastics do not come from the breakdown of larger pieces of plastic but instead are engineered additives to cosmetics and personal care products. They are most often used in skin care products and toothpaste and wash down drains, pass through water treatment plants, and end up in freshwater and marine environments. There is increased pressure for countries and states to regulate microbead use, and many large personal care product companies have pledged to find other alternatives.
- Andrady, A. 2011. Microplastics in the Marine Environment. Marine Pollution Bulletin.
- Wright et al. 2013. The Physical Impacts of Microplastics on Marine Organisms: A Review. Environmental Pollution.