Microplastics have become a more significant issue as concern has grown around plastic pollution and its environmental effects. Ongoing research has looked into biodegradability and ways to increase this. However, more recent research has focused on how plastic pollutants can damage biological organisms.
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What are Microplastics?
Microplastics are tiny pieces of plastic. Specifically, the size range given to microplastics is one micrometer to five millimeters in diameter. To give a sense of scale, one micrometer is a thousand times smaller than a millimeter.
Some primary microplastics are manufactured as microbeads for the cosmetic industry for uses within exfoliating hand creams and similar products. Microplastics also have mild abrasive properties, allowing them to be used within some cleaning products.
Another significant contributor to microplastic pollution is the textile industry. Microfibers used within products are released during manufacturing and wet processing stages, such as bleaching and dyeing. The laundering of microfiber textiles also contributes to microfiber release.
Secondary microplastics are usually formed when larger plastics undergo destructive processes, such as chemical, thermal, and photic exposure.
They have a very varied structure due to the number of products that can degrade into microplastics. For example, tires produce secondary microplastics as they wear against the road surface.
Some examples of polymers widely found within pollutant microplastics are polyethylene and polystyrene. These polymers have various uses, such as packaging or plastic bags; they are also widespread throughout the environment.
The Effects of Microplastics
The effect of microplastic on all forms of life and ecosystems has been gathering interest within the scientific community.
Common additives, such as phthalate and some biphenyls, can have adverse biological effects, including possibly causing cancers or disrupting the endocrine system which is used to regulate hormone levels in the body.
Like other organisms, humans ingest microplastics in a variety of ways. Microplastics are present in the air, food, and drinking water, to name a few occurrences.
Scientists have tried to hypothesize microplastics' effects and conducted some tests. Studies have found that smaller microplastics can pass through the lining of the gut, kidney and liver, and move into the bloodstream. This allows the plastics to then permeate throughout the body.
Plastics were also found in the brain of some fish species, but these plastics were among the smallest in diameter.
Scientists have suggested that human exposure could lead to DNA deformation and oxidative stress, including other potential health problems.
Microplastics are particularly prevalent in seawater. In 2022, a collection of studies found an average concentration of 1.75 MP/L with a variance of 5.17 MP/L between the recorded sites in the Southern Ocean and Antarctica. Wastewater had a lower concentration of 1.66 MP/L, only varying by 3.00 MP/L and showing that only some current treatment techniques remove microplastics.
While microplastic particles are harmful, their surface also contains high quantities of microorganisms, including some microbes identified as harmful pathogens to humans.
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There are two main options for microplastic pollution treatment: removing microplastics or preventing further microplastic release into ecosystems and the atmosphere.
Removal from seawater and other aquatic ecosystems is currently the most feasible solution, with some technologies already in place. Efforts, such as the Ocean Cleanup from the Netherlands, have been limited, but some methods involving cargo ships have been proposed and tested prototypically.
Research conducted by the Plymouth Marine Laboratory found that feeding microplastics and algae to specific species of mussels can turn microplastics into feces pellets that float to the water surface and are easy to collect. Subsequent steps to collect these pellets are still required, reducing the effectiveness of this method in practicality.
The Future of Microplastic Research and Removal
Removing existing microplastics from aquatic settings alone requires an unrealistic amount of time, effort, and funding, with most of the latter coming from sponsorship or donations. This is because the systems do not return a sustainable financial gain during their research and development, leading to limited research within the scientific community.
Methods used in wastewater treatment plants have proved the most effective, even though the facilities were not originally designed to remove microplastics.
These plants' chemical, physical and biological processes remove microplastics along the sewage sludge pulled from the water. However, this waste product is then returned to the environment.
Further research is needed to help combat microplastic pollution. While managing the pollutants already in ecosystems is vital, controlling the levels of pollutants entering the environment and studying the broader effects of prolonged exposure is just as crucial.
References and Further Reading
Bird, Robert, et al. Microplastics: research landscape, challenges, and remediation. Earth, Space, and Environmental Chemistry, https://doi.org/10.26434/chemrxiv-2022-xwv9h
Buckingham, J. W., et al. (2022) A record of microplastic in the marine nearshore waters of South Georgia. Environmental Pollution, vol. 306. https://doi.org/10.1016/j.envpol.2022.119379
Plastic Soup Foundation (2019) Health effects of Microplastics & Pathogens. [Online] Plastic Health Coalition.