From remote and pristine regions of the Pyrenees to the deep-sea floor, small fragments of plastic can be found the world over. With such a broad geographic spread, these microplastics – the umbrella term given to tiny plastic particles or fibers typically measuring less than 5 mm – have become ubiquitous in the modern world.
Since the health effects of microplastics are still not fully understood and our soil, waterways and the air around us are potential sources of microplastic contamination, there is a growing need to identify cases of serious contamination and stop the continued spread of microplastics.
Download this listicle to explore:
- The routes of microplastic contamination
- How microplastics can be detected
- Remediation techniques
Microplastics: How Do They Spread?
From remote and pristine regions of the Pyrenees1
to the deep-sea floor,2
small fragments of plastic can be found
the world over. With such a broad geographic spread, these microplastics — the umbrella term given to tiny
plastic particles or fibers typically measuring less than 5 mm — have become ubiquitous in the modern world.
Broadly, microplastics can be divided into two categories: primary and secondary microplastics.3
microplastics are plastic particulates designed for commercial use, such as the microbeads sometimes included
in personal care products or the synthetic fibers shed from clothes during washing. In contrast, secondary
microplastics are formed when larger plastic products, such as discarded bottles or plastic bags, begin to
decompose and break down in the environment.
Once these particles enter the environment, there is a risk that the microplastics could be ingested by fish, local
animals or humans who unknowingly eat contaminated foods. While the health effects of microplastics are still
not fully understood, current research indicates that microplastic exposure can cause tissue damage, oxidative
stress and changes in immune-related gene expression for marine life.4
In humans, accidental consumption
is also thought to be linked to problems with cytotoxicity, neurotoxicity, immune system disruption and the
accumulation of microplastics in different body tissues.4
But how does this exposure happen? Research suggests that our soil, waterways and even the air around us
can be a source of microplastic contamination. Fortunately, researchers have a number of tools at their disposal
that can help to identify and quantify cases of serious contamination,5
with several commercial-scale cleanup
technologies also helping to stop the continued spread of such microplastics.
Routes of microplastic contamination
There are three main avenues through which humans, animals and the wider environmental ecosystem might be
exposed to microplastics. These are:
There are multiple routes that microplastics might take to enter the soil.6
The breakdown of discarded plastic
items that have been sent to landfill is a major contributor. Other sources of contamination might
include tire wear and tear, soil amendments or the spreading of contaminated sewage sludges or wastewater
MICROPLASTICS: HOW DO THEY SPREAD? 2
Once they are in the soil, microplastics can have a significant impact on their local environment. Plants may
struggle with proper nutrient metabolism and absorption if microplastics are present at high enough levels, as
the microplastics can disrupt soil microorganisms and thus affect the normal microbiome.7
There is also the risk
that microplastics could enter the broader food chain once they have been introduced to fertile land, increasing
the risk of accidental consumption by animals and humans.
Current research indicates that microplastics may also act as a vector for other harmful pollutants, carrying
residual chemicals into new environments where they could present additional risks to life.8
Microplastics may be present in seawater, freshwater, wastewater or groundwater, although the exact source of
the plastic varies significantly. Microplastic fibers may be relatively common in seawater, for example, as fishing
nets begin to degrade and release material into the oceans. The microplastics found in wastewater are more
likely to be primary microplastics from personal care products being used and washed down the drain.9
Rainwater is another interesting case, as this water can act as a powerful vector that transports microplastics out
into soil or other aquatic environments, often picking up other contaminants along the way. One study conducted
in the Nakdong River, South Korea, found that 70–80% of the annual microplastic load is moved during the
country’s rainy season.10
In a marine environment, microplastics will gradually fragment into greater numbers of smaller microplastic
particles through physical abrasion, ultraviolet (UV) irradiation and biodegradation. At such small particle sizes,
these microplastics may pose even more substantial risks to aquatic life by penetrating cell membranes and
causing cellular damage.9
This presents a significant danger to the rest of the food chain too, as predators run
the risk of consuming prey containing large amounts of plastic accumulated in their tissues, thus furthering the
spread of these microplastics.
Due to their incredibly small size and low density, it is also possible for microplastics to be picked up in the wind
and blown from place to place.11 This means that humans and animals are actively breathing in atmospheric
microplastics as they go through daily life. Indeed, current research simulations suggest that humans may
breathe in nearly 300 microplastic particles during a day of light activity.12
Microplastic particles have already been found in human lung tissue samples; however, there is still a general
lack of information regarding the effects of these particles on the respiratory system and the mechanisms
through which they might contribute to lung disease.13
How is microplastic contamination detected?
Visual inspection using a microscope or stereoscope can be sufficient to detect the presence of microplastics in
simple sample matrices. Despite being a relatively time-consuming technique, even when assisted by the use of
special dyes, a recent review estimates that visual inspection is still used in just under one-third of microplastic
analyses of water and sediment samples.14
According to the same review, the most frequently used methods of analysis for water and sediment samples
are Fourier-transform infrared (FTIR) spectroscopy-based methods. This spectroscopy technique uses the
vibrational modes of different molecules in order to identify certain characteristic structures within a sample
that will indicate its chemical makeup. Raman spectroscopy, another vibrational spectroscopy method, is also
commonly used for microplastic analysis.
MICROPLASTICS: HOW DO THEY SPREAD? 3
Pyrolysis-gas chromatography-mass spectrometry (pyro-GC-MS) is another frequently used method of analysis
wherein microplastic samples are pyrolyzed in an inert atmosphere and the resulting gases are analyzed.14 By its
nature, this method is destructive and does not allow an analyst to glean any information regarding the number
of microplastic particles in a given sample. However, for the bulk analysis of a large sample, this technique can
provide very accurate characterizations of the different plastics present within very complex matrices.
An effective microplastic remediation technique must take care not to create more microplastics inadvertently,
either through incomplete degradation or additional fragmentation.
For this reason, coagulation is one of the most frequently used techniques for removing microplastics at
commercial wastewater treatment facilities.15 The technique works by using different chemical coagulants to
destabilize the microplastic particles suspended in the wastewater, promoting sedimentation and easy removal
when passed through a filter. However, this is not a perfect solution to microplastic pollution. At the industrial
level, the coagulation process will produce significant amounts of sludge that may pose its own risk to the
environment if not adequately treated.
There are other, more experimental techniques for microplastic remediation that are currently being trialed.15
One of these is photocatalytic degradation. This method makes use of a semiconductor material that absorbs
visible or UV light and, in the process, generates free radicals, which degrade the microplastics. However, while
this technique does effectively destroy microplastic particles, it still generates some sludge waste that must be
monitored and disposed of carefully to prevent damage to the environment.
Another novel technique that is attracting significant attention is electrocoagulation. A sustainable and costeffective alternative, electrocoagulation operates on the same principle as traditional coagulation but without the
use of chemical coagulating agents. In electrocoagulation, metallic electrodes are used to produce cations that
can promote flocculation between the microplastic particles. This produces significantly less sludge waste than
the traditional approach, which is a boon for both the environment and the wastewater treatment plant, that no
longer has to deal with the expensive post-processing and monitoring steps needed for proper sludge disposal.
As a material, plastic has revolutionized our modern world. Its impressive durability and strength-to-weight
ratio has enabled significant advancement in a wide variety of disciplines, including building and construction,
electronics, textiles, consumer products and transportation. But now more than ever, scientists are aware of
the dangers presented when these products are disposed of improperly and are allowed to break down to form
harmful microplastics. For today’s researchers, it is crucial that we improve our understanding of how these
plastic particles are being spread, so that actions can be taken to remediate cases of contamination and stem the
flow of these plastics into our environment.
MICROPLASTICS: HOW DO THEY SPREAD? 4
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Geosci. 2019;12(5):339-344. doi:10.1038/s41561-019-0335-5
2. Barrett J, Chase Z, Zhang J, et al. Microplastic pollution in deep-sea sediments from the Great Australian Bight. Front Mar Sci.
3. Microplastics: sources, effects and solutions. European Parliament. Published November 22, 2018. Accessed June 1, 2023.
4. Bhuyan MdS. Effects of microplastics on fish and in human health. Front Environ Sci. 2022;10. doi:10.3389/fenvs.2022.827289
5. Bose P. Microplastic detection. Technology Networks. Published August 31 2021. Accessed June 1, 2023. http://www.technologynetworks.com/applied-sciences/articles/microplastic-detection-353032
6. Guo JJ, Huang XP, Xiang L, et al. Source, migration and toxicology of microplastics in soil. Environ Int. 2020;137:105263.
7. Sun Y, Yang C, Liang H, et al. Health risk analysis of microplastics in soil in the 21st century: A scientometrics review. Front Environ
Sci. 2022;10. doi: https://doi.org/10.3389/fenvs.2022.976237
8. Sajjad M, Huang Q, Khan S, et al. Microplastics in the soil environment: A critical review. Environ Technol Innov. 2022;27:102408.
9. Kye H, Kim J, Ju S, Lee J, Lim C, Yoon Y. Microplastics in water systems: A review of their impacts on the environment and their
potential hazards. Heliyon. 2023;9(3):e14359. doi:10.1016/j.heliyon.2023.e14359
10. Eo S, Hong SH, Song YK, Han GM, Shim WJ. Spatiotemporal distribution and annual load of microplastics in the Nakdong River,
South Korea. Water Res. 2019;160:228-237. doi:10.1016/j.watres.2019.05.053
11. Abad López AP, Trilleras J, Arana VA, Garcia-Alzate LS, Grande-Tovar CD. Atmospheric microplastics: exposure, toxicity, and detrimental health effects. RSC Adv. 13(11):7468-7489. doi:10.1039/d2ra07098g
12. Vianello A, Jensen RL, Liu L, Vollertsen J. Simulating human exposure to indoor airborne microplastics using a Breathing Thermal
Manikin. Sci Rep. 2019;9:8670. doi:10.1038/s41598-019-45054-w
13. Lu K, Zhan D, Fang Y, et al. Microplastics, a potential threat to patients with lung diseases. Front Toxicol. 2022;4:958414.
14. Prata JC, da Costa JP, Duarte AC, Rocha-Santos T. Methods for sampling and detection of microplastics in water and sediment: A
critical review. TrAC Trends Anal Chem. 2019;110:150-159. doi:10.1016/j.trac.2018.10.029
15. Osman AI, Hosny M, Eltaweil AS, et al. Microplastic sources, formation, toxicity and remediation: a review. Environ Chem Lett. 2023.