A recent report discussed the presence and toxicity of microplastic pollution in the environment. Researchers believe they will not only affect living organisms living in our environment but potentially humans as well.
The global movement against plastic has gained momentum over the past few years. The Earth Day Network in the United States has identified over 8 million metric tonnes of manufactured plastic in our ocean every year.
In recent years, the classifications of plastic has extended past “environmental plastic”, with the European Commission defining new categories such microplastic and nanoplastic. Both are formed from the breakdown of larger pieces of plastic, such as shopping bags or car tires. Both micro-plastic and nano-plastic are also added to everyday items such as facial scrubs or toothpaste.
Dr. Natalia Ivelva with the Technical University of Munich (TUM) led the project for innovative methods of identification and quantification of microplastic pollution in our environment. As a major source of environmental pollution, society fights to reduce the overuse and improper elimination of plastic.
Over 400 million tons of plastic is produced worldwide, with a significant amount ending up in our environment as litter. With the overproduction and overconsumption of plastic, Dr. Ivelva predicts that there will be a huge increase in micro-plastic pollution over the next few decades. In a study published in Trends in Analytical Chemistry, researchers discussed their methods of analyzing microplastics and nanoplastics in the environment.
Identifying microplastic in environmental samples
Currently, many methods are utilized to analyze samples for microplastic. The sample must be properly prepared to avoid contamination, as most come from diverse locations. Preventative measures are taken by firstly removing the exterior matrix with an acid treatment or enzymatic protocol so that the particles can be examined. A given sample would yield low masses of particles, despite the high amounts of environmental micro-plastic pollution. Thus, samples are only ready to be examined with the methods below after being concentrated together.
Laser: Using the principle of Brownian motion, laser lights are scattered on the particles to identify their physical properties or PSD.
Imaging: This method offers the greatest depiction of the geometry and surface characteristics of particles. Different types of imaging techniques are available: optical microscopy, electron microscopy (EM), and scanning probe microscopy (SPM).
Upon examination, the chemical properties of the samples are identified to determine the presence of micro or nanoplastics. To determine the presence of either, different techniques are used.
Vibrational spectroscopy is highly used in conjunction with optical microscopy to provide the imaging of micro-plastics. This yields information on particle size, geometry, and spectroscopic identification. However, the efficacy of this method decreases with smaller particle sizes. As a result, a combination of varying techniques is used to identify the presence of nanoplastics.
Raman microspectroscopy is the preferred method of identification at TUM. The technique uses the scattering of laser lights that gives a ‘vibrational fingerprint spectrum’. Because the light source does not need infrared lighting, shorter wavelengths that yield higher spatial resolutions are utilized. With this method, researchers also have the ability to discern between synthetic (plastic) or organic (cellulose or quartz) particles. The Raman spectrometer clearly defines the number of particles, range of particle sizes, and the polymer types in the microplastics.
Humans and animals are able to absorb microplastic particles
Although the long-term dangers of microplastic pollution on our environment and its living organisms are not yet known, researchers have determined that aquatic organisms and other species, including humans, are able to absorb micro-plastic particles. The presence of these particles has been found in the digestive tracts of water fleas and mussels. This alone is not enough to prove toxicity, but it does warrant for further investigations and research into this topic. Stated in the press release, “as plastic particles degrade to ever-smaller sizes in the environment, they present an increasingly higher potential for environmental toxicity.”
In spite of all the research surrounding microplastic pollution, Dr. Ivleva expresses that she does not believe we should completely ban the plastic, as it is an “incredibly versatile material that has a lot of advantages over other plastics.” However, she notes that the amount of plastic currently being used (and overconsumed), needs to drastically decrease.
Using standardized analysis methods, she hopes to educate society on just how much plastic is present in any given sample with microplastic pollution and the negative effects it can have on our environment and surrounding living things. Throughout this journey, it will also be important to identify the specific concentrations of micro-plastics that cause toxic effects.
With the rise of the movement against microplastic pollution, consumers should become more responsible in how we use, reuse, recycle, and dispose.
Written by Stephanie C. Tsang
Reference: Schwaferts, C., Niessner, R., Elsner, M., & Ivleva, N. P. (2019). Methods for the analysis of submicrometer- and nanoplastic particles in the environment. TrAC Trends in Analytical Chemistry,112, 52-65. doi:10.1016/j.trac.2018.12.014