Plastic production, consumption and resulting waste is an international problem, with over 300 million tons being produced worldwide in 2017.1 While many countries are increasingly encouraging the avoidance of single-use plastics and greater uptake of recycling, the international demand use of plastic materials is continuing to increase. Finding suitable alternatives to plastic materials is challenging for many applications, such as healthcare. Despite clear motivation from the UN to create new resolutions for tackling the plastic lifecycle issue, plastic waste is likely to remain a problem for several years.2
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As well as large pieces of plastic waste, there has been growing concern about the potential polluting power of microplastics and their accumulation in the food chain.3 Microplastics refers to plastic particles between 1 – 5000 µm in size. They are formed from the breakdown of larger pieces of plastic, which involves physical or chemical abrasion. The resulting particles can have numerous shapes, including fiber-like or spherical forms.
Exactly whether microplastics form a threat to human health remains unclear. However, the ubiquity of microplastics in the natural environment and the presence of various chemical additives used in the manufacturing process of microplastic waste have raised concerns and calls for further investigation.4
Recent work has used analytical chemistry techniques to quantify microplastic concentrations in blood samples from patients. From the results, it is clear that microplastics can enter the bloodstream in humans and suggests that some of the types of microplastics people encounter are bioavailable and may be transported to other organs.5
Spectroscopy methods measure the interaction of light with different kinds of matter to recover qualitative and quantitative information. There is now a vast range of spectroscopy methods available that operate with light in different regions of the electromagnetic spectrum and are suitable for analyzing various sample types, from solids to gases and complex mixtures such as blood.
Spectroscopic analysis techniques are routinely used in many applications, including healthcare6 and play an important role in forensic analysis and disease identification.
Raman and infrared spectroscopy have been used for the identification of microplastics in environmental samples as they can be used to identify both the plastic type as well as the amounts present.7 Spectrometry methods are also an essential tool in analyzing these complex samples, particularly in more complex biological environments such as blood.
Microplastics in Blood
The recent work looking at the presence of microplastics in blood uses double shot pyrolysis gas-chromatography mass spectrometry (Py-GC/MS). Py-GC/MS is a destructive analytical method commonly used to look at the degradation of plastic material.
A Py-GC/MS measurement involves heating the sample and then analysis of the gases emitted from the sample over a range of different temperatures. As microplastic particles can be contaminated with other chemical species such as paints and chemical additives that have been added during the polymer manufacturing process, ramping the temperature in stages means the chemicals of different volatilities can be analyzed. Sequential heating simplifies the gas mixture analysis in the GC/MS stage as only a subset of the total chemicals present enter the spectrometer.
Double shot pyrolysis measurements are typically run over low (< 350 °C) and high temperatures (> 800 °C) for polymer species. For polymer species that may be present as a mixture of the monomer starting material and longer chain polymers, it is possible to examine the shorter and longer chains – that are more thermally resistant – separately.
Mass spectrometry methods use characteristic masses and fragmentation or degradation patterns following pyrolysis to identify chemical species and the researchers could use this in their work to identify a wide range of polymer species present in the blood, including poly(methyl methacrylate) (PMMA), polypropylene, polyethylene terephthalate (PET) and polystyrenes.5
The team identified nanograms of the plastics in the bloody samples and found that PET was present at the highest concentrations of 7.1 µg/ml. The team hopes to improve the limits of the method's detection with future refinements and improvement of the frequency of inaccurate non-detect events when microplastics were present in the sample.
There is also a great deal of work to be done on the biological implications of microplastics in human blood samples. Understanding how microplastics get into the human bloodstream is needed. Researchers understand that nanoplastics can pass through the human placenta, and it has been suggested that microplastics can potentially be inhaled via the lungs. With the ability to detect microplastics in blood, it will also be possible to routinely monitor microplastic concentrations to see if these particles start to bioaccumulate over time.
References and Further Reading
- PlasticsEurope (2017) Plastics: The Facts 2017, https://plasticseurope.org/, accessed September 2022
- UN (2022) End of Plastic Pollution, https://wedocs.unep.org/bitstream/handle/20.500.11822/38522/k2200647_-_unep-ea-5-l-23-rev-1_-_advance.pdf?sequence=1&isAllowed=y, accessed September 2022
- Hale, R. C., Seeley, M. E., La Guardia, M. J., Mai, L., & Zeng, E. Y. (2020). A Global Perspective on Microplastics. Journal of Geophysical Research: Oceans, 125(1), 1–40. https://doi.org/10.1029/2018JC014719
- Campanale, C., Massarelli, C., Savino, I., & Locaputo, V. (2020). A Detailed Review Study on Potential Effects of Microplastics and Additives of Concern on Human Health. International Journal of Environmental Research and Public Health, 17, 1212. https://doi.org/10.3390/ijerph17041212
- Leslie, H. A., Velzen, M. J. M. Van, Brandsma, S. H., Vethaak, A. D., Garcia-vallejo, J., & Lamoree, M. H. (2022). Discovery and quantification of plastic particle pollution in human blood. Environment International, 163, 107199. https://doi.org/10.1016/j.envint.2022.107199
- Hong, K., & Yaqub, M. A. (2019). Application of functional near-infrared spectroscopy in the healthcare industry: A review. Journal of Innovative Optical Health Sciences, 12(6), 1930012. https://doi.org/10.1142/S179354581930012X
- Araujo, C. F., Nolasco, M. M., Ribeiro, A. M. P., & Ribeiro-Claro, P. J. A. (2018). Identification of microplastics using Raman spectroscopy: Latest developments and future prospects. Water Research, 142, 426–440. https://doi.org/10.1016/j.watres.2018.05.060
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