Examining Microplastic Contamination in Beverages Using Laser Direct Infrared Spectroscopy

Microplastic contamination is a growing issue globally. A new study published in Heliyon examined this issue, specifically investigating whether there is a correlation between contamination levels and geographic location (1). This study, led by Yunxiang Wang from the University of Southern California, attempted to discern whether significant differences emerge in microplastic contamination between aluminum, glass, and plastic container types (1).

Close-up side shot of hands shows microplastic waste contaminated with the seaside sand. Microplastics are contaminated in the sea. Concept of water pollution and global warming. | Image Credit: © Pcess609 - stock.adobe.com

Microplastics are a common type of environmental pollutant normally found in oceans (2). These contaminants are typically smaller than 5 mm in diameter (1). Microplastics are tiny particles resulting from the breakdown of larger plastic products, and they pose threats to not only ecosystems, but also to the food and beverage supply (1,2). Ingested microplastics can release harmful chemicals and act as carriers for pathogens, leading to adverse health effects, especially with prolonged exposure (1,2). Although the threat of microplastics has been well-documented, Wang's study is among the first to investigate how both geographic location and container type influence the presence of MPs in beverages.

The research team focused on a single soda brand, which was left anonymous in the study. The team collected samples from four major U.S. cities: Atlanta, Chicago, Los Angeles, and Washington, D.C. The researchers tested the samples from three different packaging materials (aluminum, glass, and plastic). Each city-container combination was examined through a process that utilized laser infrared spectroscopy to identify and quantify the microplastics present (1).

In the end, the researchers compiled 36 different sample sets. Before filtration, the soda samples were unsealed for an hour to allow carbon dioxide to dissipate. The filtration process employed a 50 mL glass syringe combined with a polytetrafluoroethylene (PTFE) membrane filter paper to isolate MPs from the liquid (1).

Next, the containers were rinsed with microplastic-free water to capture any microplastics to make sure none remained in the container (1). The filtered material was subjected to ethanol rinses, after which the remaining solids were analyzed on specially designed glass microscope slides (1). The final examination of the MPs was conducted using Laser Direct Infrared (LDIR) spectroscopy, a cutting-edge technique that allows for precise identification of even the smallest particles.

Using LDIR spectroscopy, the research team discovered that notable differences were found based on geographic location. For example, beverages sourced from Los Angeles consistently exhibited the lowest levels of microplastic contamination, a result that Wang suggests could be linked to stricter quality control and filtration practices in the city’s manufacturing processes (1). As a result, the researchers conclude that local water sources could play a role in the microplastic content of beverages (1).

The research team used principal component analysis (PCA) to explore the relationships between the data. They identified three main principal components that highlighted the geographic differences in MP levels. However, PCA was less effective in distinguishing between container types, reinforcing the conclusion that geography plays a more significant role in microplastic contamination than packaging material (1).

Plastic population continues to be an issue globally. Over 450 million tons of plastic are produced per year, compared to only 2 million tons in 1950 (3). Understanding the nuances of microplastic contamination is crucial for developing strategies to mitigate its impact on public health and ecosystems (1). This study highlights the need for further studies to investigate how geographic factors influence microplastic contamination in other food and beverage products.

References

1. Wang, Y.; Wang, Y. Assessing Microplastic Contamination in Soda Beverages: A Multi-city, Multi-container Laser Direct Infrared Spectroscopy Study. Heliyon 2024, 10 (12), e32805.
2. Lee, Y.; Cho, J.; Sohn, J.; Kim, C. Health Effects of Microplastic Exposures: Current Issues and Perspectives in South Korea. Yonsei Med. J. 2023, 64 (5), 301–308. DOI: 10.3349/ymj.2023.0048
3. Ritchie, H.; Samborska, V.; Roser, M. Plastic Pollution. Our World in Data. Available at: https://ourworldindata.org/plastic-pollution (accessed 2024-09-25).