An article published on November 6, 2017 in the peer-reviewed journal Water Research reported on the content of microplastics in mineral waters packed in plastic or glass bottles, or beverage cartons. Darena Schymanski and colleagues from the Chemical and Veterinary Analytical Institute Münsterland-Emscher-Lippe (CVUA-MEL), Münster, Germany, used micro-Raman spectroscopy to measure microplastic fragments. In contrast to previously employed methods, this technique allowed detection of particles sized below 20 µm (down to 1 µm). The authors reported that almost 80% of all particles detected in their analysis were in this smaller size range, specifically between 5-20 µm. Since such small particles could not be measured in earlier studies on microplastics in water, their results could have been an underestimation.
Analyzed water samples were bought in German supermarkets and consisted of still or carbonated mineral water stored in plastic bottles (12 refillable and 10 single-use samples), beverage cartons (3 samples), and glass bottles (9 samples, not indicated whether of refillable or single-use type). The scientists took special precautions to avoid contamination from ambient air or equipment during sample preparation, filtration, and analysis. Despite these measures, blank samples still had 14 ± 13 particles/L on average. Very similar particle contents were found in water stored in beverage cartons (11 ± 8 particles/L) and in single-use plastic bottles (14 ± 14 particles/L). Waters stored in glass bottles were found to have 50 ± 52 particles/L. The highest content of microplastics, and the only one being statistically different from that in the blank samples, was found in waters stored in refillable plastic bottles (118 ± 88).
For microplastic counts in waters with different degrees of carbonation, a statistically significant difference was observed for water with highest carbon dioxide content (mean 99 ± 82 particles/L) compared to still water (mean 12 ± 9 particles/L), indicating a significant influence of carbonation on the release of microplastics from plastic materials. Microplastics content was also analyzed in a second batch of four brands of plastic bottled water (one single-use and three refillable), purchased six weeks later. The results obtained with both batches were very similar, indicating a lack of influence of production dates, as well as a good reproducibility of the analytical method.
The polymer composition of the microplastics detected in water from plastic bottles and beverage cartons pointed to the packaging itself as one likely source of these particles, as most were composed of the main polymers constituting the respective package. Interestingly, beverage cartons showed the highest content of large particles sized >100 µm. These were comprised of cellulose, likely originating from the carton part of the package. The authors commented that some of these large particles could have covered the smaller particles in the sample, thus potentially resulting in an underestimation of the overall particle content in beverage carton samples.
For glass bottles, the authors suggested that one source of the observed microplastics could be the plastic lid. However, polypropylene (PP), the material most commonly used to manufacture plastic lids for glass bottles, showed the lowest proportion among the polymers comprising the microplastics detected in glass-stored waters. Another potential contamination point for glass bottles could be the filling line, where outside spraying with polyethylene (PE) may be used as a cold end coating to provide slip characteristics and lubricity to resist damage.
Overall, this study’s design did not allow to conclude with high certainty on the origins of the microplastics observed in any of the samples, thus necessitating further research to better understand the contribution of different potential sources to the microplastics contamination in mineral waters. However, the facts that the highest content of microplastics was observed in water from reusable plastic bottles and that the polymer composition of these particles and the bottles matched very closely, led the authors to suggest that there could be “a potential wear with the result of packaging material leaching into the water.” Therefore, “abrasion or brittleness of the reusable bottles over time are concerning and could impact their reusability,” the authors concluded, calling for additional investigations “to further corroborate this theory.”
Further, the authors pointed out to a broader implication of their finding that plastic packaging can emit microparticles, namely with regard to the fact that a broad range of foods are currently packed in plastics, and “released microplastic particles could then be directly ingested by consumers.” They therefore called for further research on this matter “with a special focus on particles in the size range below 50 µm.”
In terms of toxicity, relatively little is known about the potential effects of microplastics in humans. It is widely assumed that microplastics will not have any toxicity due a very low uptake from the gut. However, this has been little investigated so far in humans, while the presence of microplastics in fish tissues (i.e., not only in the gut) has already been demonstrated (FPF reported). Furthermore, interference with immune system responses in the gut appears possible and may require further investigation (FPF reported). An additional concern is the exposure to other chemicals, such as additives contained in plastics (FPF reported) or hydrophobic pollutants adsorbed on the surface of microplastics particles (FPF reported), that could leach from microplastics once ingested. Drinking water is so far not considered a major source of human exposure to microplastics, with higher exposures estimated from inhalation (mostly from car tyres) but also from food (FPF reported).
Read more
Avery Dennison Corporation (2017). “Surface treatments for glass beverage containers.”
CVUA-MEL (January 15, 2018). “Untersuchung von Mikroplastik in Lebensmitteln und Kosmetika.” (in German)
Foodwatch (July 26, 2018). “Trinken wir Mikroplastik?” (in German)
Reference
Schymanski, D., et al. (2017). “Analysis of microplastics in water by micro-Raman spectroscopy: Release of plastic particles from different packaging into mineral water.” Water Research (published November 6, 2017).
