An article published on May 16, 2018 in the peer-reviewed journal Water Research reports on the analysis of bottled mineral water for small-sized particles consisting of microplastics, pigment, and additives. Barbara Ossmann and colleagues from the Bavarian Health and Food Safety Authority, Erlangen, Germany, analyzed 32 samples from 21 different brands of bottled mineral water purchased in Bavarian food stores. Evaluated bottle types included single-use (1) and reusable (9) glass bottles, single-use polyethylene terephthalate (PET) bottles (10), and 4 pairs of ‘newish’ and ‘older’ reusable PET bottles from three different brands. The ‘newish’ and ‘older’ bottles were differentiated based on the observable “scratches on the outside of the bottles and the cloudiness of the bottle material, which both enhance during reutilization.”
The scientists used micro-Raman spectroscopy to analyze the particles collected on the surface of a specially developed aluminum coated polycarbonate filter, described in their earlier publication. Prior to filtering, calcium carbonate (CAS 471-34-1) and magnesium carbonate (CAS 546-93-0) particles were dissolved by chelating the metal cations with ethylene diamine tetraacetic acid tetrasodium salt (EDTA, CAS 60-00-4). This allowed to reduce the total particle number collected on the filter and consequently decrease the measurement time. The lowest particle size analyzed was 1 µm, compared to 5 µm achieved previously by another group (FPF reported). The authors emphasize that microparticles smaller than 1.5 µm are particularly relevant for toxicological assessment, because they are more likely to penetrate deeper into the body (see, e.g., European Food Safety Authority’s (EFSA) statement on microplastics in food). Importantly, “over 90% of the detected microplastics and pigment particles were smaller than 5 µm and thus not covered by previous studies.”
Microparticles consisting of microplastics were detected in “almost all bottled water samples,” with “a high uncertainty per bottle type” due to “very different amounts of microplastics” detected in different samples. Single-use PET bottles had 2649±2857 particles per liter, reusable PET bottles 4889 ± 5432 particles per liter, and glass bottles 6292 ± 10521 particles per liter. Among the glass bottles, a very high amount, namely 35436 microplastic particles per liter, was detected in one bottle. If this outlier were removed, water in glass bottles would have a mean value of 3074±2531 particles per liter, “which is in the range of single use PET bottles.” Among the reusable PET bottles, a clear difference was observed between the ‘newish’ (2689±4371 particles per liter) and ‘older’ (8339±7043 particles per liter) bottles.
Both single-use and reusable PET bottles had a very similar distribution of microplastic particles’ sizes, with particles ≤ 1.5 µm and those sized between 1.5 µm and 5 µm representing about 47% and 50%, respectively, while much fewer larger particles were observed. In contrast, the majority (61%) of microplastic particles found in glass bottles were sized between 1.5 µm and 5 µm, with particles ≤1.5 µm representing only 16%, and 22% represented by particles >5 µm. Microplastics found in plastic bottles consisted predominantly of PET, while in glass bottles, polymers such as polyethylene and styrene-butadiene-copolymer were found.
In eight of the 10 single-use PET bottles, the quantity of pigment particles was similar to that in blank samples where 554±477 particles per liter were detected. Only two single use PET bottles showed higher amounts of pigment particles, resulting in the mean value of 1175±1179 pigmented particles per liter in this bottle type. In contrast, much higher amounts of pigment particles were detected in reusable bottles made of both PET (11074±18967 particles per liter) and glass (195047±330810 particles per liter). Among the reusable bottles, all bottles “labeled with printed paper showed significantly higher concentration (>10 000 pigmented particles per liter) than bottles labeled with plastic or the single use glass bottle.” Moreover, the ‘older’ reusable PET bottles had much higher amounts of pigment particles compared to the ‘newish’ bottles.
Most of the pigment particles were smaller than 5 µm in all bottle types, with particles smaller than 1.5 µm representing about 40% and 53% in PET and glass bottles, respectively. The distribution of the pigment types was very similar among the reusable PET and glass bottles. The same pigment types were found on the paper labels of these bottles, pointing to the printed paper labels as the likely contamination source and the bottle cleaning (during reuse) as a critical contaminating step, since the “washing liquor used in the cleaning process of the bottles . . . comes into contact with the labels and also the inner surface of the bottles.”
Water from reusable PET bottles was found to contain 708 ± 1024 particles per liter of the substance tris(2,4-di-tert-butylphenyl) phosphite (CAS 31570-04-4), a common antioxidant which could be leached out from the bottle material, the authors say. A second substance which had a similar spectrum but could not be identified was detected in one of the bottles at 542 particles per liter.
Vanessa Zainzinger (August 3, 2018). “Bottled water study flags small-sized pigment particles, microplastics.” Chemical Watch
Ossmann, B. E., et al. (2018). “Small-sized microplastics and pigmented particles in bottled mineral water.” Water Research 141: 307-316.
Ossmann, B. E., et al. (2017). “Development of an optimal filter substrate for the identification of small microplastic particles in food by micro-Raman spectroscopy.” Analytical and Bioanalytical Chemistry 409: 4099-4109.