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Published on: July 24, 2021
Smaller-sized micro-plastics (MPs) contamination in single-use PET-bottled water in Thailand
Dinuka Kankanige1, Sandhya Babel1
1School of Bio-Chemical Engineering & Technology, Sirindhorn International Institute of Technology, Thammasat University-Rangsit Center, 90 Moo 18, Khlong Luang, Pathum Thani 12120, Thailand.
Abstract:
Micro-plastic (MP) contamination of drinking water is an emerging global concern. Findings on the cytotoxic effects of MPs in human cells are an incentive to investigate the MP concentration in drinking water. The present study quantitatively and qualitatively analyzes the MPs in 10 brands of single-use PET-bottled water, sourced from Thailand. A set of glass-bottled water was similarly analyzed to compare the MP concentrations between the two packaging. Two sorting techniques were used: 1) fluorescent tagging with Nile Red (≥6.5 μm) and 2) optical microscopy (≥50 μm). ATR-FT-IR (≥50 μm) and confocal Raman spectroscopy (1-50 μm) were also used. The MP concentration was found to be 140 ± 19 p/L in single-use plastic-bottled water and 52 ± 4 p/L in glass-bottled water. Plastic bottles had a significantly higher MP quantity than the latter. Both 6.5-20 μm and 20-50 μm MPs showed significant dominance over the ≥50 μm fraction. Fibers accounted for 62.8% of the total particle content, followed by fragments. Under optical microscopy, ≥50 μm particles were 10 ± 1 p/L (on average), which did not differ largely from that of fluorescent-tagged particles in the same size range (12 ± 1 p/L), implying the suitability of both techniques to sort ≥50 μm MPs. However, fluorescent-tagging was more reliable for MP identification in drinking water, particularly in the 6.5-50 μm range. Among the particles that were confirmed to be polymeric, PET, PE, PP, and PA were dominant. Accordingly, the contamination mainly emanates from the packaging, but could also occur during the manufacturing process. Given the direct human exposure to MPs through bottled water and their cellular toxicity, further studies are encouraged on smaller-sized MPs in drinking water.
Insights
Micro-plastic (MP) contamination in bottled water is a growing concern. This study found significantly higher MP levels in plastic bottles compared to glass, with fibers being the most common type.
Area of Science:
- Environmental Science
- Analytical Chemistry
- Toxicology
Background:
- Micro-plastic (MP) contamination in drinking water is a significant global health concern.
- Emerging evidence of MP cytotoxicity in human cells necessitates investigation into drinking water contamination levels.
- Single-use plastic packaging is a suspected major source of micro-plastic pollution.
Purpose of the Study:
- To quantitatively and qualitatively analyze micro-plastic contamination in various brands of bottled water.
- To compare micro-plastic concentrations between single-use plastic (PET) bottles and glass bottles.
- To identify the types and sizes of micro-plastics present in bottled water.
Main Methods:
- Analysis of 10 brands of PET-bottled water and glass-bottled water sourced from Thailand.
- Utilized fluorescent tagging with Nile Red (≥6.5 μm) and optical microscopy (≥50 μm) for sorting.
- Employed ATR-FT-IR (≥50 μm) and confocal Raman spectroscopy (1-50 μm) for particle identification and characterization.
Main Results:
- Single-use plastic-bottled water exhibited significantly higher MP concentrations (140 ± 19 p/L) compared to glass-bottled water (52 ± 4 p/L).
- Smaller micro-plastic fractions (6.5-20 μm and 20-50 μm) were dominant over larger particles (≥50 μm).
- Fibers constituted the majority (62.8%) of the total micro-plastic content, followed by fragments. Dominant polymer types included PET, PE, PP, and PA.
Conclusions:
- Plastic bottles are a primary source of micro-plastic contamination in bottled water, with potential contributions from manufacturing processes.
- Fluorescent tagging proved more reliable for identifying micro-plastics, especially in the 6.5-50 μm size range.
- Further research is crucial to understand the health implications of smaller micro-plastic particles in drinking water due to direct human exposure and known cellular toxicity.
