Does mechanical stress cause microplastic release from plastic water bottles?

Area of Science:

• Environmental Science
• Materials Science
• Public Health

Background:

• Microplastic (MP) ingestion is a growing health concern.
• Bottled water is a known source of MP intake.
• The release of MPs from plastic bottles under daily use conditions requires further investigation.

Purpose of the Study:

• To evaluate MP release from single-use PET mineral water bottles.
• To assess the impact of mechanical stress, specifically repeated opening/closing and squeezing, on MP generation.
• To analyze MP sources from PET bottlenecks, HDPE caps, and inner bottle surfaces.

Main Methods:

• Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray Spectroscopy (EDS) for morphological and elemental analysis.
• Quantification of particle concentrations in water samples.
• Analysis of MP release from PET bottlenecks and HDPE caps after 1, 10, and 100 opening/closing cycles.
• Investigation of MP release from inner bottle surfaces after squeezing (0, 1, 10 minutes).

Main Results:

• Significant increase in MP particle occurrence on PET and HDPE surfaces after repeated bottle opening/closing, particularly on caps after 100 cycles.
• Brand-specific differences in cap abrasion were observed, indicating varying plastic material behavior.
• Squeezing treatment did not significantly increase MP concentrations in bottled water.
• No stress cracks were detected on the inner bottle surfaces after mechanical stress.

Conclusions:

• The bottleneck-cap system is a primary source of microplastic release from single-use plastic bottles during frequent use.
• While bottle squeezing has a minimal impact, repeated opening and closing significantly contributes to MP generation.
• Human ingestion risk of MPs from plastic bottles increases with frequent use, primarily due to the cap and bottleneck interface.