Testing microplastics in tap water vs bottled water can be done through several scientific methods. Here's a breakdown of how it's tested, what differences typically emerge, and how you might approach such a test practically (if you're considering doing it or commissioning one).
How Microplastics Are Tested in Water
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Sample Collection
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Collect at least 1 liter of each sample (tap and bottled).
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Use glass or stainless steel containers to avoid plastic contamination.
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Filtration
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Water is filtered through very fine filter paper (usually 0.45 µm or smaller).
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This captures particles, including microplastics.
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Digestion (Optional)
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Organic material in the sample is chemically digested (e.g., with hydrogen peroxide) to isolate plastic particles.
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Microscopy + Spectroscopy
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Use microscopes (light or fluorescence) to visually identify particles.
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Use FTIR (Fourier-transform infrared spectroscopy) or Raman spectroscopy to confirm if particles are plastic and identify the type (e.g., PET, PE, PP).
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Typical Findings
| Water Type | Avg. Microplastic Particles per Liter (approx.) | Common Polymers Found |
|---|---|---|
| Tap Water | 0–20 particles/L (depending on country/region) | PE, PP, nylon |
| Bottled Water | 50–300+ particles/L (much higher on average) | PET, PP (from bottle/cap) |
A 2018 study by Orb Media tested 259 bottles and found 93% contained microplastics.
Want to Test It Yourself?
You can:
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Send samples to a lab that does environmental or food-grade microplastic testing. Labs charge from $300–$1,000 per sample.
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DIY with microscopes and filter paper – possible but less accurate and only visual (no polymer ID).
Example certified labs:
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Eurofins (Global)
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ALS Environmental
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SGS
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Microplastic Lab (Europe-based specialized service)
Summary
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Bottled water typically contains more microplastics than tap water, largely from packaging.
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Testing requires careful filtration, identification, and polymer analysis.
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For accurate results, use lab-based FTIR/Raman testing.
Microplastics
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Size range: 1 µm (micrometer) to 5 mm (millimeters)
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Anything smaller than 1 µm is often called nanoplastics
Microplastic Size Categories (UNEP, WHO definitions)
| Category | Size Range | Examples / Notes |
|---|---|---|
| Large microplastics | 1 mm – 5 mm | Visible plastic fragments, pellets, fibers |
| Small microplastics | 1 µm – 1 mm | Invisible to naked eye, common in water |
| Nanoplastics | <1 µm (1000 nanometers) | Very difficult to detect; potential for cell entry |
Typical Sizes Found in Water Studies
| Source | Typical Size Range Observed |
|---|---|
| Tap water | 10 µm – 500 µm |
| Bottled water | 6.5 µm – 100 µm (some up to 1000 µm) |
| Ocean samples | 1 µm – several mm |
For context:
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Human hair is ~70 µm in diameter
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White blood cell is ~10–12 µm
