Microplastics in Bottled Water vs Tap Water: UK Comparison

If you are paying a premium for bottled water assuming it is cleaner than what comes out of your tap, the research on microplastics may surprise you. Multiple studies now suggest that bottled water contains significantly more microplastic particles than tap water — in some cases, orders of magnitude more.

What the Research Shows

Bottled Water

A widely cited 2018 study by the State University of New York at Fredonia tested 259 individual bottles from 11 brands across 9 countries. They found an average of 325 microplastic particles per litre — with some bottles exceeding 10,000 particles per litre. Polypropylene, the plastic used in bottle caps, was the most common polymer detected.

More striking, a 2024 study published in Proceedings of the National Academy of Sciences used advanced laser-based imaging and detected approximately 240,000 nanoplastic particles per litre in bottled water — particles too small for previous studies to detect. This represents a contamination level roughly 100 times higher than earlier estimates that only measured microplastics.

Tap Water

Tap water also contains microplastics, but at far lower concentrations. The largest published survey — Kosuth et al. in PLOS ONE (2018) — tested 159 tap water samples sourced from around the world and found anthropogenic particles in 81% of them, averaging 5.45 particles per litre, across a range of 0 to 61.

One limitation worth being upfront about: those are global figures. That study reports no UK-specific percentage or particle count, and no peer-reviewed UK-specific tap water count has been published since. UK-level numbers do circulate, but we could not trace them to a peer-reviewed source, so this comparison uses the global benchmark rather than a national figure we cannot stand behind. It does not change the conclusion — the gap between tap and bottled water runs to more than two orders of magnitude either way.

A World Health Organization report on microplastics in drinking-water concluded that, based on the limited information available, microplastics in drinking water do not appear to pose a health risk at current levels — while calling for more research, and noting that the data on particles in the nano size range is extremely limited.

Why Bottled Water Contains More Microplastics

The higher microplastic count in bottled water is likely due to several factors:

1. Plastic packaging — the bottle itself (typically PET) sheds particles, especially when exposed to heat during transport and storage
2. Cap contamination — the screwing and unscrewing of polypropylene caps generates particles that fall into the water
3. Processing — bottling plants use plastic piping, filters, and filling equipment that can introduce particles
4. Storage conditions — bottles stored in warm warehouses or delivery vehicles experience accelerated plastic degradation

UK tap water, by contrast, is treated through municipal water treatment plants that use filtration processes removing many (though not all) particles. The water then travels through a mix of metal and plastic pipes, but the overall processing involves less plastic contact than bottled water production.

What About Glass-Bottled Water?

Glass-bottled water exists but is uncommon in UK retail. In theory, water stored in glass would avoid the packaging-related contamination — but the water source and processing infrastructure still involve some plastic components. Glass-bottled water is also significantly more expensive and heavier to transport.

A more practical solution is to filter your tap water and carry it in a reusable stainless steel or glass bottle.

Filtration Options

Basic water filtration can reduce microplastic particles in tap water:

• Jug filters (e.g., Brita) use activated carbon, which can trap larger microplastic particles but may not capture the smallest nanoplastics
• Reverse osmosis systems are more effective at removing micro and nanoplastics but are expensive and waste water
• Activated charcoal sticks (e.g., binchotan charcoal) are a traditional Japanese filtration method that some reusable bottle brands now include

No consumer filtration system has been proven to remove 100% of nanoplastics, but any reduction in exposure is likely beneficial given the precautionary principle.

The Bottom Line for UK Consumers

Based on the available research:

1. Tap water has far fewer microplastics than bottled water — switching from bottled to filtered tap water is one of the simplest ways to reduce your microplastic intake
2. Carry water in stainless steel or glass — avoid refilling and reusing plastic bottles, which shed particles with repeated use
3. Basic filtration helps — even a simple jug filter can reduce larger microplastic particles
4. Avoid heat exposure — never leave plastic water bottles in warm cars or direct sunlight, as heat dramatically accelerates microplastic shedding

The irony is striking: many consumers buy bottled water believing it to be purer, when the research consistently shows it contains more microplastic contamination than the tap water they are trying to avoid.

Sources

1. Synthetic polymer contamination in bottled water — Frontiers in Chemistry, 2018
2. Rapid single-particle chemical imaging of nanoplastics — Proceedings of the National Academy of Sciences, 2024
3. Microplastics in drinking-water — World Health Organization, 2019
4. Anthropogenic contamination of tap water, beer, and sea salt — Kosuth et al., PLOS ONE, 2018 (159 globally sourced tap water samples; global figures, not UK-specific)