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Microplastics in Bottled Water: Glass vs Plastic Explained

10 min read

Microplastics in Bottled Water: Glass vs Plastic Explained

Quick answer: Some studies have found more larger detectable microplastics in certain drinks sold in glass bottles than in plastic bottles. But the likely source was often painted metal caps, not the glass itself. Newer studies capable of detecting much smaller particles have found that plastic bottled water can contain high numbers of nanoplastics - particles older studies were not designed to measure.

The “glass bottles contain more microplastics than plastic bottles” headline is real. It is also incomplete.

The fuller picture is this: glass bottles can be affected by plastic coatings and painted caps, while plastic bottled water can contain much smaller plastic particles released or introduced through packaging, bottling, processing and storage. These particles are often too small for older studies to detect.

That does not make glass perfect. It means the glass-versus-plastic debate cannot be settled by one headline or one particle count.

Do glass bottles contain more microplastics than plastic bottles?

Sometimes, yes. But that does not mean glass itself is the source or that plastic bottles are the safer option.

A 2025 French study found that several drinks sold in glass bottles contained more detectable microplastic particles than versions sold in plastic bottles, cartons or cans. However, the researchers found strong evidence that many of the particles came from paint on metal bottle caps.

The particles found in the drinks were similar in colour and composition to the cap paint. The caps also showed tiny scratches, thought to be caused by friction during storage before bottling.

For water specifically, the difference was relatively small: the study found an average of 4.5 particles per litre in glass bottles, compared with 1.6 particles per litre in plastic bottles and cartons.

The most accurate interpretation is not “glass is worse than plastic”. It is that packaging has several parts (bottle, cap, liner, coating, seal and label) and any of them can contribute particles.

Why the “glass has more microplastics” headline misses the bigger problem

The French study measured larger particles within the limits of its testing method. It could not capture the smallest particles now being found in bottled water: nanoplastics.

That matters because different studies can report wildly different totals depending on the smallest particle they are capable of detecting.

One study may count particles down to tens of micrometres. Another may detect particles down to 100 nanometres. Both studies may be accurate, but they are not counting the same part of the picture.

It is a little like comparing pebbles on a beach with grains of sand. The answer changes depending on what size you are able to see.

Glass-bottle studies can reveal larger particles linked to caps and coatings. Newer plastic-bottle studies can reveal vast numbers of much smaller particles that older equipment would miss.

This is why the glass-bottle headline should not be used as reassurance about single-use plastic bottled water.

Latest study: bottled water had more nanoplastics than treated tap water

A 2026 study compared treated drinking water from four municipal treatment plants near Lake Erie with water from six bottled-water brands sold in the United States.

Using methods designed to detect very small particles, the researchers found that bottled water contained around three times as many nanoplastic particles as the treated drinking-water samples.

The study did not publicly name the bottled-water brands. That means it cannot be used as a supermarket ranking or a claim about every bottle on every shelf.

But it does reinforce an important point: bottled water is not simply tap water in a more convenient container. It passes through additional packaging, bottling, transport and storage stages, each of which can contribute plastic particles.

Six bottled-water brands were compared with water from four treatment plants.
Bottled water contained around three times more nanoplastic particles than treated drinking water in this study.
More than half of the particles detected were nanoplastics.
The study did not identify the brands.

A separate 2024 study used highly sensitive microscopy to analyse bottled water from three unnamed popular US brands. It estimated an average of around 240,000 micro- and nanoplastic particles per litre, with around 90% classified as nanoplastics.

The key shift is not necessarily that bottled water suddenly became more contaminated. It is that researchers are becoming better at detecting particles that were previously invisible to standard testing.

Microplastics vs nanoplastics: why particle size matters

Microplastics are generally defined as plastic particles smaller than 5 millimetres. That category includes particles large enough to see as well as particles that require laboratory equipment.

Nanoplastics are much smaller. They are typically described as particles below 1 micrometre, or one thousandth of a millimetre.

Particle type	Size	Why it matters
Microplastics	Below 5 millimetres	A broad category that includes visible fragments and microscopic particles.
Nanoplastics	Usually below 1 micrometre	Much harder to detect and a major focus of current research because of their extremely small size.
Detection limit	Varies by study	The smallest particle a test can reliably detect. Lower detection limits generally reveal more particles.

Scientists are investigating how very small particles may interact with cells and biological barriers differently from larger particles. However, the precise health effects of drinking nanoplastics from bottled water, and the level of exposure that would cause harm, are still being researched.

The honest concern is not that every nanoplastic particle is proven to harm every person. It is that these particles are widespread, under-measured and small enough that older studies cannot tell us the full exposure picture.

Which bottled-water brands have been tested for microplastics?

The best-known brand-by-brand study was published in 2018. It tested 259 bottles from 11 bottled-water brands purchased across nine countries.

It found plastic contamination above laboratory background in 93% of the bottles tested. However, it focused on larger microplastics and did not measure nanoplastics.

This is a historical snapshot, not a current ranking of the “worst” bottled-water brands. Results varied substantially between individual bottles and production lots, and newer studies often do not name brands.

Brand tested in 2018	Study finding	What it does — and does not — tell us
🥤 Nestlé Pure Life	930 particles per litre	Highest reported brand-average count in this study. One bottle exceeded 10,000 particles per litre. It is not a current nanoplastic ranking.
💧 Gerolsteiner	807 particles per litre	Second-highest reported brand-average count in this study. Both glass and plastic packaging were included.
🧊 Minalba	63.1 particles per litre	Among the lower brand averages reported in this study. Lower is not the same as plastic-free.
🍾 San Pellegrino	30 particles per litre	Lowest reported brand-average count in this study. It does not establish a permanent safety advantage.
🚰 Aquafina	Tested	Results varied across bottles and lots. The published paper should not be treated as a current consumer scorecard.
💦 Dasani	Tested	Results varied across bottles and lots. The study did not measure nanoplastics.
🏔️ Evian	Tested	Included in the study, but not evidence of a current contamination level.
💧 Bisleri	Tested	Included in the study. Bottling location, bottle type and storage may all affect results.
🫧 Aqua	Tested	Included in the study. This does not show what a bottle bought today contains.
💦 Epura	Tested	Included in the study. The study is useful context, not a current buying guide.

The newer 2024 and 2026 nanoplastic studies are more relevant to today’s debate because they are able to detect smaller particles. But neither study publicly named the brands tested.

Why plastic bottles can add particles to water

Plastic particles in bottled water may come from more than one part of the process.

The bottle itself: friction, ageing and handling may release fragments from plastic packaging.
The cap and closure: caps, liners and safety seals are made from different materials and can contribute their own particles.
Bottling equipment: processing lines, filters, tubing and machinery may introduce particles.
Water treatment: some bottled water is filtered or treated before bottling, and treatment processes can use polymer-based membranes or components.
Transport and storage: time, heat and physical movement can affect packaging materials.

That does not mean every bottle continuously releases the same number of particles. It means disposable bottled water has additional food-contact materials and handling stages that tap water in a reusable bottle does not.

Does heat make plastic bottled water worse?

Heat and sunlight can accelerate the ageing of plastic packaging and can increase migration from food-contact plastics under laboratory conditions. The exact effect depends on the material, temperature, duration and storage conditions.

There is no reason to panic about the occasional bottle of water left in warm weather. But repeatedly storing bottled drinks in hot cars, direct sun or beside radiators is an avoidable habit.

More practical choices:

Do not leave plastic bottled water in a hot car for long periods.
Keep bottled drinks out of direct sunlight where possible.
Choose a glass or stainless-steel reusable bottle for everyday use.
Replace reusable plastic bottles when they become scratched, cloudy, cracked or difficult to clean.

Is tap water better than bottled water?

For most UK households, tap water is a practical everyday option. It is regulated and monitored, and it avoids the additional packaging and transport involved in single-use bottled water.

But tap water is not identical in every home. The water supplied to a property may be high quality, while the water from a kitchen tap can still be affected by the plumbing inside the building.

Potential household factors include:

Older lead service pipes: some older homes may still have lead plumbing or lead solder.
Stagnant water: water that has stood in pipes for long periods can pick up traces from plumbing and fittings.
Old tanks, fittings or appliances: these can affect taste, smell or local water quality.
Poorly maintained filters: a filter is only useful when it is the right type for the concern and the cartridge is changed on time.

Trace pharmaceutical residues can be detected in some source waters, but UK drinking-water authorities state that the very low levels found in drinking water do not pose an appreciable health risk. They are still a reminder that water quality is shaped by the entire system, source, treatment, pipes and storage, not simply whether water comes in a bottle.

A filter can be useful, but filters are not interchangeable. A simple carbon filter may improve taste or reduce chlorine. Other systems are designed for specific concerns such as lead, PFAS, particles or dissolved contaminants. Check exactly what a filter is independently certified to reduce, and replace cartridges as instructed.

For most people, the sensible default is cold kitchen tap water in a clean glass or stainless-steel bottle, with filtration chosen according to their local water and household plumbing situation.

How to refill more thoughtfully

Refilling is usually a better everyday habit than repeatedly buying single-use bottled water. But it is worth being thoughtful about where and how you refill.

Refill from a known mains drinking-water tap where possible.
Use official public refill stations, cafés or venues that clearly provide drinking water.
Avoid refilling from decorative fountains, unknown outdoor taps or water points with unclear maintenance.
Use the cold kitchen tap at home, rather than water from hot-water systems.
Wash reusable bottles and lids regularly, especially around threads, seals and straws.
Replace damaged seals, cracked lids and worn straws that are difficult to keep clean.
Keep a spare bottle in your bag, car or pushchair so convenience does not force a single-use purchase.

The bottom line: glass is not perfect, but plastic bottled water is not the answer

The glass-bottle microplastics headline is based on real research. In some drinks, glass bottles had more larger detectable particles than plastic bottles, and painted caps were the likely source.

But that finding should not become a reason to accept single-use plastic bottled water as the safer default.

Newer studies are detecting nanoplastics that older methods missed. In 2026, bottled water contained around three times more nanoplastic particles than treated drinking water in a direct comparison study. In 2024, researchers found hundreds of thousands of micro- and nanoplastic particles per litre in three unnamed bottled-water brands.

The aim is not to find one perfect bottle. It is to reduce unnecessary reliance on disposable packaging, ask better questions about the materials around our food and drink, and choose the simplest practical option more often.

Frequently asked questions

Does bottled water contain microplastics?

Yes. Studies have detected microplastics in bottled water from multiple countries and brands. Reported levels vary widely because studies use different methods, test different bottles and detect different particle sizes.

Does bottled water contain nanoplastics?

Yes. Newer studies using more sensitive methods have detected nanoplastics in bottled water. A 2024 study estimated that around 90% of the particles it detected in three unnamed bottled-water brands were nanoplastics.

Are glass bottles free from microplastics?

No. Glass bottles can still have metal caps, plastic liners, paint coatings, seals and labels. A 2025 French study found that painted caps were a likely source of microplastics in some glass-bottled drinks.

Is tap water free from microplastics?

No. Microplastics have been found in tap water as well as bottled water. Levels can vary according to source water, treatment, pipes and the testing method. The most useful comparison is not “zero plastic versus plastic”, but how much unnecessary packaging and plastic contact a choice adds.

Should I stop drinking bottled water completely?

No. Bottled water can be useful for travel, emergencies and situations where safe drinking water is not available. The practical goal is to make it a back-up rather than an everyday default when safe tap water is available.

Do water filters remove microplastics and nanoplastics?

Some may reduce certain particles, but performance depends on the filter type, particle size and certification. Check the manufacturer’s independent testing and change filters on schedule. Do not assume every jug or tap filter removes the same contaminants.

Glossary

Microplastics: Plastic particles generally smaller than 5 millimetres.

Nanoplastics: Much smaller plastic particles, generally described as being below 1 micrometre.

Micrometre: One millionth of a metre. It is written as µm.

Nanometre: One billionth of a metre. It is written as nm.

Detection limit: The smallest particle or substance a testing method can reliably detect. Different detection limits can lead to very different reported results.

Food-contact material: Any material designed to touch food or drink, including bottles, caps, liners, cups, packaging and utensils.

Particle migration: The movement of particles or chemicals from packaging into food or drink.

Reverse osmosis: A filtration process that uses a membrane to remove dissolved substances and particles from water.

Keep reading

Microplastics are not only a bottled-water issue. They are part of a wider conversation about the materials that touch our food, homes and bodies every day.