Does Boxed Water Have Microplastics? What the Carton Is Really Made Of

Is Boxed Water plastic-free?

No. Boxed Water’s help center says the box is made of “92% renewable plant-based materials”, and the rest is “5% aluminum and 3% BPA-free plastic”. That sounds like a mostly paper package. The company’s more detailed stats page gives the component weights, and they tell a different story, because the “plant-based” share includes plastic.

The stats page lists “fiber content” of 57.3% to 65.9% depending on size, and “renewable content” of 95.6% to 95.9%. Both can be true because the renewable figure treats the plastic as plant-based. Smaller cartons carry the same 2.57 cap, so the smaller the box, the larger the plastic share.

The plant-based claim rests on a mass balance system. Boxed Water says the plastic it uses “is just a portion of our supplier’s total production” and that “we can’t measure the exact renewable content in each cap and carton.” In other words, it buys enough plant-derived feedstock to match its order, but the polyethylene in your carton may be chemically indistinguishable from the fossil kind. Even fully plant-derived polyethylene is still polyethylene, as our JUST Water carton review explains for a similar package.

What touches the water inside a Boxed Water carton?

Boxed Water says the aluminum layer “serves as a barrier to light and oxygen” and “the polyethylene plastic acts as a water-tight barrier and helps the box keep its shape.” In a standard aseptic carton the paperboard gives structure and the polymer layers seal and bond it; Tetra Pak says about 70% of its cartons is paperboard. So the inner surface the water sits against for up to two years is a polyethylene film, and the cap and its pour spout are plastic too.

Boxed Water’s refill guidance confirms the inside is a lining. It warns against cleaning with “steel wool, stiff brush or anything abrasive as these may damage the carton’s inner lining”, and suggests reuse of about “twice a day for 30 days”. A thin film scrubbed and refilled 60 times is exactly the kind of wear that can shed fragments, so we wouldn’t treat the carton as a reusable bottle.

Time is the other factor. Boxed Water gives unflavored water a shelf life of two years from the production date and asks buyers to store it somewhere cool and dry. Fruit-flavored cartons are best within nine months. Two years is a long contact period for any packaged water, and nobody has measured whether particle counts in carton water change across that time. A carton bought fresh and drunk within weeks is a different exposure from one that sat in a hot warehouse for a year, even though the label reads the same.

Has Boxed Water been tested for microplastics?

Only once that we could find, and not in a peer-reviewed study. In December 2017 the Story of Stuff Project commissioned Abigail Barrows of Ocean Analytics to screen 19 US bottled waters. The summary reports about one liter per brand, filtered and counted under a stereo microscope at 45x. Particles were sorted by shape and color, not identified chemically, and 96% were 0.1 to 1.5 mm.

Boxed Water’s sample had 56 particles, or 58.6 per liter, the highest of the 19. The average across brands was 8 per liter. The group’s March 2018 release named Boxed Water among the most contaminated and called the results preliminary.

Read that number carefully. It is one sample. Visual counting can’t tell polyethylene from paper fiber, cotton lint or other non-plastic material, and a carton made largely of paperboard is a plausible source of fibers that aren’t plastic at all. The method also missed everything under roughly 0.1 mm, which is where most particles in later studies sit. It is a reason to want a proper test, not a measurement of how much plastic Boxed Water contains.

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Carton, can, glass or PET: compare what you actually buy

Scan the water on your shelf. The app reviews the declared package and cap materials, notes whether that brand has any published test, and suggests lower-plastic swaps. It does not measure particles.

What have carton studies measured?

Cartons have done well in the few studies that included them. These tested other brands, not Boxed Water:

• Germany, 2018. Schymanski and colleagues used micro-Raman spectroscopy, which identifies polymers down to a few micrometers. Water from three beverage cartons averaged 11 ± 8 particles per liter, against 14 ± 14 for single-use PET, 50 for glass and 118 for returnable PET. The lab blank was 14 ± 13, so the carton result was not distinguishable from background. Particles in carton water included polyethylene, which the authors linked to the carton’s polyethylene foil.
• France, 2025. ANSES reported 1.6 particles per liter for water in plastic bottles and cartons, against 4.5 for glass bottles.
• A nanoparticle caution. US government scientists (Zangmeister et al. 2022) found that hot beverage cups lined with low-density polyethylene released more than 10¹² nanometer-sized particles per liter, with release depending on water temperature. That was hot water in cups, not cold water in cartons, but it shows polyethylene films can shed particles too small for older methods to see.

So the carton category looks low for larger microplastics, and nobody has measured nanoplastics from a water carton at room temperature.

How does Boxed Water compare with bottles, cans, glass and other cartons?

Flow’s April 2024 release said its Tetra Pak packaging was made with up to 75% renewable materials, with a cap made from sugarcane, and that a new carton would be 81% plant-based. Like Boxed Water, that is a renewable-content claim. It doesn’t remove the polymer lining. For cans, see are cans lined with plastic? and our Liquid Death review. For glass, our Voss review covers the cap evidence.

Does Boxed Water’s purification remove microplastics?

Boxed Water uses municipal water, which it says lets it fill closer to customers. Its source page says water sold west of the Mississippi comes from water that flows through the Wasatch National Forest, and water sold east of it comes from Lake Michigan, followed by “a proprietary 8-step purification process”. The product page says its filtration “removes PFAS, BPA, and heavy metals” and that the water has no added minerals.

Those are manufacturer claims, and we found no public test report behind them or any particle claim. Even a very fine filter acts before filling. Anything the polyethylene lining or the cap contributes over a two-year shelf life comes afterward. The help center lists the water’s pH at 6.4.

Is Boxed Water better for the environment, even if it isn’t plastic-free?

That is a separate question, and it is the one Boxed Water’s marketing is built on. The company commissioned a life cycle assessment from the consultancy Anthesis in 2019, which it says followed ISO 14040 and 14044, and reports that its cartons had a lower total environmental impact than premium PET bottles and aluminum cans. It says auditors re-validated that standing in 2024. We haven’t reviewed the full study, and a commissioned assessment depends on its assumptions, such as transport distance and recycling rates.

Recycling is the weak point for any carton. Paperboard, polyethylene and aluminum are bonded together, so cartons need facilities that can separate them, and access varies by town. Boxed Water points buyers to a carton-recycling locator rather than promising curbside pickup everywhere.

None of this answers the microplastics question in either direction. Less fossil plastic in the supply chain and less plastic in contact with your water are different goals. A carton can do better on the first while still storing water against a plastic film for up to two years.

What the evidence does not establish

• That Boxed Water has the most microplastics of any brand. The 58.6 per liter screening is one sample, visually counted, not confirmed as plastic and not peer reviewed.
• That Boxed Water is microplastic-free. The water sits against polyethylene, and no current test has been published.
• How much plastic a “plant-based” carton sheds. Feedstock origin doesn’t change polyethylene’s behavior, and the company says it can’t measure renewable content per carton.
• A nanoplastic figure for cartons. The carton studies counted microplastics, not particles under a micrometer.
• A health effect. The FDA says current evidence does not demonstrate that microplastics and nanoplastics detected in foods pose a risk to human health.

What should you drink instead?

1. Filtered tap water in a reusable glass or steel bottle. Boxed Water’s about page says it hopes you “carry a refillable bottle and use tap water whenever possible.” See water filters compared and refillable bottle materials compared.
2. If you buy Boxed Water, drink it well before the best-by date, store it cool, and pour it rather than refilling the carton for weeks.
3. Don’t heat water in a carton. Polyethylene films shed more at higher temperatures.
4. Choose by the reason you buy it. If your goal is less fossil plastic waste, the carton has a case. If your goal is less plastic contact, glass with a simple cap or your own bottle does better.

The bottled water brands ranked guide shows which brands have any published data at all.