A 2024 Columbia University study using Raman scattering microscopy found an average of 240,000 nanoplastic particles per liter of bottled water sold in plastic containers. That's 100x more than previously estimated using older detection methods.
Glass bottles showed significantly fewer particles. The container you choose matters as much as the water inside it.
The nanoplastic problem
Previous microplastic studies detected particles larger than 1 micrometer. The Columbia study was the first to detect nanoplastics -- particles smaller than 1 micrometer -- using stimulated Raman scattering microscopy. Nanoplastics are more concerning because they're small enough to cross the blood-brain barrier and placental barrier.
The most common plastics found: PET (polyethylene terephthalate, the standard water bottle material), polyamide (from water processing filters), and polystyrene.
What our COA data shows
Among our verified brands, two have been independently tested for microplastics:
- Hallstein (glass bottle) -- microplastics ND (not detected)
- Acqua Carpatica (glass bottle available) -- microplastics ND
Both brands that test for microplastics use glass bottles. This is not a coincidence. Brands selling in plastic have little incentive to test for microplastics because the container itself is a contamination source.
BPA and container leaching
Beyond microplastics, plastic containers can leach chemicals into water:
- BPA (bisphenol A) -- endocrine disruptor, largely phased out of water bottles but replaced by BPS and BPF which have similar concerns
- Phthalates -- plasticizers that can leach when exposed to heat or UV light
- Antimony -- a heavy metal used as a catalyst in PET production, detectable in plastic-bottled water at higher levels than glass
Hallstein specifically tests for and confirms BPA-free status on their COA.
The cost tradeoff
Glass-bottled water costs more. Hallstein is the most expensive verified brand on our platform. Acqua Carpatica offers glass options at a more moderate price point. For daily hydration, a glass container with filtered tap water eliminates the problem entirely at the lowest cost.
Recommendations
If microplastic exposure matters to you:
- Choose glass-bottled water when buying bottled -- Hallstein and Acqua Carpatica both show microplastics ND
- Never leave plastic water bottles in heat -- car dashboards, direct sunlight, and microwaving accelerate leaching
- Use a home water filter -- RO systems remove >99% of microplastics from tap water
- Use glass or stainless steel for daily water storage
The bottom line
The container is part of the product. A water that tests clean for contaminants but is sold in a plastic bottle that introduces 240,000 nanoplastic particles per liter is not as clean as its COA suggests. Our ranking rewards brands that test for microplastics and use glass containers because these are measurable quality indicators, not marketing claims.
View the full bottled water rankings | Learn more about microplastics