Bottled Water Contains Triple the Microplastics of Tap Water, Study Finds

Bottled water contains an average of three times more micro- and nanoplastic particles than tap water, according to new research. Experts advise that filtering tap water and storing it in glass or stainless steel containers can significantly reduce plastic exposure, as plastic bottles themselves are a major source of contamination.

Science outlet StudyFinds reported on the 8th (local time) that researchers at Ohio State University compared six bottled water brands with tap water from four Ohio water treatment plants.

Bottled water contained an average of 6 million micro- and nanoplastic particles per liter. Tap water contained approximately 2 million particles per liter. The cleanest bottled water sample had plastic levels similar to the most contaminated tap water.

The research team found that each sip of bottled water delivers between 2.6 million and 11.5 million plastic particles per liter. Drinking tap water from a cup exposes consumers to 1.6 million to 2.6 million particles per liter. Nanoplastics accounted for 66% of plastic particles found in bottled water, compared to just over 50% in tap water.

The size of nanoplastics poses the greatest concern. Plastic particles larger than 150 micrometers typically pass through the digestive system unchanged, but particles between 10 and 130 micrometers can migrate into tissue. Nanoplastics smaller than 1 micrometer—100 times thinner than a human hair—circulate through blood vessels and accumulate in organs. Scientists believe these particles can even cross the blood-brain barrier.

PET (polyethylene terephthalate), the material used to make water bottles, was the most common plastic detected in bottled water. Polyamide from filtration systems ranked second, followed by rubber believed to originate from bottle cap seals. Plastic particles shed into the water each time bottles are opened, closed, shaken, or exposed to temperature changes, researchers explained.

Tap water showed different contamination patterns, with polyamide most prevalent, followed by rubber and various polyesters. Analysis indicated tap water plastics originated primarily from source rivers and lakes rather than the treatment process.

The research team used electron microscopy and photothermal infrared spectroscopy to identify particles as small as 300 nanometers. Previous technologies could only detect particles 5 to 10 micrometers or larger. Since 80% of tap water plastic particles measured smaller than 5 micrometers, earlier studies missed four out of every five particles. The actual nanoplastic count is likely far higher, as this study only measured particles down to 300 nanometers.

Dr. Megan Jamison Hart, who led the research, said reducing bottled water consumption is essential to minimize micro- and nanoplastic exposure. "Reducing single-use plastic consumption can lower plastic particle levels in the future," she said.

"Stop buying bottled water and drink tap water," Hart recommended. "Filtering tap water and storing it in glass or stainless steel bottles is the best approach." While plastics from water sources cannot be avoided entirely, additional contamination from containers can be eliminated, she noted.