Tiny bits of plastic commonly come rushing out of water taps around the world, according to a new survey of 159 water samples collected from more than a dozen nations.

Overall, 83 percent of the 159 samples contained some amount of microplastics. Those samples came from various places in the US, Europe, Indonesia, Uganda, Beirut, India, and Ecuador. No country was without a plastic-positive water sample. In fact, after testing a handful of samples from each place, the lowest contamination rate was 72 percent. The highest—found in the US—was 94-percent positive rate.

The microplastic pieces found are tiny, as small as 2.5 micrometers in size. The amounts were tiny, too. When researchers looked at the average number of plastic bits per 500mL water sample in each nation, the highest average was from US water samples—with 4.8 plastic scraps per sample. A sample taken from the US Capitol had 16 plastic fragments in it, for instance. The lowest average was 1.9 microplastic shards per 500mL sample, seen in those from Indonesia and Europe.

The water testing was conducted by the University of Minnesota School of Public Health on behalf of Orb Media, a nonprofit media organization that focuses on global development issues. The data, first reported by The Guardian, didn’t include what kinds of plastics the researchers found.

While concerning, this isn’t the first time wee shreds of plastics have shown up in unexpected places. A study earlier this year found dashes of microplastic particles in sea salt. The Guardian notes that other studies have turned up microplastics in the sea, sea-creatures, and food, beer, honey, sugar, and air. A 2014 study estimated that European shellfish lovers consume up to 11,000 tiny plastic chunks per year. Drinking two liters of US tap water each day every day would amount to just over 7,000 small scraps a year if the numbers of the new study are representative.

With such little bits and doses of plastics, it’s unclear if there are any health effects and, if so, what they would be. The fragments are not in the nano-range, so they are unlikely to be able to freely enter cells. But they could still get lodged in organs, including the lungs, or have other harmful effects. The mere ubiquity of the fragments has some researchers concerned and calling for more research.

“We don’t know what the [health] impact is, and, for that reason, we should follow the precautionary principle and put enough effort into it now, immediately, so we can find out what the real risks are,” Anne Marie Mahon at the Galway-Mayo Institute of Technology, told The Guardian. This year, Mahon published her own research finding microplastics in tap water in Ireland.

For now, there’s little to do but wait for more data. In Orb’s survey, researchers also noted that they found microplastics in a few samples taken from bottled water.