One of the planet's most remote islands is polluted with the highest density of plastic particles ever reported, with more than 3,500 pieces washing up daily, researchers said Monday.
Henderson Island is uninhabited, and lies far out in the South Pacific -- east of New Zealand and west of Chile -- some 3,100 miles (5,000 kilometers) from the nearest major land mass.
This 9,100 acre (3,700 hectare) limestone atoll, one of the UK's Pitcairn Islands -- is prized for its biodiversity.
But it is also littered with an estimated 37.7 million pieces of plastic, said the report in the Proceedings of the National Academy of Sciences, a peer-reviewed US journal.
"What's happened on Henderson Island shows there's no escaping plastic pollution even in the most distant parts of our oceans," said lead author Jennifer Lavers, a researcher at the Institute for Marine and Antarctic Studies (IMAS) at the University of Tasmania, who co-authored the report with the British conservation charity the Royal Society for the Preservation of Birds.
"Far from being the pristine 'deserted island' that people might imagine of such a remote place, Henderson Island is a shocking but typical example of how plastic debris is affecting the environment on a global scale."
The island is so remote that it is visited only once every five to 10 years for research purposes.
It was during the most recent scientific expedition to the island in 2015 that researchers discovered the extent of the pollution problem.
"Its location near the center of the South Pacific Gyre ocean current makes it a focal point for debris carried from South America or deposited by fishing boats," said the report.
"We estimated a minimum of 3,570 debris items were deposited on North Beach daily, five orders of magnitude greater than the accumulation rates reported elsewhere."
About 27 percent of the items were identifiable as being from South America, including beach equipment and fishing gear.
The beaches were found to be littered with between 21 and 671 items per square yard (meter), said researchers.
Samples were taken at five sites on the island, from as far down as four inches (10 centimeters) below the surface.
Researchers did not check cliffs or rocky coastline, leading them to warn that their report likely underestimates the true scope of the problem.
Since humans do not live there, the pollution on Henderson Island has also never been cleaned up.
Some 300 million tons of plastic are produced around the world annually, and most is not recycled.
"It's buoyant and durable, it has a long-term impact on the ocean," Lavers said.
Plastic can harm fish, turtles and seabirds. Experts say hundreds of species are at risk from ingesting it.
A separate study out last month found that some seas in the Arctic are heavily polluted with plastic because of an Atlantic ocean current which dumps debris there, particularly in the Greenland and Barents Seas.
Experts say such findings underline the importance of properly managing plastic litter at its source, and preventing it from entering the ocean through storm drains or poor waste management practices.