Australian researcher Dr Jennifer Lavers said it meant the island had the highest density of plastic rubbish anywhere in the world.
"I've been fortunate in my career as a scientist to travel to some of the remote islands in the world, but Henderson was really quite an alarming situation … the highest density of plastic I've really seen in the whole of my career," she said.
Annual production of plastic has increased from 1.7 million tonnes in 1954 to 311 million tons in 2014.
This has resulted in an estimated five trillion plastic items — mostly less than five millimetres in size — circulating in the surface layer of the world's oceans.
The team calculated there were 671.6 items per square metre on the surface of the beaches, with approximately 68 per cent of debris buried less than 10 centimetres in the sand. Each day, 17 to 268 new items washed up on a 10-metre section of North Beach, representing a daily accumulation rate of 1.7 to 26.8 items per metre.
Plastic is a major threat to many marine species.
Henderson Island is in an area of the ocean that is rarely traversed and is not near any shipping lanes or fisheries, with no major land-based industrial facilities or cities within 5,000 kilometres.
"The majority of items appear to be coming from land originally, which made its way into the ocean and that really falls on our shoulders to make a difference and to reduce our demand for these products," she said.
The nearest settlement is Pitcairn Island with a population of 40 people.
This turtle was caught in a tangle of plastic rope.
Everyday items make up bulk of garbage
Dr Lavers said only around 7 per cent of the junk on the beach was connected to fishing-related activities.She said most of the items found on the beaches were everyday household items such as cigarette lighters, plastic razors, toothbrushes, plastic scoops used in detergents or baby formula, and babies' soothers .
"It speaks to the fact that these items that we call "disposable" or "single-use" are neither of those things, and that items that were constructed decades ago are still floating around there in the ocean today, and for decades to come," Dr Lavers said.
Dr Lavers said their study showed "there is nowhere left in the world that is safe — plastic is ubiquitous".
Just over a quarter of the rubbish came from South America and was the result of the movement of currents in the South Pacific gyre, which flows anti-clockwise after travelling north up the continent.
The estimates were "alarmingly" conservative, as the survey did not include items buried deeper than 10 centimetres or debris on cliff areas or rocky sections.
Plastic pollution is a major threat to marine species, Dr Lavers said, with a study released in the past two months suggesting about 1,200 species were negatively impacted.
On Henderson Island the rubbish created a barrier for sea turtles attempting to enter the beach and led to a reduction in sea turtle-laying numbers, while also affecting two native seabird species.
However, Dr Lavers said plastic pollution was also a major threat to human health as the toxic impact of plastic-related chemicals in the food chain were well documented.
"At a very minimum, 25 per cent of world's marine fish species are consuming plastic and we know with that plastic comes a suite of chemical pollutants," she said.
"Those fish are the base of the food web ... and we know humans are at the top of the food web.
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