Scientists identified plastic as a marine pollutant by the early 1970s, whereas the term "microplastics" was coined in 2004 to describe litter in Earth's oceans — and a new study identified yet another worrisome form of plastic debris in the sea, Scientific American reports.

What's happening?

"Ocean plastic" is a catch-all term for plastic debris in water, on coastlines, or in any oceanic environment, and the identification of marine microplastics two decades ago made the scale of the problem harder to ignore.

The 2004 discovery of marine microplastics set off a domino effect in terms of research, as scientists aimed to quantify their impact on ecosystems and human health.

On July 9, the highly influential, peer-reviewed journal Nature published a new study concerning nanoplastics. Microplastics are defined as plastic particulate matter smaller than five millimeters, while nanoplastics are even tinier at under one micrometer, or 1,000 nanometers.

Researchers collected water samples across 12 sites in the North Atlantic, gathering it from three distinct depths to test for the presence of nanoplastics.

Their findings were unsettling. They identified three subsets of nanoplastic — PET (polyethylene terephthalate), PVC (polyvinylchloride), and PS (polystyrene) — and determined it comprises 18 millimeters per cubic meter, or 27 million tons on the surface of the North Atlantic alone.

In addition to the present nanoplastic particulates, researchers were stumped by the relative absence of PE (polyethylene), speculating that it evaded detection through an unidentified confounding factor.

"We faced a big mystery. [Polyethylene] fragments probably transform into something else or might fall to the sea bed," said lead author Dušan Materić.

"This [variable] suggests that PE nanoplastic cycling in the ocean follows some unusual pathway — either rapid chemical alteration or mineralization, or fast sinking," Materić surmised.

Why are these findings so alarming?

Although research into the risks microplastics pose to the environment and human health is ongoing, scientists have identified a host of adverse impacts on both counts.

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In June, research published in the Journal of the American Heart Association found that people who lived near coastlines were at greater risk due to microplastic pollution, underscoring dangers lurking on the sand and in the sea.

According to the World Wide Fund for Nature, a 2016 estimate determined that there "could be more plastic in the ocean than fish (by weight)" in 2050.

Halifax-based environmental scientist Tony Walker told Scientific American that the new research into nanoplastic ocean pollution wasn't surprising.

"The extent to which nanoplastics can infiltrate every ecosystem and living cell on the planet is even far worse than what we already know about microplastics and larger plastic pollution," Walker remarked.

Be it microplastic, nanoplastic, or macroplastic — large pieces of plastic detritus — all are dangerous to marine life and even humans.

What's being done about plastic in the ocean?

Although the problem of ocean plastic is massive by definition, there's one thing nearly everyone can do — use less plastic whenever possible.

Walker said that producing less plastic at scale would make an even bigger dent.

"One of the best strategies to mitigate future nanoplastics pollution or release into the environment is to cap plastic production," he told Scientific American.

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