Scientists warn of an “alarming” rise in microplastic pollution of the oceans

Concentrations of microplastics in the oceans have risen in the past 18 years, with researchers now estimating that there are 2.3 million tons floating in the sea worldwide.

Microplastics – defined as plastic particles less than 5 millimeters in length – are commonly found in the bodies of sea turtles, whales and fish. Studies have tracked microplastic pollution in the oceans since the 1970s, but it wasn’t until 2005 that plastic concentrations began to increase rapidly and consistently.

Marcus Eriksen and Lisa Erdel of the 5 Gyres Institute in Santa Monica, California, and their colleagues studied data on ocean surface plastic pollution collected between 1979 and 2019. This data came from more than 11,000 collection stations, mostly covering major ocean regions.

Incomplete data made it impossible to identify any clear trends regarding plastic concentrations between 1979 and 1990, while plastic concentrations between 1990 and 2004 showed fluctuations with no clear trend.

But the team found that in the past 18 years, plastic concentrations in the oceans have risen sharply, to more than 10 times their levels in 2005.

“We found an alarming trend of exponential growth of microplastics in the global oceans since the millennium, reaching over 170 trillion plastic particles,” Eriksen said in a press release.

Erdel says the sharp rise in concentrations since 2005 may be due to a boom in plastic production around this time. Global plastic production nearly doubled between 2005 and 2019, from 263 million tons to 460 million tons, according to the Organization for Economic Co-operation and Development and Our World in Data.

It may also be a result of the failure to introduce mandatory pollution-reduction measures, says Erdle, even as waste piles up as new plastic enters the oceans and old pieces break down into microplastic particles. “In recent years, there have been no binding international policies, and we are seeing a rapid increase in plastic pollution in the world’s oceans,” she says.

The study, which Erdle says is unique in its geographic breadth and four-decade time span, only looked at data through 2019. This was partly because the researchers needed to identify a “clear cut-off point” for the analysis, says Erdle.

Since then, some countries, including the UK, have introduced laws to tackle microplastic pollution, such as banning the use of plastic straws and reducing demand for disposable bags.

But Erdel believes that more radical action targeting the entire global plastics industry will be necessary to make a real impact on marine pollution levels.

In 2022, countries agreed to create a global treaty to tackle plastic pollution, with a draft text expected by 2024. Erdle says the treaty should be binding and enforceable, addressing the full life cycle of plastics.

The agreement should include a cap on overall plastic production, she says, calling the measure an “effective tool” for reducing concentrations of microplastics in the oceans.

The study warns that without a widespread shift in plastic policy, the rate of plastic flow into the world’s oceans could be 2.6 times higher by 2040 than in 2016.

Other scientists have also supported calls for a global cap on plastic production, but such a move would be highly controversial and likely to be fiercely resisted by the petrochemical industries.