Scientists Reviewed 7,000 Studies on Microplastics.: Their alarming conclusion puts humanity on notice

Karen Raubenheimer

doi:10.1515/ci-2025-0104

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Scientists Reviewed 7,000 Studies on Microplastics.

Their alarming conclusion puts humanity on notice

Karen Raubenheimer
Senior Lecturer, University of Wollongong

Veröffentlicht/Copyright: 20. Januar 2025

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Aus der Zeitschrift Chemistry International Band 47 Heft 1

Abstract

It’s been 20 years since a paper in the journal Science showed the environmental accumulation of tiny plastic fragments and fibres. It named the particles “microplastics.”

The paper opened an entire research field. Since then, more than 7,000 published studies have shown the prevalence of microplastics in the environment, in wildlife and in the human body.

So what have we learned? In a paper released 19 Sep 2024, an international group of experts, including myself, summarise the current state of knowledge. (Richard C. Thompson et al. ,Twenty years of microplastic pollution research—what have we learned?.Science386,eadl2746(2024).DOI:10.1126/science.adl2746)

In short, microplastics are widespread, accumulating in the remotest parts of our planet. There is evidence of their toxic effects at every level of biological organisation, from tiny insects at the bottom of the food chain to apex predators.

Microplastics are pervasive in food and drink and have been detected throughout the human body. Evidence of their harmful effects is emerging.

The scientific evidence is now more than sufficient: collective global action is urgently needed to tackle microplastics—and the problem has never been more pressing.

Tiny particles, huge problem

Microplastics are generally accepted as plastic particles 5mm or less in one dimension.

Some microplastics are intentionally added to products, such as microbeads in facial soaps.

Others are produced unintentionally when bigger plastic items break down – for example, fibres released when you wash a polyester fleece jacket.

Studies have identified some of the main sources of microplastics as:

cosmetic cleansers
synthetic textiles
vehicle tyres
plastic-coated fertilisers
plastic film used as mulch in agriculture
fishing rope and netting
“crumb rubber infill” used in artificial turf
plastics recycling.

A graphic of where microplastics come from, including paint, textiles, personal care products and tyres

Science hasn’t yet determined the rate at which larger plastics break down into microplastics. They are also still researching how quickly microplastics become “nanoplastics”—even smaller particles invisible to the eye.

Measuring the microplastic scourge

It’s difficult to assess the volume of microplastics in the air, soil and water. But researchers have attempted it.

For example, a 2020 study estimated between 0.8 and three million tonnes of microplastics enter Earth’s oceans in a year.

And a recent report suggests leakage into the environment on land could be three to ten times greater than that to oceans. If correct, it means between ten and 40 million tonnes in total.

The news gets worse. By 2040, microplastic releases to the environment could more than double. Even if humans stopped the flow of microplastics into the environment, the breakdown of bigger plastics would continue.

Microplastics have been detected in more than 1,300 animal species, including fish, mammals, birds and insects.

Some animals mistake the particles for food and ingest it, leading to harm such as blocked intestines. Animals are also harmed when the plastics inside them release the chemicals they contain – or those hitch-hiking on them.

Invaders in our bodies

Microplastics have been identified in the water we drink, the air we breathe and the food we eat – including seafood, table salt, honey, sugar, beer and tea.

Sometimes the contamination occurs in the environment. Other times it’s the result of food processing, packaging and handling.

More data is needed on microplastics in human foods such as land-animal products, cereals, grains, fruits, vegetables, beverages, spices, and oils and fats.

The concentrations of microplastics in foods vary widely – which means exposure levels in humans around the world also varies. However, some estimates, such as humans ingesting a credit card’s worth of plastic every week, are gross overstatements.

As equipment has advanced, scientists have identified smaller particles. They’ve found microplastics in our lungs, livers, kidneys, blood and reproductive organs. Microplastics have crossed protective barriers into our brains and hearts.

While we eliminate some microplastics through urine, faeces and our lungs, many persist in our bodies for a long time.

So what effect does this have on the health of humans and other organisms? Over the years, scientists have changed the way they measure this.

They initially used high doses of microplastics in laboratory tests. Now they use a more realistic dose that better represents what we and other creatures are actually exposed to.

And the nature of microplastics differ. For example, they contain different chemicals and interact differently with liquids or sunlight. And species of organisms, including humans, themselves vary between individuals.

Impact of Microplastics – IUPAC project 2019-026-2-600

The Environment, Health and Food Safety Impact of Microplastics is the subject of a project lead by the IUPAC Chemistry and the Environment Division. The objective is to provide scientists, policy makers, regulators, industry and general public a better understanding on the emerging issue of microplastics by analyzing the existing data, reviewing the scientific methods, tracing the source, revealing the fate, and evaluating the impact on environment and food safety, aiming to recommend future efforts to solve this globally challenging problem. The project integrates the chemistry expertise from members in all disciplines represented in IUPAC Divisions and the Committee on Chemistry and Industry. The outcome will strengthen the role of IUPAC in contributing to solve environmental problems and enhancing the quality of food and life on a global scale.

For more information and comment, contact Task Group Chair Weiping Wu <wuwp01@outlook.com> | https://iupac.org/project/2019-026-2-600

This complicates scientists’ ability to conclusively link microplastics exposure with effects.

In regards to humans, progress is being made. In coming years, expect greater clarity about effects on our bodies such as:

inflammation
oxidative stress (an imbalance of free radicals and antioxidants that damages cells)
immune responses
genotoxicity – damage to the genetic information in a cell that causes mutations, which can lead to cancer.

What can we do?

Public concern about microplastics is growing. This is compounded by our likely long-term exposure, given microplastics are almost impossible to remove from the environment.

Microplastic pollution is the result of human actions and decisions. We created the problem – and now we must create the solution.

Some countries have implemented laws regulating microplastics. But this is insufficient to address the challenge. That’s where a new legally binding agreement, the UN’s Global Plastics Treaty, offers an important opportunity. The fifth round of negotiations begins in November.

The treaty aims to reduce global production of plastics. But the deal must also include measures to reduce microplastics specifically.

Ultimately, plastics must be redesigned to prevent microplastics being released. And individuals and communities must be brought on board, to drive support for government policies.

After 20 years of microplastics research, there is more work to be done. But we have more than enough evidence to act now.

This article was first published in The Conversation September 19, 2024 and reprinted under a Creative Commons license.

Read the original article online <https://theconversation.com/scientists-reviewed-7-000-studies-on-microplastics-their-alarming-conclusion-puts-humanity-on-notice-239105>

About the author

Karen Raubenheimer

Senior Lecturer, University of Wollongong

Published Online: 2025-01-20

Published in Print: 2025-01-01

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

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