Plastic free July: should we be worried about microplastics?

What are microplastics?

Plastics have entered every environment on earth as consumer products and industrial waste. Plastic pollution can do a lot of environmental harm and witnessing it - like seeing plastic bags in the ocean - can be emotive. But what about the tiny pieces we can't see when disposed plastic breaks down?   

Called microplastics, we now know that these disintegrated synthetic pieces - usually invisible to the naked eye - are all around us: in our tap water, our food, and the air in our homes. Thanks to recent research on human body tissues, we also know that microplastics have found their way into us. 

What are the health risks posed by microplastics?

What we don't yet know is how toxic microplastics are to our bodies, and whether they can lead to health problems, as Professor Rotchell explains: "Cell-based and animal studies indicate that microplastics do cause negative biological effects, such as inflammation (internal swelling), oxidative stress (cell damage) and challenges to cellular barrier structures." 

It's thought that the chemicals in microplastics may have the power to disrupt the endocrine system - which releases hormones needed around the body for essential functions like growth, metabolism, and reproduction.  

"There has been a slight disconnect in between these studies and human tissue studies - the former usually involve bead-shaped microplastics, yet while we find fragments and fibres in the human tissues, we don't find beads," says the ecotoxicology specialist.  

"Whether these forms of microplastics negatively affect the human body is still unclear. We're starting to find correlations between their presence and negative health outcomes, such as irritable bowel and cardiovascular conditions, but the actual cause-and-effect mechanisms of how that damage might be occurring with the body is yet to be established." 

Here's a snapshot of the evidence for microplastics and human disease so far:  

• Heart problems - In 2024, researchers studied people with fatty plaque build up in their blood vessels. They detected microplastics in some people's plaque and found that these people were 4.5 times more likely to develop heart attacks, stroke, and heart-related death than those with plastic-free plaque¹.  

• Inflammatory bowel disease (IBD) - In 2022, researchers compared poo samples of people with IBD and healthy people. They found significantly more microplastics in the samples from people with IBD². 

• Endometriosis – In 2024, Professor Rotchell and her team discovered that larger microplastics in pee samples of women with endometriosis, compared to women without endometriosis³. She says "We need a further study to understand if there is a link between the presence of microplastics and the condition. Larger microplastic particles could lead to more inflammation type responses, but that has not been directly investigated yet and would be a great follow up experiment to conduct next."

Where in the body?

There are also human tissue studies that don't directly link microplastics to disease, but raise concerns. For example:  

Microplastics in testicles: In 2024, researchers discovered 12 types of microplastics in 23 human testicles⁴. The study sample was small but the findings highlight the need for more research on the effect of microplastics on sperm count and fertility.   

Microplastics in blood vessels: Professor Rotchell’s 2023 pilot study was the first to find microplastics in human blood vessels, supporting the theory that they may be able to travel through veins to major organs like the lungs⁵. 

Ingestion - microplastics in the food chain

So just how are microplastics entering our bodies? Professor Rotchell explains that microplastics range in size - from a sesame seed at their largest, to the diameter of a hair invisible to the naked eye at the smaller end of the size range. 

These tiny particles are small enough to transfer and seep into all sorts of places - including several levels of our food chain.   

"These smaller plastics can be taken up by marine organisms which we then eat as seafood. Another source can be via plastic packaging particles that transfer into the foods that they contain," says the professor.   

Microplastics are also added to many synthetic fertilisers and pesticides. These plastic-coated agrochemicals are sprayed directly onto the crops we eat, and seep into the soil where new crops grow⁶.

Microplastics in the food chain

• Food - People may be eating an estimated 50,000 plastic particles every year⁷.  

• Water - If you drink from water bottles, you could be consuming up to 90,000 extra microplastics annually - compared to the additional 4,000 microplastics per year from your tap water⁷. 

• Beer - A beer a day could amount to 520 particles each year⁸. 

Inhalation - microplastics in the home

From children's toys to cookware coating and fridge, door and window seals, plastic is used everywhere in the home. We don't know if these commonplace features affect us, but we do know that when plastic gradually breaks down into microplastics, these tiny particles can become airborne. 

"We may also inhale as well as ingest microplastics since they are floating in the indoor and outdoor air," says professor Rotchell. "We don't know much about the transport of microplastics in the outdoor and indoor air beyond knowing that they are present and at varying levels depending on location. Indoor studies have identified textile type microplastics, usually fibres, present - these could be from clothing and soft furnishings."  

Clouds and plastic rainfall

Scientists were surprised to discover microplastics on top of two misty mountain peaks in Japan. It's not clear how they got up there, but it's possible this is the first report of airborne microplastics in cloud water¹⁰.

This theory suggests that plastic litter in the ocean breaks down into microplastics and is then launched into the atmosphere through ocean spray. So-called 'plastic rainfall' has an alarming potential to contaminate vast areas of land - but there's a lot more we need to learn before this causes concern.   

What can we do to reduce our exposure to microplastics?   

Tackling microplastic pollution begins with your single-use plastics. These are things like disposable water bottles, shopping bags and plastic-coated coffee cups.   

Reduce, reuse, recycle  

Reduce what you buy: Ask yourself if you really need something, or if you can repurpose something you already own, or buy secondhand to reduce plastic waste. 

Reuse plastic items: Reuse plastic as you can or take it to a secondhand store where possible so it doesn't end up in landfill. 

Recycle: Understand what you can and can't recycle in your local area. You can also choose to buy recycled products to close the loop. 

Microplastics and climate change - a cycle

The relationship between microplastics and climate change appears to be cyclical. Global warming is expected to speed up the rate at which plastic products breakdown into microplastic particles¹¹. At the same time, if we find them in large amounts in the upper atmosphere, researchers worry that microplastics could also be contributing to the climate change problem¹⁰. 

Microplastics and climate change

Microplastics in the upper atmosphere are closer to sunlight - which means greater exposure to ultraviolet (UV) radiation. This could cause microplastics to breakdown and contribute to greenhouse gasses. More studies like the one on the Japanese mountain peaks could help us better understand whether microplastics contribute to climate change¹⁰. 

Reducing our use of plastic in everyday life is one way to try and reduce the demand for plastic production. There are also other ways to reach policy makers.  

"As a scientist, my role is to conduct experiments to establish presence, and biological impacts, of contaminants such as microplastics in a robust manner," says professor Rotchell. "Then to communicate these findings to policy makers, regulators, and the public.

“The more evidence that we produce to illustrate a negative impact of microplastics on human health, the more this influences the policy makers, regulators and politicians to introduce monitoring practices, regulation or legislation."

Further reading 

1. Marfella et al: Microplastics and nanoplastics in atheromas and cardiovascular events.

2. Yan et al: Analysis of microplastics in human feces reveals a correlation between fecal microplastics and inflammatory bowel disease status.  

3. Rotchell et al: Microplastics in human urine: characterisation using μFTIR and sampling challenges using healthy donors and endometriosis participants.  

4. Hu et al: Microplastic presence in dog and human testis and its potential association with sperm count and weights of testis and epididymis.  

5. Rotchell et al: Detection of microplastics in human saphenous vein tissue using μFTIR: A pilot study.    

6. Center for International Environmental Law: Sowing a plastic planet: how microplastics in agrochemicals are affecting our soils, our food, and our future.  

7. Cox et al: Human consumption of microplastics.  

8. Kosuth: Anthropogenic contamination of tap water, beer, and sea salt.  

9. Key et al: Influence of colourants on environmental degradation of plastic litter.  

10. Wang et al: Airborne hydrophilic microplastics in cloud water at high altitudes and their role in cloud formation.  

11. Haque and Fan: Fate of microplastics under the influence of climate change.