Thousands of tiny microplastics have been discovered in soil samples taken from parks in Al Ain.
Scientists from the UAE University in Al Ain, say that their findings point to a "looming environmental threat" and urged action to limit further growth in the amount of microplastics appearing in the environment.
"These findings highlight the need for monitoring and managing microplastic pollution in urban recreational areas to mitigate its ecological impacts," the researchers wrote in a paper published in the Journal of Environmental Protection last month.
The study underscores how tiny plastic particles, often invisible to the naked eye, have become common in the environment, although their effects remain uncertain.
Microplastics – which are typically defined as being less than 5mm in size – can come from the breakdown of larger plastic items, from being washed out of clothes, and from cosmetics.
Researchers collected 104 samples from seven parks in Al Ain – Al Fou'ah, Al Tiwayya, Al Jimi, Al Mu-tarid, Al Jahili, Al 'Iqabiyyah and Zakhir – using a probe to take out the top 30cm of soil.
Samples were dried, laid out on glass petri dishes and analysed under a microscope.
Many samples contained sludge thought to have come from wastewater treatment plants and used in UAE parks as fertiliser.
Along with reclaimed water, also from wastewater treatment plants, this sludge is likely to have been a key source of the microplastics.
A previous study, the researchers said, found that sludge from an Abu Dhabi wastewater treatment plant was contaminated with microplastics.
A growing concern
John Quinton, professor of soil science at Lancaster University in the UK, who was not connected to the study, said that the average number of particles detected per kilogram of soil at the Al Ain Parks was "more to the upper end" of what would be expected.
Although he said he has "seen values much higher and values much lower".
A likely source of microplastics in the type of environment analysed is tyre wear from roads and litter, Prof Quinton added.
He said that the use of plastic in agriculture also often leads to the release of microplastics.
In the Al Ain study, nearly 91 per cent of the microplastic particles were fibres, many of which may originally have come from clothes, while most of the rest were microfragments.
About 86 per cent were between 0.3mm and 5mm in size, with others being as small as 49 microns in size, where one micron is one thousandth of a millimetre.
The researchers found that soil samples with higher concentrations of microplastics tended to be more acidic than those with smaller quantities of the pollutants.
"The pervasive presence of plastic particles, primarily deriving from human activities, underscores a looming environmental threat," the researchers wrote.
"Therefore, it is imperative to raise public awareness and implement eco-friendly practices to mitigate the impact of microplastic pollution effectively."
Plastic pollution has become a greater concern in recent decades as the amount of plastic used in packaging, clothing fibres and many other applications, has increased significantly.
Recent analysis of soil samples collected just outside London from the end of the 19th century onwards showed, Prof Quinton said, very low levels of plastic pollution until the 1950s, after which the amount of particles "rises exponentially".
According to the environmental organisation Friends of the Earth, microplastics have been detected in drinks, salt, seafood and human faeces.
Previous research has found them in national parks in the United States, where they are thought to have arrived after travelling through the air.
Similarly, a study published in 2022 discovered microplastics in every sample of Antarctic snow analysed, with an average concentration of 29 particles per litre.
The scientists behind that research calculated that particles could have travelled as far as 6,000km, although the microplastics were made from the same materials as equipment and clothing used at research stations not far away.
While microplastics have become ubiquitous, the effect that they have in soil is poorly understood, Prof Quinton said.
"We're just at the beginning of understanding what impact they do have on both the soil itself and on the people who may come into contact with them," he said.
Davey Jones, professor of soil and environmental science at Bangor University in Wales, indicated that he was not highly concerned about microplastics in soil, saying that even smaller particles – nanoplastics – were a bigger worry.
"Microplastic levels are increasing but they haven’t reached a critical threshold when something harmful is going to happen, but that could happen in the future," he said.
Prof Jones said that research he had been involved with in which microplastics were ploughed into the soil, with more added year on year, had yet to demonstrate damaging effects on the soil's properties.
However, he cautioned that such consequences could be seen in future as concentrations grow, describing it as "a watching brief".
Nanoplastics are usually defined as particles less than one micron in size, much smaller than those analysed in the Al Ain study.
Because of their tiny size, "hardly anybody" had been measuring their concentrations in the environment, Prof Jones said.
"They’re so difficult to measure. That’s an emerging field," he said. "You have to use a different type of technology. Most university research institutions don’t have the capability."
Studies have indicated that nanoplastics are able to enter human tissue, even passing into the brain.
"They’re the things that could get into the food chain and pass the blood-tissue barrier," he said.
"For human health, maybe they're a trigger for dementia or something we don't know."
Prof Quinton said that to reduce the amount of plastic entering the environment – material that could end up being broken down into microplastics or nanoplastics – people should ensure that they do not drop litter and cut down on their use of plastics.
"We probably need to spend less time driving in our cars," he said. "The issue of tyre wear is a little bit under the radar, but it's probably quite a big source of plastic material moving into the environment."
