Microplastics in freshwater can pass through food chain into humans, UCC scientists warn

Risk of ‘metabolic disruption’ once substances are ingested by plants and animals

UCC researchers have found tiny pieces of plastic that adhere to plant surfaces in freshwater environments are being ingested by plants and animals with “potential repercussions for the entire food chain”.

They have shown the freshwater shrimp known as Gammarus, which feeds on duckweed, ingests these plastic particles which are small enough to enter living cells, potentially causing “metabolic disruption”, they warn in a major study published by the Environmental Protection Agency.

The biological impacts of these plastics in marine environments are well known but not in freshwater environments, though microplastics are categorised as “contaminants of emerging concern”.

The research by a team led by Prof Marcel Jansen shows freshwater systems do not simply transport plastics on surfaces to the marine environment, they are absorbed into plants and animals, which then act as "microplastic pollution sinks".

The only solution to this potential food contamination, they conclude, is to remove larger plastics from water before they disintegrate.

“Plastics are a key part of a modern lifestyle. They are durable, lightweight, and low cost. However, the production and use of plastics is resulting in widespread plastic pollution in the natural environment,” Prof Jansen said.

Especially worrying were microplastics as well as even smaller nanoplastics, he added. “While it was well known that microplastics are found in oceans, it is important to realise that they are found in our freshwater environments as well.”

Their study found hundreds of small plastic particles can stick to just a few square millimetres of duckweed. “The finding that microplastics adhere to plant surfaces is alarming because other creatures are feeding on these plants and ingesting the microplastics,” Prof Jansen added.

Investigations by Dr Alicia Mateos-Cárdenas showed once ingested by Gammarus, microplastics are quickly broken down into smaller nanoplastics, “which is even more worrying as nanoplastics are small enough to enter living cells, potentially causing metabolic disruption”.

Once plastics are ingested and fragmented into microscopic pieces there is currently nothing that can be done to catch these pieces of plastics, Prof Jansen said. “Therefore the only way to stop the pollution of our freshwater environment is to remove the larger plastics before they disintegrate. As a society, we need to prevent plastic pollution of the environment by reducing, reusing and recycling plastics.”

The researchers wanted their “concerning report” to be noted ahead of World Environment Day – this Saturday.

Kevin O'Sullivan

Kevin O'Sullivan

Kevin O'Sullivan is Environment and Science Editor and former editor of The Irish Times