Not long before plastic pollution is impacting human health

We’re heading for a situation where there is more plastic in the sea than fish. It has even entered the food chain, writes Carolyn Moore.


If we continue dumping our plastic waste in the sea at current levels, the ocean will contain more plastic than fish by 2050.

That sobering projection was presented to the World Economic Forum by the Ellen MacArthur Foundation in 2016, in a report which has joined a growing list of studies highlighting the shameful impact that plastic waste is having on the marine environment.

MacArthur — a record-breaking sailor — retired from racing in 2009. 

Since then, having witnessed first hand the pollution in our seas, she has dedicated herself to campaigning for a world where plastic never becomes waste, and where the negative side effects of our addiction to plastic are minimised.

Unless it’s been burned, every piece of plastic ever produced still exists today. In the sea, wave action and UV exposure breaks plastic waste down into ever-smaller fragments, called ‘microplastics’ when they hit 5mm or less. 

These particles are turning our oceans into a plastic soup and showing up in water samples from some of the remotest places on earth. Mistaken for food by sea creatures, they are entering a food chain with humans at its apex.

The MacArthur Foundation estimates there are more than 5 trillion pieces of microplastic in our oceans, and we continue to dump 8 million tonnes into the sea each year — the equivalent of one rubbish truck-full per minute. 

Our appetite for plastic is on the rise, and the foundation estimates this will increase to four trucks per minute as production of largely single-use plastics quadruples between now and 2050.

For the most part, the harm this is doing is self-evident. We’ve seen the images: floating garbage patches the size of small countries; whales cut open to reveal stomachs full of plastic; seabirds decomposing on beaches, their insides a tangle of plastic debris; a viral video of a distressed sea turtle having a six-inch straw pulled from its nasal passage. 

But researchers now know that the cumulative effect on marine ecosystems and biodiversity — the variety and abundance of organisms — while less visually shocking, is no less catastrophic.

With over 7,500 kilometers of coastline at their disposal, Irish scientists have been at the forefront of research into the movement, measurement and impact of microplastics. 

Dr Dannielle Green, a lecturer at Cambridge University, has been observing their effects on coastal ecosystems, conducting research she says, “highlights the potential for microplastic pollution to decrease biodiversity”, leading to “cascading effects on marine food webs.” 

Using “mini habitats” in outdoor tanks with natural flowing, Green observed that, exposed to microplastics, lugworms — essential for bioturbation of sediment — moved less, with the knock-on effect that so-called ‘primary producers’ — the micro-algae at the bottom of the food chain — were reduced by about half. The potential repercussions of this go right up the food chain.

In studies of sandy oyster habitats “there were fewer juvenile periwinkles and crustaceans,” she says; and “while the filtration rate of blue mussels was lowered by microplastics, the filtration rate of oysters was increased”— which could account for the fact that a UK environmental audit committee concluded last year: “If someone eats six oysters, they will likely have eaten 50 particles of microplastics.”

Dr Green’s findings mirror the results of several international studies, says Dr Annemarie Mahon, of Galway-Mayo Institute of Technology.

“Internationally, there have been several impact studies done; most of them lab-based, using elevated levels of microplastics,” she explains.

“Findings ranged from inflammation; tumors in some fish; and reduced feeding — because being full of plastic gives them the sensation of being full — which means they may not be as fast to avoid predators.” 

That could lead to increased mortality for some species.

“There’s a push now to conduct studies using environmentally relevant concentrations of microplastics to see if we find the same impacts,” she says.

 “However, if the plastics industry continues to grow at the rate it’s currently growing, we might see those elevated levels become reality.”

With figures showing plastic debris kills approximately one million seabirds and over 100,000 marine mammals each year, the plight of creatures who rely on a healthy marine environment should be enough to spur us to action, but it’s mounting evidence that plastic pollution is potentially impacting human health that could be the push we need.

Researchers at the University of Ghent carried out the first comprehensive risk assessment for human consumption of microplastics, and they estimate seafood-eaters could be consuming up to 11,000 pieces of plastic each year.

Fewer than 60 of these are likely to be absorbed, but: “In principle they could accumulate,” Dr Colin Janssen, who led the study, told Sky News in January. 

“It’s been suggested by physicians that they could accumulate around joints or certain types of tissue and cause inflammation.”

This comes hot on the heels of a 2016 UN report warning that humans consuming plastic-contaminated fish could be exposed to elevated levels of chemicals that lead to poisoning, infertility and genetic disruption. 

“The presence of microplastic in foodstuffs could potentially increase exposure of plastic-associated chemicals to humans, presenting an attributable risk to human health,” the report concluded.

Microplastics “readily absorb organic pollutants”, explains Annemarie Mahon. “There’s also the additives in the plastic itself, the polymers and plasticers, which can be endocrine disruptors.

“It’s possible some of these contaminants could be passed through the flesh of the fish, and therefore eating that meat we could be at risk of ingesting elevated levels of pollutants.”

In one study, scientists found 36% of commercially caught fish in the English Channel contained plastic, with microplastics present in all ten species studied; while in another, plastic microfibers were the dominant contaminant found in the stomachs of prawns collected from Galway Bay.

As Ireland prepares to join a host of other countries in banning microbeads — tiny plastic exfoliants found in personal care products — Labour TD for Cork East, Sean Sherlock, who proposed the legislation, acknowledges that Ireland, and the world, must do more.

Microbeads may be hogging the headlines, but they account for a relatively small percentage of microplastic pollution, with far more — like the aforementioned microfibers — coming from the washing of synthetic clothes, a source first highlighted by Irish biologist Dr Mark Browne in 2011.

“We know that around 1,400 microplastic fibres, on average, are released into your grey water if you wash something,” states Annemarie Mahon.

“In coming years, we are going to have to legislate for the amount of plastics that are used in general,” says Sean Sherlock. “We cannot have our oceans and beaches clogged with plastics.

“I believe there will have to be a global response to the proliferation of plastics — a radical response that culminates in the gradual phasing out of plastic bottles in favour of glass.

“This will involve creative solutions such as setting up dispensing machines in supermarkets,” he adds.

Green Party Senator Grace O’Sullivan, who put microbeads on the agenda last September with her own bill on the matter, agrees more needs to be done.

“Not only do we need to ban the manufacture and sale, we also need to monitor the waterways,” she says.

“This comes down to consumer demand, and consumers are now recognising the effects of microbeads and microplastics on the whole eco system, and the food chain — from little shrimp right up to the larger species that eat the shrimp.”

And as long as that includes us, it’s imperative we all start to do our part to keep our oceans clean.


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