Man-made debris has been found in 28% of fish and shellfish on sale in Indonesia – and all of it was plastic. Results demonstrate that anthropogenic debris has infiltrated marine food webs to the level of humans via seafood.
Given that plastics and fibres can be associated with a number of chemical pollutants, some of which can transfer to animals upon ingestion, the findings “support concern that chemicals from anthropogenic debris may be transferring to humans via diets containing fish and shellfish, raising important questions regarding the bioaccumulation and biomagnification of chemicals and consequences for human health”.
It isn’t the first time scientists have rung these alarm bells. A 2014 paper in the journal Environmental Pollution suggested the annual dietary exposure for European shellfish consumers can amount to 11,000 microplastics per year. The presence of marine microplastics “could” pose a threat to food safety, the Belgian researchers noted, but estimating that that risk is “not (yet) possible” given the complexity of estimating microplastic toxicity.
So, where does this leave us? Just how widespread is plastic pollution in the marine environment? What risks does it pose? And is there any sign of a real and present danger to food safety?
Plastic not fantastic
Estimating the amount of plastic in the world’s oceans isn’t easy, but there is plenty of research floating around. A recent paper in the journal Science suggested coastal communities dumped 8 million tonnes in 2010. Another international team of researchers reported 5.25 trillion pieces of marine plastic – most of them microplastics measuring less than 5mm.
Ubiquitous is a word that crops up time and again. Professor Tamara Galloway, an ecotoxicologist at the University of Exeter, says plastic is present in almost every sample her team now takes. “Until we started looking at marine litter in this lab we didn’t realise just how ubiquitous it is,” she says. “We’ve managed to contaminate the sea pretty well.”
The impact this has on marine life has been well publicised, with images of turtles eating plastic bags a popular campaign tool. However, it’s the microplastics that are currently in the spotlight.
These come in two forms:
- Primary microplastics are the manufactured particles – the pellets or ‘nurdles’ used to make virtually all plastic items, the microbeads and the industrial abrasives.
- Secondary microplastics are produced when larger plastic items, like bags and bottles, break down through chemical, biological and physical processes on land or at sea.
Though they’re tricky to see – an eggcup holds 500 of them – nurdles are one of the most common forms of marine litter, say researchers. With global plastic production up from five million tonnes per year in the 1950s to around 300 million tonnes per year now – and accelerating – the number of pellets produced and transported is growing fast.
Putting a figure on how many don’t reach their final destination or ‘escape’ during the manufacturing process is, again, almost impossible to calculate. But look closely and they’re there, says Sarah Archer project manager for The Great Nurdle Hunt at Fidra, a Scottish environmental charity.
The Firth of Forth in Scotland has become a hotspot for ‘lost’ pellets, she explains, but the problem stretches the length and breadth of the coastline. Earlier this month thousands of pellets were washed up on Cornish beaches following a spill from a shipping container.
It’s not just the UK that’s affected either. According to a Global Ocean Commission report published last year, there are 3,500 plastic pellets floating on the surface of every square kilometre of the Sargasso Sea. Near industrial centres in New Zealand, 100,000 pellets per square kilometre have been observed on the beach.
Some companies are taking positive steps to reduce pellet losses, through the Operation Clean Sweep (OCS) programme, but more needs to be done. “We would really like to see greater engagement with the shipping and haulage industries, as well as the plastics industry,” says campaigners.
In the food chain
But even if the holes were plugged tomorrow and no more plastic found it’s way into the oceans, there are still the millions of tonnes already out there. What’s more, they are turning up where they shouldn’t be with increasing regularity.
The Marine Conservation Society suggests that at least 177 marine species have ingested litter and 111 of the world’s 312 species of seabird are known to have accidentally eaten plastic. Almost every fulmar bird that’s been tested in the English Channel since 1979 has had plastic in its gut. The average amount is around 0.3g – scale that up to a human and it would be half a coffee cup in size. “Having that quantity of plastic in you is unlikely to be doing you any good,”.
Recently researchers found plastics in 184 of the 504 fish they examined, including whiting and gurnard, from the English Channel. The average was 1.9 pieces per fish, with the most common materials being polyamide and the semi-synthetic cellulosic material rayon (with potential sources ranging from clothing to nappies). Polystyrene had been ingested by just three fish from three separate species, whilst acrylic and low density polyethylene (LDPE) only cropped up once.
Another study of Norway lobsters collected in the Clyde Sea found 83% had ingested plastic including monofilament line and fragments of plastic bags, whilst other researchers in Exeter filmed zooplankton chomping on microplastics.
Earlier this year, scientists in Canada confirmed that zooplankton are doing the same in the wild. Much like British studies in the English Channel, the amounts were small – between one in 17 and one in 34 of the organisms were eating the plastic particles.
Much like fish and birds, the tiny crustaceans mistake the microplastic pieces as food. The Canadian study didn’t assess the impact this was having, but co-author and head of the ocean solution research programme at Vancouver Aquarium Peter Ross suggested that the plastics could potentially block up the guts or leach into their bodies.
Indeed, the effects of eating microplastics can be physical or chemical. Whatever size of organism, the plastics can cause blockages in the digestive system and cause a false sense of satiation.
Perhaps the bigger concern, especially for marine life that enters the human food chain, is the question of toxicity. The UK already has guidelines in place for pregnant and breastfeeding women to reduce consumption of certain species of fish due to the high levels of mercury found in them, but do plastics and the chemicals bound to them pose a similar threat?
That we don’t yet know. What we do know is that microplastic particles readily attract persistent bioaccumulating toxins (PBTs), as well as other chemicals including DDT. The plastics can suck up the PBTs like a sponge, giving the unknowing organism a shot of chemicals when they’re ingested. Most PBTs are banned, and although current manufacture has been reduced these chemicals continue to persist in the marine environment.
Charles Clover picked up on this recently in a piece for the Sunday Times. He posed the big questions that scientists are trying to answer and (perhaps) industry and governments are unwilling to tackle, or even willing to ignore.
“We know some plastics contain toxic chemicals that cause problems with animals’ sexual development, and we know nurdles in particular are good at accumulating persistent organic compounds such as DDT. We also know that as plastic breaks down in the sea, smaller and smaller creatures, including zooplankton, ingest it.
“What will be the effect of contaminated plankton on filter feeders, such as whales, or on the oceans’ ability to absorb carbon dioxide? What will be the effect on human health of eating fish contaminated with plastic or the pollution that sticks to it? What will be the effect on human health of eating fish contaminated with plastic or the pollution that sticks to it? We do not know — and the likelihood is that only when we do know will anything drastic be done.”
Responding, the British Plastics Federation (BPF) claimed “the notion that plastics materials and products are ‘toxic’ is both misleading and incorrect”. In a statement, BPF’s industrial issues executive Laura Hindley highlights the European Chemicals Regulation (REACH) that ensures “vigorous evaluation and testing of chemicals and their uses”.
“Chemicals used in the production of plastic packaging, including plastic bags, are some of the most widely studied chemicals in the world and rigorous EU risk assessments and studies by other internationally respected scientific bodies have consistently proved their safety for current uses,”.
Hindley asserts that behaviour change is the only way to reduce marine litter, but there is a responsibility for industry too, as campaigners suggest. Indeed, what OCS has achieved since its inception in terms of reduced pellet loss and pollution is unclear.
Lots of unknowns
There is another school of thought suggesting that the chemicals stick to the particles so tightly that microplastics are actually de-toxifying the ocean. Thompson in Plymouth doesn’t subscribe to that theory, but he’s not sure there’s clear evidence that there’s a danger to our food systems – yet.
“These chemicals can come off in the gut quite rapidly,” he explains, “but that doesn’t prove harm. My intuition is that the quantities are low in individual [fish] and there’s no clear evidence that the transfer of chemicals is that substantial.”
Keen to play down the recent “scare story” from Belgium – the one involving the ingestion of 11,000 plastic particles a year for the average seafood consumer – he says: “In order to do that, by my calculation, you’d have to eat 22,000 mussels a year. Having said that, we know the occurrence of microplastics in the marine environment is patchy so some species may have greater exposure.”
Indeed, the research in Indonesia also tested fish from markets in the US. There, only a fifth was plastic. The team couldn’t explain the “stark difference”, but it’s likely to relate the way in which waste is managed in the two countries: in Makassar, Indonesia where fish were collected, 30% of solid waste generated is not processed and an increasing amount of waste is directly discarded along the coast, rivers and into drainage channels; in California, there are advanced recycling systems in place.
Of course, plastics floating in the sea don’t respect international boundaries, and the seafood consumed in the UK comes from all over the world. Consumption levels dipped during the recession but are expected to rise in the next few years, so does this mean consumers will be exposed to more risk?
Currently, it’s impossible to say. Given all the unknowns the likes of Galloway and Thompson are reluctant to ring the alarm bell just yet. However, that’s not reason to turn a blind eye. “The message isn’t ‘toxic seafood is going to ruin our health’,” says Galloway, but given the “massive amounts” of microplastics circulating in the marine environment it’s “only sensible that we look at this”.
The evidence to date may have raised more questions than answers but it’s certainly on the radar for the Food Standards Agency (FSA). A spokesman said: “We are aware of the evidence of a potential risk that chemicals present in plastic particles could contribute to the transfer of chemical contaminants through the marine food chain. This is an emerging issue and we are currently assessing the available information.”