Maybe it was the baby sperm whale on the BBC’s Blue Planet II with a plastic bucket snagged in its mouth. Or the photograph of a seahorse clutching a drifting cotton bud, or perhaps a visit to a rubbish-strewn beach? Whatever it was that awakened you to the problem, there’s no doubt that in recent months more people than ever have been shocked into noticing the issue
of plastic pollution.
As scientists venture out to gauge the scale of the problem, the plastic facts are being laid bare: a trillion plastic fragments frozen into the Arctic sea ice; a plastic bag at the bottom of the Mariana Trench, almost 11 kilometres down at the oceans’ deepest point; each square metre of a riverbed in Manchester infested with half a billion microplastic particles, the highest concentration measured anywhere on the planet so far. Plastic is showing up in the food we eat, the water we drink, even the air we breathe. The details quickly become overwhelming but the message is loud and clear: the world, and our daily lives, are filling up with plastic. What’s less clear is what damage this is causing to wildlife and people, and what we should do about it.
“Our picture of the environmental impact is still patchy,” says Richard Thompson, Professor of marine biology at Plymouth University, who published a landmark paper in 2004 revealing the widespread pollution of the oceans with microplastics, under 5mm in size. A major health concern is the possibility that those plastic fragments percolate through ocean food webs and end up in the seafood we eat. Many studies have already shown that microplastics are eaten by hundreds of aquatic animals, including fish, krill, plankton, seabirds, crabs, worms and corals. Some species even seem to prefer plastic over their normal food, perhaps because of the way it smells. And it’s no surprise that having a gut-full of indigestible plastic tends to make life difficult: animals grow more slowly, run down their energy reserves, reproduce less and many simply give up and die.
The Food Chain
Part of the picture that’s still fuzzy is whether microplastics get passed on as animals eat each other. Does a shark or a seal inherit a plastic payload from their prey? Several studies are beginning to suggest this could be the case. In the Celtic Sea, out of a sample of 109 plaice, just over half had fragments of microplastics in their guts. Researchers also found similar traces inside sand eels, making a tentative link between these plankton-feeders and the flatfish that eat them. In Australia, scientists fed microplastics to little beach-dwelling crustaceans, known as sand hoppers, then fed those hoppers to small fish called gobies. Again, the plastics were passed one step up the food chain. Whether this has any lasting impact on the eels, plaice or gobies is an unresolved matter. And while we’re still a long way off understanding how microplastics impact simple duos of predators and prey, we’re even further from getting a handle on what’s going on across entire, complex ecosystems.
Coming back to haunt us
If plastics are contaminating aquatic food webs, are they also getting into our food? There’s no doubt that when you eat a bowl of moules marinière, you could be consuming microplastics that the mussels pick up as they filter seawater. A recent study found plastics inside mussels on supermarket shelves and living all around the British coasts. The question is does eating them do us any harm? Well, besides the plastics themselves, there’s the chemicals they’re coated in. Chemicals such as phthalates and bisphenol A are added to plastics to make them more flexible, transparent and durable, and when they leach off they’re known to disrupt hormones in vertebrates.
As yet, no major medical horrors have been uncovered, but it’s not easy proving a link between health problems and plastics creeping into our diets. “If it was suddenly shown that plastic particles, in some shape, form or dimension, had the same effect as asbestos, that would, of course, accelerate the process towards change,” says Thompson. “We just don’t know that at the moment.”
It’s really important that we make the right decisions now and we don’t jump to knee-jerk reactions
Thompson worries that if we wait until we fully understand the environmental and human harm of ocean plastics, then decision-makers may rush towards solutions that look tempting but could end up causing more trouble. “It’s really important that we make the right decisions now and we don’t jump to knee-jerk reactions.” He points towards the focus on banning plastic drinking straws as a misguided effort. “It’s great to encourage people to do without them,” he says, “but on its own it isn’t going to solve the problem and some would argue it’s a bit of a distraction.”
Thompson is convinced the key to finding the right ways to solving plastic pollution will
be to bring together teams of experts from different disciplines. It won’t just be ecologists and toxicologists studying the impacts of plastics, but material scientists working on making them easier to reuse and recycle, and psychologists who understand what changes people’s habits. “We need to change our relationship with plastic,” he says.
Thompson takes a positive outlook and believes we’ve reached a crucial stage. “Things have never been as aligned as they are now,” he says. Not only are the public aware and demanding changes, he points out, but policy makers are eager to respond to those demands, as are industry leaders, either because they see a financial threat if they don’t act, or because they see an opportunity if they do.
There’s no doubt that the public are engaging with the plastic debate more than any other modern environmental threats. “People can see this marine litter and they can identify with it,” Thompson says. Of course, there are other, less visible problems to deal with, such as climate change, but he argues that solving the plastic problem could set a good example of how to get things right. He likens ocean plastics to the issue of CFCs and the ozone layer 30 years ago. “There’s an environmental challenge here,” he says. “I think it’s a problem we can solve.
A bigger problem than microplastics?
Nanoplastics, smaller than a micron (1000nm), could be floating through the oceans and piling up on the seabed, but at the moment there’s no way of detecting them. “The smaller it gets, the less we know,” says professor of marine biology, Richard Thompson. Scientists are developing automated machines to trace the chemical signatures of these tiny plastics, so we should know more soon. Already there are fears that nanoplastics could cause even bigger problems than microplastics because they’re likely to hold more chemical contaminants on their relatively large surface area and there’s a possibility they could get inside living cells. In a lab study, when zebrafish were fed nanoplastics, the particles moved into the fishes’ blood and built up in their nervous systems. This changed their behaviour and possibly caused brain damage: the fish explored their surroundings less and ate more slowly. Contaminated female zebrafish even passed on nanoplastics to their young, via the egg yolk. Another study shows that animals may produce nanoplastics. Antarctic krill fed fluorescent green microplastics, ground them down in their guts and glowing nanoplastic particles appeared in their faeces. It seems likely that krill are doing something similar in the wild.
The new ‘plastics’
In the next few years we could start seeing traditional oil-based plastics increasingly replaced by biodegradable plastics, including some made from unusual materials…
Shrimp shells and silk
A major waste from the food industry is chitin, the main component of shrimp, crab and lobster shells. Researchers at Harvard University have combined it with silk protein
to form a degradable plastic they’ve named Shrilk.
Mango seeds and skins are being investigated as possible sources of bioplastics for use
in plastic bottles and cups.
Tough woody material from trees called lignin is a byproduct in the paper-making industry that’s usually burned. Scientists are now feeding it to genetically-modified bacteria, which break it down into molecules for making bioplastics.
Dutch designers have developed a bioplastic made from algae, which can be used in 3D printers.
A New York-based firm is developing foam packaging from the thread-like roots (called mycelium) of mushrooms, as a replacement for polystyrene.
An art student in London has made a chair from human hair. A single chair was made from three full bin bags of hair, swept from the floors of hairdressers and glued together with another bioplastic.
Watch Drowning In Plastic which discusses the dangers of plastics bbc.in/2IsDbkh
Want to be updated when there is Science Focus news?
Thanks! Our best wishes for a productive day.