New research suggests that microplastics have penetrated the food chain more than previously documented.
Share on PinterestNew research shows that the prevalence of microplastics in seafood is higher than originally thought.
Photo credit: Louisa Gouliamaki / AFP via Getty Images
Millions of tons of plastic end up in the oceans every year. Some of it is clearly visible in the Pacific Garbage Vortex, also known as the Great Pacific Garbage Patch, which lies between North America and Japan.
However, the most common types of debris in our oceans – microplastics – are less visible.
Microplastics are tiny pieces of plastic that are less than 5 millimeters long, which is roughly the size of a sesame seed. Nanoplastics less than 100 nanometers in size are also found in the marine environment.
A new study by scientists at the QUEX Institute, a research partnership between the University of Exeter in the UK and the University of Queensland in Australia, analyzed seafood from an Australian microplastic market.
The scientists found microplastics in every sample of commercial seafood they tested.
Francisca Ribeiro, lead author of the study, says, “Given an average serving, a fish eater could be exposed to approximately 0.7 milligrams (mg) of plastic when ingesting an average serving of oysters or squid, and up to 30 mg of plastic when eating sardines . “
The authors recently published their study in the journal Environmental Science & Technology.
The researchers bought five types of seafood: five wild blue crabs, 10 oysters, 10 farmed tiger prawns, 10 wild squids, and 10 wild sardines.
Before preparation, each sample was weighed and washed to remove residues from plastic packaging. Only the edible part of each species was tested.
To extract any plastic that was present, the scientists placed each sample in a flask with an alkaline solvent and stirred it in a shaking incubator at 60 degrees Celsius. After the solvent had completely digested the sample, the solution was analyzed for plastic.
The researchers then used a technique called pyrolysis gas chromatography-mass spectrometry to identify the presence of five types of plastics: polystyrene, polyethylene, polyvinyl chloride, polypropylene, and poly (methyl methacrylate).
These plastics are commonly found in packaging, synthetic textiles, and marine debris.
While the team found plastic in all of the samples, Ribeiro says, “Our results show that the amount of plastic present varies widely between species and differs between individuals of the same species.” The authors explain:
“Each of the seafood species examined in this study has different biological, physiological and anatomical characteristics and lives in different compartments of the marine environment, which influences the uptake and possible accumulation of microplastics.”
The study found:
- 0.04 mg of plastic per gram of tissue in the squid
- 0.07 mg in shrimp
- 0.1 mg in oysters
- 0.3 mg in crabs
- 2.9 mg in sardines.
All samples contained polyvinyl chloride. The largest concentrations of plastic consisted of polyethylene.
“Of the seafood tested, sardines had the highest plastic content, which was a surprising result,” says Ribeiro. A grain of rice weighs about 30 mg, about the same amount of plastic as a sardine.
Exeter University co-author Tamara Galloway said, “We don’t fully understand the risks to human health from ingesting plastic, but this new method will make it easier for us to find out.”
About 17% of the protein that people consume worldwide is seafood. Therefore, the results suggest that people who eat seafood regularly also eat plastic on a regular basis.
Scientists previously found microplastics and nanoplastics in sea salt, beer, honey and bottled water. They can also collect as dust particles on food.
The study describes how species consume food differently as a possible explanation for the different amounts of plastic they contain. Other potential sources are also suggested.
The researchers say that plastic can get from an animal’s gastrointestinal tract to its edible parts during processing – including gutting if done incorrectly – and general handling. Plastics can also attach to seafood via “particles, machines, devices and textiles in the air, handling and transport of fish”.
Regarding the high concentration of plastic in sardines, the authors note that the fish were purchased in low-density polyethylene bags.
Citing recent research showing that opening such a bag can cause microplastics to peel off, they predict that these types of packaging could be an additional and significant pollution mechanism for seafood.