Researchers at the University of Exeter and the University of Queensland discovered microplastic in 100% of the seafood samples tested. The research team obtained oysters, prawns, squid, crabs and sardines from a market in Australia and analyzed them using a newly developed method that identifies and measures five different plastic types simultaneously.
Their findings demonstrated plastic levels of 0.04 milligrams (mg) per gram of tissue in squid, 0.07mg in prawns, 0.1mg in oysters, 0.3mg in crabs and 2.9mg in sardines.
"Considering an average serving, a seafood eater could be exposed to approximately 0.7mg of plastic when ingesting an average serving of oysters or squid, and up to 30mg of plastic when eating sardines, respectively," said lead author Francisca Ribeiro, a QUEX Institute Ph.D. student. "For comparison, 30mg is the average weight of a grain of rice. Our findings show that the amount of plastics present varies greatly among species, and differs between individuals of the same species. From the seafood species tested, sardines had the highest plastic content, which was a surprising result."
Co-author Professor Tamara Galloway, of Exeter's Global Systems Institute, commented, "We do not fully understand the risks to human health of ingesting plastic, but this new method will make it easier for us to find out."
In the novel method, edible tissues are treated with chemicals to dissolve the plastics present in the samples. The solution is analyzed using a highly sensitive technique called Pyrolysis Gas Chromatography-Mass Spectrometry. Polyvinyl chloride was found in all samples, while polyethylene was discovered in the highest concentrations. The new testing method will help enable researchers and regulators to effectively determine the microplastic levels that should be considered harmful.