A study of five different kinds of seafood has found traces of plastic in every sample.

Researchers from the University of Exeter and the University of Queensland bought oysters, prawns, squid, crabs and sardines from a market in Australia and found 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.

Tiny plastic particles can be absorbed by plankton and are then carried up the food chain, where they can ultimately be consumed by humans.

The types of plastic recovered were polystyrene, polyethylene, polyvinyl chloride, polypropylene and polymethyl methacrylate, materials commonly used in plastic packaging and synthetic textiles.

Polyvinyl chloride was found in all samples, while polyethylene was the plastic found in the highest concentrations.

Lead Author Francisca Ribeiro, a QUEX Institute PhD student, said: “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.

“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.”