Microplastics are discovered in every sample of seafood purchased at a food market – with the equivalent of a grain of rice found in sardine flesh

  • Scientists from universities of Queensland and Exeter bought seafood at market 
  • They dissolved microplastics in the edible tissue of each sample and studied it 
  • Discovered the microplastic polyvinyl chloride in every single specimen
  • Most abundant was polyethylene which is the world's most popular plastic  
  • Sardines were the worst affected delicacy, with up to 30mg of plastic per serving, approximately the same weight as a grain of rice  

By JOE PINKSTONE FOR MAILONLINE

Published: | Updated:

Microplastics have been discovered inside every single sample of seafood bought at a market as part of a scientific study. 

Researchers cut open oysters, prawns, crabs, squids and sardines and studied them for any sign of microplastics. 

Sardines were found to be the worst affected and had ingested the largest amount of plastic, up to 30mg per serving - the same weight as a grain of rice.  

Microplastics are tiny particles which are less than five millimetres (0.2 inches) in length. 

The health impact of humans ingesting these particles remains a concerning mystery. 

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Researchers  from the universities of Queensland and Exeter cut open oysters, prawns, crabs, squids and sardines purchased at an Australian market and studied them for any sign of microplastics

Researchers  from the universities of Queensland and Exeter cut open oysters, prawns, crabs, squids and sardines purchased at an Australian market and studied them for any sign of microplastics

The study was led by the University of Exeter and the University of Queensland and has been published in the journal Environmental Science & Technology. 

Academics report 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 PhD student who led the research. 

'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.'

Academics 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

Academics 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 

Sardines were found to be the worst affected of the animals tested and ingested the largest amount of plastic, up to 30mg per serving - the same weight as a grain of rice. Microplastics are tiny particles which are less than five millimetres (0.2 inches) long

Sardines were found to be the worst affected of the animals tested and ingested the largest amount of plastic, up to 30mg per serving - the same weight as a grain of rice. Microplastics are tiny particles which are less than five millimetres (0.2 inches) long

Microplastics contaminate fruit and veg, study finds   

Microplastics have been discovered in apples, carrots, pears, broccoli and lettuce, studies have revealed.

Root vegetables including radishes, turnips and parsnips could also be contaminated with the man-made waste, prompting fears over the health impact. 

The tiny pollutants are thought to have been sucked into plants roots with water, and then travelled up the stem into the leaves and, where possible, fruits.

Scientists have argued for decades that this was 'impossible', claiming they were 'too large' to fit through the pores in the roots.

Microplastics have previously been identified in meats including chicken, canned fish and shellfish.

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The researchers wanted to see if and how plastic was affecting a wide range of ocean-dwelling creatures so bought five wild blue crabs, ten oysters, ten farmed tiger prawns, ten wild squid and ten wild sardines.

While they were still raw and fresh, the animals were analysed for five different types of known plastic pollution,: polystyrene, polyethylene, polyvinyl chloride, polypropylene and poly(methyl methacrylate).

All of these polymers are commonly used in plastic packaging and textiles and previous studies have found they make up a lot of marine litter. 

Researchers used chemicals to dissolve any plastics in the tissues of the samples and the liquid produced was then put into a machine to determine what type of plastic it was.   

'We found polyvinyl chloride – a widely used synthetic plastic polymer – in all samples we tested, but the most common plastic in use today – polyethylene – was the highest concentrate we found,' Ms Ribeiro said. 

'Another interesting aspect was the diversity of microplastic types found among species, with polyethylene predominant in fish and polyvinyl chloride, the only plastic detected in oysters.' 

Microplastics are being increasingly found around the world, with evidence of them now seen at the bottom of the deepest ocean as well as in the Alps and Antarctica.  

Researchers found the microplastic polyvinyl chloride in every single specimen, and this was the only microplastic spotted in oysters (pictured). However, overall, the most abundant microplastic was polyethylene which is the world's most popular plastic

Researchers found the microplastic polyvinyl chloride in every single specimen, and this was the only microplastic spotted in oysters (pictured). However, overall, the most abundant microplastic was polyethylene which is the world's most popular plastic

Microplastics enter the waterways through a variety of means and finish suspended in the liquid. They can be transported long distances both in water and via the air, taking them to the furthest corners of the world

Microplastics enter the waterways through a variety of means and finish suspended in the liquid. They can be transported long distances both in water and via the air, taking them to the furthest corners of the world

They are created when plastics degrade, are washed or broken up, and are hard to catch and destroy. 

Due to their prevalence, researchers are desperately trying to understand how harmful they are to human and animal health. 

A report commissioned by the United Nations last year found microplastics in drinking water. 

This was the first attempt by the WHO to examine the potential human health impacts of exposure to microplastics. 

Some of the key findings include the revelation that larger microplastic particles, bigger than 150 micrometres, are likely to be passed out of our bodies without harm.

Smaller particles could potentially be absorbed into our organs, however.

It also suggests microplastics have the potential to both carry disease-causing bacteria and help bacteria become resistant to antibiotics.

WHAT FURTHER RESEARCH IS NEEDED TO ASSESS THE SPREAD AND IMPACT OF MICROPLASTICS?

The World Health Organisation's 2019 report 'Microplastics in Drinking Water' outlined numerous areas for future research that could shed light on how far spread the problem of microplastic pollution is, how it may impact human health and what can be done to stop these particles from entering our water supplies.

How widespread are microplastics?

The following research would clarify the occurrence of microplastics in drinking-water and freshwater sources:

  • More data are needed on the occurrence of microplastics in drinking-water to assess human exposure from drinking-water adequately. 
  • Studies on occurrence of microplastics must use quality-assured methods to determine numbers, shapes, sizes, and composition of the particles found. They should identify whether the microplastics are coming from the freshwater environment or from the abstraction, treatment, distribution or bottling of drinking-water. Initially, this research should focus on drinking-water thought to be most at risk of particulate contamination. 
  • Drinking-water studies would be usefully supplemented by better data on fresh water that enable the freshwater inputs to be quantified and the major sources identified. This may require the development of reliable methods to track origins and identify sources. 
  • A set of standard methods is needed for sampling and analysing microplastics in drinking-water and fresh water. 
  • There is a significant knowledge gap in the understanding of nanoplastics in the aquatic environment. A first step to address this gap is to develop standard methods for sampling and analysing nanoplastics. 

What are the health implications of microplastics?

Although water treatment can be effective in removing particles, there is limited data specific to microplastics. To support human health risk assessment and management options, the following data gaps related to water treatment need to be addressed: 

  • More research is needed to understand the fate of microplastics across different wastewater and drinking-water treatment processes (such as clarification processes and oxidation) under different operational circumstances, including optimal and sub-optimal operation and the influence of particle size, shape and chemical composition on removal efficacy. 
  • There is a need to better understand particle composition pre- and post-water treatment, including in distribution systems. The role of microplastic breakdown and abrasion in water treatment systems, as well as the microplastic contribution from the processes themselves should be considered. 
  • More knowledge is needed to understand the presence and removal of nanoplastic particles in water and wastewater treatment processes once standard methods for nanoplastics are available. 
  • There is a need to better understand the relationships between turbidity (and particle counts) and microplastic concentrations throughout the treatment processes. 
  • Research is needed to understand the significance of the potential return of microplastics to the environment from sludge and other treatment waste streams. 

To better understand microplastic-associated biofilms and their significance, the following research could be carried out:

  • Further studies could be conducted on the factors that influence the composition and potential specificity of microplastic-associated biofilms. 
  • Studies could also consider the factors influencing biofilm formation on plastic surfaces, including microplastics, and how these factors vary for different plastic materials, and what organisms more commonly bind to plastic surfaces in freshwater systems. 
  • Research could be carried out to better understand the capacity of microplastics to transport pathogenic bacteria longer distances downstream, the rate of degradation in freshwater systems and the relative abundance and transport capacity of microplastics compared with other particles.
  • Research could consider the risk of horizontal transfer of antimicrobial resistance genes in plastisphere microorganisms compared to other biofilms, such as those found in WWTPs. 

Can water treatment stop microplastics entering our water supplies?

Although water treatment can be effective in removing particles, there is limited data specific to microplastics. To support human health risk assessment and management options, the following data gaps related to water treatment need to be addressed: 

  • More research is needed to understand the fate of microplastics across different wastewater and drinking-water treatment processes (such as clarification processes and oxidation) under different operational circumstances, including optimal and sub-optimal operation and the influence of particle size, shape and chemical composition on removal efficacy. 
  • There is a need to better understand particle composition pre- and post-water treatment, including in distribution systems. The role of microplastic breakdown and abrasion in water treatment systems, as well as the microplastic contribution from the processes themselves should be considered.
  • More knowledge is needed to understand the presence and removal of nanoplastic particles in water and wastewater treatment processes once standard methods for nanoplastics are available. 
  • There is a need to better understand the relationships between turbidity (and particle counts) and microplastic concentrations throughout the treatment processes. 
  • Research is needed to understand the significance of the potential return of microplastics to the environment from sludge and other treatment waste streams.
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