FactCheck: do Australians with an average seafood diet ingest 11,000 pieces of plastic a year?

Well, if you’ve got an average seafood diet in Australia today, you’re probably ingesting about 11,000 pieces of plastic every year. – Dave West, National Policy Director and founder of environmental group, Boomerang Alliance, speaking with a Fairfax video journalist.

Australians are growing increasingly aware of the real danger posed by the vast amount of plastic dumped in our seas every year. It’s an important issue, so it’s crucial we get the facts right.

Ahead of a Senate committee hearing on the threat of marine plastic pollution in Australia, Dave West from the environmental group Boomerang Alliance told a Fairfax video journalist that an average seafood diet in Australia would result in ingesting about 11,000 pieces of plastic a year.

Is that accurate?

Checking the source

When asked for a source to support his assertion, West referred The Conversation to a BBC article published in October 2015 that said:

Prof Tamara Galloway of Exeter University quotes research estimating that anyone consuming an average amount of seafood would ingest about 11,000 plastic particles a year.

The Conversation asked Galloway, a professor of ecotoxicology, to clarify and provide sources. She said by email:

The stats came from another published paper, by [Belgium-based researchers] Van Cauwenberghe and Janssen in which the authors had made a Fermi estimate (or order of magnitude estimate) based on their field data for cultured shellfish.

Professor Galloway also said she had co-written a commentary article for the journal PNAS which

covers a similar topic, but includes some data from another paper too, in which the authors found even higher concentrations of microplastics in seafood. Clearly, there is going to be variation in the levels of contamination depending on location and local sources of pollution, ocean conditions, etc. This does suggest however, that the Van Cauwenberghe results are not just a one-off.

You can read Professor Galloway’s full reply here.

The 2014 Van Cauwenberghe and Janssen paper to which Galloway refers was published in the journal Environmental Pollution.

However, that paper does not show that anyone consuming an average amount of seafood would ingest about 11,000 plastic particles a year. The figure of 11,000 is an upper-end estimate for Europeans who eat quite a lot of molluscs. The paper estimates that:

European top consumers will ingest up to 11,000 microplastics per year, while minor mollusc consumers still have a dietary exposure of 1800 microplastics year.

In that paper, the researchers note that shellfish consumption differs greatly among countries.

In Europe, for instance, mollusc consumption can differ over a factor of 70 between consumers and non-consumers. European top consumers can be found in Belgium (elderly), with a per capita consumption of 72.1g day, while mollusc consumers in France (adolescents) and Ireland (adults) have the lowest per capita consumption: only 11.8g day for both countries.

The researchers also noted that

The presence of marine microplastics in seafood could pose a threat to food safety, however, due to the complexity of estimating microplastic toxicity, estimations of the potential risks for human health posed by microplastics in food stuffs is not (yet) possible.

What does this mean for the average Australian seafood consumer?

The 11,000 figure applies to an estimate for “European top consumers” of molluscs, not an average Australian seafood diet.

We don’t yet have all the data needed to make a good estimate of how much plastic an average Australian seafood consumer ingests per year.

The Boomerang Alliance’s Dave West acknowledged the limitations of applying the 11,000 figure to Australia, telling The Conversation by email that:

Only comment I’d make is that I agree the comment referring to Australia rather than a generic average seafood diet was clumsy.

Small plastic particles can be ingested by bivalves (such as mussels, cockles, oysters, pipi and scallops) and remain there for some time. And these bivalves can be eaten by larger predators, pushing the plastic up the food chain.

It’s worth noting the important difference between eating fish and shellfish. Unless you’re eating sardines and anchovies, humans don’t typically consume the digestive tract of a fish (where plastics would be found). But if you’re eating molluscs and shellfish, particularly from urban centres, you may be adding plastic to your diet.

Australians are not the world’s top shellfish consumers, trailing behind Belgium, most East Asian countries, the US and many European nations.

Verdict

There is insufficient published research to support the statement that a person with an average seafood diet in Australia today is probably ingesting about 11,000 pieces of plastic every year.

The 11,000 figure applies to an estimate for “European top consumers” of molluscs, not an average Australian seafood diet. This is an important issue that needs more attention. – Britta Denise Hardesty

Review

This article is factually correct and represents a sound analysis.

In fact, our own studies found levels of microplastics in mussels from the Dutch coast that are one order of magnitude higher than those reported in the 2014 Belgian study by Van Cauwenberghe and Janssen: 13.2 particles per gram of mussel.

However, it should be noted that microplastics are everywhere and that humans are broadly exposed to them through the food. For example, microplastics have been recently detected in a range of terrestrial products such as milk, beer, honey and sea salt. Therefore, an analysis and assessment of the potential health risk of microplastics for humans should comprise dietary exposure from a range of foods across the total diet, in order to assess the contributing risk of contaminated marine food items.

Although it is evident that humans are exposed to microplastics through their diet and the presence of microplastics in seafood could pose a threat to food safety, our understanding of the fate and toxicity of microplastics in humans constitutes a major knowledge gap that deserves special attention. – Dick Vethaak

Have you ever seen a “fact” worth checking? The Conversation’s FactCheck asks academic experts to test claims and see how true they are. We then ask a second academic to review an anonymous copy of the article. You can request a check at checkit@theconversation.edu.au. Please include the statement you would like us to check, the date it was made, and a link if possible.