Analysis: the emerging risk posed by microplastic in food
Tiny pieces of plastic, mainly degraded over time on the ocean waves, are ending up in our food. EU legislation on so-called “microplastics” and “nanoplastics” in food is non-existent and the risks to humans of consuming the material is, as yet, unquantifiable. Peter Rixon delves into this new risk to the food chain.
Through a number of different routes, microplastic and nanoplastic particles are increasingly finding their way into the food we eat.
The biggest sources of these particles are the oceans, where vast gyres of plastic debris, some as big as France in size, float in suspension in a kind of “plastic soup”. Much of the debris has been thrown out to sea by humanity as junk. Some of it has washed into the sea via the inland sewers and waterways from the bathrooms and washing machines of private households and the forecourts of industrial operations.
Once in the ocean, the plastic debris slowly degrades, particularly when exposed to sunlight, creating trillions of pieces of microplastic that are mistaken for food by fish, which ingest the particles and thereby bring them to our dinner plates. Estimates vary, but about 20% of small fish are believed to carry these plastic particles in their systems.
Among the studies that have documented microplastics in fish, one found that of 504 fish taken from the English Channel, 184 had microplastics (Lusher et al). In another study, research on fish caught off the Portuguese coast found that 17 out of 26 fish species had microplastics in their bodies (Neves et al).
The particles sit in the gastrointestinal tract of the fish and, for that reason, often get thrown out when the fish is gutted before being consumed by humans. But, in the case of smaller fish and shellfish, where the intestinal tracts are not removed, the particles eventually make their way into the human stomach.
One type of microplastic finding its way into shellfish is the “microbead”. Less than 5 millimetres wide, microbeads get into water courses because they are used by the cosmetic industry in products like shower gels and facials scrubs as a cheap ingredient to exfoliate skin. During an inquiry into microbeads by the UK government’s Environmental Audit Committee last year, the committee was told that a plate of oysters can contain up to 50 microbeads.
Whilst seafood appears to be the predominant source of microplastics on the dinner table, it is not the only one.
Beer, table salt and honey
A number of scientific studies have been published over the last three years that have raised awareness of the extent of microplastic contamination of food.
An examination in 2013 uncovered the presence of microplastic particles in 19 honey samples, mainly taken from Germany but also from France, Italy, Spain and Mexico. Researchers believe the plastic had got into the honey after being transported to the hives by bees or introduced during honey processing, or both.
A food analysis carried out in 2014 on 24 different brands of German beer, by the same researchers at Germany’s Oldenburg University, found all the beer samples contained fibres, fragments and granular material of microplastic.
Waste water and drinking water at five waterworks were tested in 2014 for microplastics by a team of researchers from Germany’s Alfred Wegener Institute. The results detected the presence of microplastic particles in both the waste and drinking water, but the amount per cubic metre in drinking water was “extremely low” (seven pieces per cubic metre).
In 2015, researchers from two universities in Shanghai tested 15 brands of table salts sold in Chinese supermarkets and discovered up to 600 microplastic particles per kilogram in the sea salt. Microplastic was also found in table salt that had been sourced from lakes and rock, but the amount was less than half than that in the salt of ocean origin.
Concern has also been raised that there is potential for microplastics to get into poultry and pigs because fish discards are used for the fishmeal fed to farm animals.
As the studies accumulated, Germany’s risk assessor, the Bundesamt fuer Risikobewertung, called on the European Food Safety Authority (EFSA) to investigate the dangers that microplastics consumption posed to humans.
The EFSA assessment was inconclusive and identified significant “knowledge gaps”. No studies were found that addressed the potential effects of microplastics on human health. EFSA currently takes that the view that it is too early to say whether microplastics are harmful to consumers but it seems “unlikely”.
One potential concern at EFSA is that over high concentrations of pollutants like polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) can accumulate in microplastics. There might also be residues of compounds used in packaging such as bisphenol A (BPA). So estimating the average intake of microplastics will be important here.
There is no data on the effects of nanoplastics on human health either, though research has already found that nanoparticles of the food additive titanium dioxide can cross the gut barrier into the bloodstream of animals.
For EFSA’s part, it has recommended that analytical methods are developed which can assess how much microplastic and nanoplastic is in food so that dietary exposure can be quantified. EFSA also recommends further research into the toxicity of microplastics once in the human gut, and whether microplastics can degrade in the stomach into nanoplastics.
In the UK, the Environmental Audit Committee, following its inquiry in 2016, has recommended that microbeads are banned by the end of 2017. The EU cosmetic industry has already made voluntary commitments to phase out the use of microbeads by 2020.
In the US, a report also found that evidence was lacking to ascertain the effect on humans of consuming microplastics, but the report acknowledged that adverse effects on human health were “plausible”.
Where microbeads are concerned, the US has taken definitive action and passed the “Microbead-Free Waters Act” in December 2015. The legislation will ban rinse-off cosmetics that contain intentionally-added plastic microbeads from January 1, 2018.
Resolving the problem
Progress in the field of establishing the health risks posed by microplastics hangs on the development of analytical tools. But the scope of the problem is bigger than the risk posed to human health, as described in a report on the wider effect of marine litter, published on March 17th by the European Commission’s Joint Research Council.
Ways of capturing microplastics through enhanced washing machine filtration systems and improved waste and water sewage treatment processes will need to be explored to reduce the amount of plastic getting into the waterways.
Subsidising fishermen to catch plastic rather than fish, and promoting regular beach cleaning will also reduce the mass of plastic in the ocean that is currently fragmenting into micro and nano particles. Banning micobeads from cosmetics and microplastics that are purposefully made for industrial cleaning will be a logical step.
French legislation that bans plastic plates, cups and cutlery is the kind of measure that also contributes to tackling the problem. Manufacturers in France have until January 1st 2020 to ensure all their products are from biologically sustainable sources and can be composted.
However, policy and legislative measures can only do so much. The UN has warned that even if all releases of plastic into the environment were to cease immediately, the number of microplastics in the ocean would be expected to continue to increase as a result of continuing fragmentation.
Plastic fibres are everywhere and will likely take years, if not centuries, to degrade. For the food industry, the focus will be on ensuring that microplastics are filtered out of the food processing system. And EU policymakers and industry will have to take a very wide-angled approach to this.