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How Microplastics Are Infiltrating the Food You Eat

Increasingly microplastics are finding their way into our wastewater, and whilst the fact that this may lead to plastics in our oceans is well known, the fact that this can also lead to plastics in our food is rarely discussed. This is because a byproduct of cleaning this wastewater is sewage sludge, which unfortunately, due to its high levels of nutrients, is frequently used as fertiliser across farmland. 


From waste water to sewage sludge

As much as ten million tonnes of sewage sludge is produced each year with around 40% of this being used as fertiliser. One study estimated that this is leading to as much as 42000 tonnes of microplastics accumulating in European farmland every year. Even areas where the sludge is not directly applied can be contaminated as ploughing can spread the microplastics from field to field. Furthermore, the runoff caused by rain can transport plastics into drainage systems and, ultimately, into waterways. This leads to even more microplastics finding their way into the oceans. 


This is concerning for a number of reasons, one of which is that microplastics have the capacity to disrupt food chains. There is evidence that microplastics can stunt the growth of earthworms. This could lead to a reduction in the available food for those species that prey on earthworms. If the numbers of those species were to reduce then other animals that in turn prey on them could also be impacted.


Added toxins

As well as the potentially dangerous chemicals microplastics already contain, they can also pose a risk to our food another way, by acting as a vector for other toxins. Microplastics can absorb other substances that can then be released into the soil as the plastics break down, allowing them to adversely affect the growth of our crops or remain in the crops and be ingested by humans.


Ingesting microplastics can cause immune responses to be triggered such as inflammation, allergic reactions, damage to cell walls and even cell breakdown leading to tissue damage. They have also been shown to cause disruption in the endocrine system which regulates hormones that control growth and development. Such disruption can affect the development of foetuses and even lead to the proliferation of cancer cells by increasing the release of hormones that promote cell division.


The answer: higher standards of water treatment?

Though it may seem like the obvious solution is to simply ban farmers from using sewage sludge as fertiliser, as some countries already have, that is not necessarily the answer to all our problems. If the nutrient rich sewage sludge was unavailable to farmers, then they would mostly likely use nitrogen-based fertilisers instead. These are produced from fossil fuels and therefore pose their own risk to the environment. Furthermore, such a move would still not solve the problem of what to do with sewage sludge. 


Instead of banning its use, another option available to governments is to increase the standards of water treatment so that a greater proportion of the microplastics are removed before the sludge is used as a fertiliser. This can be done by removing fats and oils from the wastewater. Fats and oils often contain high levels of microplastics and typically collect at the surface of the wastewater in what is often referred to as, ‘surface scum’. The removal of ‘surface scum’ would make the sewage sludge far safer to use and biofuel could be produced from the fats and oils collected.


Though more research is needed on how to best deal with the issue of microplastics, with the UK having some of the highest concentrations of microplastics in Europe (between 500 and 1,000 microplastic particles spread on farmland each year) it is clear that inaction on this matter would lead to an alarming escalation in what is already a serious environmental and health issue.



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For more information contact: info@scarabtrust.org.uk


Images:

tractor spreading water fertilizer ditch field - Image by corlaffra (ST ref: 1134)

sewage plant top view - Image by Ivan Bandura (ST ref: 1305)

examining the crops by WIx (ST ref: 1306)

Sewage sludge MP contamination - Image from sciencedirect.com (ST ref: 1307)

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