Five surprising sources of microplastics in your food and drink

People are increasingly aware that microplastics can be present in food, especially seafood. Yet exposure through many other foods is much more widespread than most people appreciate.

Research suggests that daily consumption of microplastics through food and drink may range from zero to 1.5 million particles a day. Bottled water is likely to be the largest source.

Here are five less obvious ways microplastics can get into your food and drink.

1. Chewing gum

Chewing gum is, in effect, chewing a piece of plastic. Most varieties contain a gum base made from plastics and rubber, alongside added sweeteners and flavourings. As it is chewed, this base sheds microplastics. One gram of chewing gum may release as many as 637 microplastic particles.

Plant-polymer natural gums are not greatly different. They release roughly the same quantity of microplastics as synthetic gum. This indicates that the particles may not come solely from the gum base, but could also be introduced during manufacturing or packaging.

The majority of particles are released during the first eight minutes of chewing. To lower exposure, it may therefore be better to chew a single piece for longer instead of repeatedly putting in new pieces.

2. Salt

Although salt appears to be a basic, pure ingredient, research has found microplastic contamination in 94% of salt products tested around the world. It is so common that sea salt has been suggested as a marker of microplastic pollution in marine environments.

Levels of contamination have been found to be greater in land-based salts, including Himalayan salt, than in marine salts. Technologies are being explored to clean sea salt, although a substantial proportion of contamination is likely to arise during its production and packaging.

A salt grinder may add to the problem. Disposable plastic spice grinders can shed up to 7,628 particles when just 0.1g of salt is ground in a plastic grinder. To reduce exposure, choose a grinder with a ceramic or metal mechanism and keep salt in containers that are not plastic.

3. Apples and carrots

Several studies have detected microplastic contamination in fruit and vegetables. Nanoplastics - plastic particles measuring less than 1,000 nanometres - can enter plants through their roots. Microplastics have also been detected on the surfaces of numerous fruits and vegetables.

In one study, apples and carrots were the most contaminated, while lettuce was the least contaminated. Even so, the level of microplastic contamination is comparatively low beside that of more heavily processed foods.

Although the effects of microplastics are not yet understood, it is known that fruit and vegetable antioxidants - including anthocyanins, which produce red, blue and purple colours - support health. Keep eating them.

4. Tea and coffee

Teabags are not the only potential source of microplastics in a hot drink. Tea leaves, coffee and milk may each contain them. Disposable takeaway cups with plastic linings are among the most significant sources of contamination in hot beverages, as high temperatures can cause microplastics to move from the cup into the drink.

Hot drinks contain more microplastics than their iced counterparts, so opting for a cold drink can lower exposure. Purchasing milk in glass bottles has likewise been associated with a lower microplastic load.

However, this is not true for every beverage. A study of bottled drinks found that soft drinks and beer in glass bottles had greater microplastic contamination than those in plastic bottles, potentially because of contamination from painted metal bottle caps.

Some genuinely plastic-free teabags are available, sealed with cotton rather than biodegradable plastics. Finding them can be difficult, however, because there is no consistent labelling system and not every company clearly discloses what its products contain.

In general, using loose-leaf tea and reusable metal or glass cups are effective ways to reduce microplastic contamination.

5. Seafood

Studies indicate that most seafood contains microplastics. What may be more surprising, however, is how much attention seafood receives in comparison with other food sources.

One study found that so-called "filter feeders", including mussels, contained only 0.2-0.70 microplastic particles per gram. That is considerably lower than the 11.6 billion microplastics released by brewing one cup of tea with a plastic teabag.

Other ways to reduce microplastic exposure

Keeping food in plastic containers and eating highly processed foods are both linked to high concentrations of microplastics in stool samples, so avoiding them may help. Heating food in glass containers rather than plastic ones is also sensible, as it can prevent microplastics leaching into food.

Finally, bottled water is likely to be the single biggest contributor of microplastics in food and drink, containing up to 240,000 particles per litre. Changing to tap water can substantially reduce exposure.

Completely removing plastics from the diet may be impossible, but these changes should help reduce exposure.

Catherine Rolph, Lecturer in Environmental Engineering, The Open University

This article is republished from The Conversation under a Creative Commons licence. Read the original article.