It’s on our plates and in our poo, but are microplastics a health risk?

18 May 2021

Dr Jake O’Brien from UQ’s Queensland Alliance for Environmental Health Sciences features in The Guardian about microplastics. 

This week, a study of rice bought from supermarkets and a bulk-food store in Queensland became the latest to deliver a warning.

Researchers found plastic in every sample, whether the rice was grown in Thailand, India, Pakistan or Australia and whether the rice was packaged in plastic or paper.

Washing the rice reduced the amount of plastic likely to be ingested. But the study used special filtered water for rinsing. Most households only have access to tap water (which contains microplastics).

Precooked rice – the kind that comes in microwaveable sachets – had the most plastic. But the amounts are tiny.

The study says a 100g serve of rice typically contains 3.7mg of microplastics if it’s unwashed, 2.8mg if it’s washed or 13.3mg for instant rice (in the microwaveable pouches). A single grain of rice weighs roughly 30mg.

Dr Jake O’Brien, a lead author of the study from the Queensland Alliance for Environmental Health Sciences, says the higher levels of plastic in precooked samples was more likely down to the extra processing it goes through before it’s packaged, rather than the plastic packaging itself.

According to the study, there are multiple opportunities for rice to pick up plastics, from the soils to the machines used to pick, store, move and process the rice, to the packaging and handling.

For an average Australian’s rice consumption, this would equal about 1g a year of plastic.

O’Brien has also been finding levels of microplastics in prawns, oysters and sardines. He also took part in a study that found microplastics in the solid sludge left over at sewage works.

That sludge – known as biosolids – is widely used as a fertiliser and soil improver on agricultural land. Some scientists have asked if this process means agricultural soils are an unforeseen dump for domestic microplastics.

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