Research calculates: human consumes less than a grain of salt of microplastics per week

March 19, 2021

Microplastics are tiny plastic particles that can end up in the environment and the human body. It is not yet clear how harmful microplastic particles are to human health, but researchers from Wageningen University & Research calculated that we ingest about 0.0041 mg microplastics particles a week (less than a grain of salt) and 12.3 mg in a lifetime. Their new calculation method means a big step forward in predicting the health risks of microplastics and the corresponding uncertainties.

Microplastics are found in all kinds of products, such as clothing and cosmetics, or are created when plastic breaks or shreds. Because the environment barely breaks down plastic particles, they often last and may end up in our drinking water and food among other things. People are exposed to microplastics throughout their lives.

So far there are only two studies that calculated how much microplastic people have been exposed to. But these studies did not yet give a complete picture of the actual number of particles that the body absorbs. “For example, they looked at part of our diet and didn't calculate how much of the smallest particles the body absorbs,” says PhD candidate and first author Nur Hazimah Mohamed Nor. “Our new model does all of this. It can look at the entire diet and can intelligently estimate the missing data.”

Accumulation in a human life

The researchers used a new way to describe the microplastics. “We have not divided the plastics into fixed categories, but have classified them on a continuous scale. Just like temperature is measured in Celsius and not described as hot, warm, lukewarm or cold.” This unified approach makes it possible to precisely quantify an uncertainty, that previous models did not include. Another new feature is that the model calculates how many toxic substances you ingest with the plastic. They found that in the most extreme scenario, a person receives up to 20% more lead through microplastics than without.

The researchers calculated the consumption of microplastics for both children and adults. They show that the majority of the world population takes in 0.0041 mg of microplastics per week, based on 20% of an average human diet. For a small minority of 1 in 20 people, this can be as high as 676 mg of microplastics per week, depending on eating habits and concentrations of microplastics found in food products. The study predicts that the accumulated amount of microplastics an average human consumes over a lifetime is 12.3 mg. A small fraction (41 ng) of this is absorbed in the body.

Health risks

There is a loud call in the scientific community to improve the quality of research into microplastics and the even smaller nanoplastics. Also concerns in society are high. "There is still a lot unclear about the risks of microplastics to human health," says Professor Bart Koelmans and leader of the Wageningen research team. "With this model, we are breaking new grounds. We are showing for the first time that it is possible to describe the exposure to the plastic particles, their build-up in the body and the toxic substances. With all the information about the source, plastic diversity, kinetics, and chemical properties in place. Most importantly, we also quantify the uncertainty of the model. We are in the process of further refining the model to also describe, for example, the distribution of microplastics between organs, and to cover the full diet. With this, we are taking a big step towards predicting health risks".

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