Graffiti spray paints pollute soils with microplastics

A research team has demonstrated that spray paints used for graffiti cause an extensive amount of microplastic pollution in the surrounding soil. Analysing soil samples, scientists recorded hundreds of thousands of microplastic particles per kilogram of dry soil.

A wall sprayed with graffiti in a park.
The team recommends that spray painting of larger structures that cannot be carried out in enclosed spaces be monitored more closely in order to reduce the risk of environmental contamination. Image source: SmartNomadilly - Pixabay (symbol image).

According to the researchers, the soil samples taken near the famous graffiti walls in Berlin’s Mauerpark had the highest microplastic concentration ever reported in the scientific literature. The researchers also suspect that similarly high amounts of microplastics would be found in comparable samples taken from sites exposed to industrial paints.

“Our results provide the first indications that spray painting, a technique with applications ranging from industry to art, leaves behind an unprecedented amount of microplastics in the soil,” says biologist Prof. Dr. Matthias C. Rillig. The aim of his team’s research project was to find out whether microplastics are transferred into the soil through spray paint and, if so, to what extent.

New method

To do so, the researchers first had to develop a new method for distinguishing between microplastic particles derived from spray paints and microplastic particles from other sources. They did so by adapting the standard procedure for demonstrating the existence of microplastics. This was necessary because microplastics from spray painting are denser than other microplastics. Had the researchers not adapted the procedure, the particles collected as part of the study would have run the risk of not being detected because part of the traditional extraction process relies on the low density of the microplastics.

Soil samples were taken from various locations and soil depths at Berlin’s Mauerpark and analyzed using the new extraction procedure. The results showed that microplastics from graffiti were present in the soil – sometimes in very high concentrations. The numbers of particles that were found are more than one order of magnitude greater than other concentrations found in polluted soils.

Further information can be found on the website of the Freie Universität Berlin.

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