Their findings, presented at the American Chemical Society's spring conference, could offer an alternative to the use of chemicals in wastewater treatment plants, which themselves pose health risks.

To filter out these microplastics and other unwanted elements, "we should use natural materials that are non-toxic," lead researcher Rajani Srinivasan of Tarleton State University in Texas explained in a video.

Okra, also called okra, is used as a thickener in a number of recipes, particularly from the West Indies, Louisiana or South Asia.

Rajani Srinivasan, after having studied the ability of this type of plant to purge the water of pollutants of textile origin, looked into an application for microplastics.

With a size of 5 millimeters or less, these particles harm fish, in particular by disturbing their reproductive system or their growth.

Microplastics come from the huge amount of plastic produced since the 1950s, estimated at some 8 billion tonnes, of which only 10% has been recycled.

The rest has scattered to the four corners of the planet, from the oceans to the rivers, in the air and even in our food.

Their consequences on human health, still poorly known, could be harmful.

Microplastics can also be carcinogenic and mutagenic.

Wastewater treatment plants usually remove them in two stages: those that float to the surface are retained, and then chemicals called flocculants allow the rest to clump together to form clumps that are easier to filter.

But these flocculants, like polyacrylamide, can decompose into other toxic substances.

Rajani Srinivasan and his colleagues therefore investigated whether easily accessible plants such as okra, aloes, cacti, fenugreek, tamarind or psyllium could replace them.

Tests, using extracts from a single plant or several, have been carried out with water polluted with microplastics.

At the end of their experiment, they determined that the combination of okra and fenugreek extracts were the most effective in saltwater, and that an okra-tamarind variant was the best solution for freshwater.

The natural compounds derived from these plants, polysaccharides, are at least as effective, if not more so, than synthetic polyacrylamide.

And, above all, plant-based products are both non-toxic and already usable in wastewater treatment plants as they exist today.

Researcher Rajani Srinivasan hopes to eventually be able to commercialize this process to allow greater access to clean water.

© 2022 AFP