Heavy metals such as lead and copper flow into waterways from a variety of sources, including agricultural runoff and industrial wastes. These pollutants can be harmful to humans. But a new study shows that banana peels can remove metal contamination from river water.

During the study, Gustavo Castro, a researcher at the Biosciences Institute at Botucatu, Brazil and his team dried and ground banana peels, then combined them in flasks of contaminated water. They also built water filters out of peels and pushed water through them. In both tests, “the metal was removed from the water and remained bonded to the banana peels,” Castro said, adding that the banana peels outperformed the traditional more expensive methods of metal removal.

Other tests have shown that apple and sugar cane wastes, coconut fibers, and peanut shells, can also remove potential toxins from water.

Read more about the study on National Geographic News.