Reactive oxygen species (ROS) cause oxidative stress at the cellular level. Research shows that this way, amongst others, they inhibit the germination capacity of plants, produce cytotoxins or exert toxic effects on aquatic invertebrates. Environmentally persistent free radicals (EPFR) are potential precursors of ROS because they can react with water to form these radical species. "Therefore, EPFR are associated with harmful effects on the ecosystem and human health," explains Gabriel Sigmund, the lead investigator of the study.