EUROPE - Residues from billions of doses of antibiotics, painkillers and antidepressants pose a significant risk to freshwater ecosystems and the global food chain, a new analysis said Thursday. There are growing fears that the unchecked use of antibiotics in both medicine and agriculture will have adverse effects on the environment and on human health. When animals and humans ingest medicines, up to 90 percent of active ingredients are excreted back into the environment. Many medicines are simply discarded - in the United States alone an estimated one third of the four billion drugs prescribed each year ends up as waste. Another study cited said "extremely high" concentrations of pharmaceutical products had already been detected in water ways in China, India, Israel, South Korea and the United States.