Biodegradable plastic bags and product packaging are touted as green alternatives to their traditional counterparts. A new study indicates this may not be the case, after all. Researchers at Loughborough University in England found that compounds commonly added to eco-friendly, “oxo-degradable” plastic to help it break down — typically metal salts like cobalt, iron or nickel — make it unfit for composting and recycling. The study also expressed concern about insects and fish that may eventually ingest bits of the degraded plastic, though researchers said there is no evidence so far indicating the plastic poses a problem for wildlife.