Decabromodiphenyl ether (also referred to as decaBDE, DBDE, BDE-209) is a brominated flame retardant which belongs to the group of polybrominated diphenyl ethers (PBDEs). It was commercialised in the 1970s and was initially thought to be safe, but is now recognised as a hazardous and persistent pollutant. It was added to Annex A of the Stockholm Convention on Persistent Organic Pollutants in 2017, which means that treaty members must take measures to eliminate its production and use. The plastics industry started switching to decabromodiphenyl ethane as an alternative in the 1990s, but this is now also coming under regulatory pressure due to concerns over human health.