Endrin is a solid, white, almost odourless substance that was used as a pesticide to control insects, rodents, and birds. It is based on 1,2,3,4,10,10-hexachloro-6,7-epoxy-1,4,4a,5,6,7,8,8a-octahydro-,endo,endo-1,4:5,8-dimethanonaphthalene; it is classified as a POP. Under the Stockholm Convention on Persistent Organic Pollutants, use of this chemical in Europe is subject to restriction.