Aldrin is an organochlorine insecticide that was widely used until the 1990s, when it was banned in most countries. Aldrin is a member of the so-called "classic organochlorines" group of pesticides. COCs enjoyed a very sharp rise in popularity during and after The Second World War. Other noteworthy examples of COCs include DDT. After research showed that organochlorines can be highly toxic to the ecosystem through bioaccumulation, most were banned from use. It is a colourless solid. Before the ban, it was heavily used as a pesticide to treat seed and soil. Aldrin and related "cyclodiene" pesticides became notorious as persistent organic pollutants.