Various foods contain cyanide, such as cassava roots, apples, almonds, and lima beans. However, the quantities of cyanide in these foods are sufficiently low that people do not have to avoid consuming them. Some types of bacteria, fungi, animals, and plants also synthesize cyanide as a source of nitrogen and as a self-defense mechanism. Additionally, cyanide is present in smoke from fire, cigarettes, and some industrial settings. Smoke inhalation from household fires is responsible for most cases of cyanide poisoning in middle and high income countries.