The active substances in pyrethrums are contact poisons for insects and cold-blooded vertebrates. The concentrations of pyrethrum powder used in insecticides are nontoxic to plants, birds, and mammals; therefore, these insecticides find wide use in household and livestock sprays as well as in dusts for edible plants. Naturally derived pyrethrin insecticides are an important means of chemical control in organic farming. Synthetic pyrethrin compounds, known as pyrethroids, have been developed. Both synthetic and non-synthetic pyrethrins can accumulate in water and wetland sediments and are toxic to fish and aquatic invertebrates.