A pesticide first developed in 1949, is slightly more stable and so more persistent than pyrethrum.

Health effects
First generation pyrethroids are considered to be of low toxicity to people and other mammals because they are rapidly broken down in the body. They may irritate the mucous membranes, particularly in asthmatics.

Environmental effects
First generation pyrethroids decompose quickly in sunlight and air and thus pose little risk in the environment but all pyrethroids are toxic to aquatic animals.