Pyrethroids are manufactured chemicals that are very similar in structure to the pyrethrins, but are often more toxic to insects, as well as to mammals, and last longer in the environment than pyrethrins. More than 1,000 synthetic pyrethroids have been developed, but less than a dozen of them are currently used in the United States. Pyrethrins and pyrethroids are often combined commercially with other chemicals called synergists, which enhance the insecticidal activity of the pyrethrins and pyrethroids. The synergists prevent some enzymes from breaking down the pyrethrins and pyrethroids, thus increasing their toxicity.

Technical-grade (concentrated) pyrethrins and pyrethroids are usually mixed with carriers or solvents to produce a commercial-grade formulated product. The formulated product contains many inert ingredients that can increase the toxicity of the product when compared to the technical-grade material. By law, the active ingredient must be identified by name on the pesticide label and its percentage must be provided. Nonactive ingredients (sometimes called inert ingredients) do not need to be identified by name on a pesticide label, only the percentage of nonactive ingredients must be specified, so it is often difficult to determine what other chemicals are included in the final formulated product.
What happens to pyrethrins and pyrethroids when it enters the environment?

Pyrethrins and pyrethroids are primarily released to air because of their use as insecticides. Sometimes they are sprayed on crops from planes and helicopters or sprayed from the ground by trucks, tractors, or hand-held applicators. They are also used to control flying insects like mosquitos and flies on livestock and pets. These compounds are also in aerosol bombs and sprays that can be used indoors. Pyrethrins can be released naturally from chrysanthemum flowers, but these releases are small compared with the amounts used as commercial insecticides. Manufacturing facilities that produce these compounds can also release them to the environment during the production process.

http://www.minotdailynews.com/page/content...htmlPyrethroids have been linked to hormonal disruptions especially to Estrogen and Androgens, which can result in breast cancer and lowered sperm counts. Pyrethroids have also been linked to childhood brain cancers and to severe neurological damage. Long-term neurological effects may manifest as short-term memory loss, personality disorders, visual disturbances, polyneuropathies, and vegetative nervous disorders including increased heat sensitivity and the reduction in exercise tolerance. There are also studies, which show that Pyrethroids can produce thyroid damage, which may result in reproductive dysfunction, developmental impairment, and cancer.

There must be a concerted effort to establish a safer and effective mosquito control, which is not harmful to humans and the ecosystems.