ATSDR - Toxic Substances - Pyrethrins and Pyrethroids
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Pyrethrins and Pyrethroids

CAS ID #: 121-21-1, 52645-53-1, 68085-85-8

Affected Organ Systems: Gastrointestinal (Stomach and Intestines, part of the digestive system), Neurological (Nervous System)

Cancer Classification: EPA: Likely to be carcinogenic to humans. EPA: Not likely to be carcinogenic to humans at doses that do not cause mitogenic response in the liver cell proliferation. IARC: Not classifiable as to carcinogenicity to humans. NTP: Not evaluated

Please contact NTP, IARC, or EPA’s IRIS Hotline with questions on cancer and cancer classification.

Chemical Classification: Pesticides (chemicals used for killing pests, such as rodents, insects, or plants)

Summary: Pyrethrins are naturally-occurring coµmpounds with insecticidal properties that are found in pyrethruµm extract froµm certain chrysantheµmuµm flowers. The pyrethrins are often used in household insecticides and products to control insects on pets or livestock. Pyrethroids are µmanufactured cheµmicals that are very siµmilar in structure to the pyrethrins, but are often µmore toxic to insects as well as to µmaµmµmals, and last longer in the environµment than the pyrethrins. More than 1,000 synthetic pyrethroids have been developed, but less than a dozen of theµm are currently used in the United States. Perµmethrin is the µmost frequently used pyrethroid in the United States.

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