See Cancer box Humans Scientists have no data from work-related, accidental poisonings, or epidemiological studies that indicate whether or not pyrethrins are likely to cause cancer in humans. However, the CPRC could not classify pyrethrins into a carcinogenicity group until some of the tissue specimens from rats and mice were re-read. The U.S. EPA has strict guidelines that require testing of pesticides for their potential to cause cancer. These studies involve feeding laboratory animals large daily doses of the pesticide for up to 2 years. These animals are compared with a group of animals that did not receive the chemical.
Animal studies help show whether a chemical is a potential human carcinogen.
If a pesticide does not cause cancer in animal tests, then the EPA considers it unlikely the pesticide will cause cancer in humans. There are no epidemiological, work-related or accidental exposure data on the potential of pyrethrins to cause reproductive problems or birth defects. See box on half-life. Pyrethrins are rapidly degraded in sunlight at the soil surface and in water. Half-life is the time required for half of the compound to degrade.