Permethrin

Description

A synthetic, light stable pyrethroid that was discovered in 1973 by Michael Elliott in Great Britain in 1973. Permethrin was registered as an insecticide in the US in 1979 where it quickly became the commonly used to repel/kill mosquitos, mites, ticks, flies, bees, chiggers, lice, and spiders. Pyrethrins work by paralyzing the insects on contact and the compound is effective when delivered as a liquid, powder, dust, spray, or plastic ear tags/collars. Because of its low toxicity to humans, permethrin is used in cremes/lotions for the treatment of lice and scabies as well as in sprayable insecticides intended for use on fabrics (clothing, sleeping bags, tents, etc.) but not direct use on skin. While permethrin is a component some tick collars and medication for dogs and livestock, it is highly toxic to cats, even in small amounts, as well as to some aquatic organisms.

Permethrin is effective for about 3 months in controlled, indoor, environments. Chemically, pyrethrins break down fairly rapidly at leave no harmful residues.

Synonyms and Related Terms

[(3-phenoxyphenyl) methyl-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylate]; 3-phenoxybenzyl (1RS)-cis-trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylate; Constrain; Nix; Ambush; Eksmin; Talcord; Pounce

Collection Risks

• Pure or water-based formulations do not damage plastics or synthetic fabrics
• Petroleum based commercial concentrates can stain or degrade sensitive materials

Personal Risks

• Highly toxic to cats, fish and aquatic invertebrates
• Low toxicity to humans and birds
• Breaks down rapidly in sunlight within 12-24 hours
• Toxic by ingestion, inhalation and skin contact. LD50 = 584-900 mg/kg.
• Persons sensitive to ragweed will be prone to pyrethrin allergic reactions.
• EChemi: SDS

Environmental Risks

• Degradation half-life in soil is 51-71 days
• Permethrins have a low toxicity to birds and most mammals (exception is cats). Toxicity to aquatic life is high.

Physical and Chemical Properties

• Soluble in most organic solvents.
• Insoluble in water.
• Stable to light
• Composition = C21H20Cl2O3 (mol. wt. = 391.3 g/mol)
• CAS = 52645-53-1
• Melting Point = 35 C
• Density = 1.190-1.272 g/ml
• Boiling Point = 200 C

Resources and Citations

• MuseumPests.net: Pesticide Database
• Catherine Hawks, Michael McCann, Kathryn Makos, Lisa Goldberg, David Hinkamp, Dennis Ertel, Patricia Silence, 'Health and Safety for Museum Professionals' SPNHC, 2011. Link
• National Pesticide Information Center (NPIC): Permethrin Fact Sheet
• EPA: Permethrin Facts
• Richard S. Lewis, Hawley's Condensed Chemical Dictionary, Van Nostrand Reinhold, New York, 10th ed., 1993
• Marie Svoboda, Conservation Survey Index, unpublished, 1997
• The Merck Index, Martha Windholz (ed.), Merck Research Labs, Rahway NJ, 10th edition, 1983 Comment: entry 7321
• Wikipedia: Permethrin (Accessed Mar. 20, 2006 and July 2023)