Permethrin
Encyclopedia
Permethrin is a common synthetic
chemical, widely used as an insecticide
, acaricide, and insect repellent
. It belongs to the family of synthetic chemicals called pyrethroid
s and functions as a neurotoxin
, affecting neuron
membrane
s by prolonging sodium channel activation. It is not known to rapidly harm most mammal
s or bird
s, but is dangerously toxic to cat
s and fish
. In general, it has a low mammalian toxicity and is poorly absorbed by skin.
In medicine, permethrin is a first-line treatment for scabies
; a 5% (w/w) cream is marketed by Johnson & Johnson
under the name Lyclear. In nordic countries it is marketed under trade name Nix, often available over the counter.
, wheat
, maize
, and alfalfa
crops. Its use is controversial because, as a broad-spectrum chemical, it kills indiscriminately; as well as the intended pests, it can harm beneficial insects including honey bee
s, and aquatic life.
Permethrin kills ticks on contact with treated clothing. A method of reducing deer tick populations in terms of rodent vectors involves utilizing biodegradable cardboard tubes stuffed with permethrin-treated cotton. Mice collect the cotton for lining their nests. Permethrin on the cotton instantly kills any immature ticks that are feeding on the mice. It is important to put the tubes where mice will find them, such as in dense, dark brush, or at the base of a log; mice are unlikely to gather cotton from an open lawn.
Permethrin is used in tropical areas to prevent mosquito
-borne disease such as dengue fever
and malaria
. Mosquito nets used to cover beds may be treated with a solution of permethrin. This increases the effectiveness of the bed net by killing parasitic insects before they are able to find gaps or holes in the net. Military personnel training in malaria-endemic areas may be instructed to treat their uniforms with permethrin, as well. An application should last several washes.
; the common prescription is Permethrin with 5% concentration for scabies, and OTC (over-the-counter) treatment for head lice/crabs is usually permethrin with 1% concentration. However, the British National Formulary
states that permethrin has low efficacy in eradicating head lice.
Permethrin is also used in industrial and domestic settings to control pests such as ant
s and termite
s.
(two enantiomeric pairs
), arising from the two stereocentres
in the cyclopropane
ring. The trans enantiomeric pair is known as transpermethrin.
, slowing down the nervous system
through binding
to sodium channels. This action is negatively correlated to temperature
, thus, in general, showing more acute effects on cold-blooded animals (insects, fish, frogs...) over warm-blooded
animals (mammal
s and birds):
Permethrin is listed as a "restricted use" substance by the United States
Environmental Protection Agency due to its high toxicity to aquatic organisms.
Due to high toxicity for aquatic life, permethrin and permethrin-contaminated water should be properly disposed of. Degradation
is quick and should the chemical be disposed of far from any aquatic life, the negative effects would be minimized. In a non-industrial context, the contaminant may be placed in direct sunlight to induce photodegradation
. Contaminated water exposed to direct sunlight will be cleared of the permethrin and any known pollutant subproducts after a few hours.
Excessive exposure to permethrin can cause nausea
, headache, muscle weakness, excessive salivation, shortness of breath, and seizure
s. Worker exposure to the chemical can be monitored by measurement of the urinary metabolite
s, while severe overdosage
may be confirmed by measurement of permethrin in serum
or blood plasma
.
Permethrin does not present any notable genotoxicity or immunotoxicity in humans and farm animals, but is classified by the United States Environmental Protection Agency
(EPA) as a likely human carcinogen
, based on reproducible studies in which mice fed permethrin developed liver and lung tumor
s. Carcinogenic action in nasal
mucosal cells due to inhalation
exposure is suspected, due to observed genotoxicity in human tissue samples, and in rat livers the evidence of increased pre-neoplastic lesion
s raises concern over oral
exposure.
Studies by Bloomquist et al., 2002 suggested a link of permethrin exposure to Parkinson's disease
, including very small (per kg.) exposures:
However a more recent 2007 study by the same researcher concluded that there was "little hazard to humans"
A 2006 study in South Africa
, found residues of permethrin in breast milk
, together with DDT, in an area that experienced DDT
treatment for malaria
control, as well as the use of pyrethroid
s in small-scale agriculture.
Chemical synthesis
In chemistry, chemical synthesis is purposeful execution of chemical reactions to get a product, or several products. This happens by physical and chemical manipulations usually involving one or more reactions...
chemical, widely used as an insecticide
Insecticide
An insecticide is a pesticide used against insects. They include ovicides and larvicides used against the eggs and larvae of insects respectively. Insecticides are used in agriculture, medicine, industry and the household. The use of insecticides is believed to be one of the major factors behind...
, acaricide, and insect repellent
Insect repellent
An insect repellent is a substance applied to skin, clothing, or other surfaces which discourages insects from landing or climbing on that surface. There are also insect repellent products available based on sound production, particularly ultrasound...
. It belongs to the family of synthetic chemicals called pyrethroid
Pyrethroid
A pyrethroid is an organic compound similar to the natural pyrethrins produced by the flowers of pyrethrums . Pyrethroids now constitute a major commercial household insecticides...
s and functions as a neurotoxin
Neurotoxin
A neurotoxin is a toxin that acts specifically on nerve cells , usually by interacting with membrane proteins such as ion channels. Some sources are more general, and define the effect of neurotoxins as occurring at nerve tissue...
, affecting neuron
Neuron
A neuron is an electrically excitable cell that processes and transmits information by electrical and chemical signaling. Chemical signaling occurs via synapses, specialized connections with other cells. Neurons connect to each other to form networks. Neurons are the core components of the nervous...
membrane
Cell membrane
The cell membrane or plasma membrane is a biological membrane that separates the interior of all cells from the outside environment. The cell membrane is selectively permeable to ions and organic molecules and controls the movement of substances in and out of cells. It basically protects the cell...
s by prolonging sodium channel activation. It is not known to rapidly harm most mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
s or bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
s, but is dangerously toxic to cat
Cat
The cat , also known as the domestic cat or housecat to distinguish it from other felids and felines, is a small, usually furry, domesticated, carnivorous mammal that is valued by humans for its companionship and for its ability to hunt vermin and household pests...
s and fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
. In general, it has a low mammalian toxicity and is poorly absorbed by skin.
In medicine, permethrin is a first-line treatment for scabies
Scabies
Scabies , known colloquially as the seven-year itch, is a contagious skin infection that occurs among humans and other animals. It is caused by a tiny and usually not directly visible parasite, the mite Sarcoptes scabiei, which burrows under the host's skin, causing intense allergic itching...
; a 5% (w/w) cream is marketed by Johnson & Johnson
Johnson & Johnson
Johnson & Johnson is an American multinational pharmaceutical, medical devices and consumer packaged goods manufacturer founded in 1886. Its common stock is a component of the Dow Jones Industrial Average and the company is listed among the Fortune 500....
under the name Lyclear. In nordic countries it is marketed under trade name Nix, often available over the counter.
Uses
Permethrin is used:- as an insecticide
- in agriculture, to protect crops
- in agriculture, to kill livestock parasites
- for industrial/domestic insect control
- as an insect repellent or insect screen
- in timber treatment
- as a personal protective measure (cloth impregnant, used primarily for US military uniforms and mosquito nets)
- in pet flea preventative collars or treatment.
Pest control
In agriculture, permethrin is mainly used on cottonCotton
Cotton is a soft, fluffy staple fiber that grows in a boll, or protective capsule, around the seeds of cotton plants of the genus Gossypium. The fiber is almost pure cellulose. The botanical purpose of cotton fiber is to aid in seed dispersal....
, wheat
Wheat
Wheat is a cereal grain, originally from the Levant region of the Near East, but now cultivated worldwide. In 2007 world production of wheat was 607 million tons, making it the third most-produced cereal after maize and rice...
, maize
Maize
Maize known in many English-speaking countries as corn or mielie/mealie, is a grain domesticated by indigenous peoples in Mesoamerica in prehistoric times. The leafy stalk produces ears which contain seeds called kernels. Though technically a grain, maize kernels are used in cooking as a vegetable...
, and alfalfa
Alfalfa
Alfalfa is a flowering plant in the pea family Fabaceae cultivated as an important forage crop in the US, Canada, Argentina, France, Australia, the Middle East, South Africa, and many other countries. It is known as lucerne in the UK, France, Australia, South Africa and New Zealand, and known as...
crops. Its use is controversial because, as a broad-spectrum chemical, it kills indiscriminately; as well as the intended pests, it can harm beneficial insects including honey bee
Honey bee
Honey bees are a subset of bees in the genus Apis, primarily distinguished by the production and storage of honey and the construction of perennial, colonial nests out of wax. Honey bees are the only extant members of the tribe Apini, all in the genus Apis...
s, and aquatic life.
Permethrin kills ticks on contact with treated clothing. A method of reducing deer tick populations in terms of rodent vectors involves utilizing biodegradable cardboard tubes stuffed with permethrin-treated cotton. Mice collect the cotton for lining their nests. Permethrin on the cotton instantly kills any immature ticks that are feeding on the mice. It is important to put the tubes where mice will find them, such as in dense, dark brush, or at the base of a log; mice are unlikely to gather cotton from an open lawn.
Permethrin is used in tropical areas to prevent mosquito
Mosquito
Mosquitoes are members of a family of nematocerid flies: the Culicidae . The word Mosquito is from the Spanish and Portuguese for little fly...
-borne disease such as dengue fever
Dengue fever
Dengue fever , also known as breakbone fever, is an infectious tropical disease caused by the dengue virus. Symptoms include fever, headache, muscle and joint pains, and a characteristic skin rash that is similar to measles...
and malaria
Malaria
Malaria is a mosquito-borne infectious disease of humans and other animals caused by eukaryotic protists of the genus Plasmodium. The disease results from the multiplication of Plasmodium parasites within red blood cells, causing symptoms that typically include fever and headache, in severe cases...
. Mosquito nets used to cover beds may be treated with a solution of permethrin. This increases the effectiveness of the bed net by killing parasitic insects before they are able to find gaps or holes in the net. Military personnel training in malaria-endemic areas may be instructed to treat their uniforms with permethrin, as well. An application should last several washes.
Personal healthcare
Permethrin is used on humans to eradicate parasites such as head lice and mites responsible for scabiesScabies
Scabies , known colloquially as the seven-year itch, is a contagious skin infection that occurs among humans and other animals. It is caused by a tiny and usually not directly visible parasite, the mite Sarcoptes scabiei, which burrows under the host's skin, causing intense allergic itching...
; the common prescription is Permethrin with 5% concentration for scabies, and OTC (over-the-counter) treatment for head lice/crabs is usually permethrin with 1% concentration. However, the British National Formulary
British National Formulary
The British National Formulary is a medical and pharmaceutical reference book that contains a wide spectrum of information and advice on prescribing and pharmacology, along with specific facts and details about all medicines available on the National Health Service , including indication,...
states that permethrin has low efficacy in eradicating head lice.
Permethrin is also used in industrial and domestic settings to control pests such as ant
Ant
Ants are social insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from wasp-like ancestors in the mid-Cretaceous period between 110 and 130 million years ago and diversified after the rise of flowering plants. More than...
s and termite
Termite
Termites are a group of eusocial insects that, until recently, were classified at the taxonomic rank of order Isoptera , but are now accepted as the epifamily Termitoidae, of the cockroach order Blattodea...
s.
Stereochemistry
Permethrin has four stereoisomersStereoisomerism
Stereoisomers are isomeric molecules that have the same molecular formula and sequence of bonded atoms , but that differ only in the three-dimensional orientations of their atoms in space. This contrasts with structural isomers, which share the same molecular formula, but the bond connections...
(two enantiomeric pairs
Enantiomer
In chemistry, an enantiomer is one of two stereoisomers that are mirror images of each other that are non-superposable , much as one's left and right hands are the same except for opposite orientation. It can be clearly understood if you try to place your hands one over the other without...
), arising from the two stereocentres
Stereocenter
A stereocenter or stereogenic center is an atom, bearing groups such that an interchanging of any two groups leads to a stereoisomer.A chirality center is a stereocenter consisting of an atom holding a set of ligands in a spatial arrangement which is not superposable on its mirror image...
in the cyclopropane
Cyclopropane
Cyclopropane is a cycloalkane molecule with the molecular formula C3H6, consisting of three carbon atoms linked to each other to form a ring, with each carbon atom bearing two hydrogen atoms...
ring. The trans enantiomeric pair is known as transpermethrin.
Toxicology and safety
Permethrin acts as a neurotoxinNeurotoxin
A neurotoxin is a toxin that acts specifically on nerve cells , usually by interacting with membrane proteins such as ion channels. Some sources are more general, and define the effect of neurotoxins as occurring at nerve tissue...
, slowing down the nervous system
Nervous system
The nervous system is an organ system containing a network of specialized cells called neurons that coordinate the actions of an animal and transmit signals between different parts of its body. In most animals the nervous system consists of two parts, central and peripheral. The central nervous...
through binding
Neural binding
According to the neural binding hypothesis, neurons within neuronal assemblies fire in synchrony to link different features of neuronal representations together. These features can include, shape, motion, color, depth, and other aspects of perception. Neural oscillations have been suggested as the...
to sodium channels. This action is negatively correlated to temperature
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
, thus, in general, showing more acute effects on cold-blooded animals (insects, fish, frogs...) over warm-blooded
Warm-blooded
The term warm-blooded is a colloquial term to describe animal species which have a relatively higher blood temperature, and maintain thermal homeostasis primarily through internal metabolic processes...
animals (mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
s and birds):
- Permethrin is extremely toxic to fish and aquatic life in general, so extreme care must be taken when using products containing permethrin near water sources.
- Permethrin is also highly toxic to cats, and flea and tick-repellent formulas intended and labeled for (the more resistant) dogs may contain permethrin and cause feline permethrin toxicosis in cats.
- Very high doseDose (biochemistry)A dose is a quantity of something that may impact an organism biologically; the greater the quantity, the larger the dose. In nutrition, the term is usually applied to how much of a specific nutrient is in a person's diet or in a particular food, meal, or dietary supplement...
s will have tangible neurotoxic effects on mammalMammalMammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
s and birds, including human beings.
Permethrin is listed as a "restricted use" substance by the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
Environmental Protection Agency due to its high toxicity to aquatic organisms.
Due to high toxicity for aquatic life, permethrin and permethrin-contaminated water should be properly disposed of. Degradation
Chemical decomposition
Chemical decomposition, analysis or breakdown is the separation of a chemical compound into elements or simpler compounds. It is sometimes defined as the exact opposite of a chemical synthesis. Chemical decomposition is often an undesired chemical reaction...
is quick and should the chemical be disposed of far from any aquatic life, the negative effects would be minimized. In a non-industrial context, the contaminant may be placed in direct sunlight to induce photodegradation
Photodegradation
Photodegradation is degradation of a photodegradable molecule caused by the absorption of photons, particularly those wavelengths found in sunlight, such as infrared radiation, visible light, and ultraviolet light. However, other forms of electromagnetic radiation can cause photodegradation...
. Contaminated water exposed to direct sunlight will be cleared of the permethrin and any known pollutant subproducts after a few hours.
Human exposure
According to the Connecticut Department of Public Health, permethrin "has low mammalian toxicity, is poorly absorbed through the skin and is rapidly inactivated by the body. Skin reactions have been uncommon."Excessive exposure to permethrin can cause nausea
Nausea
Nausea , is a sensation of unease and discomfort in the upper stomach with an involuntary urge to vomit. It often, but not always, precedes vomiting...
, headache, muscle weakness, excessive salivation, shortness of breath, and seizure
Seizure
An epileptic seizure, occasionally referred to as a fit, is defined as a transient symptom of "abnormal excessive or synchronous neuronal activity in the brain". The outward effect can be as dramatic as a wild thrashing movement or as mild as a brief loss of awareness...
s. Worker exposure to the chemical can be monitored by measurement of the urinary metabolite
Metabolite
Metabolites are the intermediates and products of metabolism. The term metabolite is usually restricted to small molecules. A primary metabolite is directly involved in normal growth, development, and reproduction. Alcohol is an example of a primary metabolite produced in large-scale by industrial...
s, while severe overdosage
Drug overdose
The term drug overdose describes the ingestion or application of a drug or other substance in quantities greater than are recommended or generally practiced...
may be confirmed by measurement of permethrin in serum
Blood serum
In blood, the serum is the component that is neither a blood cell nor a clotting factor; it is the blood plasma with the fibrinogens removed...
or blood plasma
Blood plasma
Blood plasma is the straw-colored liquid component of blood in which the blood cells in whole blood are normally suspended. It makes up about 55% of the total blood volume. It is the intravascular fluid part of extracellular fluid...
.
Permethrin does not present any notable genotoxicity or immunotoxicity in humans and farm animals, but is classified by the United States Environmental Protection Agency
United States Environmental Protection Agency
The U.S. Environmental Protection Agency is an agency of the federal government of the United States charged with protecting human health and the environment, by writing and enforcing regulations based on laws passed by Congress...
(EPA) as a likely human carcinogen
Carcinogen
A carcinogen is any substance, radionuclide, or radiation that is an agent directly involved in causing cancer. This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes...
, based on reproducible studies in which mice fed permethrin developed liver and lung tumor
Tumor
A tumor or tumour is commonly used as a synonym for a neoplasm that appears enlarged in size. Tumor is not synonymous with cancer...
s. Carcinogenic action in nasal
Human nose
The visible part of the human nose is the protruding part of the face that bears the nostrils. The shape of the nose is determined by the ethmoid bone and the nasal septum, which consists mostly of cartilage and which separates the nostrils...
mucosal cells due to inhalation
Inhalation
Inhalation is the movement of air from the external environment, through the air ways, and into the alveoli....
exposure is suspected, due to observed genotoxicity in human tissue samples, and in rat livers the evidence of increased pre-neoplastic lesion
Lesion
A lesion is any abnormality in the tissue of an organism , usually caused by disease or trauma. Lesion is derived from the Latin word laesio which means injury.- Types :...
s raises concern over oral
Oral administration
Oral administration is a route of administration where a substance is taken through the mouth.-Terminology:Per os is an adverbial phrase meaning literally from Latin "by mouth" or "by way of the mouth." The expression is used in medicine to describe a treatment that is taken orally. The...
exposure.
Studies by Bloomquist et al., 2002 suggested a link of permethrin exposure to Parkinson's disease
Parkinson's disease
Parkinson's disease is a degenerative disorder of the central nervous system...
, including very small (per kg.) exposures:
- 2002 study - "Our studies have documented low-dose effects of permethrin, doses below one-one thousandth of a lethal doseLethal doseA lethal dose is an indication of the lethality of a given substance or type of radiation. Because resistance varies from one individual to another, the 'lethal dose' represents a dose at which a given percentage of subjects will die...
for a mouse, with effects on those brain pathways [that are] involved in Parkinson's Disease [...] We have found effects consistent with a pre-parkinsonsian condition, but not yet full-blown parkinsonismParkinsonismParkinsonism is a neurological syndrome characterized by tremor, hypokinesia, rigidity, and postural instability. The underlying causes of parkinsonism are numerous, and diagnosis can be complex...
."
However a more recent 2007 study by the same researcher concluded that there was "little hazard to humans"
- 2007 study - "long-term, low-dose exposure to permethrin alone did not cause signs of neurotoxicity to striatal dopaminergicDopaminergicDopaminergic means related to the neurotransmitter dopamine. For example, certain proteins such as the dopamine transporter , vesicular monoamine transporter 2 , and dopamine receptors can be classified as dopaminergic, and neurons which synthesize or contain dopamine and synapses with dopamine...
neural terminals, or enhance the effects of MPTPMPTPMPTP is a neurotoxin precursor to MPP+, which causes permanent symptoms of Parkinson's disease by destroying dopaminergic neurons in the substantia nigra of the brain...
. We conclude that, under typical use conditions, permethrin poses little Parkinsonian hazard to humans, including when impregnated into clothing for control of biting flies"
A 2006 study in South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
, found residues of permethrin in breast milk
Breast milk
Breast milk, more specifically human milk, is the milk produced by the breasts of a human female for her infant offspring...
, together with DDT, in an area that experienced DDT
DDT
DDT is one of the most well-known synthetic insecticides. It is a chemical with a long, unique, and controversial history....
treatment for malaria
Malaria
Malaria is a mosquito-borne infectious disease of humans and other animals caused by eukaryotic protists of the genus Plasmodium. The disease results from the multiplication of Plasmodium parasites within red blood cells, causing symptoms that typically include fever and headache, in severe cases...
control, as well as the use of pyrethroid
Pyrethroid
A pyrethroid is an organic compound similar to the natural pyrethrins produced by the flowers of pyrethrums . Pyrethroids now constitute a major commercial household insecticides...
s in small-scale agriculture.
Domestic animals
Permethrin is toxic to cats. Many cats die after being given flea treatments intended for dogs, or by contact with dogs having recently been treated with permethrin.External links
- Permethrin Technical Fact Sheet - National Pesticide Information Center
- Permethrin General Fact Sheet - National Pesticide Information Center
- Permethrin-treated Clothing Hot Topic - National Pesticide Information Center
- "Health Effects of Permethrin-Impregnated Army Battle-Dress Uniforms", National Research Council (1994, US)
- "Permethrin summary report", Committee for Veterinary Products, European Agency for the Evaluation of Medical Products (1998, EU(
- Pesticide link to Parkinson Disease
- Permethrin Pesticide Information Profile - Extension Toxicology Network
- Permethrin chemical data