DEET
Encyclopedia
N,N-Diethyl-meta-toluamide, abbreviated DEET, is a slightly yellow oil. It is the most common active ingredient in insect repellent
s. It is intended to be applied to the skin
or to clothing
, and provides protection against tick
bites, mosquito
bites, chiggers, and other insects that can transmit disease.
, following its experience of jungle warfare
during World War II
. It was originally tested as a pesticide on farm fields, and entered military use in 1946 and civilian use in 1957. It was used in Vietnam
and Southeast Asia.
, it can be prepared by converting m-toluic acid
(3-methylbenzoic acid) to the corresponding acyl chloride
, and allowing it to react with diethylamine
:
s for 1-octen-3-ol
, a volatile
substance that is contained in human sweat
and breath. The prevailing theory was that DEET effectively "blinds" the insect's senses so that the biting/feeding instinct
is not triggered by humans or other animals which produce these chemicals. DEET does not appear to affect the insect's ability to smell carbon dioxide
, as had been suspected earlier.
However, more recent evidence shows that DEET serves as a true repellent in that mosquitoes intensely dislike the smell of the chemical repellent. A type of olfactory receptor neuron
in special antenna
l sensilla of mosquitoes that is activated by DEET as well as other known insect repellents such as eucalyptol
, linalool, and thujone
has been identified. Moreover, in a behavioral test DEET had a strong repellent activity in the absence of body odor
attractants such as 1-octen-3-ol
, lactic acid
, or carbon dioxide
. Female and male mosquitoes showed the same response.
A recent structural study has revealed that DEET binds to Anopheles gambiae
Odorant binding protein
1 (AgamOBP1) with high shape complementarity, suggesting that AgamOBP1 is a molecular target of DEET and perhaps other repellents.
found a direct correlation
between DEET concentration and hours of protection against insect bites. 100% DEET was found to offer up to 12 hours of protection while several lower concentration DEET formulations (20%-34%) offered 3–6 hours of protection. Other research has corroborated the effectiveness of DEET. The Center for Disease Control recommends 30-50% DEET to prevent the spread of pathogens carried by insects.
in rare cases, it may cause skin reactions.
In the DEET Reregistration Eligibility Decision (RED), the United States Environmental Protection Agency (EPA) reported 14 to 46 cases of potential DEET-associated seizure
s, including 4 deaths. The EPA states: "... it does appear that some cases are likely related to DEET toxicity
," but observed that with 30% of the US population using DEET, the likely seizure rate is only about one per 100 million users.
The Pesticide Information Project of Cooperative Extension Offices of Cornell University
states that "Everglades National Park
employees having extensive DEET exposure were more likely to have insomnia, mood disturbances and impaired cognitive function than were lesser exposed co-workers".
When used as directed, products containing between 10% to 30% DEET have been found by The American Academy of Pediatrics
to be safe to use on children as well as adults but recommends that DEET not be used on infants less than two months old.
Citing human health reasons, Health Canada
barred the sale of insect repellents for human use that contained more than 30% DEET in a 2002 re-evaluation. The agency recommended that DEET based products be used on child
ren between the ages of 2 and 12 only if the concentration of DEET is 10% or less and that repellents be applied no more than 3 times a day, children under 2 should not receive more than 1 application of repellent in a day and DEET based products of any concentration not be used on infants under 6 months.
Recently, DEET has been found to inhibit the activity of a central nervous system
enzyme
, acetylcholinesterase
, in both insects and mammals. This enzyme is involved in the hydrolysis
of the neurotransmitter acetylcholine
, thus playing a role in the function of the neurons which control muscles. Because of this property, many insecticides are used to block acetylcholinesterase, which leads to an excessive accumulation of acetylcholine at the synaptic cleft, causing neuromuscular paralysis and death by asphyxiation. DEET is commonly used in combination with insecticides and has the capacity to strengthen the toxicity of carbamates, a class of insecticides known to block acetylcholinesterase. These findings bring evidence that, besides having known toxic effects on the olfactory system, DEET also acts on the brain of insects, and that its toxicity is strengthened in combination with other insecticides.
, and may dissolve some plastics, rayon
, spandex
, other synthetic fabrics
, leather
, and painted or varnish
ed surfaces including nailpolish. It can also be used effectively to remove permanent marker ink from whiteboards.
, it has been found to have a slight toxicity for coldwater fish
such as the rainbow trout
and the tilapia
, and it has also been shown to be toxic for some species of freshwater zooplankton
. DEET has been detected at low concentrations in waterbodies as a result of production and use, such as in the Mississippi River
and its tributaries, where a 1991 study detected levels varying from 5 to 201 ng/L.
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...
s. It is intended to be applied to the skin
Skin
-Dermis:The dermis is the layer of skin beneath the epidermis that consists of connective tissue and cushions the body from stress and strain. The dermis is tightly connected to the epidermis by a basement membrane. It also harbors many Mechanoreceptors that provide the sense of touch and heat...
or to clothing
Clothing
Clothing refers to any covering for the human body that is worn. The wearing of clothing is exclusively a human characteristic and is a feature of nearly all human societies...
, and provides protection against tick
Tick
Ticks are small arachnids in the order Ixodida, along with mites, constitute the subclass Acarina. Ticks are ectoparasites , living by hematophagy on the blood of mammals, birds, and sometimes reptiles and amphibians...
bites, 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...
bites, chiggers, and other insects that can transmit disease.
History
DEET was developed by the United States ArmyUnited States Army
The United States Army is the main branch of the United States Armed Forces responsible for land-based military operations. It is the largest and oldest established branch of the U.S. military, and is one of seven U.S. uniformed services...
, following its experience of jungle warfare
Jungle warfare
Jungle warfare is a term used to cover the special techniques needed for military units to survive and fight in jungle terrain.It has been the topic of extensive study by military strategists, and was an important part of the planning for both sides in many conflicts, including World War II and the...
during World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
. It was originally tested as a pesticide on farm fields, and entered military use in 1946 and civilian use in 1957. It was used in Vietnam
Vietnam
Vietnam – sometimes spelled Viet Nam , officially the Socialist Republic of Vietnam – is the easternmost country on the Indochina Peninsula in Southeast Asia. It is bordered by China to the north, Laos to the northwest, Cambodia to the southwest, and the South China Sea –...
and Southeast Asia.
Preparation
A slightly yellow liquid at room temperatureRoom temperature
-Comfort levels:The American Society of Heating, Refrigerating and Air-Conditioning Engineers has listings for suggested temperatures and air flow rates in different types of buildings and different environmental circumstances. For example, a single office in a building has an occupancy ratio per...
, it can be prepared by converting m-toluic acid
M-Toluic acid
m-Toluic acid, , is an aromatic carboxylic acid, with formula C6H4. It is an isomer of p-toluic acid and o-toluic acid....
(3-methylbenzoic acid) to the corresponding acyl chloride
Acyl chloride
In organic chemistry, an acyl chloride is an organic compound with the functional group -CO-Cl. Their formula is usually written RCOCl, where R is a side chain. They are usually considered to be reactive derivatives of carboxylic acids. A specific example of an acyl chloride is acetyl chloride,...
, and allowing it to react with diethylamine
Diethylamine
Diethylamine is a secondary amine with the molecular structure CH3CH2NHCH2CH3. It is a flammable, strongly alkaline liquid. It is miscible with water and ethanol. It is a colorless liquid which often appears brown due to impurities...
:
Mechanism of action
DEET was historically believed to work by blocking insect olfactory receptorOlfactory receptor
Olfactory receptors expressed in the cell membranes of olfactory receptor neurons are responsible for the detection of odor molecules. Activated olfactory receptors are the initial player in a signal transduction cascade which ultimately produces a nerve impulse which is transmitted to the brain...
s for 1-octen-3-ol
1-Octen-3-ol
1-Octen-3-ol, octenol for short , is a chemical that attracts biting insects such as mosquitos. It is contained in human breath and sweat, and it was once believed that insect repellent DEET works by blocking the insects' octenol odorant receptors.Octenol is used in combination with carbon dioxide...
, a volatile
Volatility (chemistry)
In chemistry and physics, volatility is the tendency of a substance to vaporize. Volatility is directly related to a substance's vapor pressure. At a given temperature, a substance with higher vapor pressure vaporizes more readily than a substance with a lower vapor pressure.The term is primarily...
substance that is contained in human sweat
SWEAT
SWEAT is an OLN/TSN show hosted by Julie Zwillich that aired in 2003-2004.Each of the 13 half-hour episodes of SWEAT features a different outdoor sport: kayaking, mountain biking, ice hockey, beach volleyball, soccer, windsurfing, rowing, Ultimate, triathlon, wakeboarding, snowboarding, telemark...
and breath. The prevailing theory was that DEET effectively "blinds" the insect's senses so that the biting/feeding instinct
Instinct
Instinct or innate behavior is the inherent inclination of a living organism toward a particular behavior.The simplest example of an instinctive behavior is a fixed action pattern, in which a very short to medium length sequence of actions, without variation, are carried out in response to a...
is not triggered by humans or other animals which produce these chemicals. DEET does not appear to affect the insect's ability to smell carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
, as had been suspected earlier.
However, more recent evidence shows that DEET serves as a true repellent in that mosquitoes intensely dislike the smell of the chemical repellent. A type of olfactory receptor neuron
Olfactory receptor neuron
An olfactory receptor neuron , also called an olfactory sensory neuron , is a transduction cell within the olfactory system. J. Rospars, Dendritic integration in olfactory sensory neurons: a steady-state analysis of how the neuron structure and neuron environment influence the coding of odor...
in special antenna
Antenna (biology)
Antennae in biology have historically been paired appendages used for sensing in arthropods. More recently, the term has also been applied to cilium structures present in most cell types of eukaryotes....
l sensilla of mosquitoes that is activated by DEET as well as other known insect repellents such as eucalyptol
Eucalyptol
Eucalyptol is a natural organic compound which is a colorless liquid. It is a cyclic ether and a monoterpenoid.Eucalyptol is also known by a variety of synonyms: 1,8-cineol, 1,8-cineole, limonene oxide, cajeputol, 1,8-epoxy-p-menthane, 1,8-oxido-p-menthane, eucalyptol, eucalyptole,...
, linalool, and thujone
Thujone
Thujone is a ketone and a monoterpene that occurs naturally in two diastereomeric forms: -α-thujone and -β-thujone. It has a menthol odor. Even though it is best known as a chemical compound in the spirit absinthe, recent tests show absinthe contains only small quantities of thujone, and may or may...
has been identified. Moreover, in a behavioral test DEET had a strong repellent activity in the absence of body odor
Body odor
Body odor or body odour, sometimes colloquially abbreviated as B.O., is the smell of bacteria growing on the body. The bacteria multiply rapidly in the presence of sweat, but sweat itself is almost completely odorless to humans....
attractants such as 1-octen-3-ol
1-Octen-3-ol
1-Octen-3-ol, octenol for short , is a chemical that attracts biting insects such as mosquitos. It is contained in human breath and sweat, and it was once believed that insect repellent DEET works by blocking the insects' octenol odorant receptors.Octenol is used in combination with carbon dioxide...
, lactic acid
Lactic acid
Lactic acid, also known as milk acid, is a chemical compound that plays a role in various biochemical processes and was first isolated in 1780 by the Swedish chemist Carl Wilhelm Scheele. Lactic acid is a carboxylic acid with the chemical formula C3H6O3...
, or carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
. Female and male mosquitoes showed the same response.
A recent structural study has revealed that DEET binds to Anopheles gambiae
Anopheles gambiae
Anopheles gambiae is a complex of at least seven morphologically distinguishable species of mosquitoes in the genus Anopheles. This complex was recognised in the 1960s and includes the most important vectors of malaria in sub-Saharan Africa and the most efficient malaria vectors known.This species...
Odorant binding protein
Odorant binding protein
Odorant binding proteins are abundant small soluble proteins secreted in the nasal mucus of many animal species and in the sensillar lymph of chemosensory sensilla of insects....
1 (AgamOBP1) with high shape complementarity, suggesting that AgamOBP1 is a molecular target of DEET and perhaps other repellents.
Concentrations
DEET is often sold and used in spray or lotion in concentrations up to 100%. Consumer ReportsConsumer Reports
Consumer Reports is an American magazine published monthly by Consumers Union since 1936. It publishes reviews and comparisons of consumer products and services based on reporting and results from its in-house testing laboratory. It also publishes cleaning and general buying guides...
found a direct correlation
Correlation
In statistics, dependence refers to any statistical relationship between two random variables or two sets of data. Correlation refers to any of a broad class of statistical relationships involving dependence....
between DEET concentration and hours of protection against insect bites. 100% DEET was found to offer up to 12 hours of protection while several lower concentration DEET formulations (20%-34%) offered 3–6 hours of protection. Other research has corroborated the effectiveness of DEET. The Center for Disease Control recommends 30-50% DEET to prevent the spread of pathogens carried by insects.
Effects on health
As a precaution, manufacturers advise that DEET products should not be used under clothing or on damaged skin, and that preparations be washed off after they are no longer needed or between applications. DEET can act as an irritant;in rare cases, it may cause skin reactions.
In the DEET Reregistration Eligibility Decision (RED), the United States Environmental Protection Agency (EPA) reported 14 to 46 cases of potential DEET-associated 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, including 4 deaths. The EPA states: "... it does appear that some cases are likely related to DEET toxicity
Toxicity
Toxicity is the degree to which a substance can damage a living or non-living organisms. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a substructure of the organism, such as a cell or an organ , such as the liver...
," but observed that with 30% of the US population using DEET, the likely seizure rate is only about one per 100 million users.
The Pesticide Information Project of Cooperative Extension Offices of Cornell University
Cornell University
Cornell University is an Ivy League university located in Ithaca, New York, United States. It is a private land-grant university, receiving annual funding from the State of New York for certain educational missions...
states that "Everglades National Park
Everglades National Park
Everglades National Park is a national park in the U.S. state of Florida that protects the southern 25 percent of the original Everglades. It is the largest subtropical wilderness in the United States, and is visited on average by one million people each year. It is the third-largest...
employees having extensive DEET exposure were more likely to have insomnia, mood disturbances and impaired cognitive function than were lesser exposed co-workers".
When used as directed, products containing between 10% to 30% DEET have been found by The American Academy of Pediatrics
American Academy of Pediatrics
The American Academy of Pediatrics is the major professional association of pediatricians in the United States. The AAP was founded in 1930 by 35 pediatricians to address pediatric healthcare standards. It currently has 60,000 members in primary care and sub-specialist areas...
to be safe to use on children as well as adults but recommends that DEET not be used on infants less than two months old.
Citing human health reasons, Health Canada
Health Canada
Health Canada is the department of the government of Canada with responsibility for national public health.The current Minister of Health is Leona Aglukkaq, a Conservative Member of Parliament appointed to the position by Prime Minister Stephen Harper.-Branches, regions and agencies:Health Canada...
barred the sale of insect repellents for human use that contained more than 30% DEET in a 2002 re-evaluation. The agency recommended that DEET based products be used on child
Child
Biologically, a child is generally a human between the stages of birth and puberty. Some vernacular definitions of a child include the fetus, as being an unborn child. The legal definition of "child" generally refers to a minor, otherwise known as a person younger than the age of majority...
ren between the ages of 2 and 12 only if the concentration of DEET is 10% or less and that repellents be applied no more than 3 times a day, children under 2 should not receive more than 1 application of repellent in a day and DEET based products of any concentration not be used on infants under 6 months.
Recently, DEET has been found to inhibit the activity of a central nervous system
Central nervous system
The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...
enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
, acetylcholinesterase
Acetylcholinesterase
"Acetylcholinesterase, also known as AChE or acetylcholine acetylhydrolase, is an enzyme that degrades the neurotransmitter acetylcholine, producing choline and an acetate group. It is mainly found at neuromuscular junctions and cholinergic nervous system, where its activity serves to terminate...
, in both insects and mammals. This enzyme is involved in the hydrolysis
Hydrolysis
Hydrolysis is a chemical reaction during which molecules of water are split into hydrogen cations and hydroxide anions in the process of a chemical mechanism. It is the type of reaction that is used to break down certain polymers, especially those made by condensation polymerization...
of the neurotransmitter acetylcholine
Acetylcholine
The chemical compound acetylcholine is a neurotransmitter in both the peripheral nervous system and central nervous system in many organisms including humans...
, thus playing a role in the function of the neurons which control muscles. Because of this property, many insecticides are used to block acetylcholinesterase, which leads to an excessive accumulation of acetylcholine at the synaptic cleft, causing neuromuscular paralysis and death by asphyxiation. DEET is commonly used in combination with insecticides and has the capacity to strengthen the toxicity of carbamates, a class of insecticides known to block acetylcholinesterase. These findings bring evidence that, besides having known toxic effects on the olfactory system, DEET also acts on the brain of insects, and that its toxicity is strengthened in combination with other insecticides.
Effects on materials
DEET is an effective solventSolvent
A solvent is a liquid, solid, or gas that dissolves another solid, liquid, or gaseous solute, resulting in a solution that is soluble in a certain volume of solvent at a specified temperature...
, and may dissolve some plastics, rayon
Rayon
Rayon is a manufactured regenerated cellulose fiber. Because it is produced from naturally occurring polymers, it is neither a truly synthetic fiber nor a natural fiber; it is a semi-synthetic or artificial fiber. Rayon is known by the names viscose rayon and art silk in the textile industry...
, spandex
Spandex
Spandex or elastane is a synthetic fibre known for its exceptional elasticity. It is strong, but less durable than natural Latex, its major non-synthetic competitor. It is a polyurethane-polyurea copolymer that was co-invented in 1959 by chemists C. L. Sandquist and Joseph Shivers at DuPont's...
, other synthetic fabrics
Synthetic fiber
Synthetic fibers are the result of extensive research by scientists to improve on naturally occurring animal and plant fibers. In general, synthetic fibers are created by forcing, usually through extrusion, fiber forming materials through holes into the air, forming a thread...
, leather
Leather
Leather is a durable and flexible material created via the tanning of putrescible animal rawhide and skin, primarily cattlehide. It can be produced through different manufacturing processes, ranging from cottage industry to heavy industry.-Forms:...
, and painted or varnish
Varnish
Varnish is a transparent, hard, protective finish or film primarily used in wood finishing but also for other materials. Varnish is traditionally a combination of a drying oil, a resin, and a thinner or solvent. Varnish finishes are usually glossy but may be designed to produce satin or semi-gloss...
ed surfaces including nailpolish. It can also be used effectively to remove permanent marker ink from whiteboards.
Effects on the environment
Though DEET is not expected to bioaccumulateBioaccumulation
Bioaccumulation refers to the accumulation of substances, such as pesticides, or other organic chemicals in an organism. Bioaccumulation occurs when an organism absorbs a toxic substance at a rate greater than that at which the substance is lost...
, it has been found to have a slight toxicity for coldwater 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...
such as the rainbow trout
Rainbow trout
The rainbow trout is a species of salmonid native to tributaries of the Pacific Ocean in Asia and North America. The steelhead is a sea run rainbow trout usually returning to freshwater to spawn after 2 to 3 years at sea. In other words, rainbow trout and steelhead trout are the same species....
and the tilapia
Tilapia
Tilapia , is the common name for nearly a hundred species of cichlid fish from the tilapiine cichlid tribe. Tilapia inhabit a variety of fresh water habitats, including shallow streams, ponds, rivers and lakes. Historically, they have been of major importance in artisan fishing in Africa and the...
, and it has also been shown to be toxic for some species of freshwater zooplankton
Zooplankton
Zooplankton are heterotrophic plankton. Plankton are organisms drifting in oceans, seas, and bodies of fresh water. The word "zooplankton" is derived from the Greek zoon , meaning "animal", and , meaning "wanderer" or "drifter"...
. DEET has been detected at low concentrations in waterbodies as a result of production and use, such as in the Mississippi River
Mississippi River
The Mississippi River is the largest river system in North America. Flowing entirely in the United States, this river rises in western Minnesota and meanders slowly southwards for to the Mississippi River Delta at the Gulf of Mexico. With its many tributaries, the Mississippi's watershed drains...
and its tributaries, where a 1991 study detected levels varying from 5 to 201 ng/L.
See also
- ChikungunyaChikungunyaChikungunya virus is an insect-borne virus, of the genus Alphavirus, that is transmitted to humans by virus-carrying Aedes mosquitoes. There have been recent breakouts of CHIKV associated with severe illness...
- IcaridinIcaridinIcaridin, also known as picaridine, KBR 3023, under the INCI name hydroxyethyl isobutyl piperidine carboxylate, and the trade names Bayrepel and Saltidin, is an insect repellent...
- PermethrinPermethrinPermethrin is a common synthetic chemical, widely used as an insecticide, acaricide, and insect repellent. It belongs to the family of synthetic chemicals called pyrethroids and functions as a neurotoxin, affecting neuron membranes by prolonging sodium channel activation. It is not known to...
, a pyrethroidPyrethroidA pyrethroid is an organic compound similar to the natural pyrethrins produced by the flowers of pyrethrums . Pyrethroids now constitute a major commercial household insecticides... - Citronella oilCitronella oilCitronella oil is one of the essential oils obtained from the leaves and stems of different species of Cymbopogon. The oil is used extensively as a source of perfumery chemicals such as citronellal, citronellol and geraniol...
- lemon eucalyptus
- BeautyberryBeautyberryBeautyberry is a genus of shrubs and small trees in the family Verbenaceae; between 40-150 species are accepted by different botanists. They are native to east and southeast Asia , Australia, southeast North America and Central America.-Growth:The temperate species are deciduous, the tropical...
- Mosquito coilMosquito coilMosquito coil is mosquito-repelling incense, usually shaped into a spiral, and typically made from a dried paste of pyrethrum powder. The coil is usually held at the center of the spiral, suspending it in the air, or wedged by two pieces of fireproof nettings to allow continuous smoldering...
External links
- DEET General Fact Sheet - National Pesticide Information Center
- DEET Technical Fact Sheet - National Pesticide Information Center
- West Nile Virus Resource Guide - National Pesticide Information Center
- Health Advisory: Tick and Insect Repellents, New York State
- US Centers for Disease Control information on DEET
- US Environmental Protection Agency information on DEET
- Review of scientific literature on DEET (from a RAND Corporation report on Gulf WarGulf WarThe Persian Gulf War , commonly referred to as simply the Gulf War, was a war waged by a U.N.-authorized coalition force from 34 nations led by the United States, against Iraq in response to Iraq's invasion and annexation of Kuwait.The war is also known under other names, such as the First Gulf...
illnesses)