|Jmol-3D images||Image 1
|Molar mass||422.87 g mol−1|
|Solubility in water||0.1 mg/L|
| (what is: / ?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Bifenthrin is a pyrethroid insecticide used primarily against the red imported fire ant by influencing its nerve system. It has a high toxicity to aquatic organisms. Although it is listed as a restricted use chemical in the United States, it is allowed to be sold for daily use, provided that the product sold has a low concentration of bifenthrin. The chemical has been discovered and developed by FMC Corporation. Products containg Bifenthrin include Talstar, Maxxthor, Capture, Brigade, Bifenthrine, Ortho Home Defense Max, Bifen IT, Bifen L/P, Torant, Zipak, Scotts LawnPro Step 3, Wisdom TC Flowable, FMC 54800 and OMS3024.
Bifenthrin is poorly soluble in water and often remains in soil. Its residual half-life in soil is between 7 days and 8 months, depending on the soil type, with a low mobility in most soil types. Bifenthrin has the longest known residual time in soil of insecticides currently on the market. It is a white, waxy solid with a faint sweet smell. It is chemically synthesized in various forms, including powder, granules and pellets. However, it is not naturally occurring.
Like other Pyrethroids, bifenthrin is chiral. This means that there are different enantiomers which can have completely different effects on the human body, which is a chiral environment (If the environment would be achiral, the effects of the different enantiomers would be the same). Bifenthrin is found in 2 enantiomers: 1S-cis-Bifenthrin and 1R-cis-Bifenthrin. 1S-cis-Bifenthrin is 3-4 times more toxic to humans than 1R-cis-Bifenthrin, while the latter is more than 300 times more effective as a pesticide.
There are two types of pyrethroids, the ones with α-cyanogroup and the ones without an α-cyanogroup. The neurotoxicity of bifenthrin is based on the affinity with voltage-gated sodium channels (both in insects as in mammals). The pyrethroids with an α-cyano-group block the closing of the sodium-channel permanently, causing the membrane to be permanently depolarized. The resting potential will not be restored, and no further action potential can be generated. The pyrethroids without an α-cyanogroup, to which bifenthrin belongs, are only able to bind to the sodium-channel transiently. This will result in so-called after potentials and eventual continuous firing of axons. The resting potential is not affected by these pyrethroids.
Bifenthrin will open the sodium-channel for a shorter period than other pyrethroids. The mechanism in mammals and invertebrates is not different, however, the effect on mammals is much less due to higher body temperature, higher body volume and lower affinity of bifenthrin to sodium-channels.
There have been numerous studies conducted to the half life of bifenthrin in soil, water and air under different conditions like aerobic, anaerobic and at different temperatures and pH. It is more likely to remain in the soil and not so much in water (it is hydrophobic), nor in the air (it is unlikely to volatize because of its physical properties). Because of the water-insolubility of bifenthrin, it will not rapidly cause contamination of ground water. However, there might be some contamination by bifenthrin that is soil-bound to surface water through runoff.
For an overview of the environmental degradation of bifenthrin: see figure below. The main path of degradation results in 4’-hydroxy bifenthrin.
Pyrethroids are much less toxic in mammals than they are in insects and fish. The main reason for this is that mammals have ability to rapidly break the ester-bond in bifenthrin and break the substance into its inactive acid- and alcohol components:
On a large scale bifenthrin is often used against red imported fire ants. It is also effective against aphids, worms, ants, gnats, moths, beetles, grasshoppers, mites, midges, spiders, ticks, yellow jackets, maggots, thrips, caterpillars, flies and fleas. It is mostly used in orchards, nurseries and homes. In the agricultural sector, it is used in great amounts on certain crops, like corn. About 70% of all hops and raspberries cultured in the United States are treated with bifenthrin.
Bifenthrin is very toxic to many insects, fish and other aquatic animals. It is only slightly toxic to mammals and not at all toxic to plants. Even though it does not have a large toxicological risk towards mammals or birds, bifenthrin is able to accumulate in food, and therefore might be dangerous to mammals or birds in some scenarios.
Toxicity in animals
Bifenthrin is an effective pesticide to use against malaria mosquitoes. Bifenthrin is still effective when there is a resistance for other pyrethroides. Mosquito nets can be treated with bifenthrin. When this is done the nets keep more mosquitoes away. At this moment bifenthrin is an effectively used insecticide but there is a high risk that bifenthrin only works for a short time. The mosquitoes will develop a resistance against bifenthrin as well.
- Aquatic life
Bifenthrin is hardly soluble in water so nearly all bifenthrin will stay in the sediment. Although there is not much bifenthrin in the water, it is very harmful for the aquatic life. Even in small concentrations fishes and other aquatic animals are affected by bifenthrin. One of the reasons for the high sensitivity of fish for bifenthrin is because fish have a slow metabolism. Bifenthrin will stay longer in the system of the fish. Another reason for the high sensitivity for fish is the effect of bifenthrin as ATPase-inhibitor. The gills need a lot of ATP to control the osmotic balance of oxygen. If the fish is no longer capable to take up oxygen because ATP can no longer be used, the fish will die. In cold water bifenthrin is even more dangerous. pH and calcium concentration are also factors that influence the toxicity. Vertebrates are less sensitive for the effects of bifenthrin as ATPase-inhibitor.
In bees, the lethal concentration (LC50) of bifenthrin is about 17 mg/L. At sublethal concentrations, bifenthrin reduces the fecundity of bees, decreases the rate at which bees develop into adulthood, and increases their immature periods.
- Table of LD50 values
|Female rats||54 mg/kg|
|Male rats||70 mg/kg|
|Mallard ducks||1280 ppm|
|Bobwhite quail||4450 ppm|
|Rainbow trout||0.00015 mg/L|
Toxicity in mammals
- Chemical consequences
Bifenthrin (and other synthetic pyrethroids) are being used in agriculture in an increasing fashion. The reason for this increase is based on the high efficiency of these substances in killing insects, the low toxicity for mammals, and good biodegradability. However, because of its success, these pyrethroids are being used more often (also indoors) and high exposure of bifenthrin to humans can occur.
Scientific tests in vitro have concluded that cytotoxic damage like DNA-breakdown and gene-mutation can be done by bifenthrin. Cytotoxic effects are not seen directly, but are more long-term-based. These effects can differ in severity based on which enantiomer the body is exposed to and the dose. Cytotoxic damage in humans results from increased oxidative stress, which leads to Single-strand-DNA-breaking and degrading of lipids in the plasma membrane and F-Actine. The exact mechanims included in this path are not completely known yet, though several groups have found matching results regarding increased ROS-production which induces apoptosis. Bifenthrin also activates the LFA-1/ICAM function of T-cells. This function is a marker for inflammation. This means that T-cells will be recognized by your body as if they were inflamed. This can ultimately lead to autoimmune diseases like asthma, bronchitis, arthritis and cancer.
- Neurotoxicity for humans
Exposure to bifenthrin can be achieved either via skin contact or ingestion. Skin-contact is not toxic, apart from a slight tingling sensation on the specific location of contact. Ingestion is toxic, although only slightly. Concentrations up to 10-4 M are not inducing toxic effects. Commercially available bifenthrin (Ortho Home Defense Max, for example) however, can induce toxic effects in those concentrations, because the added chemicals to Ortho Home Defense Max which for instance improve the sustainability either potentiate bifenthrin or are toxic of their own. Symptoms of excessive exposure to bifenthrin are nausea, headaches, hypersensitivity for touch and sound and irritation of the skin and the eyes.
The U.S. Environmental Protection Agency (EPA) is monitoring and regulating the use of pesticides in the United States. Bifenthrin is classified as a restricted use pesticide, meaning it is allowed to be legally sold only by Certified Pesticide Applicators. For everyday use it is allowed to be sold in lower concentrations in the entire country.
Bifenthrin has been approved for use against the Rasberry crazy ant in the Houston, Texas area, under a special "crisis exemption" from the Texas Department of Agriculture and the Environmental Protection Agency. The chemical is only approved for use in Texas counties experiencing "confirmed infestations" of the newly discovered ant species.
The EPA has classified bifenthrin as a class C carcinogen, a possible human carcinogen. This is based on a test with mice, which showed increased development of certain tumors.
There have been established an acute and chronic reference dose (RfD) for bifenthrin, based on animal studies. The reference dose resembles the estimate quantity of a chemical to which a person could be exposed to every day (or a one-time exposure for the acute RfD) without any appreciable risk of adverse health effects.
The acute reference dose (RfD) for bifenthrin is 0.328 mg/kg bodyweight/day. The chronic reference dose (RfD) for bifenthrin is 0.013 mg/kg bodyweight/day.
Bifenthrin was included in a biocide ban proposed by the Swedish Chemicals Agency, because of the carcinogenic effect of bifenthrin. This was approved by the European Parliament in 2009. Pesticides containing bifenthrin were withdrawn from use in the European Union. They have since been reinstated.
- , Toxipedia
- , Enantioselective cytotoxicity of the insecticide bifenthrin on a human amnion epithelial (FL) cell line
- , Kinetics of sodium channel modification as the basis for the variation in the nerve membrane effects of pyrethroids and DDT analogs
- , Bifenthrin Technical Fact Sheet, NPIC
- , In Vitro Metabolism of Pyrethroid Pesticides by Rat and Human Hepatic Microsomes and Cytochrome P450 Isoforms
- , Bifenthrin: A Useful Pyrethroid Insecticide for Treatment of Mosquito Nets
- , Efficacy of bifenthrin-impregnated bednets against Anopheles funestus and pyrethroid-resistant Anopheles gambiae in North Cameroon
- , Extension Toxicology Network
- , Effects of acute exposure to bifenthrin on some haematological, biochemical and histopathological parameters of rainbow trout (Oncorhynchus mykiss)
- Dai, Ping-Li; Wang, Qiang; Sun, Ji-Hu; Liu, Feng; Wang, Xing; Wu, Yan-Yan; Zhou, Ting (2010). "Effects of sublethal concentrations of bifenthrin and deltamethrin on fecundity, growth, and development of the honeybeeApis mellifera ligustica". Environmental Toxicology and Chemistry 29 (3): 644–9. doi:10.1002/etc.67. PMID 20821489.
- , Pesticide Action Network
- , Urban Entomology
- , List of active substances in plant protection products which have been banned or withdrawn in Sweden during the period 1966 to 2000.