Wasp killer concentrate for pump sprayer

wasp killer concentrate for pump sprayer

Can you recommend a liquid concentrate that I can put into a pump sprayer? We have railings with spindles around our porch. Wasps love the “nooks” created at the top between spindles. Only way to get to spray up is from right underneath. Aerosol cans don’t work due to need to angle can to almost horizontal. Thanks!

We’ve got two options that will work. The first is a liquid known as CYPERMETHRIN CONCENTRATE. You can find it mentioned in our WASP CONTROL article. As the article details, wasps and other flying insects hate cypermethrin and will avoid anywhere it’s been applied. You can use it on your homes siding, soffits, railings, around windows, shutters, etc. Basically anywhere wasps want to make nests. Treatments will last 30-60 days and will both kill and repel any that come to the treated areas so you can use it to control existing nests and to help stop nests from being formed.

The second option is actually an aerosol. Now unlike a standard “wasp freeze” type aerosol, this product can be used to spot treat by “misting” the spray over the areas you want to treat. This means you won’t have to spray with the can pointed directly upside down which can no doubt cause issues. I actually use this product all the time on my boat to get wasps that want to make nests on my boats bimini top. I have to point the aerosol slightly “up”, at about a 45 degree angle, but it works fine at that angle. And it only takes 2-3 seconds of mist to get the surface treated. I’m mostly treating mud daubers but it will work on any kind of wasp.

So if you can get close to the “nooks” you mention are having the problem, PHANTOM AEROSOL might be something you can employ. It’s odorless, goes on dry and is very easy to use – especially if spraying a liquid can be messy where you need to treat. Just keep in mind Phantom is not a contact killer like the Cypermethrin. So even if you spray a wasp directly, it will not die. Now this is very much by design; Phantom takes 2-3 days to kill targeted insects but by taking this long to work, it can actually affect many other wasps so this feature is very much a “good thing”. Its also the reason for the products name; phantom insinuates that the treatment is undetectable by the wasps so they’ll readily walk over it without being repelled or concerned. And by not noticing it’s present, they will be picking up the treatment and as a consequence, die.

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Cypermethrin: https://www.bugspraycart.com/insecticide/liquid/viper-cypermethrin

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Insects in the City

The best in science-based, pest management solutions from Texas A&M AgriLife Extension Service

Understanding Common House and Garden Insecticides

Last updated: August 9, 2016 at 11:05 am

Pesticides include any substances used to kill, control or repel pests. We use pesticides almost every day, from ant and roach sprays for the kitchen, to weed killers for the lawn, mildew cleaners for the bathroom and mosquito repellents outdoors. Pesticides have become a widely accepted way to keep our homes and gardens relatively pest-free. About 85% of all American households keep at least one pesticide in storage.

Despite our willingness to use them, most consumers associate pesticides with pollution, health risks and toxic chemicals. Surveys show that about 75% of consumers are wary of using pesticides in the home. Many people today are avoiding certain synthetic (man-made) pesticides in favor of natural or “organic” products. But regardless of whether a substance comes from natural or artificial sources, if it controls pests, it’s a pesticide. And as long as pests are around, chances are that we will use pesticides.

There are many types of pesticides. Insecticides are pesticides designed to control insects. Herbicides are pesticides designed to kill weeds. There are dozens of others. In this [email protected] we will learn about the different kinds of insecticides and how to choose the right one for the job.

Choosing the right formulation

The first decision to make when selecting a pesticide is what formulation to use. A formulation is the way the pesticide active ingredient is mixed with inert ingredients to make it convenient and effective to use. Factors that influence the choice of formulation include cost, convenience in mixing and use, effectiveness against your target pest and safety. The following table describes the most important types of insecticide formulations and how they should be used.

An insecticide active ingredient is sprayed onto a finely ground dust.

Dusts are best used to deliver an insecticide to difficult-to-reach areas. Common uses include treatment of ants in a wall, or wasps in the ground. Ants and other social insects will track the applied dust deeper into a nest. Dusts are often sold for garden use, but application there is inefficient and much of the insecticide is likely to be blown or washed off the intended target. Best to apply with a crank duster or squeeze bottle designed for applying dusts.

Low to moderate. Easy to inhale, may drift from the intended target site.

Insecticide is sprayed onto an inert, absorptive granule; usually consisting of clay, ground corn cob, or nut husks.

Granular insecticides are designed to provide control of soil dwelling insects. They are less effective against surface crawling pests, unless these also spend much time underground in the treatment zone. Commonly used for control of ants, grubs, millipedes, etc. Easy to apply with a rotary, drop, or hand-held seed spreader.

High. Because insecticide is impregnated inside an inert carrier, spills are easily contained and little exposure risk to exposed skin.

Insecticide mixed with gas in a metal can. Can be designed to produce a various particle sizes from fine aerosol to liquid stream.

Easy to use and apply, designed for application of residual sprays for crawling insects as well as for aerosol fogs for flying insects, depending on product. Commonly sold for ant and roach control, or flying insect control. Despite the impression given by advertisements, aerosol fogs do not penetrate well into cracks and crevices where pests hide.

Low to moderate. Some formulations are flammable. Solvents may add to toxicity, and exposure risk to skin is higher. Empty cans should be wrapped in newspaper for disposal to prevent accidental punctures.

Consist of an insecticide mixed with a food or attractant to entice the insect to ingest. Come in various forms including pellets, dusts, gels, liquids and granules.

One of the most effective control methods for controlling social insects, like ants and termites. Also very effective on cockroaches and crickets. Various ways to apply.

High safety due to the low percentage active ingredient needed to produce control. Containerized baits are exceptionally safe. Broadcast treatments of low rates is generally the safest application method.

Low to moderate

Spray – Ready to Use (RTU)

Premixed liquid, usually in a pump spray bottle or as a hose-end attachment.

Designed for convenience, RTU sprays require the user to just point and pump or attach to a garden hose. No mixing required. Usually designed for tree, lawn and garden sprays, flea sprays.

Moderate. Because there is no mixing, risk of your exposure to the concentrate is eliminated. User should avoid exposure to spray drift by using gloves and long-sleeves.

Moderate to high

Concentrated active ingredient in an emulsion or solution. Designed to be mixed with water before application.

Wide range of uses include both indoor and outdoor sprays, lawn and garden sprays and soil drenches.

Higher risk because of need to mix concentrated product and potential for exposure to spillage, drift or splashing.

Common types of pesticides

One way to think of pesticides is as low-impact or as conventional. Low impact products include those that are low in toxicity to people and pets (i.e., meets EPA Category IV standards) and have minimal impact on the environment, including beneficial insects. This classification is somewhat subjective, but still provides a useful way to select pesticides that meet most people’s definition of green or safer. Some, but not all, low-impact pesticides may be classified as “organic.” Some organic products may not be considered low-impact if they are highly toxic. Here are a few examples of common low-impact insecticides that are widely available in hardware stores and garden centers.

Table 2. Classification of low impact insecticides, with examples.

Type Description Where and how to use Relative Safety Cost
Type Common Name Examples (Trade names) Pests
Insect Growth Regulators halofenozide Scott’s Grub-Ex, Ortho Grub-B-Gone, Mach 2 white grubs
methoprene Precor, vIGRen, Extinguish, others fleas, fire ants
pyriproxifen Nylar, Spectracide fire ant bait, others fleas, fire ants
Microbially-derived Bacillus thuringiensis Dipel, Thuricide, Mosquito Dunks, others caterpillars, mosquitoes
spinosad Fertilome Bagworm and Tent Caterpillar spray, others caterpillars, thrips, fire ants
Contact insecticides (kill only when sprayed directly on the pest) soap Safer’s Soap, others small, soft-bodied pests (aphids, mites, caterpillars, mealybugs)
horticultural oil GreenLight Dormant Oil, Sunspray, Neem oil, Rose Defense, others small, soft-bodied pests (aphids, mites, caterpillars, mealybugs, scale insects)
Botanical (plant derived products) pyrethrum, synergized pyrethrins Raid Flying Insect Killer, Schulz’s Plant Spray, many others quick acting killer for many garden and house plant pests, flying and crawling insects
d-limonene Citrus oil spray, Citrex, others fire ants, others
azadirachtin Neem concentrate, others aphids, whiteflies, spider mites, scale insects, others
Baits hydramethylnon Amdro, MaxForce, others fire ants, cockroaches, other ants
sulfluramid Combat Roach Killing Gel, Raid Ant Bait ants, cockroaches
Low toxicity inorganics sulfur dusting sulfur, various brands mites, chiggers
boric acid and derivatives Roach Pruf, Boracare, various baits roaches, ants, termites, other crawling indoor pests
diatomaceous earth DE, various brands of diatomaceous earth crawling insects, fleas, indoor pests only

Conventional insecticides include pesticides that are not considered low-impact because they are more likely to be hazardous to humans or pets (without careful attention to standard safety practices and following the label), or because they may impact beneficial insects or the environment even when used according to the label. Most of the products listed below have the potential to harm at least some beneficial insects and for this reason should be used when cost-effective, low-impact products will not adequately control the pest.

Just because a product carries the potential for harm, does not mean it cannot be used safely. Conventional pesticides include many useful and effective products that can be used safely by most gardeners. However, it is especially important to follow label safety directions when using conventional pesticides. Here are some of the common types of conventional insecticides.

Table 3. Classification of conventional insecticides, with examples.

Type Common Name Examples (Trade names) Pests
Systemics (water-soluble insecticides that can be taken up by plants) acephate Orthene, others chewing and sucking insects, mites and lacebugs
imidacloprid Bayer Advanced Garden products sucking insects, beetle larvae, white grubs
dinotefuran Spectracide Systemic Tree and Shrub Insect Control + Fertilizer sucking insects including armored scale, beetle larvae, some borers
disyston Bayer Advanced Garden Rose Insect Killer Granules sucking and chewing insects (moderate-high toxicity)
Pyrethroids permethrin Conquest, Spectracide, others sprays and granules for chewing and crawling insects, borers
resmethrin, allethrin Wasp and Hornet spray, others short residual sprays for flying insects, spiders, household insects, mosquitoes
esfenvalerate, cyfluthrin, bifenthrin, deltamethrin, lambda-cyhalothrin, tralomethrin, cypermethrin, others Ortho Home Defense, Bayer Advanced Garden, Zep, others… these newer pyrethroids generally provide longer residual and higher activity on chewing and crawling insects
Other residual insecticides (leave a killing residue on surfaces) carbaryl Garden Tech Sevin, others chewing and crawling insects, slugs, snails
malathion Malathion, others short-lived residual treatment for a variety of chewing, crawling insects, mosquitoes
fipronil Over N Out, MaxForce ant baits, others long-residual granular product for fire ant control, termites, general treatment for crawling insects, especially ants

Organic vs. Synthetic pesticides

In recent years a growing number of pesticide products advertised as “organic” have become available to consumers. To be considered organic a pesticide must be composed of only naturally occurring substances. Advertizers and others commonly imply that organic pesticides are safer and more environmentally desireable than synthetic products. While this may be true in some cases, there is no guarantee that natural substances are inherently safer than synthetic pesticides.

Organic pesticides usually consist of plant extracts with insect-killing or repelling properties. Plants produce many chemical compounds to protect themselves from diseases, insects and other threats. From a toxicology perspective, there is no difference between plant-derived pest control compounds and man-made pesticides. Both are chemicals. Both have some effect on the physical structure, development or metabolism of insects. And both organic and synthetic pesticides can be toxic to humans.

Most commonly sold “organic” insecticides, however, are reasonably low in toxicity and break down quickly upon exposure to water and sunlight. Their ability to degrade quickly and their relatively low toxicity is why botanical insecticides are usually classified as low-impact. However, there are exceptions. Rotenone, for example, is a popular insecticide with many gardeners because it is organic, effective in controlling many chewing pests and does not leave long-lasting residues on plants. In its concentrated form, however, rotenone is more toxic than many conventional insecticide active ingredients.

Don’t be misled by sales claims for many so-called “natural” products. Advertising which claims that any insecticide is “safe”, “pure”, “all-natural”, “EPA-approved”, “pesticide-free” and “chemical free” are at best misleading; and at worst, false and/or illegal. Many people get great satisfaction from using only substances found in nature in their garden. This is generally a good thing. However, use of synthetic pesticides can also be a safe and environmentally sound practice if practiced with care and discretion.



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Use of Tea (Camellia sinensis [L.] Kuntze) as a Hepatoprotective Agent in Geriatric Conditions

10.7.5 Effect of Tea on Hepatotoxicity of Insecticides

Cypermethrin is a synthetic pyrethroid used as an insecticide in large-scale commercial agricultural applications as well as in consumer products for domestic purposes. Induction of the CYP system and oxidative stress have been implicated as the key mechanisms in the hepatotoxic effects of these insecticides. Preclinical studies have observed protective effects of black tea extract against hepatotoxicity of chlorpyrifos and cypermethrin [36] . Administering aqueous black tea extract at a dose of 200 mg/ml to mice before the combination dose of chlorpyriphos and cypermethrin (20 mg/kg each) on alternate days over a 15-day period prevented and mitigated elevation in serum levels of enzymes ALP, AST, and ALT; decrease in hepatic antioxidant enzymes SOD, GPx, GR, GST, and CAT in liver; and increase in lipid peroxidation in liver, when compared to insecticide-alone treated cohorts [36] .

Occupational, industrial and environmental agents

Pyrethrin (pyrethrum, pyrethroids)


Pyrethrins ( cypermethrin , deltamethrin, permethrin, tetramethrin) are a group of synthetic analogs of the natural substance pyrethrum, which comes from dried chrysanthemum flowers. The pyrethrins are widely used as both domestic and agricultural insecticidal sprays and dusting powders. They have also been used in topical preparations for the treatment of pediculosis (see Chapter 2.17 , and overview in Schardein 2000 ). Low toxicity for human subjects has been reported following pyrethroid exposure.

The National Teratology Information Service in the UK obtained follow-up data (unpublished) on the outcomes of pregnancy in 48 women exposed to this group of pesticides during pregnancy (35 permethrin, 5 deltamethrin, 4 cypermethrin and 4 tetramethrin). There were 41 normal babies, two spontaneous abortions (no post-mortem data available), and five children with anomalies (mild talipes, unilateral inguinal hernia, an abnormal right little toe, bilateral talipes, a heart murmur). No cause-effect relationship with the pyrethroid exposure could be established in any of these infants. A teratogen information program in Australia ( Kennedy 2005 ) published about the safety of permethrin exposure. The data on 113 pregnancies where the mothers had used 1% creme permethrin in the treatment of lice some time during pregnancy indicated that the use of such products was relatively safe. In summary, there are few data on the effects of the pyrethroids in human pregnancy and none that allow any firm conclusions to be drawn.


Exposure to pyrethrins should be minimized in pregnancy. When there has been significant exposure, this is not an indication for termination of pregnancy, and additional prenatal diagnostic tests are not required. Occupational or environmental exposure to pyrethrins at or below accepted safety limits is unlikely to produce a teratogenic risk, but the data are insufficient to state that there is no risk for therapeutic pyrethrum/pyrethroid administration (see Chapter 2.17 ).

Occupational Neurology

Potential developmental neurotoxicity of pyrethroids

Young animals are more sensitive to the acute toxicity of certain pyrethroids, such as deltramethrin and cypermethrin ( Sheets, 2000 ), most likely because of a lesser capacity for metabolic detoxification ( Anand et al., 2006 ); however, only minor age-related differences were found for other compounds ( Sheets, 2000 ). Some studies have suggested that certain pyrethroids may cause developmental neurotoxicity. For example, behavioral and biochemical alterations have been reported in rats and mice upon pre- or postnatal exposure to pyrethroids ( Eriksson and Fredriksson, 1991; Lazarini et al., 2001 ). Nav1.3β3 channels, which predominate in the developing rat brain, are particularly susceptible to disruption by type II compounds ( Meacham et al., 2008 ). However, overall evidence for a clear developmental neurotoxicity of pyrethroids has been judged inadequate ( Shafer et al., 2005 ), and developmental neurotoxicity studies carried out with some pyrethroids (e.g., deltamethrin) according to regulatory guidelines have provided negative results ( European Food Safety Agency, 2009 ). Furthermore, levels of background pyrethroid exposure (presumably through residues in the diet) in children have been found to be orders of magnitude lower than the corresponding acceptable daily intake ( Heudorf et al., 2004 ). Also, the use of deltamethrin-impregnated bed nets does not appear to pose any health risk in children and neonates, while substantially reducing infant mortality from malaria ( Alonso et al., 1991; Barlow et al., 2001 ).

Toxicology and Mode of Action of Pyrethroid Insecticides

77.3.5 Age-Related Differences in Pyrethroid Sensitivity

Information on differences in pyrethroid sensitivity between immature and adult animals is limited. Neonatal rats were six- to 17-fold more sensitive than adults to the pyrethroids permethrin, cypermethrin , and deltamethrin ( Cantalamessa, 1993 ; Sheets et al., 1994 ). The use of synergists to block metabolic detoxication ( Cantalamessa, 1993 ) and the measurement of concentrations in whole brain at equitoxic doses ( Sheets et al., 1994 ) suggested that the greater sensitivity of young animals was due to age-related differences in pharmacokinetics rather than intrinsically greater sensitivity of the neonatal CNS. A subsequent study failed to identify age-related differences in the sensitivity of rats to cismethrin (the 1R,cis isomer of resmethrin) or permethrin at either high (lethal) or low (behaviorally active) doses ( Sheets, 2000 ). The same study also found differential sensitivity to deltamethrin and cypermethrin only at high doses. It is possible that the age-related differences observed at high doses in these studies results are due to the reduced ability of the incompletely developed detoxication enzyme systems of the neonatal liver to metabolize a large bolus of insecticide.

Toxicology and Human Environments

7.1.6 Steric hindrance

Other factors affecting the extent of metabolism are the presence of certain groups which can hinder metabolism. For example, there is far more metabolism by esterases and CYPs of permethrin versus cypermethrin which differ only by the presence of a cyano group. This cyano group limits the cleavage of the ester bond by both CYPs and esterases. A similar example of cyano groups limiting metabolism is the presence of two cyano groups in letrozole (shown in Fig. 3.8 ), which has a half-life of 2 days.

Figure 3.8 . Letrozole chemical structure showing its two cyano groups.

Even though they have identical atomic compositions, chemical isomers have different orientations, and some of these orientations are less well suited toward metabolism. Enzymes often have strict stereochemistry requirements. For example, glucose, one of the major cellular fuels, is almost always found as d -glucose and the enzymes which metabolize glucose reflect this fact in their stereochemical requirements. l -Glucose when given to rats had essentially no contribution to energy metabolism. 98 A similar difference in metabolic capacity has been found for a number of xenobiotic isomers.

The isomers of permethrin differ in their lability, and the cis isomer is less readily metabolized than the trans isomer. Permethrin-containing compounds designed to be used on humans as pharmaceuticals are have more trans permethrin than permethrin-containing compounds used for pest control, reflecting the over tenfold greater mammalian toxicity of the cis isomer as compared to the trans isomer of permethrin.

Another example of steric hindrance is the inability of monoamine oxidases to metabolize amines with a methyl group on the α carbon (e.g., caffeine). Steric hindrance is also found with oral availability where have fewer than 10 rotatable bonds is associated with improved movement across the intestinal wall. 93 One example of a xenobiotic with a simple structure is that of naphthalene (shown in Fig. 3.9 ), which has no rotatable bonds and has mirror symmetry. Thus, there is less opportunity for the molecule to enter the wrong way, and the major metabolites of naphthalene can be produced equally well irrespective of which end of the molecule enters the active site, something unusual but something that explains how in effect naphthalene has four ways to make the same metabolite.

Figure 3.9 . Naphthalene metabolism by CYPs predominately occurs through the epoxidation then hydroxylation of the double bond. Naphthalene is unusual in that its great symmetry allows four ways to make the same metabolite.

The Regulatory Evaluation of the Skin Effects of Pesticides

Irritation Data

A 26% EC caused severe (category II) irritation in the Draize assay. Six formulations (including two 25.3% ECs, an 18.1% EC, and three formulations containing cypermethrin ) caused moderate irritation in the Draize assay.

Nine formulations (including a 24.8% EC, 17.1% concentrate in oil, a cattle ear tag with 16% cypermethrin and 20% PBO, two foggers with 1.7% cypermethrin, two aerosols with 1% or less AI, and two mixtures with pyrethrins and synergists containing

Toxic effects of pesticides (agrochemicals)

17.4.5 Pyrethroid Insecticides

As stated, pyrethrins are nonpersistent, which led pesticide chemists to develop compounds with a similar structure with insecticidal activity but that are more persistent. This class of insecticides, known as pyrethroids, has greater insecticidal activity and is more photostable than pyrethrins. There are two broad classes of pyrethroids depending on whether the structure contains a cyclopropane ring (eg, cypermethrin (( ±)-α-cyano-3-phenoxybenzyl (±)-cis,trans-3-(2,2-dichlorovinyl 2,2-dimethyl cyclopropanecarboxylate))) or whether this ring is absent in the molecule (eg, fenvalerate ((RS)-α-cyano-3-phenoxybenzyl(RS)-2-(4-chlorophenyl)-3-methylbutyrate)). They are generally applied at low doses (eg, 30 g/ha) and have low mammalian toxicities (eg, cypermethrin, oral (aqueous suspension), LD50=4123 mg/kg (rat) and dermal LD50 >2000 mg/kg (rabbit)). Pyrethroids are used in both agricultural and urban settings (eg, termiticide). Pyrethrins affect nerve membranes by modifying the sodium and potassium channels, resulting in depolarization of the membranes. Formulations of these insecticides frequently contain the insecticide synergist piperonyl butoxide (5-(2-(2-butoxyethoxy) ethoxymethyl)-6-propyl-1,3-benzodioxole), which acts to increase the efficacy of the insecticide by inhibiting the cytochrome P450 enzymes responsible for the breakdown of the insecticide.

Signs and symptoms

There are two types of pyrethroids, type I and type II. The signs of toxicity depend on the type of pyrethroid consumed. The usual signs of poising include restlessness, lack of coordination, sensory hyperactivity to external stimuli, fine tremors progressing to other parts of body, and hyperthermia.


There is no specific treatment. Treatment is based on symptoms and supportive; sedatives and central nervous system (CNS) muscle relaxants are recommended. Oils and fats should be avoided. Use of phenothiazine derivatives is contraindicated.

Pyrethroid Chemistry and Metabolism

76.7 Cypermethrin (α-, β-, θ-, ζ-Cypermethrin)

Chemical name (RS)-α-Cyano-3-phenoxybenzyl (1RS)-cis-trans -3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylate. α- Cypermethrin is a racemate comprising (( S)-(1R)-cis) and ((R)-(1S)-cis). β-Cypermethrin is a mixture comprising two enantiomeric pairs in the ratio of approximately 2:3. θ-Cypermethrin is a mixture of enantiomers ((S)-(1R)-trans) and ((R)-(1S)-trans) in the ratio of 1:1. ζ-Cypermethrin is a mixture comprising ((S)-(1RS)-cis-trans).

Synonyms Cypermethrin (BSI, ISO, ANSI, BAN) is the common name in use. Trade names are Basathrin, Cymbush, Cymperator, Cynoff, Cypersan, and several other names. Code designations include NRDC149, PP383, FMC30980, WL43467, and LE79-600. The CAS registry number is 52315-07-8.

Physical and chemical properties The empirical formula is C22H19Cl2NO3; molecular weight is 416.3. Its form is a yellow-brown viscous semisolid; its specific gravity is 1.24 at 20°C; log Kow = 6.6. It is less soluble (0.004 mg/l) in water at 20°C, but it is soluble in most organic solvents. It is relatively stable to light in weakly acidic water, but it is unstable in alkaline medium.

Metabolism On single oral administration of each of 14 C-(1RS)-trans— and (1RS)- cis-cypermethrin labeled in the benzyl ring, the cyclopropane ring, or the CN group to male and female rats at 1–5 mg/kg, 14 C from the acid and alcohol moieties was rapidly and almost completely excreted into the urine and feces. The 14 C from the CN group was relatively slowly excreted in the urine and feces, with the total recovery being 50–67%. The tissue residues of rats treated with the acid- or alcohol-labeled preparations were generally very low except for the fat (∼1 ppm). In contrast, the CN-labeled preparation showed relatively high residue levels, especially in the stomach (contents), intestines, and skin ( Crawford et al., 1981a ).

The major metabolic reactions ( Figure 76.6 ) of trans— and cis-cypermethrin were cleavage of ester linkage, oxidation at the trans— and cis-methyl cyclopropane ring and at the 4’ position of the phenoxy group, and conversion of the CN group to SCN ion. The following minor species differences were observed: (1) oxidation at 5 and 6 positions of the alcohol moiety was observed in mice but not in rats; and (2) ester metabolites such as 2′-OH-, 5-OH-, and trans-OH,4′-OH-cypermethrin were detected in feces of mice but not of rats. The remarkable species difference in metabolites was the Pb acid–taurine conjugate, which was the predominant metabolite in mice, but it was not detected in rats. The ester linkage of cis-cypermethrin seems to be more stable than that of the corresponding trans isomer, based on the nature of urinary and fecal metabolites and excretion rate ( Crawford et al., 1981b ; Edwards et al., 1990 ; Hutson and Casida, 1978 ; Hutson et al., 1981 ).

Figure 76.6 . Metabolic pathways of cypermethrin in animals.

There are also species differences of conjugation reactions of the alcohol moiety in other species; PB acid–glycine is predominant in sheep, cat, gerbil, and ferret; PB acid–taurine in ferret; PB acid–glycylvaline in mallard duck; and PB acid–glucuronide and/or 4′-OH-PB acid–glucuronide in hamster, guinea pig, marmoset, and rabbit. The rat was unique in utilizing sulfuric acid for conjugation of 3-phenoxybenzyl moiety among animal species tested ( Huckle et al., 1981 ).

Metabolism of cypermethrin (cis:trans = 1:1) in humans was investigated after oral administration to six male volunteers at 3.3 mg per person. The four metabolites from the acid and alcohol moieties were analyzed in urine. The amount of cis— and trans-Cl2CA was approximately equal to that of PB acid and 4′-OH-PB acid. The ratio of trans— to cis-Cl2CA was on average 2:1, implying that ester hydrolysis is the major metabolic pathway and that the trans isomer was more rapidly hydrolyzed than the cis isomer, as is the case with rats. On the other hand, dermal application of cypermethrin (cis:trans = 56:44) led to formation of a different ratio of metabolites (the ratio of trans— to cis-Cl2CA is 1:1.2) from oral administration. The estimated percutaneous absorption rate (1.2%) for 24 h is much less than that with rats (12% in vivo and 34% in vitro), indicating that the rat model may overestimate percutaneous absorption for humans ( Capt et al., 2007 ; Woollen et al., 1992 ).

Species differences for ester hydrolysis were examined with carboxylesterases from porcine, rabbit (mixture of carboxylesterases), human hCE1 (a major isoform in liver), hCE-2, and mouse (NM133960 and BAC36707) for the eight isomers of cypermethrin derivatives with fluorescence. It was found that all carboxylesterases consistently hydrolyzed the trans-isomers more rapidly than the corresponding cis-isomers ( Huang et al., 2005 ; Nishi et al., 2006 ). Cypermethrin isomers were good substrates in vitro for rat CYP1A1, 2A1, 2C6, 2C11, 3A1, and 3A2 and for human CYP1A2, 2C8, 2C19, and 3A4 ( Scollon et al., 2009 ).


Ramesh C. Gupta, Dejan Milatovic, in Biomarkers in Toxicology , 2014


Pyrethrins and pyrethroids are structurally diverse, and understanding their chemistry and toxicology plays a vital role in the development of biomarkers. Significant advancements in analytical chemistry and toxicology have led to the development of biomarkers to assess biomonitoring in the environment and exposure in the general population ( Sudakin, 2006; Barr et al., 2010; Gammon et al., 2012 ). Future challenges in the application of these biomarkers in epidemiological studies are being explored, as there is a need for improved understanding of the toxicokinetics and pharmacodynamics of pyrethroids in mammalian species, including humans.

Pyrethroids are of low to moderate toxicity due to their moderate absorption (40–60%) and rapid metabolism following oral administration ( Anand et al., 2006; Barr et al., 2010; Gammon et al., 2012 ). Oxidases and esterases, primarily in the liver, metabolize pyrethroids at varying rates. The most rapidly metabolized pyrethroids have the lowest toxicity. Based on experimental data, Gammon et al. (2012) have described that brain or blood plasma concentrations of parent pyrethroids correlate with acute toxicity and that metabolites (especially hydrolytic products) generally have little or no effect on neurotoxicity. In the context of biomarkers, most studies have investigated urine as the analytical matrix ( Barr et al., 2010 ). Leng et al. (1996) and Leng and Gries (2005) detected metabolites of some pyrethrins and pyrethroids (permethrin, cypermethrin , cyfluthrin, and deltamethrin), using GC-MS, in the urine of pesticide applicators. Using the same methodology, Wei et al. (2012) assayed metabolites of these pyrethroids in the urine of commercial flight attendants. Elflein et al. (2003) also used GC-MS to detect metabolites of some other commonly used pyrethroids, including allethrin, resmethrin, phenothrin, and tetramethrin in human urine. HPLC and LC-MS-based methods have also been employed to determine the residues of pyrethroids and their metabolites in body tissues and fluids ( Baker et al., 2004; Anand et al., 2006; Kim et al., 2006; Barr et al., 2010 ). Recently, Ishibashi et al. (2012) developed a high-throughput assay for cypermethrin and tralomethrin using supercritical fluid chromatography-tandem mass spectrometry. Metabolites of some of the commonly used pyrethrins/pyrethroids determined in urine as biomarkers are summarized in Table 23.2 .

Table 23.2 . Metabolites of pyrethroids in urine used as biomarkers for an exposure to pyrethroid insecticides

Parent Compound Specific Metabolite(s)
Allethrin trans-Chrysanthemumdicarboxylic acid
Cyfluthrin 4-Fluoro-3-phenoxybenzoic acid
3-Phenoxybenzoic acid
cis— and trans-3-(2,2-Dichlorovinyl)-2,2-dimethylcyclopropane carboxylic acid
Cypermethrin trans-Chrysanthemumdicarboxylic acid
cis— and trans-3-(2,2-Dichlorovinyl)-2,2-dimethylcyclopropane carboxylic acid;
3-Phenoxybenzoic acid
Deltamethrin cis— and trans-3-(2,2-Dichlorovinyl)-2,2-dimethylcyclopropane carboxylic acid;
cis— 3-(2,2- Dibromovinyl)-2,2-dimethylcyclopropane carboxylic acid;
3-Phenoxybenzoic acid
Permethrin cis— and trans-3-(2,2-Dichlorovinyl)-2,2-dimethylcyclopropane carboxylic acid;
3-Phenoxybenzoic acid
Phenothrin trans-Chrysanthemumdicarboxylic acid
Pyrethrum trans-Chrysanthemumdicarboxylic acid
Resmethrin trans-Chrysanthemumdicarboxylic acid
Tetramethrin trans-Chrysanthemumdicarboxylic acid

Note: Adapted from Malik et al. (2011) .

Barr et al. (2010) reported that 3-phenoxybenzoic acid (3-PBA), a metabolite common with many pyrethroid insecticides, was detected in>70% of urine samples tested in the US. Non-Hispanic blacks had significantly higher 3-PBA concentrations than non-Hispanic whites and Mexican Americans, and children had significantly higher concentrations of 3-PBA than adolescents and adults. Cis— and trans-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane-1-carboxylic acid (cis— and trans-Cl2CA) were highly correlated with each other and with 3-PBA, suggesting that 3-PBA was primarily derived from exposure to permethrin, cypermethrin, or their degradates. In a recent investigation, Wei et al. (2012) found that the flight attendants working on pyrethroid-disinsected commercial aircraft had significantly higher concentrations of 3-PBA and cis— and trans-Cl2CA in the post-flight urine samples than those working on non-disinsected aircrafts and the general US population. Increase of pyrethroid metabolites in the preflight urine samples suggested an elevated body burden from a long-term exposure for those flight attendants routinely working on pyrethroid treated aircraft. Interestingly, flight attendants working on international flights connected to Australia had higher urinary levels of 3-PBA and cis— and trans-Cl2CA than those on either domestic and other international flights flying between Asia, Europe and North America. At veterinary diagnostic labs, residues of pyrethrins/pyrethroids have been detected in the brains of cats that died from overexposure to these insecticides.

Recently, Tornero-Velez et al. (2012) proposed a pharmacokinetic model for cis— and trans-permethrin disposition in rats and humans with aggregate exposure application. In this investigation, the description of pharmacokinetics in humans was based on the properties of permethrin, PBPK models of deltamethrin in rats, and permethrin in vitro clearance data. The model was adapted with a biomarker submodel to evaluate exposure estimation in probabilistic risk assessment applications. Starr et al. (2012) investigated cumulative risk assessment of pyrethroid pesticides (permethrin, cypermethrin, β-cyfluthrin, deltamethrin, and esfenvalerate) taking into account pharmacokinetics, pharmacodynamics, and neurobehavioral assays. Findings supported the additive model of pyrethroid effect on motor activity and suggested that variation in the neurotoxicity of individual pyrethroids is related to toxicodynamic rather than toxicokinetic differences.

In addition to residue detection of pyrethrins and pyrethroids and their metabolites, hematological, biochemical, and histopathological alterations have been reported in target and nontarget tissues, and these changes can be used as biomarkers of pyrethrins/pyrethroids toxicity ( Sayim et al., 2005; Yavasoglu et al., 2006 ).


See also:  Red Bug Bites and Treatment, Truly Nolen
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