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Topic: Pyrethroids

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	ATSDR - Public Health Statement: Pyrethrins and Pyrethroids
		Pyrethroids are manufactured chemicals that are very similar in structure to the pyrethrins, but are often more toxic to insects, as well as to mammals, and last longer in the environment than pyrethrins.
		Most commercial pyrethroids are not one single molecule; rather, they are several molecules with the same chemical formula that have their atoms joined together in the same sequence, but have a different arrangement of the atoms in space.
		Certain pyrethroids, such as permethrin, phenothrin, and resmethrin, are sprayed to control mosquitos during the spring and summer.
	www.atsdr.cdc.gov /toxprofiles/phs155.html (3395 words)

	05.06.2004 - Sediments in many Central Valley streams contain toxic levels of pyrethroid pesticides
		Pyrethroids are a class of compounds represented by permethrin, first marketed in 1973, and various other chemicals usually ending in the suffix -thrin.
		Though pyrethroids are used far less than organophosphates like diazinon and chlorpyrifos, their use in California has risen rapidly in recent years because of increased regulation of the spraying of organophosphates, due to health threats to farm workers and increased toxic runoff from fields.
		He and his colleagues are now trying to measure the level of pyrethroid that kills amphipods, which is around 3 parts per billion in sediments, and whether levels of PBO need to be considered in order to estimate the true toxicity of pyrethroid pesticides.
	www.berkeley.edu /news/media/releases/2004/05/06_pyrethroid.shtml (1296 words)

	PANNA: Toxicology and Environmental Fate of Synthetic Pyrethroids. Doria Mueller-Beilschmidt. Journal of Pesticide ...
		There are three main routes of degradation by light in pyrethroids: ester cleavage (splitting the molecule where a carbon atom and an oxygen atom are connected with a double bond), reductive dehalogenation (removal of chlorine, flourine, or bromine atoms), and isomerization (conversion from one isomer to another).
		Pyrethroids that are not light-stable usually degrade much more quickly than those that are light-stable, and degradation is usually much faster in aerobic (oxygen-containing) soils than anaerobic (not oxygen-containing) soils.51 Missing Data There are significant data gaps for the older, less persistent pyrethroids such as allethrin, resmethrin and phenothrin, as well as for pyrethrins.
		In vitro covalent binding of the pyrethroids cismethrin, cypermethrin and deltamethrin to rat liver homogenate and microsomes.
	www.panna.org /resources/pestis/PESTIS.1996.14.html (2354 words)

	PCO Directory: Non-Toxic Pest Management
		Synthetic pyrethroids are synthesized derivatives of naturally occurring pyrethrins, which are taken from pyrethrum, the oleoresin extract of dried chrysanthemum flowers (the term “pyrethrum” is often used as a generic term to describe either natural pyrethrins or synthetic pyrethroids).
		However, the pyrethroids, the synthetic analogues of naturally occurring pesticides, were developed to capture the effective insecticidal activity of this botanical insecticide, with increased stability in light, yielding longer residence times (Gosselin et al., 1984).
		Because pyrethroids are toxic to all insects, both beneficial insects and pests are affected by pyrethroid applications.
	www.beyondpesticides.org /infoservices/pesticidefactsheets/toxic/pyrethroid.htm (3238 words)

	Flumethrin (UK PID)
		Metabolism Pyrethroids are hydrolyzed rapidly in the liver to their inactive acid and alcohol components (Hutson, 1979; Ray, 1991), probably by microsomal carboxylesterase (Hutson, 1979).
		Animal studies have shown that pyrethroid hydrolysis is inhibited by dialkylphosphorylating agents such as organophosphorus insecticides (Abou-Donia et al, 1996; He et al, 1990; Hutson, 1979), and urinary excretion of unchanged pyrethroid was higher in sprayers using a methamidophos/ deltamethrin or methamidophos/fenvalerate mixture than from those using the pyrethroid alone (Zhang et al, 1991).
		Haemotoxicity Among 235 cases of occupational or accidental acute pyrethroid poisoning in whom a full blood count was performed, 15 per cent showed a leucocytosis (He et al, 1989); this was probably a non-specific response.
	www.intox.org /databank/documents/chemical/flumeth/ukpid66.htm (6391 words)

	Cyhalothrin (EHC 99, 1990)
		Pyrethroids commercially available to date include allethrin, resmethrin, d-phenothrin, and tetramethrin (for insects of public health importance), and cypermethrin, deltamethrin, fenvalerate, and permethrin (mainly for agricultural insects).
		The pyrethroids are strongly adsorbed on soil and sediments, and hardly eluted with water.
		Cow In common with other structurally related pyrethroids, the main routes of metabolism of cyhalothrin in the cow have been found to be similar to those observed in rats and dogs, i.e cleavage of the ester bond with subsequent excretion of the cyclopropyl carboxylic moiety, either free, hydroxylated, or as a glucuronide conjugate.
	www.inchem.org /documents/ehc/ehc/ehc99.htm (15337 words)

	Bloomquist: Insecticides
		The pyrethroid insecticides are typically esters of chrysanthemic acid having a high degree of lipophilicity (fat solubility).
		The stereoisomerism of pyrethroids is important for their toxic action, but a detailed discussion of this topic is beyond the scope of this course on IPM.
		Pyrethroid intoxication results from their potent effects on nerve impulse generation within both the central and peripheral nervous systems.
	ipmworld.umn.edu /chapters/bloomq.htm (3634 words)

	Phenothrin, d- (EHC 96, 1990)
		The results suggest that alpha-cyano pyrethroids primarily affect the sodium channels in the nerve membrane and cause a long- lasting prolongation of the transient increase in sodium permeability of the membrane during excitation.
		Pyrethroids without an alpha-cyano group (allethrin, d-phenothrin, permethrin, and cismethrin) cause a moderate prolongation of the transient increase in sodium permeability of the nerve membrane during excitation.
		Pyrethroids also cause pronounced repetitive activity and a prolongation of the transient increase in sodium permeability of the nerve membrane in insects and other invertebrates.
	www.inchem.org /documents/ehc/ehc/ehc96.htm (15444 words)

	Cyfluthrin. TOXNET profile from Hazardous Substances Data Bank. (Site not responding. Last check: 2007-11-07)
		The relative resistance of mammals to the pyrethroids is almost wholly attributable to their ability to hydrolyze the pyrethroids rapidly to their inactive acid and alcohol components, since direct injection into the mammalian CNS leads to a susceptibility similar to that seen in insects.
		The synthetic pyrethroids delay closure of the sodium channel, resulting in a sodium tail current that is characterized by a slow influx of sodium during the end of depolarization.
		Pyrethroid esters /containing the alpha-cyano substituent/ produce an even longer delay /than those lacking the substituent/ in sodium channel inactivation, leading to a persistent depolarization of the nerve membrane without repetitive discharge, a reduction in the amplitude of the action potential, and an eventual failure of axonal conduction and a blockade of impulses.
	www.fluoridealert.org /pesticides/cyfluthrin.toxnet.hsdb.htm (8161 words)

	Allethrins (EHC 87, 1989)
		Other pyrethroids are also available including furamethrin, kadethrin, and tellallethrin (usually for household insects), fenpropathrin, tralocythrin and tralomethrin, cyhalothrin, lambda-cyhalothrin, tefluthrin, cyfluthrin, flucythrinate, fluvalinate, and biphenate (for agricultural insects).
		Pyrethroids were classified into 2 classes based on the signs and symptoms produced by acutely-toxic doses in mammals (Verschoyle & Aldridge, 1980; Lawrence & Casida, 1982) and on the neurophysiological responses in cockroaches (Gammon et al., 1981).
		The mechanism of interaction of the 2 pyrethroids, allethrin and fluvalinate, with the nicotinic acetylcholine (ACh) receptor was investigated by means of their effects on the binding of radioligands to the Torpedo electric organ receptor and tracer ion flux.
	www.intox.org /databank/documents/chemical/allethrn/ehc87.htm (14783 words)

	News - Pesticide Poisoning from Synthetic Pyrethroids
		Pyrethroids are a synthetic derivative of pyrethrins, a natural insecticide produced from chrysanthemums.
		Pyrethroids are replacing OPs in insecticides in bugbombs, head lice treatments, and flea sprays for pets, and are commonly used in fruit orchards.
		SYNTHETIC PYRETHROIDS AND PARESTHESIAS Scenario: A 58-year old adult male with a history of well-controlled insulindependent diabetes mellitus visits his physician, complaining of tingling and numbness on the fingers and dorsum of the hands.
	www.headlice.org /news/2004/ohd5306.htm (701 words)

	PYRETHROIDS Sumithrin (Anvil) and Resmethrin (Scourge) : What Everyone Should Know : West Nile Virus : NYC DOHMH
		Pyrethroids are a group of synthetic pesticides used to control adult mosquitoes.
		Pyrethroids are effective against adult mosquitoes including the species most commonly associated with West Nile virus.
		Pyrethroids are toxic to bees, fish, and other aquatic life forms and will not be applied to bodies of water.
	www.nyc.gov /html/doh/html/wnv/wnvfaq21.shtml (727 words)

	EXTOXNET PIP - PYRETHRINS AND PYRETHROIDS
		In this report, the term "pyrethrins" refers to the natural insecticides derived from chrysanthemum flowers; "pyrethroids" are the synthetic chemicals, and "pyrethrum" is a general name covering both compounds.
		Pyrethroids can cause two quite different responses at near lethal doses in rats; aggressive sparring and a sensitivity to external stimuli progressing to tremors is the one response and pawing and burrowing behavior, and salivation leading to chronic seizures is the other (105).
		Overall, pyrethrins and pyrethroids are of low chronic toxicity to humans and the most common problems in humans have resulted from the allergenic properties of pyrethrum (104).
	extoxnet.orst.edu /pips/pyrethri.htm (1371 words)

	Lewey's Eco Blends (Site not responding. Last check: 2007-11-07)
		Pyrethroids are toxic to insects whether the insects are beneficials or pests; they initially cause knock down (the inability of the insect to maintain its normal position) followed by recovery or death.
		Pyrethroids are highly toxic to bees, with the exception of fluvalinate, which is used to control mites in bee hives.
		Pyrethroids' principal mechanism of action is believed to be disruption of the permeability of nerve membranes to sodium atoms.
	www.buzzoff.us /equine.asp (4313 words)

	Pyrethroids: Not as safe as you think
		To ensure long-lasting effects, the pyrethroid may be mixed with a fixative to make it stay on plants and soil longer, and other chemicals, such as piperonyl butoxide, which prevent the insects from detoxifying, and "inert ingredients".
		An increasing number of insects have developed high levels of resistance to pyrethroids, such as cockroaches, head lice, and tobacco budworm, pear psylla, fall army-worm, German cockroach, spotted tentiform leafminer, diamondback moth, house fly, stable fly, head lice, and tobacco budworm.
		Pyrethroids, like all toxins, are indiscriminate: they affect all the organisms who come into contact with them in the air, on plants, on the ground, in the soil, and in the water.
	www.anapsid.org /pyrethroids.html (1133 words)

	MR1018/8 -- Chapter Six: Pyrethroids
		Pyrethroids are formulated as emulsifiable concentrates, wettable powders, granules, and concentrates for ULV application.
		Synthetic pyrethroids are among the newest pesticides to enter the marketplace, and they account for a large percentage of the pesticides in use today.
		A review of 573 cases of acute pyrethroid poisoning in the Chinese medical literature (He et al., 1989) focuses primarily on exposure to deltamethrin, fenvalerate, and cypermethrin, although it indicates that the spectrum of acute poisoning is similar for all pyrethroids.
	www.gulflink.osd.mil /library/randrep/pesticides_paper/mr1018.8.ch6.html (3003 words)

	Nat' Academies Press, Environmental Neurotoxicology (1992)
		Pyrethroid poisoning is associated with an increase in electric activity of the central and peripheral nervous systems: a single presynaptic stimulation in the presence of pyrethroids causes repetitive excitation of presynaptic nerve and nerve terminals, thereby evoking repetitive postsynaptic discharges.
		The sodium current that generates action potentials is markedly prolonged after the preparation is exposed to pyrethroids, and that causes a sustained depolarization after an action potential (Narahashi and Lund, 1980).
		That was based on several observations, including pyrethroid inhibition of ligand binding to the GABA receptor channel (Lawrence and Casida, 1983).
	www.nap.edu /books/0309045312/html/35.html (634 words)

	Health Risks Linked to Pyrethroids
		Pyrethroids are closely related to each other and therefore the following studies may relate to pyrethroids generally, not just the chemical(s) focused on in a particular study.
		These findings suggest that pyrethroids should be considered to be hormone disruptors, and their potential to affect endocrine function in humans and wildlife should be investigated." [Environmental Health Perspectives, Vol.
		Several studies have indicated neurological damage resulting from exposure to pyrethroids, and some of the damages have been found to be long term.
	www.mdpestnet.org /Pyrethroid_studies.htm (1446 words)

	Environmental Health Perspectives 105-8, 1997: Article by Prohl et al.
		The maximum amount of pyrethroids found in dust was 5,000 mg permethrin per kilogram after use of pesticides for pest control.
		Although acute intoxication with pyrethroids is described by several authors (42-46), the potential of adverse health effects on adults and children after low chronic indoor exposure to this neurotoxic substance is disputed (14,17,43,47,48).
		Similar symptoms have been described by approximately 10-30% of 75 clients of the EAV with elevated concentrations of pyrethroids and who were included in the follow-up study.
	www.herc.org /news/mcsarticles/prohl-full.html (4987 words)

	Head Lice Treatments - Pyrethrins and Pyrethroids - facts you shoud know
		For example, the female rat’s acute oral LD50 of permethrin increases from 224 milligrams of the pyrethroid per kilogram of body weight (mg/kg) to 6,000 mg/kg as the proportion of trans isomer increases from 20% to 80%.
		Synthetic pyrethroids principal mechanism of action is believed to be the disruption of the permeability of nerve membranes to sodium atoms.
		Pyrethrum or pyrethroids, e.g., permethrin, should not be used by persons sensitive to ragweed; should not be used near the eyes; should not be inhaled or swallowed; should not come in contact with mucous membranes, e.g., the eyes, nose or mouth.
	www.safe2use.com /pests/lice/poisons.htm (1132 words)

	Q's and A's About Pyrethroids (Site not responding. Last check: 2007-11-07)
		Sumithrin (Anvil) and Permethrin are the two pyrethroid-containing pesticides that may be used in the State of Maryland to control the spread of West Nile Virus.
		Since pyrethroids bind to soil, it is unlikely for them to contaminate surface waters and groundwaters if they are applied correctly.
		However, Pyrethroids are toxic to fish, and other aquatic life forms, so they should not be applied directly to water bodies.
	www.cha.state.md.us /oeh/html/pyrethoids.html (343 words)

	Metabolism of synthetic pyrethroids in chickpea plant (Site not responding. Last check: 2007-11-07)
		The use of these synthetics pyrethroids for protecting crops from pest-infestation inevitably leads to the accumulation of their residues in food and feed crop.
		Present paper describes the study carried out to investigate the metabolism of these pyrethroids in chickpea.
		The plants were raised in fields and sprayed with higher doses of the pesticides.
	www.teriin.org /division/bbdiv/pmb/docs/abs07.htm (273 words)

	Least Toxic Insect Control for Horses (Site not responding. Last check: 2007-11-07)
		Pyrethroids are a diverse class of pesticides that contains more than 1000 powerful broad-spectrum synthetic insecticides.
		Pyrethroid toxicity varies widely, and is highly dependent on the specific molecular struction of the individual pyrethroid.
		The "inerts" in the specific formulation used for pyrethroids are quite important and can account for a 10-fold increase in toxicity compared to the pure pesticide, especially since some inerts specifically act as synergists with pyrethroids.
	my.execpc.com /~mjstouff/articles/horsefly.html (4183 words)

	Medical Studies show health hazard from pyrethroid Poisons
		Sumithrin and resmethrin were not among the pyrethroids specifically studied in all medical studies reported on this page, but these pesticides are closely related to each other.
		The study concludes "The specific chemicals associated with children's brain cancers were pyrethrins and pyrethroids (which are synthetic pyrethrins, such as permethrin, tetramethrin, allethrin, resmethrin and fenvalerate) and chlorpyrifos (trade name: Dursban)." [Janice M. Pogoda and Susan Preston-Martin, "Household Pesticides and Risk of Pediatric Brain Tumors," Environmental Health Perspectives, vol.
		If you would like to be included in our mailing list for continuing information on pesticides, please email us at list@safe2use.com with "subscribe" in the subject line.
	www.safe2use.com /ca-ipm/00-11-16a.htm (752 words)

	Studies: Pyrethroids lead to brain damage
		Sumithrin (Anvil), resmethrin (Scourge) and permethrin (often used in household bug sprays) each belong to a class of pesticides known as pyrethroids.
		It concludes ³Overall, our studies imply that each pyrethroid compound is unique in its ability to influence several cellular pathways.
		Tulane University: This study, conducted by six scientists at three Tulane medical institutions, suggests that combinations of chemicals could have much greater effect that the individual chemicals would on their own, even when an individual chemical has relatively low potential for endocrine disruption by itself.
	www.safe2use.com /ca-ipm/00-09-18.htm (854 words)

	JAIC 1982, Volume 21, Number 2, Article 1 (pp. 01 to 34) (Site not responding. Last check: 2007-11-07)
		In general, the organophosphates, organochlorines, pyrethroids, and carbamates are residual-type insecticides with long-lasting effects.
		39, 40 Synthetic pyrethroids are similar to naturally occurring pyrethrins; they exhibit low mammalian toxicity and are biodegradable.
		The effectiveness of residual insecticides and mothproofing agents may be reduced by washing, dry cleaning, and exposure to light.
	aic.stanford.edu /jaic/articles/jaic21-02-001.html (9256 words)

	[No title]
		The Roger Williams General Hospital, Brown University: This study on pyrethroids concludes "Chronic exposure of humans or animals to pesticides containing these compounds may result in disturbances in endocrine effects." [Journal of Steroid Biochemistry, March 1990, volume 35, issue 3-4, pages 409-414.]
		Cambridge University: A report issued in June 2000 by the Royal Society in England and written by a group from Cambridge University called for international cooperation to deal with the dangers posed by endocrine-disrupting chemicals, including pyrethroids, and recommends reducing human exposure to these chemicals.
		Uppsala University: This study, conducted by the Department of Environmental Toxicology at Uppsala University in Sweden studied mice, not humans, but found that "low-dose exposure" to pyrethroids "resulted in ³irreversible changes in adult brain function in the mouse" when exposed during the growth period.
	www.nospray.org /pyrethroids.html (853 words)

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