J O U R N A L O F P E S T I C I D E R E F O R M / SPRING 2002 鈥? VOL. 22, NO. 1
鈼? INSECTICIDE FACTSHEET
PYRETHRINS/PYRETHRUM
Pyrethrins and pyrethrum are the most frequently used home and garden insecticides in the U.S. They are often used
in indoor sprays, pet shampoos, and aerosol bombs to kill flying and jumping insects.
Pyrethrins are a common cause of insecticide poisonings. According to a U.S. Environmental Protection Agency
(EPA) survey of poison control centers, they cause more insecticide poisoning incidents than any other class of
insecticides except the organophosphates. Symptoms include headaches, dizziness, and difficulty breathing.
Pyrethrins can trigger life-threatening allergic responses including heart failure and severe asthma.
In laboratory animals exposed through eating, by injection, or through breathing, pyrethrins have caused anemia.
Experiments with dairy cows suggest that nursing mothers exposed to pyrethrins can pass them on to their children.
Pyrethrins disrupt the normal functioning of sex hormones. They inhibit binding of sex hormones to human genital
skin and proteins in human blood.
Pyrethrins are classified as 鈥渓ikely to be human carcinogens鈥? by EPA because they cause thyroid tumors in
laboratory tests. Farmers who use pyrethrins have an increased risk of developing leukemia.
Pyrethrins are extremely toxic to bees, fish, and other aquatic animals.
Following indoor treatments, pyrethrins have persisted up to 2 1/2 months in carpet dust.
BY CAROLINE COX A large family of insecticides, the
Figure 1 synthetic pyrethroids, are structurally
P Two of the Pyrethrin Esters similar to pyrethrins but have been
yrethrum and pyrethrins have chemically modified to make them
more toxic and more persistent.1 For
been used as insecticides since at least
18001 and for decades have been the information about the hazards of three
most commonly used home and gar- commonly used synthetic pyrethroids
O
den insecticides in the U.S.2,3 Pyre- see JPR 14(2): 28-34 (cyfluthrin); JPR
thrum is a natural insecticide, an ex- 16(2): 15-20 (cypermethrin); and JPR
O
O
tract made from two daisy-like flow- 18(2): 14-20 (permethrin).
ers, Chrysanthemum cinerariaefolium
Use
and Chrsanthemum cineum. Pyrethrins pyrethrin I
In the early part of the twentieth
are the six insecticidally active com-
pounds in pyrethrum.1 (See Figure 1 century pyrethrum was 鈥渢he most com-
monly used household insecticide.鈥?2
for two examples.) Pyrethrins are O
O The most recent U.S. Environmental
mainly used as indoor sprays, pet
Protection Agency (EPA) home and
shampoos, and aerosol bombs to kill O
flying and jumping insects.1 Although garden pesticide survey estimated that
O
O over 240 million of these applications
pyrethrins are natural insecticides, they
are made annually in the U.S., more
do pose important hazards to human
than any other insecticide.3 There are
and environmental health. This article
pyrethrin II more registered uses for pyrethrins
summarizes those hazards.
than for any other insecticide.5 World-
Pyrethrin insecticides often contain
wide, about 200,000 kilograms (440,000
piperonyl butoxide, a chemical that
increases the potency of pyrethrins.4 The health and environmental hazards pounds) of pyrethrins are used each
year.6
of piperonyl butoxide will be summa-
rized in the summer 2002 issue of the Other than home and garden uses,
pyrethrins are used on a variety of
Journal of Pesticide Reform.
Caroline Cox is NCAP鈥檚 staff scientist.
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Inert Ingredients
agricultural crops and for structural and
public health pest control. The amount Like most pesticides, commercial Figure 2
Pyrethrin Use in California
used in agriculture is small relative to pyrethrin-containing insecticides con-
the other uses.7 (See Figure 2.) tain ingredients other than pyrethrins Other
which, according to U.S. pesticide law,
Mode of Action are called 鈥渋nert.鈥?11 Except for acute
Pyrethrins, like all members of the toxicity testing, all toxicology tests re-
pyrethroid insecticide family, kill in- quired for registration of pyrethrin Agricultural
sects by disrupting their nervous sys- products were conducted with pyre- pest Structural
control
tems. Pyrethrins are toxic to the 鈥渟o- thrins, not with the combination of pest
control
dium channel,鈥? the cellular structure ingredients found in commercial prod-
ucts.12 Most inert ingredients are not
that allows sodium ions to enter a cell Public
health
as part of the process of transmitting identified on product labels, and little pest
a nerve impulse. This leads to repeti- information about them is publicly control
tive discharges by the nerve cell which available. For more information about
causes paralysis and death.8 DDT and the hazards of some of the inert in-
related insecticides have the same gredients in pyrethrin products see
mode of action.9 Note: This chart does not
鈥淗azards of Inert Ingredients,鈥? below.
include household use.
Nerves in humans and other mam-
Acute poisoning Source: Calif. EPA. Dept. of Pesticide
mals are also susceptible to pyre-
Regulation. 2001. Summary of pesticide
thrin poisoning. However, mammals Frequency: Pyrethrins are a com- use report data: 2000, indexed by
have enzymes that more rapidly mon cause of insecticide poisonings. chemical. Pp. 341-343. www.cdpr.ca.gov.
detoxify pyrethrins into compounds When EPA summarized calls to poi-
that don鈥檛 disrupt the nervous son control centers in 1991, the agency California data suggest that agricultural uses
system.10 found that pyrethrins, and pyrethrins of pyrethrin are small relative to other uses.
HAZARDS OF INERT INGREDIENTS
1. Whitmire Micro-Gen. 1998. MSDS: P.I. Contact Insecticide.
Propane is used as an inert propellant in pyrethrin
www.wmmg.com/pest/products/pdf/MSDS/pi.pdf.; Value Garden Supply.
products. (See footnote 1 for some examples.) It can Undated. MSDS: Black Leaf Home Insect Fogger.
cause dizziness when inhaled. It is also 鈥渆xtremely flam- www.valuegardens.com/msds/Home%20Insect%20Fogger.pdf; Amrep,
Inc. 1997. MSDS: Misty Fog Plus Fogger. www.amrep.com/ii/products/
mable鈥?2 and easily ignited by heat, sparks, or flame.2 msds/aerosols/476.pdf.
Isobutane is also used as an inert propellant in 2. Hazardous Substance Data Bank. 2001. Propane. http://toxnet.nlm.nih.gov.
pyrethrin products. (See footnote 3 for some examples.) 3. Value Garden Supply. Undated. MSDS: Black Leaf Home Insect Fogger.
www.valuegardens.com/msds/Home%20Insect%20Fogger.pdf; Amrep, Inc.
It depresses the central nervous system and can cause 1997. MSDS: Misty Fog Plus Fogger. www.amrep.com/ii/products/msds/
dizziness when inhaled. Like propane, it is 鈥渆xtremely aerosols/476.pdf.
flammable鈥?4 and easily ignited.4 4. Hazardous Substance Data Bank. 2001. Isobutane. http://
toxnet.nlm.nih.gov/.
Hydrotreated light petroleum distillates 5. Cardinal Chemical Company. Undated. MSDS: Py-Dry.
(hydrotreated kerosene) are used as an inert solvent www.cardinalproproducts.com/MSDS/PY-Dry%20msds%202.pdf; Aventis.
2001. MSDS: Pyrenone 25-5 Public Health. www.adapcoinc.com/pdf/
in pyrethrin products. (See footnote 5 for some ex- PYR25m.pdf Southern Agricultural Insecticides, Inc. 1997. MSDS: Natu-
amples.) The Chemical Abstract Services number for ral Pyrethrin Concentrate. www.southernag.com/ms1040.pdf; Waterbury
this solvent is 64742-47-8. This solvent has caused skin Co., Inc. 2001. MSDS: Pro Exterminator Crawling & Flying Insect Killer.
www.timemist.com/proexterminator/msds/ProExtCrawlingFlying.pdf; Water-
tumors when applied to the skin of laboratory mice.6 bury Companies, Inc. 2001. MSDS: Country Vet Farm & Home CV-38 for
Hydrotreated heavy naptha (white spirits) is also Insect Control. www.country-vet.com/products/347300CV.pdf
6. International Agency for Research on Cancer. 1989. Occupational expo-
used as an inert solvent in pyrethrin products. (See
sures in petroleum refining. IARC Monographs 45:39. http://193.51.164.11/
footnote 7 for some examples.) The Chemical Abstract htdocs/monographs/Vol45/45-01.htm.
Services number for this solvent is 64742-48-9. It is 7. Whitmire Micro-Gen. 1998. MSDS: P.I. Contact Insecticide.
damaging to kidneys and the nervous system.8 In a www.wmmg.com/pest/products/pdf/MSDS/pi.pdf;
8. United Nations Environment Prog. et al. 1996. White spirit (Stoddard
recent laboratory study, the offspring of animals ex- Solvent). Environmental Health Criteria 187. Geneva, Switzerland: World
posed to white spirits developed 鈥渓ong-lasting and pos- Health Organization. Pp.73-75, 77-78, 90-128.
9. Edelfors, S., U. Hass, and A. Ravn-Jonsen. 1999. The effect of in vitro
sibly irreversible changes鈥? in brain cells. This damage to
exposure to white spirit on [Ca+2] in synaptosomes from rats exposed
the brain was caused by an inability to maintain normal prenatally to white spirit. Pharmacol. Toxicol. 84: 197-200.
calcium concentrations.9
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Allergic Responses to
with the synergist piperonyl butoxide, disruption that results in their toxic
Pyrethrins
caused over 9,000 incidents. Only the effects in insects, or an additional ef-
organophosphate insecticides caused fect. (See 鈥淢ode of Action,鈥? p. 1 5.) Pyrethrins can trigger allergic re-
more insecticide poisoning incidents.13 For example, researchers from the Uni- sponses that range from unpleasant to
(See Figure 3.) versity of Maryland School of Medi- life-threatening. Skin rashes, asthma,
Symptoms: Some symptoms of cine and the University of Alexandria and hives caused by exposure to pyre-
pyrethrin poisoning in people, head- (Egypt) showed that pyrethrins inhib- thrins or pyrethrum have been reported
aches and dizziness, are related to dis- ited calcium uptake in rat brain cells. in medical literature since the 1920s
Calcium plays a 鈥渧ital role鈥?15 in the and 1930s.19
ruptions of the nervous system. For
example, the Centers for Disease Con- nervous system, promoting the nor- More serious reports were published
trol compiled reports of pyrethrin ex- mal release of transmitter chemicals in 1994 and 2000. Physicians in New
posure incidents including one in from junctions between nerves and sta- York reported that a woman devel-
which a cook developed these symp- bilizing the membrane surrounding oped shortness of breath five minutes
nerve cells.15 Two groups of research-
toms following installation of pyrethrin after beginning to wash her family
insecticide dispensers in the restaurant ers, from the University of Mississippi dog with a pyrethrin shampoo. Al-
Medical Center16 and the University of
where he worked. A customer in the most immediately she suffered heart
Tampere Medical School (Finland)17
same restaurant developed similar failure and died after paramedics
symptoms.14 transported her to a hospital.20 An
showed that pyrethrins disrupt energy
The patients also developed other production in brain cells. Oregon physician reported that an 11-
symptoms that may not be related di- Pyrethrins also affect physiological year-old girl developed a severe asth-
rectly to pyrethrins鈥? effect on the ner- processes that are not related to the matic attack when washing the family
vous system: sore throat and difficulty nervous system. For example, research- dog with a pyrethrin shampoo. She
breathing.14 ers at the Osaka City Institute of Pub- died a few hours later, despite medical
treatment.21
Physiological mechanisms: Labo- lic Health and Environmental Sciences
ratory tests have demonstrated that (Japan) showed that in rat livers pyre- The refined pyrethrins in the prod-
pyrethrins cause several neurological thrins inhibit mitochondria, the cellu- ucts that caused these incidents are
disruptions in mammals. These may lar bodies that convert food to usable less allergenic than unrefined pyre-
energy.18 thrum22 but still have caused these
be the cause of the sodium channel
serious reactions.
Eye irritation
Figure 3
People exposed to commercial pyre-
Frequency of Pyrethrin Poisonings
thrin products have reported swelling,
redness, and burning of the eyes
20,000
Number of calls to poison control centers (1991)
following exposure.14
Effects on the Circulatory
System
15,000
Pyrethrins affect both sugar levels
and oxygen-carrying ability of blood.
Researchers from the University in
Rajasthan (India) showed that an in-
10,000
jection of pyrethrins caused gerbil
blood sugar levels to rise between 30
and 70 percent (depending on dose).
Blood sugar peaked an hour after treat-
5,000
ment, but the increase persisted for
several days.23 The same researchers
showed that an injection of pyrethrins
0 caused a decrease in the amount of
hemoglobin (oxygen-carrying mol-
Veterinary
Organophosphates Pyrethrins Carbamates Repellants insecticides
ecules) in the blood,24 as well as a
decrease in the number of red blood
Sources: U.S. EPA. Office of Pesticides and Toxic Substances. Undated memo. Human
cells.25 Hemoglobin concentration re-
insecticide exposures reported to Poison Control Centers in 1991. Prepared by J. Blondell,
Health Effects Division. mained low for 2鈥?3 weeks (see Figure
4);24 the reduced number of red blood
cells persisted for 2 days.25
Pyrethrin poisonings are more frequent than poisoning cause by any other class of insecticide
except the organophosphates. Other types of exposures with a
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longer duration caused similar effects.
A three-month feeding study with rats Figure 4
Exposure to Pyrethrins Causes Anemia
found pyrethrins caused a decrease in
the amount of hemoglobin in females
15
at doses at or above 170 milligrams of
pyrethrins per kilogram of body weight
(grams per 100 ml blood in male gerbils)
(mg/kg) per day (the middle dose in
unexposed
this experiment). Similar effects were
Hemoglobin concentration
found in males at higher exposures. A
three month inhalation study found
that pyrethrins caused anemia at doses
at or above 0.07 milligrams per liter of 10
air in males (all but the lowest dose
in this experiment). They also caused exposed
anemia in females, although at higher
exposures.26
Effects on the Kidney
A three-month feeding study with
rats showed that pyrethrins caused 5
degeneration of tubules (small tube- 1 7 14 21
like structures) in the kidney at doses Days after treatment
equal or greater than 170 mg/kg.27
Source: Saxena, S.C. and A.K. Karel. 1974. A note on the effect of pyrethrum on haemoglobin
Effects on Reproduction concentration of Indian desert gerbils, Meriones hurrianae. Pyreth. Post 12:161-162.
Pyrethrins can disrupt successful
reproduction in both males and fe- A single dose of pyrethrins (by injection) caused anemia which persisted for two weeks.
males. In a two-month feeding study
with dogs, the weight of the testes in
animals exposed to pyrethrins at doses Figure 5
at or above 30 mg/kg (all but the low- Exposure to Pyrethrins Disrupts Normal Hormone Functions
est dose tested) was less than that of
unexposed animals.28 In a two-gen- Displacement of a Inhibition of the binding
sex hormone from of testosterone to a
eration feeding study with rats, the hormone receptors hormone-binding protein
weight of offspring at birth and dur-
Binding of a synthetic hormone to androgen receptors
Binding of testosterone to sex hormone binding protein
ing nursing was less for rats fed pyre- 100 100
thrins at doses at or above 65 mg/kg
in human genital skin (% of unexposed cells)
(all but the lowest dose tested) than
in human blood (% of unexposed cells)
for unexposed animals.29
Concerns about pyrethrins鈥? effects
on reproduction are heightened by
studies of dairy cows. Following treat-
ment of the cows with pyrethrins, pyre-
thrins were detected in the cows鈥? 50 50
milk.30 This study provides support for
the concern that exposed nursing
mothers could pass pyrethrins on to
their children.
Disruption of Hormone
Systems
0 0
The impact that environmental pol-
Unexposed Exposed Unexposed Exposed
lutants can have on the normal func-
tion of human and animal hormone
Source: Eil, C. and B.C. Nisula, 1990. The binding properties of pyrethroids to human skin
systems has been a significant con- fibroblast androgen receptors and to sex hormone binding globulin. J. Steroid Biochem. 35:
cern in the last decade.31 Hormones 409-414.
are biologically active molecules that
control all responses and functions of In experiments with human cells, pyrethrins inhibited the normal binding of sex hormones.
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frequency of several cancers in rats.
The incidence of liver tumors was
Figure 6
Exposure to Pyrethrins is Associated with Increased Cancer higher in exposed female rats than in
Risks in Farmers and Laboratory Animals unexposed ones. Also, in both sexes,
the incidence of thyroid tumors was
15
4
Leukemia risk in farmers who use pyrethrins as a
greater in exposed rats than in unex-
Number of thyroid tumors (in 120 rats tested)
Laboratory
Livestock
posed ones.36
Animals
Farmers
Other carcinogenicity studies showed
livestock insecticide (odds ratio)
that the incidence of lung cancers in
3
exposed male mice was greater than
10
in unexposed ones37 and that the inci-
dence of parathyroid tumors was
greater in exposed rats than in unex-
2
posed ones.38
Effect of Gender
5
Several laboratory studies suggest
1
that females may be more susceptible
to pyrethrins than males. The distribu-
tion of pyrethrins in rats after expo-
0 sure is highest in body fat. However,
0
0 50 100 150
Handled
Never the concentration in female fat was
pyrethrins Amount of pyrethrins in food
handled
approximately double that found in
(milligrams/kilogram of body weight)
pyrethrins
male fat. Also, the median oral lethal
Sources:
dose for male rats was over twice the
Brown, L.M. et al. 1990. Pesticide exposures and other agricultural risk factors for leukemia
dose required to kill females.39
among men in Iowa and Minnesota. Cancer Res. 50: 6585-6591.
World Health Organization and Food and Agricultural Organization. 2000. Pesticide residues in
food 鈥? 1999. [Part II] Toxicological evaluations. Geneva, Switzerland: World Health
Human Exposure
Organization. p. 281.
Pyrethrins are absorbed slowly
through the stomach, intestines, and
Pyrethrins are associated with an increased leukemia risk in farmers who use them to control
skin. However, pyrethrins can be ab-
livestock pests. They also cause an increased frequency of thyroid tumors in laboratory studies.
sorbed 鈥渕ore quickly through the
lungs.鈥?40 This suggests that exposure
the body. Dramatic changes in the ac- roid metabolism or hormonal respon-
tivity of cells in humans and other siveness.鈥? As in the study summarized through breathing droplets or airborne
animals 鈥渁re caused by extremely small in the previous paragraph, in this ex- particles deserves particular attention.
amounts鈥? of hormones or other chemi- periment pyrethrins were more potent
Synergy
cals that disrupt this system.32 than the synthetic pyrethroids tested.34
Pyrethrins appear to disrupt the Carboxyesterases, enzymes that
Carcinogenicity
normal functioning of sex hormones. detoxify pyrethrins, are inhibited by
Researchers from Brown University and Pyrethrins are associated with in- organophosphate insecticides, thus or-
the National Institutes of Health creased cancer risks among farmers ganophosphate insecticides increase
pyrethrins鈥? toxicity.10
showed that pyrethrins displace hor- and have also caused cancer in labo-
mones from androgen receptors in cell ratory tests. (See Figure 6.)
Effects on Cats
cultures of human genital skin. An- Researchers from the National Can-
drogens are sex hormones that pro- cer Institute studying risk factors for Cats are particularly susceptible to
mote development of male sex char- leukemia found that farmers exposed pyrethrin poisoning because their liv-
acteristics; testosterone is a familiar ex- to pyrethrins used for pest control on ers inefficiently detoxify this insecti-
cide.41 As a consequence, there are a
ample. The same researchers also livestock had an increased risk of de-
showed that pyrethrins block the bind- veloping leukemia. Exposure to pyre- large number of poisoning incidents.
ing of testosterone to the a sex hor- thrins was associated with a 3.7-fold Veterinarians summarizing calls made
increase in risk.35
mone binding protein in human blood. to an animal poison control center in
In both experiments pyrethrins were In 1999, EPA evaluated the ability 1986 found that pyrethrin-related inci-
more potent than the synthetic pyre- of pyrethrins to cause cancer. The dents were more numerous than inci-
throids tested.33 (See Figure 5.) dents involving any other insecticide.42
agency concluded that pyrethrins
Pyrethrins also inhibit binding to should be classified as 鈥渓ikely to be a Symptoms of pyrethrin poisoning in
peripheral benzodiazepine receptors, human carcinogen by the oral route.鈥? cats include excessive salivation, al-
found in high concentration in the tes- This EPA evaluation was based on tests tered behavior, depression, anorexia,
and high body temperature.42
tes and thought to be involved in 鈥渟te- which demonstrated increases in the
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appear to increase knockdown
Young cats (less than four years Pyrethrins persist much longer in-
potency.51
old, but especially if less than one doors than they do outdoors. Studies
year old) are more susceptible to pyre- conducted at the University of Ulm and
Effects on Other Beneficial
thrins than older cats.41 the Fraunhofer Institute of Toxicology
Insects and Spiders and Aerosol Research (Germany) found
Effects on Birds It is not surprising that pyrethrins, that pyrethrins persisted 60 hours af-
ter treatment on horizontal surfaces,57
because they are insecticides, are toxic
In general, relatively large amounts
to agriculturally useful insects and spi-
of pyrethrins are required to kill two weeks after treatment on airborne
birds.43 However effects other than ders. The International Organization for particles, and over two months in car-
pet dust.58 (See Figure 7.)
Biological Control found that a com-
death have been found at lower ex-
mercial pyrethrin product killed over
posures. Scientists from the University
Effects on Soil Fertility
99 percent of two parasitoid wasps
of Rajasthan (India) found that doses
and a predatory fly. (Parasitoids are
between 10 and 50 mg/kg of pyre- Insecticides are generally not ex-
insects which develop in and kill the
thrum caused excitability and de- pected to have impacts on plants.
creased appetites in pigeons.44 In spar- eggs or larvae of another species.) This However, they can indirectly affect
study also found pyrethrins caused 80
rows, doses of 400 mg/kg caused ex- plant growth if they change the growth
percent mortality of two other parasi-
citability and an increase in flying, as or abundance of soil microorganisms
toid species, a fly and a wasp.52 Cornell
well as a decrease in food consump- that are important in the maintenance
University Agricultural Experiment Sta-
tion and weight. The weight of the of soil fertility. Scientists at the Uni-
tion researchers found that pyrethrins
liver, intestine, pancreas, kidney, and versity of Ibadan (Nigeria) showed that
testes also decreased.45 killed four common species of wasp treatment of agricultural soils with
that are parasitoids of house and stable pyrethrin caused an increase in the
Effects on Fish flies in dairies.53 The web-building spi- abundance of soil bacteria and a de-
Pyrethrins are 鈥渆xtremely toxic to der Argiope argentata is also suscep- crease in the abundance of soil fungi.
fish,鈥? according to the Agency for Toxic tible to pyrethrins; two commercial In addition, the number of these spe-
Substances and Disease Registry.46 Me- pyrethrin products caused more than cies was less in treated soil than in
dian lethal concentrations (the concen- 50 percent mortality of this spider in a
tration that kills half of a test population) test conducted at the University of
Regensburg (Germany).54
range from 9 to 58 parts per billion. A Figure 7
Persistence of Pyrethrins
summary by the U.S. Fish and Wildlife
Development of Resistance in after Treatment
Service found that channel catfish and
Pest Insects
coho salmon were the most suscep-
75
tible species.47 At least fifteen species of insects,
including lice, cockroaches, weevils,
Pyrethrins are more toxic to fish in
warm water than in cold water.47
Persistence after treatment (in days)
bedbugs, house flies, mosquitos, meal
moths, and aphids have developed
Effects on Other Aquatic pyrethrin resistance, the ability to sur-
Animals 50
vive treatment. Resistance ratios (the
Aquatic animals other than fish are ratio between the amount needed to
also killed by low concentrations of kill a resistant individual and the
pyrethrins. The most susceptible lar- amount needed to kill a susceptible
val stage of the American lobster is individual) are often relatively low, but
killed by concentrations of 1 part per in four species resistance ratios are 25
billion.48 The scud (a fresh water crus- above 100. The four species are the
tacean) is killed by concentrations of German cockroach, the granary wee-
12 parts per billion.49 vil, and two house flies.55
Repeated exposure to synthetic
Effects on Honey Bees pyrethroids can cause the development 0
of resistance to pyrethrins.55
Pyrethrins are 鈥渉ighly toxic鈥? to bees; On In carpet
airborne dust
0.02 micrograms is sufficient to kill a
Persistence particles
bee.50 Toxicity of commercial pyrethrin
products to bees was demonstrated by Outdoors, pyrethrins persist only for Source: Berger-Prei脽, E., K. Levssen, and
A. Prei脽. 1997. Analysis of individual
an entomologist at Auburn University a short time. For example, after appli-
natural pyrethrins in indoor matrices by
who showed that a commercial pyre- cation of pyrethrins to bare soil, the HRG/ECD. J. High Resol. Chromatogr.
thrin insecticide caused 100 percent half life (the time required for half of 20: 284-289.
鈥渒nockdown,鈥? the inability of the bee the applied pyrethrin to break down
to walk or fly. Some of the inert in- or move away from the application Pyrethrins persisted in carpet dust for over
site) was two hours or less.56
gredients used in pyrethrin products two months after treatment.
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Ther. 10: 97-113.
untreated soil. The end result was a sociated with inhalation of a pyrethrin shampoo.
Clin. Toxicol. 32: 457-460. 43. Hudson, R. H., R.K. Tucker, and M.A. Haegele.
reduction in the amount of the impor- 21. Wagner, S.L. 2000. Fatal asthma in a child after 1984. Handbook of toxicity of pesticides to wild-
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NORTHWEST COALITION FOR ALTERNATIVES TO PESTICIDES/NCAP
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