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Managing Fleas Without Poisons

Journal of Pesticide Reform v.17, n.3 Fall97

This article was written cooperatively by many NCAP staff members. It could not have been written without the assistance of interns Iris Porter and Dietra Lynn.

Northwest Coalition For Alternatives To Pesticides/NCAP
PO Box 1393, Eugene Oregon 97440/541-344-5044

Flea control insecticides are a hazardous group of chemicals. Looking at twenty flea control chemicals, over two-thirds are neurotoxic, and almost that many have caused reproductive problems in laboratory tests. Half of the chemicals are classified as carcinogens by EPA, or have been associated with increased cancer risks in epidemiological or laboratory studies. A quarter of them are known to cause genetic damage in at least one test. Almost all have environmental concerns. Children and veterinarians, as well as our rivers and estuaries, are impacted by these chemicals.

These hazards are unnecessary. Vigilance and preventive techniques allow most pet owners to keep flea populations under control without using poisons.

Key nonchemical techniques include frequent vacuuming of areas that pets use in order to remove flea eggs and larvae, washing pet bedding regularly (also to remove eggs and larvae), and combing pets with a flea comb to remove adult fleas. Insecticide-free flea traps and flea-killing nematodes are other useful options. Regular use of these techniques means that we can have flea-free pets, health for ourselves and our families, and a healthy environment.

Fleas can be an enormous problem for the 110 million dogs and cats living in the United States, as well as for their owners.1 During summer months, half the money spent at veterinary clinics is flea related.2 The American Pet Product Manufacturing Association estimates that seven out of ten dog owners annually purchase flea and tick products, primarily flea collars and shampoos.3

While these pet owners may feel that they are making their pets more comfortable, they may actually be poisoning their pets and themselves. However, these poisons are not necessary. The good news for pet owners is that with early vigilance and preventive techniques, fleas can be controlled effectively without insecticides.

Flea Control Products and Their Hazards

Many flea control pesticides have significant hazards. In Table 1 we have outlined the effects of twenty ingredients in flea control products. The chart uses data from published studies, as well as information from the U.S. Environmental Protection Agency (EPA) and other government agencies. (Complete references are given on page 10.)

The chart is dense and not easy to read, but the stark conclusions from studying the chart are straightforward. In general, flea control insecticides are a hazardous group. Over two-thirds of the chemicals in the table are neurotoxic, and almost that many have caused reproductive problems in laboratory tests. Half of the chemicals are classified as carcinogens by EPA, or have been associated with increased cancer risks in epidemiological or laboratory studies. A quarter of them are known to cause genetic damage in at least one test. Almost all have environmental concerns.

If you are considering the use of a flea pesticide, please carefully read the section of the chart about that chemical before you make your decision. If you would like more detailed information about any of the chemicals, contact NCAP.

Impacts of Flea Pesticides on Children

All of the hazards described in Table 1 take on special urgency because children can be exposed to these chemicals when they are used to kill fleas. In fact, children are more heavily exposed to pesticides and are more seriously impacted than adults.

Per pound of body weight, children breathe more air, drink more water, and eat more food than adults. This means that the amount of toxic chemicals a child receives per pound of body weight is higher.4

In addition, children are more sensitive because they are growing and some of their organs are still developing.4 Children are also more susceptible because they are more likely to come into contact with materials that may be contaminated, such as carpets that have been treated for fleas.5

One of the tools used by researchers to study the impacts of home pesticides on children is "epidemiology," associating real-life exposures with disease. Consider the findings of these studies:

In addition to these epidemiological studies, researchers evaluating specific flea control chemicals in the laboratory have found problems that are significant for children's health.

For example, a commonly used chemical in flea control products is chlorpyrifos. Laboratory tests have suggested that infants are more susceptible to chlorpyrifos than adults. In newborn rats, the highest dose of chlorpyrifos without visible effects was only one-sixth that measured in adult rats.10 Another test showed that chlorpyrifos is more easily absorbed through the skin of young rats than that of adult rats.11 A third chlorpyrifos study looked at the air residues of this chemical following treatment. The study showed that carpets are a source of chlorpyrifos vapors following application, particularly for children. Air concentrations were up to 5 times higher in the infant breathing zone (1 foot above the carpet) than in the adult breathing zone (3-1/2 feet above the carpet).5

Together, these studies indicate that children are especially vulnerable to pesticides. This is borne out by statistics from poison control centers. Well over half of all reported pesticide poisonings occur in children under the age of 6!12

Impacts of Flea Pesticides on Vets

During the summer months, half of the money spent at veterinary clinics is flea related.2 This means that veterinarians, their assistants, and other pet handlers are exposed to chemicals used in flea control products. Studies of pet handlers demonstrate that exposure to these chemicals is having an impact:

Impacts of Flea Pesticides on Water

California's Central Contra Costa Sanitary District has found flea pesticides in the wastewater from homes, kennels, and pet groomers. The district calculated that only two applications of chlorpyrifos flea products per day would cause the effluent from their water treatment plant to be toxic to aquatic animals.15

Are Flea Insecticides Effective?

Despite tremendous expenditures on flea control insecticides, many people are not satisfied. Why? Because many treatments are simply not effective.

For example, flea collars emit continuous vapors into the air in your home and around your pet. However, these vapors may not affect fleas at the tail end of your pet and may not affect flea eggs. Many people rely on foggers to control fleas in their homes. However, foggers not only release a lot of poison into your home, they also are not effective against flea larvae and eggs. Consider what the 1995 Pacific Northwest Insect Control Handbook had to say about the effectiveness and safety of highly promoted foggers:

"Aerosol space foggers have received extensive media publicity with claims of virtual eradication of household pests. These foggers seem to offer a simple solution to serious problems but rarely are effective except to exposed insect stages. Exposed adult fleas (few are truly exposed) may be killed but eggs and larvae are not exposed and, except when the fogger has a persistent ingredient, there is no residual toxicant to contact the insect when it is vulnerable. What really happens when foggers are used is that all interior home surfaces - walls, ceilings, floors, and furnishings, (most of which never harbor insects) - are coated with a toxic residue."16

The Good News: Least Toxic Flea Control

None of the hazards of flea control chemicals is necessary. By understanding the flea's life cycle and targeting your management activities, an effective and least-toxic flea control program is possible.

Flea Biology

The most common and annoying species of flea is the cat flea (Ctenocephalides felis). Feasting on dogs, cats and humans, the cat flea is responsible for most flea bites and allergies in humans and pets.17,18

Fleas go through four stages of development: egg, larva, pupa and adult. Warm, moist conditions (65-80oF and 70 percent relative humidity) are optimal for flea hatching and development. A female can lay up to 800 eggs in her lifetime. Eggs are laid both on and off the pet. Those laid on the pet later fall off and accumulate on the floor, in cracks, on furniture, and in dust.17

Flea development is directly tied to external conditions making the flea a resilient pest. In 2 to 12 days the eggs hatch into hairy wormlike larvae. The larval stage generally lasts 1 to 3 weeks, but under unfavorable conditions it can last up to 200 days. The larvae then spin a cocoon and transform into pupae.17

Pupae remain dormant until they detect a host (by warmth and vibrations) and hatch out as adults. The pupal stage lasts from 1-2 weeks under favorable conditions but can extend to nearly a year. After emerging, the adult fleas immediately seek a blood meal. Adults can live 1 to 2 months without a meal and can survive 7 to 8 months with just one meal.17

The wide fluctuation in duration of the various stages accounts for the sudden emergence of massive numbers of fleas in "flea season." They've actually been there all along, waiting for optimal temperature and humidity conditions to occur before maturing en masse.

Managing the Fleas' Environment

Are Flea Control Products Safe?

Many pet owners feel that if they buy a flea control product in a grocery store it must be safe. Or, if they have their homes treated by a "professional" applicator or use products recommended by their veterinarians, the products must be safe. In fact, researchers found that many pet owners were so complacent about pesticide hazards that even during pregnancy and the first 6 months of a new child's life parents "failed to recognize and reduce the pervasive exposures associated with the use of no-pest-strips and flea collars." 1 To dispel this myth of safety, it is crucial to understand a few points about how pesticides work and how they get on the market.

First, pesticides are poisons; they are primarily intended to kill living organisms. Many pesticides affect a broad range of living things. For example, organophosphate and carbamate compounds (two classes of pesticides commonly used for flea control) act on the nervous system of insects and mammals in the same manner.2 When you use these chemicals you can affect not only fleas, but your pet and yourself.

Second, the law that regulates pesticides - the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) - does not use safety as the fundamental basis for allowing a pesticide on the market. FIFRA is based on a risk-benefit standard. This allows pesticides to be used even if they pose hazards to humans and the environment so long as the benefits outweigh the hazards.3 Any health or environmental hazards can be acceptable if the estimated economic benefits are large.

Third, many products on the market today do not meet current standards for health and safety testing. These products were already registered when FIFRA's testing requirements were passed in 1972. While the law was amended in 1988 to set deadlines for bringing the testing up to current standards, the deadlines have not been met.4 This means that we have limited information on some older pesticides.

Fourth, pesticide products are made up of more than one chemical. Most pesticides are composed of "active" ingredient(s) , whose identity must be listed on the label, and "inert" ingredients whose identities most manufacturers claim are trade secrets. The term "inert" is misleading, because these secret ingredients are neither biologically, chemically, nor toxicologically inactive. Much of the testing required for EPA registration is done on the active ingredient only.5 Therefore, adverse effects of the pesticide as it is used are untested and unknown.

1. Davis, J.R., R.C. Brownson, and R. Garcia. 1992. Family pesticide use in the home, garden, orchard, and yard. Arch. Environ. Contam. Toxicol. 22:260-266.

2. Cremlyn, R.J. 1991. Agrochemicals: Preparation and mode of action. Chichester, UK: John Wiley & Sons. Pp.123 and 149.

3. Federal Insecticide, Fungicide and Rodenticide Act 2(bb).

4. U.S. EPA. Pesticides and Toxic Substances. 1992. Pesticide reregistration. Washington, D.C., May. Pp.2-3.

5. U.S. EPA. 1987. Inert ingredients in pesticide products; Policy statement. Fed. Reg. 52(77):13305, Apr. 22.


At any given time, fleas may be present in any or all four life cycle stages. Thus an effective program must address the flea at all four stages of development. Vacuuming areas your pet frequents, bathing your pet, washing pet bedding, and combing for fleas can effectively keep your flea population at a tolerable level. It is important to recognize that as the flea population rises and falls, physical control measures must be adjusted accordingly.

Fleas tend to accumulate where pets sleep. If possible, establish a single, regular sleeping place with bedding that is easily removable and washable. Wash bedding about once a week to break up the flea life cycle. A towel or blanket makes excellent bedding. Pick bedding up by the four corners so that eggs and larvae aren't scattered throughout the area.17,19

Pet access to hard-to-clean areas like basements and attics must be restricted. Access to bedrooms where a flea infestation would be particularly annoying can also be limited. Since pets bring in fleas from outside, consider the possibility of having either an inside or an outside pet.

If your pet does go in and out of the house, keep your lawn cut short and either very dry or very wet. Fleas don't do well in either extreme.17,19

Regularly use a flea comb on your pet. The fleas are caught in the closely spaced tines of the comb and can be flicked into a container of soapy water where they drown. Dish soap works well. Don't crush fleas with your fingers since they carry parasites and disease organisms.20

Many pets actually come to enjoy this grooming process. You can monitor the extent of your flea population by keeping a count of fleas captured during these combing sessions. A rising flea count will herald an increasing flea population in time for you to take preventive measures. Flea combs come in a variety of sizes and are available in most pet supply stores.

Bathe your pet. It's not necessary to use insecticidal shampoos; most soaps will kill fleas. Read the label; frequently all the ingredients are listed. Test your favorite shampoo or soap by mixing it with water and dropping a few fleas from your flea comb into it. Fleas should die within seconds. Some soaps are strong desiccants so be sure to monitor your pet's hair and skin. Change products if your pet's skin becomes dry and itchy.

Vacuuming floors, carpets, furniture, crevices and cracks once a week is an excellent means of controlling the flea population. Vacuuming is especially effective at picking adults and eggs. The vibration from vacuuming can result in the emergence of adult fleas from the pupal stage. The newly hatched fleas are vacuumed up prior to ever meeting you or your pet. However, vacuuming is not particularly effective in removing the flea larvae in carpeting. Larvae wrap themselves around the base of carpet fibers, and hang on.17

Vacuum more frequently if the flea population increases, every two or three days during peak season. After vacuuming, the bag must be dealt with immediately or the fleas will escape and reinfest the area. The bag can be thrown away, burned or placed in a sealed black plastic bag in the freezer or in the sun for several days. A water vacuum eliminates the need to deal with the vacuum cleaner bag.

If you have a high level flea infestation, having your carpets professionally steam-cleaned may be worth the investment. Steam-cleaning kills fleas in the adult and larval stages. However, the steam can trigger the hatching of the remaining flea eggs a few days later.

Raising temperatures within a structure can kill the fleas. Isothermics Inc., of Anaheim, California, sells a heating unit that raises the temperature in a structure to the point where it kills fleas and other insects (termites, cockroaches and ants) without damaging the house or its contents. This technology is available only to pest control operators.17

Flea Traps

Flea population explosions tend to occur when their food sources are on vacation. How often have you and your pet come home from a relaxing trip only to be assaulted by a horde of ravenous fleas? You might want to try leaving behind a flea trap. Traps can also reduce flea populations when used routinely in rooms where flea populations are high.


A vacuum cleaner and a flea comb are 
the two most important elements of a 
nonchemical flea management tool kit.

To make your own, hang a light bulb six to twelve inches above a pan of soapy water or a sticky trap. The warmth of the bulb will attract fleas, especially if no other warm-blooded animals are around.19

Flea traps are also available commercially. Traps with a flickering, yellow-green light source are most effective.21 They are available under the brand name Ultralight, manufactured by Whitmire Research. (St. Louis, MO.; 800/325- 3668).

Biological Controls

Predatory nematodes that prey on flea larvae and pupae as they are developing in soil are available commercially. The nematodes are mixed with water and watered into lawns to reduce outdoor flea populations. Strong reductions in flea populations are possible if temperature and humidity conditions allow the nematodes to thrive.22 Nematodes are available from Gardens Alive! (812/537-8650) and other garden supply stores.

Least-toxic Chemical Control Measures

NCAP does not recommend the use of any chemicals for flea control. However, we recognize that some pet owners will be in a situation where they feel they cannot avoid the use of an insecticide. The following chemicals should be considered if you must choose this type of flea control. For a brief summary of the health and environmental hazards associated with these pesticides, see the chart on pages 8 and 9.

Desiccating dusts, such as diatomaceous earth and silica aerogels, kill fleas by drying them out, causing the insect to lose moisture and eventually die. Always wear goggles and a dust mask during application to avoid breathing in desiccating dusts. Cover or remove electronic equipment that can be damaged by dust. People with respiratory problems should not use diatomaceous earth. Be sure not to use glassified diatomaceous earth manufactured for use in swimming pool filters; it causes the lung disease silicosis.20

Diatomaceous earth can be lightly applied to pets and their bedding. Work it in using a brush or broom. Lightly vacuum afterwards to remove loose dust.19,20

Silica aerogel, despite its misleading name, is in fact another desiccating dust that effectively kills fleas. Silica gel can be applied to the pet and to bedding.17

Lufenuron is a drug that prevents a new generation of fleas from developing. It is an insect growth regulator that is passed from the pet's blood to the flea.

Adult fleas feeding on a pet given lufenuron will not be killed, but they will not lay eggs that can successfully develop. 23,24 Although it has some toxicological problems for pets, its primary advantage is that only the pet with the flea problem is exposed to the chemical control.

Flea Repellents

Cedar chips are widely known as a flea-repellent bedding material. However, over time the wood chips lose their odor and the bedding is difficult to vacuum or wash effectively. The bed becomes a safe haven for flea larvae. If you choose to use cedar chip bedding, replace it (or freshen with cedar oil) when the aroma wears off. A removable, washable cover is a good idea.

Fed to your pet, vitamin B1 (found in nutritional yeast) is a flea repellent. However, it should be given only in small doses, 1/2 teaspoon for a small cat and 2 to 3 teaspoons for large dogs, since large amounts can result in gas and cramps. A better source of vitamin B1 for pets is Bcomplex vitamins at a dosage of 1/4 to 1/2 of a 10-milligram pill per day. Chopped garlic cloves added to your pet's food also can repel fleas. One large clove a day is recommended for a large dog.20,25

In general, a healthy, well-nourished pet is able to withstand and repel flea attacks.20,25


1. American Veterinary Medical Association. 1993. U.S. Pet Ownership and Demographics Sourcebook. Center for Information Management, AVMA, 1931 North Meacham Road, Suite 100, Schaumburg, IL 60173.

2. PRNewswire. 1994. Vets wage war on fleas...naturally, June 28.

3. American Pet Product Manufacturer's Association. 1994. National pet owners survey. Scarsdale, NY.

4. National Research Council. Committee on Pesticides in the Diets of Infants and Children. 1993. Pesticides in the diets of infants and children. Washington, D.C. National Academy Press.

5. Fenske, R.A. et al. 1990. Potential exposure and health risks of infants following indoor residential pesticide applications. Am. J. Public Health 80(6):689-693.

6. Lowengart, R.A., et al. 1987. Childhood leukemia and parents' occupational and home exposures. J. Nat. Cancer Inst. 79(1):39-46.

7. Gold, E., et al. 1979. Risk factors for brain tumors in children. Amer. J. Epidemiol. 109(3):309- 319.

8. Leiss, J.K. and D.A. Savitz. 1995. Home pesticide use and childhood cancer: A case-control study. Am. J. Public Health 85(2):249-252.

9. Davis, J.R., R.C. Brownson, and R. Garcia. 1992. Family pesticide use in the home, garden, orchard, and yard. Arch. Environ. Contam. Toxicol. 22:260-266.

10. Pope, C.N. et al. 1991. Comparison of in vivo cholinesterase inhibition in neonatal and adult rats by three organophosphorothioate insecticides. Toxicol. 68:51-61.

11. Shah, P.V. et al. 1987. Comparison of the penetration of 14 pesticides through the skin of young and adult rats. J. Toxicol. Environ. Health 21:353-366.

12. Blondell, J. 1993. Human pesticide exposures reported to poison control centers for 1990, 1991, and 1992. Washington, D.C.: U.S. EPA. Office of Pesticides and Toxic Substances. Health Effects Division.

13. Ames, R.G. et al. 1989. Health symptoms and occupational exposure to flea control products among California pet handlers. Am. Ind. Hyg. Assoc. J. 50(9):466-472.

14. Rosenberg, J. and S.G. Quenon. 1988. Organophosphate toxicity associated with flea dip products - California. Morbid. Mortal. Weekly Report 37(21)329-330, 335-336.

15. Brandenburg, B. 1995-96. Central San's experience with diazinon and chlorpyrifos. Regional Monitoring News 2(1):1,10,11.

16. Fisher, G. et al. 1995. Pacific Northwest insect control handbook. Corvallis, OR: Oregon State University.

17. Olkowski, W., S. Daar, and H. Olkowski. 1991. Common-sense pest control: Least-toxic solutions for your home, garden, pets and community. Newtown, CT: Taunton Press.

18. Borror, D., D. DeLong, and C. Triplehorn. 1976. An introduction to the study of insects. New York, NY: Holt, Rinehart and Winston.

19. Stein, D. 1991. Dan's practical guide to least toxic home pest control. Eugene, OR: Hulogosi Communications, Inc.

20. Graf, D. 1990. Pest control you can live with: Safe and effective ways to get rid of common household pests. Sterling, VA: Earth Stewardship Press.

21. Dryden, M.W. and A.B. Broce. 1993. Development of a trap for collecting newly emerged Ctenocephalides felis (Siphonaptera: Pulicidae) in homes. J. Med. Entomol. 30(5):901-906.

22. Quarles, B. 1993. BioFlea(r) and Vector(r) -- Biological control of fleas. IPM Practitioner 15(8):18. Berkeley, CA: BioIntegral Resource Center.

23. U.S. Food and Drug Administration. 1995. FOI summary. NADA 141-026 (original). Washington, D.C, Mar. 28.

24. U.S. Food and Drug Administration. 1995. FOI summary. NADA 141-035 (original). Washington, D.C., Nov. 23.

25. Jesiolowski, J. and C. Long. 1992. 10 steps to a flea-free life! Organic Gardening (July/August): 34-38.

Table 1 - Hazards of Flea Control Pesticides


Class of Chemical 

Examples of Adverse Health Effects In Humans or Pets

Adverse Effects in Laboratory Studies

Environmental Concerns (See note, p.10)


synthetic pyrethroid 

Dogs fed allethrin over a two-year period suffered from convulsions and died sooner than unexposed dogs.1 

Allethrin is neurotoxic. In rats and/or mice it causes convulsions, decreased weight gain, increased liver, kidney, or thyroid weight, and pneumonia.1 

Allethrin is very highly toxic to most fish, including salmon, rainbow trout, steelhead, catfish, and perch. It is also very highly toxic to water fleas and stoneflies (both aquatic invertebrates). It is moderately toxic to bees.1



Boric acid causes diseased testicles in dogs.2 

Boric acid causes testicular atrophy, lung hemorrhages, decreased sperm counts, and decreased fetal weight in mice. It also increases the frequency of a birth defect in rabbit fetuses.2 

Boric acid is toxic to plants and has damaged commercially important species. It has the potential to harm threatened and endangered species.2



Workers exposed to carbaryl developed abnormal sperm.3 Children exposed to household carbaryl treatments were more likely to develop childhood brain cancer,4 and farmers using carbaryl were more likely to develop a cancer (non-Hodgkin’s lymphoma.).5 

Carbaryl is neurotoxic.6 EPA classifies it as a carcinogen (it causes malignant blood vessel tumors).7 In rats, it causes abnormal sperm,8 fetal loss, and birth defects.9 It damages hamster chromosomes.10 

Carbaryl has been found in groundwater in six states.11 It is highly toxic to red-winged blackbirds, “extremely toxic” to earthworms, moderately to highly toxic to fish, highly toxic to bees, and very highly toxic to water fleas.12



About 1,000 chlorpyrifos poisonings are reported to poison control centers each year.13 Undescended testicles have been reported in boys exposed prenatally.14 Also, a veterinarian’s cat suffered anorexia and profound weakness after a flea treatment.15 

Chlorpyrifos is neurotoxic.16 In pregnant rats, chlorpyrifos caused fetal death and reduced birth weight.17 It also causes genetic damage in many tests, including tests using human cells.16 

Chlorpyrifos has contaminated groundwater in nine states.11 It is highly toxic to birds, moderately toxic to fish, very highly toxic to aquatic invertebrates, very highly toxic to oysters, and highly toxic to shrimp.18



NCAP was unable to locate any reports of adverse health effects in humans or pets. 

EPA classifies diatomaceous earth and silica gel as “low to moderate” acute toxicity. According to EPA, lung cancer rates doubled in mice inhaling silica gel over a one-year period.19 

As naturally occurring, ubiquitous materials, EPA did not require ecological effects testing for either diatomaceous earth or silica gel.19


organophosphate 8 

A family became ill after moving into an apartment that had been treated with diazinon, Contamination of the apartment, and their symptoms, persisted for 4 months.20 Farmers using diazinon were more likely to develop a cancer (non-Hodgkin’s lymphoma).5 

Diazinon is neurotoxic.6 Symptoms include headache, nausea, and incoordination. In rats, it reduces litter size, weight of pups, and pup survival.21 It damages chromosomes in human cells.22 

Diazinon has contaminated groundwater in 8 states.11 It is very highly toxic to birds, fish, and aquatic invertebrates. EPA cancelled some diazinon uses because of the large number of documented diazinon-related bird kills.23



A family had their home sprayed for fleas with a dichlorvos-containing insecticide, and experienced headaches, lightheadedness, wheezing, shortness of breath, nausea, and fatigue. Their symptoms lasted for over six weeks.24 

Dichlorvos is neurotoxic.25 EPA classifies it as a carcinogen (it causes stomach tumors and leukemia).7 It damages testes in rats and mice, and has caused genetic damage in many tests.25 

Dichlorvos is highly toxic to birds, highly or moderately toxic to fish, and very highly toxic to aquatic insects, other freshwater invertebrates, shrimp and crab.25

FIPRONIL (Frontline) 


NCAP was unable to locate any reports of adverse health effects in humans or pets. This is a new chemical and such reports are unlikely to be available. 

Fipronil is neurotoxic.26 EPA classifies it as a carcinogen (it causes thyroid tumors).7 In rats, it causes seizures, decreased weight gain, damage to kidneys, and alterations in thyroid hormones.26 

Fipronil is highly toxic to upland game birds, rainbow trout, water fleas, and oysters, and very highly toxic to bluegill sunfish. An important metabolite is more toxic to birds and fish than fipronil. It bioaccumulates in fish.26



NCAP was unable to locate any reports of adverse health effects in humans or pets. This is a new chemical and such reports are unlikely to be available. 

Imidacloprid is neurotoxic, and causes incoordination and labored breathing.27 It also causes thyroid lesions, reduces pup weights, and increases the frequency of a birth defect in rats.28 

Imidacloprid is persistent in soil and has “properties and characteristics associated with chemicals detected in groundwater.”28 It is very highly toxic to shrimp29 and bees, and is highly toxic to house sparrows.28

LUFENURON (Program) 


Lufenuron accumulates in fatty tissues of pets given the drug.30 In dogs and cats, the following adverse effects have been observed: vomiting, depression, lethargy, diarrhea, loss of appetite, and itchy, scratchy skin.31,32 

Lufenuron is a close chemical relative of the growth regulator diflubenzuron,30 which has a metabolite that is classified as a carcinogen by EPA.7 

Because lufenuron is a veterinary drug, tests for impacts on nontarget species have not been done.


insect growth regulator 

Following a commercial treatment of a building with a methoprene-containing insecticide, six of the people who worked in the building reported headaches, eye and throat irritation, difficulty breathing, confusion, dizziness, and nausea.33 

Methoprene caused increased liver weights in test animals and degeneration of parts of the kidney.34 

Methoprene is “toxic” to amphibians.35 It causes intoxication in birds,35 and reproductive impairment in ducks.34 It is very highly toxic to water fleas, and juvenile shrimp and crabs.34 it is moderately toxic to bluegill sunfish.34


synthetic pyrethroid 

A teacher became ill with nausea, dizziness, and breathing trouble shortly after she arrived at her school for work. The school had been treated the night before with a permethrin-containing insecticide.36 

Permethrin is a neurotoxin.37 EPA classifies it as a carcinogen (it causes lung cancer and liver tumors in mice).7 It is embryotoxic in rabbits, and causes liver damage in mice.37 

Permethrin is very highly toxic to fish, including salmon, trout, catfish, bass, and bluegill sunfish. It bioaccumulates in fish. It is also very highly toxic to algae, crayfish, lobster, shrimp, crab, water fleas, and caddis flies.37



A dog groomer became ill with nausea, sweating, diarrhea, abdominal cramps, vomiting, headache, and dizziness 30 minutes after using phosmet. A woman developed cramps, vomiting, and diarrhea after playing with her dog who had been bathed in a flea dip.38 

Phosmet is a neurotoxin.39 EPA classifies it as a carcinogen (it causes liver tumors in mice).7 Embryos from rats exposed to phosmet during pregnancy developed brain damage.39 

Phosmet is very toxic to bees. It is very highly toxic to red winged blackbirds, and highly toxic to pheasants. It causes reproductive problems in birds. It is highly or very highly toxic to fish.39



A man sprayed furniture with a piperonyl butoxide-containing insecticide. He was wearing rubber gloves and a mask. He developed burning of the nose and mouth, tingling of the arms, and a severe headache. Symptoms persisted two days.33 

Piperonyl butoxide is classified by EPA as a carcinogen (it causes liver tumors).7 It also causes lung lesions, hemorrhages, and anemia in rats.40 It decreases the survival of mouse pups.41 

Piperonyl butoxide is highly toxic to tadpoles and water fleas. It is moderately toxic to oyster larvae, shrimp, and many fish, including rainbow trout, goldfish, carp, yellow perch, and bluegill sunfish.42



A veterinary technician who was accidentally splashed with a pesticide containing propoxur had symptoms including headache, nausea, vomiting, diarrhea, difficulty breathing, and chemical pneumonia. The technician was hospitalized for 13 days.43 

Propoxur is neurotoxic.44 In rats, it causes bladder cancer.45 It also causes reproductive problems, including reduced litter size, low birth weight, and impaired nervous systems in the pups.44 

Propoxur is very highly toxic to mourning doves and house finches, and highly toxic to mallard ducks, pheasants, and quail. It is very highly toxic to fathead minnows and highly toxic to honey bees.44


botanical insecticide 

A 37-year-old woman developed severe shortness of breath after bathing her dog with a pyrethrin shampoo. Her heart stopped and she died after being taken to the hospital.46 Farmers who applied pyrethrins increased their risk of developing leukemia four-fold.47 

Pyrethrins are neurotoxic.48 They also can produce skin irritation, itching, and burning. In rats, they cause fetal loss49 and low birth weights.48 

Pyrethrins are “extremely toxic” to fish such as bluegill sunfish and lake trout. They are also “toxic” to bees.48


insect growth regulator 

NCAP was unable to locate any reports of adverse health effects in humans or pets. This is a new chemical and such reports are unlikely to be available. 

In a chronic feeding study, pyriproxyfen caused a decrease in normal weight gain. Reduced weight gain also occurred in a study of reproductive effects, along with toxicity to the pups.50 

Pyriproxyfen is very highly toxic to water fleas.51 It also causes deformities in dragonflies,52 prevents juvenile ladybugs from developing into adults,53 and suppresses egg hatch of a beneficial bug.53


synthetic pyrethroid 

A custodian at a school developed a headache, a choking feeling, tightness in his chest, and a scratchy throat from a nearby resmethrin application which drifted to the area where he was working.36 

Resmethrin is neurotoxic, causing tremors and rapid breathing. In rats, it reduces weight gain, increases kidney weight, increases the number of stillborn pups, and reduces pup weight.54 

Resmethrin is very highly acutely toxic to fish, including carp, killifish, rainbow trout, coho salmon, steelhead, perch, and bluegill fish, It is also very highly toxic to some aquatic arthropods.54



Adverse effects were observed in dogs fed tetrachlorvinphos in chronic toxicity studies: a decreased red blood cell count, an increased white blood cell count, increased prostate weight, increased liver weight, and increased kidney weight.55 

Tetrachlorvinphos is neurotoxic.55 EPA classifies it as a carcinogen (it causes liver and thyroid tumors).7 It causes fetal loss in pregnant rabbits, and damages hamster chromosomes.55 

Tetrachlorvinphos is highly toxic to fish (trout, sunfish, and catfish) and bees. It is very highly toxic to water fleas and shrimp.55


synthetic pyrethroid 

A child entered her house to use the bathroom while her parent was fogging with tetramethrin-containing foggers. The parent later discovered the child unconscious and not breathing on the bathroom floor. The child required artificial respiration.56 

Tetramethrin is neurotoxic.57 EPA classifies it as a carcinogen (it causes testicular tumors).7 In rats, it reduces pituitary, thyroid, and spleen weight, inhibits ovulation, and reduces fetal growth.57 Environmental Concerns (See note, p.10) 

Tetramethrin is very highly or highly toxic to fish, including bluegill sunfish, rainbow trout, and killifish. It is also very highly toxic to water fleas. It is toxic to bees.57

References for Table 1

1. United Nations Environment Prog., International Labor Org., and World Health Org. 1989. Allethrins: Allethrin, d-allethrin, bioallethrin, and s-bioallethrin. Environmental Health Criteria 87. Geneva, Switzerland: WHO.

2. U.S. EPA. Prevention, Pesticides and Toxic Substances. 1993. Reregistration eligibility decision (RED): Boric acid and its sodium salts. Washington, D.C., Sept.

3. Wyrobeck, A.J. et al. 1981. Sperm shape abnormalities in carbaryl-exposed employees. Envir. Health. Persp. 40:255-265.

4. Davis, J.R. et al. 1993. Family pesticide use and childhood brain cancer. Arch. Environ. Contam. Toxicol. 24:87-92.

5. Cantor, K.P. et al. 1992. Pesticides and other agricultural risk factors for non-Hodgkin's lymphoma among men in Iowa and Minnesota. Cancer Res. 52:2447-2455.

6. Morgan, D.P. 1989. Recognition and management of pesticide poisonings. Fourth ed. Washington, D.C.: U.S. EPA. Office of Pesticide Programs. Health Effects Div.

7. U.S. EPA. 1997. Office of Pesticide Programs list of chemicals evaluated for carcinogenic potential. Memo from W.L. Burnam, Health Effects Div., to Health Effects Div. Branch Chiefs, et al. Washington, D.C., Feb. 19.

8. U.S. EPA. Office of Pesticides and Toxic Substances. 1980. Carbaryl decision document. Pp. 45-46, Dec.

9. Mather, A. and P. Bhatnagar. 1991. A teratogenic study of carbaryl in Swiss albino mice. Fd. Chem. Toxicol. 29:629-632.

10. Calif. Dept. of Food and Agriculture. Medical Toxicology Br. 1990. Summary of toxicology data: Carbaryl. Sacramento, CA., July 31.

11. U.S. EPA. Prevention, Pesticides and Toxic Substances. 1992. Pesticides in groundwater database: A compilation of monitoring studies: 1971-1991. Washington, D.C., Sept.

12. United Nations Environment Program, International Labor Org., and World Health Org. 1994. Carbaryl. Environmental Health Criteria 153. Geneva, Switzerland: WHO.

13. U.S. EPA. Office of Prevention, Pesticides and Toxic Substances. 1997. Review of chlorpyrifos poisoning data. Memo from J. Blondell, Health Effects Div., to L. Probst, Special Review and Reregistration Div. Washington, D.C., Jan. 14.

14. Sherman, J. 1996. Chlorpyrifos (Dursban)- associated birth defects: Report of four cases. Arch. Environ. Health 51(1):5-8.

15. Levy, J.K. 1993. Chronic chlorpyrifos toxicosis in a cat. JAVMA 203(12):1682-1686.

16. U.S. Dept. of Health and Human Services. Public Health Service. Agency for Toxic Substances and Disease Registry. 1995. Toxicological profile for chlorpyrifos. (Draft.)

17. Muto, M.A. et al. 1992. Embryotoxicity and neurotoxicity in rats associated with prenatal exposure to Dursban. Vet. Hum. Toxicol. 34(6):498-501.

18. U.S. EPA. 1984. Pesticide factsheet: Chlopyrifos. No. 37. Washington, D.C., Sept. 30.

19. U.S. EPA. Prevention, Pesticides and Toxic Substances. 1991. Reregistration Eligibility Decision (RED): Silicon dioxide and silica gel. Washington, D.C., Sept.

20. Richter, et al. 1992. Illness and excretion of organophosphorous metabolites four months after household pest extermination. Arch. Environ. Health 47(2):135-138.

21. Calif. Dept. of Food and Agriculture. Medical Toxicology Branch. 1990. Summary of toxicological data. Diazinon. Sacramento, CA, Feb. 27.

22. Sobti. R.C. et al. 1982. Cytokinetic and cytogenetic effects of some agricultural chemicals on human lymphoid cells in vitro: Organophosphates. Mut. Res. 102:89-102.

23. U.S. EPA. Office of Pesticide Prog. 1986. Pesticide fact sheet: Diazinon. Washington, D.C., Sept.

24. Markowitz, S.B. 1992. Poisoning of an urban family due to misapplication of household organophosphate and carbamate pesticides. Clin. Toxicol. 30(20:295-303.

25. United Nations Environment Program, International Labor Org., and World Health Org. 1989. Dichlorvos. Environmental Health Criteria 79. Geneva, Switzerland: WHO.

26. U.S. EPA. Office of Pesticide Prog. 1996. New pesticide fact sheet: Fipronil. Washington, D.C., May.

27. U.S. EPA. Office of Pesticide Programs. 1996. Imidacloprid. Evaluation of product labeling data submitted and identification of outstanding toxicology data requirements. Memo from M.S. Ottley, Health Effects Div., to P. Jenkins, Registration Div. Washington, D.C., Mar. 5.

28. U.S. EPA. Office of Pesticide Programs. 1994. Pesticide fact sheet: Imidacloprid. Washington, D.C., Mar. 18.

29. U.S. EPA. 1994. Registration for imidacloprid (NTN 33983). Memo from S.L. Johnson, registration Division, to D.D. Campt, Office of Pesticide Programs. Washington, D.C., Mar. 10.

30. Adams, H.R. (ed.) 1995. Veterinary pharmacology and therapeutics. Ames, IA: Iowa State University. Pp. 989, 998-999.

31. U.S. Food and Drug Admin. 1996. FOI summary NADA 141-035. Washington, D.C., Dec. 31.

32. U.S. Food and Drug Admin. 1996. FOI summary NADA 141-018. Washington, D.C., Dec. 31.

33. Washington State Dept. of Health. 1992. Pesticide incident reporting and tracking review panel. Annual report 1991. Olympia, WA.

34. U.S. EPA. Prevention, Pesticides and Toxic Substances. 1991. Reregistration Eligibility Document (RED): Methoprene. Washington, D.C., Mar.

35. Extension Toxicology Network (EXTOXNET). 1994. Methoprene pesticide information profile. May.

36. Calif. EPA. Dept. of Pesticide Regulation. Case reports by the California pesticide illness surveillance program in which health effects were attributed to exposure to pesticide in schools, 1992-1994. Unpublished.

37. United Nations Environment Program, International Labor Org., and World Health Org. 1990. Permethrin. Environmental Health Criteria 94. Geneva, Switzerland: WHO.

38. Oregon Health Div. 1989. Pesticide alert: Poisoning from flea control products containing phosmet. Commun. Disease Summ. 38(10). May.

39. Extension Toxicology Network (EXTOXNET). 1993. Phosmet pesticide information profile. Sept.

40. Takahashi, O. et al. 1994. Chronic toxicity studies of piperonyl butoxide in F344 rats: Induction of hepatocellular carcinoma. Fund. Appl. Toxicol. 22:293-303.

41. Tanaka, T., O. Takahashi, and S. Oishi. 1992. Reproductive and neurobehavioral effects in three-generation study of piperonyl butoxide administered to mice. Fd. Chem. Toxic. 30:1015- 1019.

42. U.S. EPA. Undated. Database of ecological effects tests. Unpubl. Maintained by B. Montague, Office of Pesticide Prog. Washington, D.C.

43. Sidhu, K.S. and M.B. Collisi. 1989. A case of accidental exposure to a veterinary insecticide product formulation. Vet. Hum. Toxicol. 31(1):63- 64.

44. Extension Toxicology Network (EXTOXNET). 1993. Propoxur pesticide information profile. Sept.

45. U.S. EPA. Office of Drinking Water. 1988. Health advisory: (Baygon) propoxur. Washington, D.C., Aug.

46. Wax, P.M. and R.S. Hoffman. 1994. Fatality associated with inhalation of a pyrethrin shampoo. Clin. Toxicol. 32(4):457-460.

47. Brown, L.M. et al. 1990. Pesticide exposures and other agricultural risk factors for leukemia among men in Iowa and Minnesota. Cancer Res. 50:6585-6591.

48. Extension Toxicology Network (EXTOXNET). 1994. Pyrethrins pesticide information profile. Mar.

49. Khera, K.R., C. Whalen, and G. Angers. 1981. Teratogenicity study on pyrethrins and rotenone (of natural origin) and ronnel in pregnant rats. Teratol. 23(2):45A-46A. (Abst.)

50. U.S. EPA. 1997. Pyriproxyfen; Pesticide tolerances for emergency exemptions. Fed. Reg. 62(143):39962-39967. July 25.

51. Trayler, K.M. and J.A. Davis. 1996. Sensitivity of Daphnia carinata sensu lato to the insect growth regulator, pyriproxyfen. Ecotoxicol. Environ. Safety 33:154-156.

52. Schaefer, C.H. and T. Miura. 1990. Chemical persistence and effects of S-31183, 2- [methyl-2-(4-phenoxyphenoxy)ethoxy]- pyridine, on aquatic organisms in field tests. J. Econ. Entomol. 83(5):1768-1776.

53. Mendel, Z., D. Blumberg, and I. Ishaaya. 1994. Effects of some insect growth regulators on natural enemies of scale insects (Hom: Coccoidea). Entomophaga 39(2):199-209.

54. United Nations Environment Program, International Labor Org., and World Health Org. 1989. Resmethrin. Environmental Health Criteria 92. Geneva, Switzerland: WHO.

55. U.S. EPA. Prevention, Pesticides and Toxic Substances. 1995. Reregistration Eligibility Decision (RED): Tetrachlorvinphos. Washington, D.C., Sept.

56. Washington Dept. of Health. 1993. Pesticide incident reporting and tracking review panel. Annual report 1992. Olympia, WA.

57. United Nations Environment Program, International Labor Org., and World Health Org. 1990. Tetramethrin. Environmental Health Criteria 98. Geneva, Switzerland: WHO.


This table uses EPA acute toxicity designations based on the median lethal dose (LD50) or concentration (LC50). Both the LD50 and the LC50 indicate the amount of a pesticide needed to cause death of half of a population of test animals. Quotation marks are used where these toxicity designations are unavailable.

For birds, a pesticide is very highly toxic if the LD50 is less than 10 milligrams per kilogram (mg/kg) of the bird's weight or the dietary LC50 (concentration in food) is less than 50 parts per million (ppm). A pesticide is highly toxic if the LD50 is between 10 and 50 mg/kg or the dietary LC50 is between 50 and 500 ppm. For aquatic animals, a pesticide is very highly toxic if the LC50 (concentration in water) is less than 0.1 ppm, highly toxic if the LC50 is between 0.1 and 1 ppm, and moderately toxic if the LC50 is between 1 and 10 ppm. For bees, a pesticide is highly toxic if the LD50 is less than 2 micrograms per bee and moderately toxic if the LD50 is between 2 and 11 micrograms per bee.

source: http://www.pesticide.org/factsheets.html 22oct01

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