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The following information relevant to Poisons Centres has been extracted from the CHEMINFO database produced by CCOHS. Complete CHEMINFO records also contain comprehensive hazard control and regulatory information. For more information about the complete CHEMINFO database contact CCOHS.

CHEMINFO Record Number: 339
CCOHS Chemical Name: Pyrethrin II

Chrysanthemum dicarboxylic acid monomethyl ester pyrethrolone ester
Pyrethrolone, chrysanthemum dicarboxylic acid methyl ester ester
Pyrethrine II

CAS Registry Number: 121-29-9
Other CAS Registry Number(s): 39668-02-5
RTECS Number(s): GZ0700000
EU EINECS/ELINCS Number: 204-462-6
Chemical Family: Pyrethrins (natural) and pyrethroids (synthetic)
Molecular Formula: C22-H28-O5


Appearance and Odour:
Viscous liquid or oil

Odour Threshold:
Not available. Pyrethrin II has a low vapour pressure.

Warning Properties:
Information not available

Composition and purity depend on the method of preparation. Pyrethrin II may be concentrated from natural pyrethrins, reconstituted from component alcohols and acids obtained from the natural material or synthesized. This material is often only a small percentage of pesticide formulations. The overall physical, chemical and toxic characteristics of the product may depend on other ingredients such as solvents.

Uses and Occurrences:
Pyrethrin II makes up about 32% of the active ingredients of natural pyrethrins, and contributes the rapid 'knock-down' effect. Natural pyrethrins are used extensively as insecticides. Pure pyrethrin II appears to be used primarily in laboratories for research on pyrethrin and pyrethroid insecticides.



Effects of Short-Term (Acute) Exposure

No animal or human information is available for pyrethrin II. Based on data available for natural pyrethrins (of which pyrethrin II is a major component) and on ease of metabolism in animals, health effects are unlikely by inhalation, unless exposure is severe.

Skin Contact:
Based on similarity to natural refined pyrethrins, pure pyrethrin II is unlikely to cause skin irritation.
However, pyrethrins have been shown to cause contact dermatitis. Pyrethrin II may cause sensitization especially in those sensitive to ragweed pollen(1).

Eye Contact:
Based on animal testing of natural pyrethrins, eye contact may cause irritation. No data available to indicate whether damage would occur.

Based on animal data, no effects are expected from ingestion with normal use and handling. Accidental ingestion of large amounts might result in nausea, vomiting, convulsions and other signs of disturbance of the central nervous system.

Effects of Long-Term (Chronic) Exposure

Based on similarity to natural pyrethrins and on ease of metabolism, chronic effects are not expected with normal use and handling of pyrethrin II.

No information available. Related pyrethrins are not carcinogenic.

The International Agency for Research on Cancer (IARC) has not evaluated the carcinogenicity of this chemical.

The American Conference of Governmental Industrial Hygienists (ACGIH) has no listing for this chemical.

Pyrethrin II makes up 32% of pyrethrum (natural pyrethrins), which has an ACGIH carcinogenicity designation of A4 (not classifiable as a human carcinogen).

The US National Toxicology Program (NTP) has not listed this chemical in its report on carcinogens.

Teratogenicity and Embryotoxicity:
No information available. Animal tests on natural pyrethrins showed no teratogenic or embryotoxic effects.

Reproductive Toxicity:
No information available

No information available

Toxicologically Synergistic Materials:
In animal testing, a pyrethrin "synergist" (piperonyl butoxide) did not enhance the acute toxicity of pyrethrins to rats.

Potential for Accumulation:
Pyrethrins are rapidly broken down in the body and are unlikely to accumulate.


If symptoms are experienced, remove source of contamination or move victim to fresh air. Obtain medical advice immediately.

Skin Contact:
Remove contaminated clothing, shoes and leather goods (e.g. watchbands, belts). Gently blot or brush away excess chemical quickly. Wash gently and thoroughly with water and non-abrasive soap. If irritation persists, obtain medical advice immediately. Completely decontaminate clothing, shoes and leather goods before reuse, or discard.

Eye Contact:
Gently blot or brush away excess chemical quickly. Immediately flush the contaminated eye(s) with lukewarm, gently flowing water for 20 minutes, by the clock, holding the eyelid(s) open. If irritation persists, obtain medical attention immediately.

Never give anything by mouth if victim is rapidly losing consciousness, or is unconscious or convulsing. Have victim rinse mouth thoroughly with water. DO NOT INDUCE VOMITING. Have victim drink 240 to 300 mL (8 to 10 oz.) of water. If vomiting occurs naturally, rinse mouth and repeat administration of water. Obtain medical advice immediately.

First Aid Comments:
Provide general supportive measures (comfort, warmth, rest).

Consult a physician and/or the nearest Poison Control Centre for all exposures except minor instances of inhalation or skin contact.

All first aid procedures should be periodically reviewed by a physician familiar with the material and its conditions of use in the workplace.


Flash Point:
No data available. For natural pyrethrins, flash point has been reported as 82-88 deg C (180-199 deg F) (open cup).

Lower Flammable (Explosive) Limit (LFL/LEL):
Not available

Upper Flammable (Explosive) Limit (UFL/UEL):
Not available

Autoignition (Ignition) Temperature:
Not available

Sensitivity to Mechanical Impact:
Probably not sensitive

Sensitivity to Static Charge:
Information not available

Extinguishing Media:
Carbon dioxide, dry chemical powder, alcohol foam, polymer foam

Fire Fighting Instructions:
Treat as combustible liquid. Cool fire-exposed containers.


NFPA - Comments:
NFPA has no listing for this chemical in Codes 49 or 325.


Molecular Weight: 372.50

Conversion Factor:
Not applicable

Melting Point: No data available
Boiling Point: Decomposes above 200 deg C, even at reduced pressure.
Relative Density (Specific Gravity): Not available
Solubility in Water: Practically insoluble
Solubility in Other Liquids: Soluble in ethyl alcohol, petroleum ether, kerosene, carbon tetrachloride, ethylene dichloride and nitromethane.
Coefficient of Oil/Water Distribution (Partition Coefficient): Not available
pH Value: Not applicable
Vapour Density: Not applicable
Vapour Pressure: Practically zero
Saturation Vapour Concentration: Not applicable
Evaporation Rate: Practically zero
Critical Temperature: Not applicable


Stable when protected from air and light. Oxidizes readily and becomes inactive in air and light.

Hazardous Polymerization:
Does not occur

Incompatibility - Materials to Avoid:
STRONG OXIDIZING AGENTS - May cause fire and explosions.

STRONG BASES - Breakdown (hydrolysis) occurs. The reaction may be vigorous and loss of activity occurs.

Hazardous Decomposition Products:
None reported.

Corrosivity to Metals:


LD50 (oral, rat): 200 mg/kg (6)
In another study, it was reported that the oral LD50 for pure pyrethrin II could not be calculated but was greater than 600 mg/kg with rats surviving cumulative doses of 2900 mg/kg(2).

LD50 (iv, rat): 1 mg/kg (pure reconstituted pyrethrin II) (1,2,6)
Differences between oral and iv (intravenous) toxicities are presumably due to rapid breakdown of pyrethrin II when given orally(1,2). Animals surviving an iv dose bordering on lethal showed rapid, complete recovery(2).

Lethal dose (intraperitoneal, mouse): 240 mg/kg; 4 of 6 mice died. The survivors were normal(2).

Doses of 240 mg/kg (intraperitoneal, rat or guinea pig) produced diarrhea but no convulsions(2).

METABOLISM: Studies with rats and mice showed rapid oxidation of pyrethrin II. Within 48 hours of oral administration of 14C-pyrethrin II to rats, 53% was recovered as exhaled CO2 and 7% was recovered in urine. Some was excreted in the feces, at least partially in metabolized form(1).

IRRITATION: Irritating to the eyes and mucous membranes. No permanent damage to the eyes appears to have been reported(5).


Selected Bibliography:
(1) Gosselin, R.E., et al. Clinical toxicology of commercial products. 5th ed. Williams & Wilkins, 1984. p. III-352 - III-355
(2) Casida, J.E. Pyrethrum : the natural insecticide. Academic Press, 1973
(3) Hutson, D.H. The metabolic fate of synthetic pyrethroid insecticides in mammals. Progress in Drug Metabolism. Vol. 3 (1979). p. 215-252
(4) Hayes, W.J. Pesticides studied in man. Williams and Wilkins, 1982. p. 75-80
(5) Grant, W.M. Toxicology of the eye. 3rd ed. Charles C. Thomas, 1986. p. 774
(6) RTECS record for cyclopropaneacrylic acid, 3-carboxy-alpha,2,2-trimethyl-, 1-methyl ester, ester with 4- hydroxy-3-methyl-2-(2,4-pentadienyl)-2-cyclopenten-1-one. Date of last update 8806
(7) Schwope, A.D., et al. Guidelines for the selection of chemical protective clothing. 3rd ed. Vol. I : field guide. American Conference of Governmental Industrial Hygienists, February 1987. p. 122
(8) NIOSH pocket guide to chemical hazards. NIOSH, June 1990. p. 190-191
(9) European Communities. Commission Directive 98/98/EC. December 15, 1998

Information on chemicals reviewed in the CHEMINFO database is drawn from a number of publicly available sources. A list of general references used to compile CHEMINFO records is available in the database Help.

Review/Preparation Date: 1989-05-24

Revision Indicators:
PEL-TWA 1993-03-01
Trans PEL-TWA 1993-04-01
TDG 1994-03-01
US transport 1995-12-01
EU number 1995-12-01
Sampling 1995-12-01
TLV comments 1996-09-01
Resistance of materials 1998-05-01
EU Class 2000-05-01
EU Risk 2000-05-01
EU Safety 2000-05-01
Bibliography 2000-05-01
UN/NA No 2002-12-18
Carcinogenicity 2003-07-24

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