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    WORLD HEALTH ORGANIZATION             FOOD AND AGRICULTURE
                                          ORGANIZATION
    ORGANISATION MONDIALE DE LA SANTE     ORGANISATION POUR L'ALIMENTATION
                                          ET L'AGRICULTURE

  
                                          VBC/DS/75.11
                                          ORIGINAL: ENGLISH


    DATA SHEETS ON PESTICIDES No. 11

    1975

    PYRETHRINS



         It must be noted that the issue of a Data Sheet for a
    particular pesticide does not imply endorsement of the pesticide by
    WHO or FAO for any particular use, or exclude its use for other
    purposes not stated. While the information provided is believed to
    be accurate according to data available at the time when the sheet
    was compiled, neither WHO nor FAO are responsible for any errors or
    omissions, or any consequences therefrom.

    The issue of this document does    Ce document ne constitue pas une
    not constitute formal              publication. Il ne doit faire
    publication. It should not be      l'objet d'aucun compte rendu ou
    reviewed, abstracted or quoted     résumé ni d'aucune citation sans
    without the agreement of the       l'autorisation de l'Organisation
    Food and Agriculture               des Nations Unies pour
    Organization of the United         l'Alimentation et l'Agriculture
    Nations or of the World Health     ou de l'Organisation Mondiale de
    Organization.                      la Santé.


     
                                     PYRETHRINS

    Part 1 - General information   

              CLASSIFICATION

              Primary use:  insecticide 
       
              Secondary uses:  insect repellent and flushing agent 

              Chemical group:  chrysanthemumic acid ester 

              Data sheet No. 11 

              Date issued: March 1975



    1.1   COMMON NAME: Pyrethrins
        
    Identity: The term refers generally to the mixed active ingredients
    as present in commercially available extracts of the pyrethrum flower, 
    largely  Chrysanthemum cinerariaefolium. Such extracts contain 20-25% 
    total pyrethrins, the main active constitutents being pyrethrin I and
    pyrethrin II plus smaller amounts of the related cinerins and 
    jasmolins.  The chemical names are: 

    Pyrethrin I: cis 4-hydroxy-3-methyl-2(2,4-pentadienyl)-2-cyclopenten-l-
    one d-trans 2,2-dimethyl-3-(2-methylpropenyl)-cyclopropanecarboxylate, 
    or pyrethrolone ester of d-trans chrysanthemic acid.

    Pyrethrin II:  cis 4-hydroxy-3-methyl-2(2,4-pentadienyl)-2-cyclopenten-
    l-one d-trans 2,2-dimethyl-3-(3-methoxycarbonyl-3-methylpropenyl)-
    cyclopropane-carboxylate or pyrethrolone ester of pyrethric acid. 
                                                                          
    Figure 1

    Synonyms:                                    Local synonyms:

    Pyrethrum extract
    Pyrethrum oleoresin


    1.2   SYNOPSIS: A highly insecticidal extract which is of weak 
    mammalian toxicity.  It is rapidly detoxified in the gastrointestinal 
    tract, and on exposure to sunlight. 


        
    1.3   SELECTED PROPERTIES

    1.3.1 Physical characteristics: Pyrethrins I and II are refined to 
    pale non viscous liquid oleoresin solutions. 

    I - b.p. 170°C at 0.1 mm Hg with decomposition.  

    II - b.p. 200°C at 0.1 mm Hg with decomposition. 

    1.3.2 Solubility: Water at 20°C virtually insoluble, soluble in 
    hydrocarbons and many other organic solvents. 

    1.3.3 Stability: Rapidly oxidized and inactivated in sunlight:
    decomposed by exposure to light with loss of insecticidal activity.
    Rapidly hydrolysed by alkali. 

    1.3.4 Vapour pressure: Not known, virtually non-volatile at ambiant 
    temperature.

            
    1.4 AGRICULTURE, HORTICULTURE AND FORESTRY

    1.4.1 Common formulations:

    0.2-0.4% dusts; 0.5-1.0% ULV sprays; 0.1-0.5% pressure packs, 
    emulsifiable concentrates to give 0.003%-O.015% final pyrethrins 
    content (high volume usage).  Most formulations contain a synergist 
    usually piperonyl butoxide and stabilizers; UV screens are also now 
    being included.  Also used at a low concentration, admixed with other 
    insecticides as a "flushing" agent. 

    1.4.2 Susceptible pests

    Effective against a wide range of agricultural, horticultural and 
    forest pests, including sawfly larvae, lepidopterous caterpillars, 
    leafhopers, aphids, beetles, and thrips.  Particularly useful where 
    rapid "knockdown" paralysis is required, less effective in killing the 
    target pest unless synergised. 

    1.4.3 Use pattern

    As pre-harvest treatment, applied just before harvest on growing bush 
    and vine fruits, deciduous fruits and nuts, forage crops and 
    vegetables, ornamentals. 

    Spray or dust formulations are used on freshly picked fruits and
    vegetables in the field, in storage and in processing plants.  Widely 
    used as sprays or dusts directly on commodities, for protection of 
    dried fruit, tree-nuts, grains, oil seeds and animal feeds during 
    storage. Applied as repellant to the outside of bags containing stored 
    cereals, cocoa, etc.  Aerosols and sprays are used for treating food-
    handling, processing and storage premises, agricultural premises and 
    households. Used as spray for control of ectoparasites of livestock 
    (including dairy and meat cattle) and poultry.  Also used for control 
    of blowfly during fish drying. 

    1.4.4 Unintended effects
         
    Pyrethrins are toxic to cold-blooded animals: avoid contamination of 
    watercourses.  Not phytotoxic.  Not persistent.
        

    1.5   PUBLIC HEALTH PROGRAMME

    1.5.1 Common formulations

    0.2-0.4% dusts; 0.2-0.4% solutions in kerosene or petroleum 
    distillate; 0.05-0.10% solution, with additional agents, in kerosene as 
    flying insect sprays; synergists are included in the formulations. 0.5-
    2% shampoos for human and pet usage.  Repellant to mosquitos and biting 
    flies: used in insect repellant creams (including aerosols) and 
    mosquito coils. 

    1.5.2 Susceptible pests

    Active against mosquitos, flies, cockroaches, lice, including human 
    body lice, and other public health insects.

    1.5.3 Use pattern

    Applied as thermal fogs, mists for non-residual control on a 
    repetitive application basis in situations such as kitchens, food 
    stores, factories, etc., where toxic residual insecticides cannot be 
    used.  Thermal fogs of 0.05% pyrethrins + 0.40% piperonyl butoxide used 
    for fly Control.  ULV sprays used against mosquitos, houseflies, and 
    tetse.  Alcohol solutions applied to free water mains of arthropod 
    infestations. 

        
    1.6    HOUSEHOLD USE

    1.6.1 Common formulations

    0.15-0.30% dusts; 0.15-1.2 "aerosol" pressure packs; 0.05-0.10% 
    sprays; synergists and additional killing agents are often included. 
    Mosquito coils containing 0.15-0.5% (unsynergised) pyrethrins. 

    1.6.2 Susceptible pests

          Mosquitos, houseflies, midges, cockroaches, etc.

    1.6.3 Use patterns

    Aerosol fly sprays use more than half the total production of
    pyrethrum and mosquito coils about one third.  Used in aerosols and 
    sprays to give rapid knockdown, killing power being increased by use of 
    a synergist.  Flushing action useful in expelling insects from hiding 
    places.  Mosquito coils give protection from biting for five to seven 
    hours, depending on mosquito density and ventilation. 

                                     PYRETHRINS

    Part 2 - Toxicology and risks      

             Common name:  pyrethrins

             Date sheet No. 11
                   
             Date issued:  March 1975


    2.1   TOXICOLOGY - MAMMALS

    2.1.1 Absorption route: Absorbed by the respiratory route and poorly 
    from the gastrointestinal tract.  Not absorbed to a significant degree 
    through the skin.  Allergic reactions may result from dermal exposure; 
    incidence is probably related to degree of refinement of extract being 
    lower as degree of refinement increases. 

    2.1.2 Mode of action: nervous system stimulation proceeding from
    excitation to convulsions to tetanic paralysis and muscular
    fibrillation. 

    2.1.3 Excretion products: oxidation and hydrolysis products are
    excreted in the urine.  Oxidation of the isobutenyl side chain of the
    chrysanthemumic acid portion of the molecule may be a more important
    route to detoxification than hydrolysis of the ester linkage.  Some
    pyrethrins are also excreted unchanged. 

    2.1.4 Toxicity, single dose 

          Oral:  LD50 rat 500-1000 mg/kg 

          Dermal:  LD50 rat. > 1800 mg/kg 

          Most susceptible species:  not known 

    2.1.5 Toxicity, repeated doses
        
          Oral:  see dietary studies
        
          Inhalation:  no information
        
          Cumulation of compound: does not accumulate in mammalian 
          tissues.

    2.1.6 Dietary studies
        
          Short-term:  no information
        
          Long-term:  no significant effect on growth and survival of 
          rats was seen when the animals were fed a maximum dietary level 
          of 5000 ppm for two years.  Slight though definite liver damage
          was seen at 1000 and 5000 ppm but not of 200 ppm.  A further 
          trial is being carried out.


            
    2.1.7 Supplementary studies of toxicity

          No information.

    2.1.8 Modifications of toxicity

    There is some doubt whether methylenedioxy synergists such as 
    piperonyl butoxide increase the toxicity of pyrethrins to mammals as 
    they do to insects. 


    2.2   TOXICOLOGY - MAN 

    2.2.1 Dangerous doses

          Single: no information

          Repeated:  no information.

    2.2.2 Observations of occupationally exposed workers

    Allergic manifestations, particularly contact dermatitis have been
    encountered in persons occupationally exposed to pyrethrum flowers or 
    crude extracts of pyrethrum. 

    2.2.3 Observations on exposure of the general population

    The general population Will not be expected to be affected by 
    pyrethrins under normal conditions of use.

    2.2.4 Observations of volunteers

    Two hundred human subjects (177 females, 23 males) were patch tested 
    for skin sensitivity and irritation using pyrethrins at 1% in water 
    simulating formulation.  This level did not produce primary irritation 
    and was not a sensitizer to human skin. 

    2.2.5 Reported mishaps
         
          None.

    2.3   TOXICOLOGY TO NON-MAMMALIAN SPECIES

    The entries in these sections are intended to draw attention to
    special risks and to give warnings of any needs for special 
    precautions. 

    2.3.1 Fish

          Toxic to fish.

    2.3.2 Birds

          Not toxic to birds.

    2.3.3 Other species

    Not toxic to bees under the conditions of use.  Toxic to cold-blooded 
    animals generally.


                                     PYRETHRINS

    Part 3 - For regulatory authorities 

               Common name:  pyrethrins

               Data sheet No. 11

               Date issued:  March 1975


    RECOMMENDATIONS ON REGULATION OF COMPOUND

    3.1   RECOMMENDED RESTRICTION ON AVAILABILITY

          (For definition of categories, see introduction.) Liquid 
          formulations over 50% category 4.   All other formulations, 
          category 5. 

        
    3.2   TRANSPORTATION AND STORAGE

          Should be transported or stored in clearly labelled leak-proof 
          containers out of reach of children, away from food and drink.  
          Avoid contact with metals other than aluminium or tin. 


    3.3.  HANDLING

          All formulations

    Pyrethrum flowers and crude pyrethrum extract may cause contact
    dermatitis and other allergic responses in some subjects.

    3.4   DISPOSAL AND/OR DECONTAMINATION OF CONTAINERS

          All formulations

    Containers may be decontaminated (for method see paragraph 4.3 on
    part 4).  Decontaminated containers should not be used for food and 
    drink.  Containers that are not decontaminated should be burned or 
    should be crushed and buried below topsoil.  Care must be taken to 
    avoid subsequent contamination of water sources. 

    3.5   SELECTION, TRAINING AND MEDICAL SUPERVISION OF WORKERS

    Persons with a history of asthma, hay-fever or allergies should be
    excluded from contact.  Warning of workers to avoid contact desirable. 
    Pre-employment and periodic medical examination not required. 

        
    3.6   ADDITIONAL REGULATIONS RECOMMENDED IF DISTRIBUTED BY AIRCRAFT
        
          No special regulations recommended.

        
    3.7   LABELLING

          Minimum cautionary statement

          None.

                
    3.8   RESIDUES IN FOOD

    3.8.1 Maximum residue levels

          The Joint FAO/WHO Meeting on Pesticide Residues (1972) has 
          recommended the following limits:

          Raw cereals.......................................       3 ppm

          Fresh fruit and vegetables, dried fruit
              and vegetables, oil seeds, tree nuts..........       1 ppm

          Dried codfish.....................................       3 ppm

                                     PYRETHRINS
                                     
    Part 4 - Prevention of poisoning in man and emergency aid

             Common name:  pyrethrins
                                        
             Data sheet No. 11
                  
             Date  issued:  March  1975


    4.1   PRECAUTIONS IN USE

    4.1.1 General

    Pyrethrins comprise a slightly toxic insecticidal extract from
    pyrethrum flowers. it is rapidly detoxified in the gastrointestinal 
    tract. 

    4.1.2 Manufacture and formulation

          T.L.V.

          ACGIH 5 mg/m3;  USSR -
        
    Pyrethrins are not "manufactured" but are obtained by extraction of 
    the pyrethrum flower.  Because of possible allergic responses contact 
    with the crude extract should be avoided as far as possible. 

    4.1.3 Mixers and applicators

    When opening the container and when mixing care should be taken to
    avoid contact with the mouth and eyes.  If necessary a facial visor and 
    gloves should be worn.  Mixing, if not mechanical, should always be 
    carried out with a paddle of appropriate length.  Splashes must be 
    washed from the skin and eyes with large quantities of water. Before 
    eating, drinking or smoking, hands and other exposed skin should be 
    washed. 

    4.1.4 Other associated workers (including flagmen in aerial operations)

    Persons exposed to pyrethrins and associated with their application 
    should observe the precautions described in 4.1.3 under "mixers and 
    applicators". 

    4.1.5 Other populations likely to be affected

          None.


    4.2   ENTRY OF PERSON INTO TREATED AREAS

    Persons can enter treated areas immediately after spraying without
    being exposed to hazardous amounts of pyrethrins.


    4.3   DECONTAMINATION OF SPILLAGE AND CONTAINERS

    Residues in containers should be emptied in a diluted form into a
    deep pit taking care to avoid ground waters.  The empty container may 
    be decontaminated by rinsing two or three times with water and 
    detergent and scrubbing the sides.  Hands should be protected during 
    this work.  Decontaminated containers should not be used for food and 
    drink. 

    Spillage should be removed as much as possible by washing the area 
    with 5% sodium hydroxide solution and then rinsing with large 
    quantities of water. 

        
    4.4   EMERGENCY AID

    4.4.1 Early symptoms of poisoning

    Contact dermatitis is by far the most common manifestation of 
    toxicity.  This effect may be due to impurities in the extract. 
    Sometimes other allergic symptoms are evident such as sneezing, serous 
    nasal discharge and nasal "stuffiness".  A few cases of extrinsic 
    asthma have been reported. 

    4.4.2 Treatment before person is seen by a physician if these symptoms 
          appear following exposure 

    If the above symptoms appear following exposure to pyrethrins the
    person should stop work, remove contaminated clothing and wash the 
    affected skin with soap and water, if available, and flush the area 
    with large quantities of water.  In mild cases of ingestion, no active 
    measures.  If oil-based materials are swallowed, give a glass of milk; 
    do not give an emetic.  In severe cases, avoid regurgitation of oil in 
    the lungs.  Give gastric lavage.  In case of respiratory symptoms, give 
    oxygen and atropine. 

                
                                     PYRETHRINS

    Part 5 - For medical and laboratory personnel  

            Common name:  pyrethrins
        
            Data sheet No. 11

            Date issued:  March 1975

    5.1   MEDICAL DIAGNOSIS AND TREATMENT OF CASES OF POISONING 

    5.1.1 General information

    Pyrethrins comprise a slightly toxic extract of the pyrethrum flower 
    which is of high insecticidal activity.  The active ingredients are 
    poorly absorbed from the gastrointestinal tract and also by the 
    respiratory route but not to a significant degree through the skin. The 
    compounds are excreted as oxidation and hydrolysis products in the 
    urine.  Allergic reactions are by far the most common toxic effect in 
    humans. 

    5.1.2 Symptoms and signs

    The most common symptom of pyrethrins toxicity is contact dermatitis.  
    This manifestation is caused by impurities in crude extract and ground 
    flowers.  There is usually mild erythematous vescicular dermatitis with 
    papules in moist areas and intense pruritis. A bullous dermatitis may 
    also develop.  Some individuals have nasal symptoms including sneezing, 
    nasal congestion, and serous discharge.  A few cases of extrinsic 
    asthma have been reported; these cases appear most common in 
    individuals with a previous history of asthma.  There have been rare 
    cases of severe anaphylactic shock with peripheral vascular collapse 
    and respiratory difficulty.  Little information is available on direct 
    toxic effect of pyrethrins; based upon animal studies, injection of 
    high doses could presumably lead to central nervous system stimulation 
    resulting in convulsions, muscular fibrillation and finally tetanic 
    paralysis. 

    5.1.3 Laboratory

    There are no practical laboratory methods for determining the degree of 
    absorption of pyrethrins.  Presence of chrysanthemumic acid or its 
    derivatives in the urine would presumably be indicative of absorption 
    but their absence cannot be construed to imply that pyrethrins have not 
    been ingested. 

    For dermatological effects positive patch tests with pyrethrins are 
    helpful in diagnosis.  Eosinophilia may accompany an acute allergic 
    reaction and mucous nasal smears should be examined for the presence of 
    eosinophils. 

    5.1.4 Treatment

    If a large quantity of pyrethrins has been ingested, unless the patient 
    is vomiting, gastric lavage should be performed using 5% sodium 
    bicarbonate solution if available. if there are convulsions or muscular 
    fibullation, diazepam should be used.  For allergic reactions, 
    antihistamines taken orally are of value. 

    5.1.5 Prognosis

    Chance of complete recovery from any toxic effect of pyrethrins is
    good, provided that there is no further direct contact with the 
    insecticide. 

    5.1.6 References of previously reported cases

    The following reference gives methods of treatment to be used in 
    cases of poisoning:

    Hayes, W. J., jr (1963) Clinical Handbook on Economic Poisons, U.S.
          Publ.  Hlth Ser. Pubi. No. 476, p. 76
     

    5.2   SURVEILLANCE TESTS

          There are no practical surveillance tests.

        
    5.3   LABORATORY METHODS

          References only are given.

    5.3.1 Detection a compound

    For analysis of pyrethrins in crops, etc., see McClellan (1964). Moore 
    (1970) discussed residues of pyrethrins in foodstuffs and referred to 
    suitable gas-chromatographic methods of analysis.  He has described a 
    method suitable for eggs, animal tissues and milk and its products 
    (1971).  A gas-chromatographic method applicable to milk and animal 
    tissues is also described by the US Food and Drug Administration (1971) 
    and quoted by Zweig & Sherma (1972).  See also Head (1967). 

                                     REFERENCES

    Head, S. W. (1967) The quantitative determination of pyrethrins by gas-
          liquid chromatography, Part I:  detection by electron capture, 
          Part II:  detection by hydrogen flame ionisation, Pyrethrum Post, 
          9(1), 12

    McClellan, D. B. (1964) In:  Zweig, G., ed., Analytical methods for 
          pesticides, plant growth regulators and food additives, Vol- II, 
          Academic Press New York and London, p. 408 

    Moore, J. B. (1970) Terminal residues of pyrethrin-type insecticides 
          and their synergists in foodstuffs, Residue Reviews, 33, 87 

    Moore, J. B. (1971) Paper submitted to the International Symposium on 
          Recent Advances in Research on Pyrethrum, The Natural 
          Insecticide, Minneapolis, USA, 30-31 August, (Unpublished) 

    US Food and Drug Administration (1971) Pesticide analytical manual, 
          Vol. II, Section 120, 128 

    Zweig, G., ed., (1972) Analytical methods for pesticides, plant growth 
          regulators and food additives, Vol.  VI, Academic Press, New York 
          and London, p. 465

	Pyrethrin (Group PIM G026)
	Pyrethrin I (CHEMINFO)
	Pyrethrin II (CHEMINFO)
	Pyrethrins (CHEMINFO)
See Also:
        Pyrethrin (Group PIM G026)