FAO Meeting Report No. PL/1965/10/1
    WHO/Food Add./27.65


    The content of this document is the result of the deliberations of the
    Joint Meeting of the FAO Committee on Pesticides in Agriculture and
    the WHO Expert Committee on Pesticide Residues, which met in Rome,
    15-22 March 19651

    Food and Agriculture Organization of the United Nations
    World Health Organization

    1 Report of the second joint meeting of the FAO Committee on
    Pesticides in Agriculture and the WHO Expert Committee on Pesticide
    Residues, FAO Meeting Report No. PL/1965/10; WHO/Food Add./26.65


    Chemical name

         d1-2-allyl-4-hydroxy-3-methyl-2-cyclopenten-1-one esters of cis
    and trans d1-chrysanthemum monocarboxylic acid.


         allyl homologue of cinerin I (see monograph on pyrethrins)

    Empirical formula

         C19H26O3 (Mol. wt. 302.4)

    Structural formula


    Relevant physical and chemical properties

         Allethrin is a synthetic pyrethroid and has chemical properties
    similar to those of pyrethrins, however it is more stable on exposure
    to heat and sunlight. Detoxification occurs by double bond
    hydrogenation of acid or allyl side chains, and it hydrolyses to
    chrysanthemic acid and 2-allyl-3-methyl-2, 4-cyclopentadienone.
    Allylrethrolone and chrysanthemic acid exist as optical isomers.
    Chrysanthemic acid also exists as geometric isomers. There are eight
    optical and geometric isomers of allethrin, all possibly present in
    the technical material. Insecticidal activity depends on the
    proportions of the various isomers present (Negherbon, 1959).


         Allethrin, alone or in combination with synergists, is used in
    many instances where pyrethrins are used for the same purpose. If
    price is reduced in the future, use may be expanded. Principal
    formulations are technical allethrin (usually 95%); 1% dust; 0.1% to
    0.6% aerosol formulations and in distillate formulations with or
    without synergists and other ingredients. When used alone it is exempt
    from tolerances for residues (in Canada and U.S.A.) except for
    post-harvest application to grain, with no limitations on use. Residue
    tolerances have been established when used in conjunction with
    synergists. It is particularly useful as dusts on a wide range of
    horticultural crops when other pesticides cannot be used close to date
    of harvest. It is recommended in synergized formulations as aerosols
    or dips for post-harvest use on fruits and berries, in storage and in
    processing plants. Agricultural premises, including milk rooms, are
    treated with allethrin aerosols or surface sprays where residues of
    other pesticides must be avoided. Direct application is approved for

    beef and dairy cattle, sheep, goats, poultry and swine. Post-harvest
    use for stored grain (surface treatment) has also been approved in
    some countries.


         Methods described for pyrethrins residue analysis are applicable
    for allethrin, except that the standard is made from allethrin. A
    colorimetric method for allethrin residues in milk and meat has been
    described (McClelland and Moore, 1958). The method is reported
    accurate to 0.1 ppm or 10 mmg/100g sample. Allethrin was not found in
    the milk of dairy cows, which had been sprayed daily for three weeks,
    or in the meat tissue of a female goat that had been sprayed daily for
    five weeks, all with a large overdose of spray. No information is
    available on the chemical nature of terminal residues in treated

    Effect on treated crop

         There is no information available on the effect of allethrin on
    treated crops.


    Acute toxicity

    Animal           Route      LD50 mg/kg           Reference

    Rat, male        Oral           920         Carpenter et al., 1950

    Rat, female      Oral           900                  "

    Mouse, male      Oral           480                  "
                              20% in Deo-base

    Mouse, male,     Oral          1580                  "
                              5% in Deo-base

    Rabbit, male     Oral          4290                   "

    Short-term studies

         Rat. Rats showed a slight decrease in growth-rate when fed
    commercial allethrin at a dietary level of 5000 ppm and a more nearly
    normal growth-rate when fed the same concentration of purified
    allethrin. A dietary level of 2500 ppm apparently produced no clinical
    effect. No examination of the liver was reported (Ambrose & Robbins,

         In another study rats that were fed allethrin for 16 weeks showed
    no gross effect at 5000 ppm but did show tremor and convulsions at 10
    000 ppm (Lehman, 1952).

         It was shown that rats (and dogs) withstand repeated inhalation
    of allethrin aerosols at many times the concentration in air that
    would possibly be reached under practical conditions. The method of
    dosage did not lend itself to measurement on the basis of milligram
    per kilogram of body-weight (Carpenter et al., 1950).

         Dog. Four male and four female dogs fed allethrin at a rate of
    50 mg/kg/day for two years showed no gross or microscopical effects.
    At higher dosage levels in other groups, there were convulsions,
    progressively shortened survival, and non-specific pathological
    changes (Lehman, 1965).

         Man. There are apparently no reports of allergy to allethrin
    comparable to those associated with pyrethrum and pyrethrins. However,
    since the types of exposure have not been the same the possibility of
    allergy to allethrin cannot be excluded.

    Comments on the experimental studies reported and evaluation

         Rats apparently tolerate prolonged feeding at a rate of 125
    mg/kg/day but the exact duration of the test was not stated.

         A dosage of 50 mg/kg/day for 2 years produced no detectable
    effect in dogs.

         Because no study of the liver seems to have been made in rats and
    because no study has been made in any species for more than half its
    life-span, it is not possible to estimate an acceptable daily intake
    for man.

    Further work required

         Long-term studies in at least two species are required in which
    particular attention is paid to possible effects on the liver. The
    metabolism of the substance should be explored.


    Ambrose, A. M. & Robbins, D. J. (1951) Fed. Proc., 10, 276

    Carpenter, C. P., Weil, C. S., Pozzani, U. C. & Smyth, J. F., jr
    (1950) Arch. industr. Hyg., 2, 420

    Lehman, A. J. (1952) Quart. Bull. Assoc. Food and Drug Officials
    U.S., 16, 47

    Lehman, A. J. (1965) Summaries of pesticide toxicity (In press)

    McClellan, D. B. & Moore, J. B. (1958) J. Agr. Food Chem., 6, 463

    Negherbon, W. (1959) Handbook of Toxicology, vol. 3, Saunders,

    See Also:
       Toxicological Abbreviations
       Allethrin (ICSC)
       Allethrin (UKPID)