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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/77.28

                                                      ORIGINAL: ENGLISH






    DATA SHEETS ON PESTICIDES No. 28

    METHOXYCHLOR






         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.

                               CLASSIFICATION:

                               Primary Use:      Insecticide

                               Secondary Use:    Acaricide

                               Chemical Group:   Organochlorine compound

                               Date Issued:

    1.  GENERAL INFORMATION

    1.1  COMMON NAME:

    Methoxychlor (ISO)

    1.1.1  Identity:

    1,1'-(2,2,2-trichloroethylidene)-bis[4-methoxybenzen]

    1.1.2  Synonyms:

    DMDT OMS-466
    Dimethoxy-DT
    Dianisyl trichloroethane

    CHEMICAL STRUCTURE

    Local synonyms:

    1.2  SYNOPSIS

    An organochlorine insecticide of low mammalian toxicity, chemically
    similar to DDT but, being more biodegradable, much less liable to
    accumulate in body tissues and environment. It is of low hazard to
    man.

    1.3  SELECTED PROPERTIES

    1.3.1  Physical characteristics

    When pure a colourless crystalline solid m.p. 89°C. Technical
    methoxychlor has a fruit-like odour, and consists of up to 12%
    o,p'-isomer, the balance being the insecticidally active
    p,p'-isomer. Setting point of technical material 77°C.

    1.3.2  Solubility

    Virtually insoluble in water but readily soluble in most aromatic
    solvents, trichloroethane 70 g/100 ml at 20°C; methylene chloride
    133 g/100 ml at Moderately soluble in alcohol, petroleum oils.

    1.3.3  Stability

    Relatively stable toward heat and oxidation and less readily
    dehydrochlorinated than DDT by alcoholic alkali; it is stable toward
    ultra-violet light susceptible to dehydrochlorination by heavy metal
    catalysts.

    1.3.4  Vapour pressure (volatility)

    No information.

    1.4  AGRICULTURE, HORTICULTURE AND FORESTRY

    1.4.1  Common formulations

    Wettable powders 25% and 50%. Emulsifiable concentrates 2 lb per US
    gall. Compatible in mixtures except with highly alkaline materials.

    1.4.2  Pests mainly controlled

    Wide range of larval and insects affecting fruit, vegetables, forage
    crops, livestock - range similar to DDI. It is not aphicidal or
    acaricidal, but effective against livestock parasites (ticks, lice,
    etc.).

    1.4.3  Use pattern

    Effective for control of susceptible flies in dairy barns.

    1.4.4  Unintended effects

    Phytotoxic to some curcubits.

    1.5  PUBLIC HEALTH PROGRAMMES:

    Used against sensitive mosquitos as a 3% space spray indoors
    increased to 5% for residual activity, and applied by air by high
    and low volume spray in some countries.

    1.6  HOUSEHOLD USE:

    Active against sensitive houseflies, mosquitos, cockroaches, lice,
    etc.

    2.  TOXICOLOGY AND RISKS

    2.1  TOXICOLOGY - MAMMALS

    2.1.1  Absorption route

    Absorbed from the gastrointestinal tract as well as by inhalation
    or, in oily solutions, through the intact skin.

    2.1.2  Mode of action

    Central nervous stimulant, producing hyperactivity, tremors and
    convulsions.

    2.1.3  Excretion products

    Methoxychlor is metabolised in the liver; possibly the major route
    of excretion is by the bile and the faeces as water soluble
    hydroxyphenyl metabolites.

    2.1.4  Toxicity, single dose

    Oral:   LD50 rat* 6000 mg/kg
                 rat (F) 5000 mg/kg

    Dermal:  LD50 rat (M) and rat (F) 6000 mg/kg   (*sex not stated)
    Dermal:  LD50 rabbit*  6000 mg,/kg

    Most susceptible species:  cattle - maximum dose 500 mg/kg

    2.1.5  Toxicity, repeated doses

    Oral: Rabbits were dosed daily with 200 mg/kg of methoxychlor. All
    the animals died within four to 15 days with an average of 50% for
    the group at eight days. Diarrhoea and anorexia were observed prior
    to death and at post-mortem there was evidence of fatty degeneration
    of the liver and the heart. Dogs were unaffected at 20, 100 and
    300 mg/kg/day for one year.

    Inhalation: Rats exposed to 10% methoxychlor dust for two hours
    daily for a period of five weeks showed evidence of toxicity.

    Dermal: Repeated application of methoxychlor in rabbits as a 30%
    solution in kerosene at 2000 and 3000 mg/kg for 13 weeks, five days
    a week, caused no deaths at 2000 mg/kg, but reduced weight gain was
    observed. At 3000 mg/kg, one out of three animals died after eight
    days. One rabbit at each dose level developed foot paralysis. At
    post-mortem there was evidence of diffuse fatty degeneration of the
    liver.

    Cumulation of compound: Methoxychlor shows a slight tendency to
    accumulate in the body fat; levels reach a plateau after four weeks
    exposure and the stored material is mobilized within two to four
    weeks of the ending of exposure.

    2.1.6  Dietary studies

    Short-term: 30 000 mg methoxychlor/kg feed in the diet killed
    eight out of 10 rats (male and female) in 45 days. Female rats died
    within a week at 10 000 mg/kg feed in diet and 5000 mg/kg feed
    produced toxic effects without deaths over a period 16 weeks.
    10 000 mg/kg feed produced toxic effects in dogs in the course of
    six months.

    Long-term: Rats were maintained for two years on a diet containing
    2.5 ppm, 200 ppm and 1600 ppm methoxychlor. The two lower doses had
    no effect. At 1600 ppm there was some growth reduction, but life
    span was unaffected.

    2.1.7  Supplementary studies of toxicity

    Carcinogenicity: Methoxychlor was tested by the oral route in the
    rat. Three experiments, including one employing dietary levels of up
    to 1600 ppm, provided no evidence of carcinogenicity. No tumours
    were reported in limited skin application and subcutaneous injection
    (single dose) studies.

    Teratogenicity:  No information available.

    Mutagenicity:  No information available.

    2.1.8  Modification of toxicity

    Liver damage prior to exposure interferes with the metabolism of
    methoxychlor and increases its toxicity. Pre-treatment of rats with
    carbon tetrachloride increased toxicity and the resultant tremors
    and convulsions were more apparent than with non-pretreated animals;
    under these conditions deposition of methoxychlor in liver and fat
    is increased 10 to 100 times.

    2.2  TOXICOLOGY - MAN

    2.2.1  Absorption

    Methoxychlor may be absorbed from the gastrointestinal tract, by
    inhalation, or, in oily solutions, through the skin.

    2.2.2  Dangerous doses

    Single: No information.

    Repeated: No information but see 2.2.5 below.

    2.2.3  Observations of occupationally exposed workers

    Investigations were carried out on a group of 51 persons employed in
    producing chlorinated insecticides (DDT, HCH, dieldrin,
    methoxychlor) to detect changes in enzyme activity in the blood. The
    results of enzymatic determinations in the group show that the
    activity of red blood cell acetylcholinesterase, serum aldolase and
    alkaline phosphatase was significantly higher in this group than in
    the control group. No significant differences were observed [n the
    activity of serum aminotransferases cholinesterase and lactate
    dehydrogenases isozymes.

    2.2.4  Observations on exposure of the general population

    No information available.

    2.2.5  Observations of volunteers

    Male volunteers were fed 0.5, 1.0 and 2.0 mg/kg day for eight weeks.
    Haematology, biochemistry and urinanalysis and biopsies of fat,
    testis, bone marrow, liver and small intestine were all normal.

    2.2.6  Reported mishaps

    None.

    2.3  TOXICITY TO NON-MAMMALIAN SPECIES

    2.3.1  Fish

    96 hour TL50 for yellow perch: 30 µg/l. Half life in water varies
    1-18 days.

    2.3.2  Birds

    Slightly toxic (greater than 2000 mgms/kilo)

    2.3.3  Other species

    No information.

    3.  FOR REGULATORY AUTHORITIES - RECOMMENDATIONS ON REGULATIONS
        OF COMPOUND

    3.1  RECOMMENDED RESTRICTIONS ON AVAILABILITY

    (for definition of categories, see introduction)

    All formulations above 10%, Category 4

    All formulations 10% or less, Category 5

    3.2  TRANSPORTATION AND STORAGE

    All formulations in Category 4 - Should be transported or stored in
    clearly labelled, rigid and leakproof containers. No food or drink
    should be transported or stored in the same compartment. Storage
    should be under lock and key and secure from access by unauthorized
    persons and children.

    Formulations in Category 5 - Should be transported in clearly
    labelled, leakproof containers, out of reach of children and away
    from food and drink.

    3.3  HANDLING

    All formulations in Category 4 - Protective clothing should be used
    by those handling concentrates (see part 4). Adequate washing
    facilities should be available close at hand. Eating, drinking and
    smoking should be prohibited during handling and before washing
    after handling.

    Formulations in Category 5

    No special facilities other than those needed for handling of any
    chemical need to be required during handling.

    3.4  DISPOSAL AND/OR DECONTAMINATION OF CONTAINER

    Decontamination of containers is probably not practical. Container
    must either be burned or crushed and buried below the topsoil. Care
    must be taken to avoid subsequent contamination of water sources.

    3.5  SELECTION, TRAINING AND MEDICAL SUPERVISION OF WORKERS

    Formulations in Category 4 - Pre-employment medical examination for
    workers desirable. Workers suffering from active hepatic or renal
    disease should be excluded from contact. Training of workers in
    techniques to avoid contact essential.

    Formulation in Category 5 - Warning of workers to minimize contact
    essential.

    3.6  ADDITIONAL REGULATIONS RECOMMENDED IF DISTRIBUTED BY AIRCRAFT

    All formulations - Pilot and loaders should have special training
    in application methods and early symptoms of poisoning. Flagmen, if
    used, should wear overalls and be located well away from the
    dropping zone.

    3.7  LABELLING

    Formulations in Category 4 - Minimum cautionary statement

    "Methoxychlor is an organochlorine insecticide. It is poisonous if
    swallowed. Keep the material out of the reach of children and well
    away from foodstuffs, animal feed and their containers."

    Formulations in Category 5 - Minimum cautionary statement

    "This formulation contains methoxychlor, an organochlorine
    insecticide which is poisonous if swallowed. Keep the material out
    of the reach of children and well away from foodstuffs, animal feed
    and their containers."

    3.8  RESIDUES IN FOOD

    Maximum residue levels have not yet been recommended by the joint
    FAO/WHO Meeting on Pesticide Residues.

    4.  PREVENTION AND POISONING IN MAN AND EMERGENCY AID

    4.1  PRECAUTIONS IN USE

    4.1.1  General

    Methoxychlor is an organochlorine insecticide of low toxicity which
    is moderately accumulative and can act as both an acute and chronic
    poison. It can be absorbed by mouth, by inhalation and in liquid
    formulations through the intact skin. It is important that
    concentrated formulations be washed immediately from the skin and
    eyes.

    4.1.2  Manufacture and formulation

    TLV: (ACGIH) 10 mg/m3. Although volatility is vapour and dusts
    should be controlled, preferably by mechanical means. Protective
    equipment for the skin and respiratory protection is usually
    necessary.

    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. The applicator
    should avoid working in spray mist and avoid contact with the mouth.
    Splashes must be washed immediately from the skin or 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 methoxychlor and associated with its application
    should observe the precautions described above in 4.1.3 under
    "mixers and applicators".

    4.1.5  Other populations likely to be affected

    With good agricultural practice subject to 4.2 below, other
    populations should not be exposed to hazardous amounts of
    methoxychlor.

    4.2  ENTRY OF PERSONS INTO TREATED AREAS

    The general population should be kept out of treated areas for at
    least one day.

    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 contamination of ground water.
    Decontamination of containers in order to use them for other
    purposes should not permitted. Spillage should be removed by washing
    with large quantities of water.

    4.4  EMERGENCY AID

    4.4.1  Early symptoms of poisoning

    No reported cases, but would probably include headache, nausea,
    vomiting, dizziness, diarrhoea and weakness and possibly also
    disturbances equilibrium, tremor and convulsions.

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

    The person should stop work immediately, remove contaminated
    clothing, wash the affected area with soap and water, if available,
    and flush the area with large quantities of water. If swallowed,
    vomiting should be induced if the person is conscious. Patient
    should be removed to a shaded area and kept in conditions as quiet
    as possible until medical help arrives.

    5.  FOR MEDICAL AND LABORATORY PERSONNEL

    5.1  MEDICAL DIAGNOSIS AND TREATMENT IN CASES OF POISONING

    5.1.1  General information

    Methoxychlor is an organochlorine insecticide of low toxicity. It is
    absorbed from the gastrointestinal tract and by inhalation. To a
    lesser extent it may be absorbed by the intact skin, especially
    liquid formulations. Its mode of action is as a CNS stimulant
    causing tremors and convulsions. The toxic dose from repeated
    exposure is well below the dangerous acutely toxic dose.

    5.1.2  Symptoms and signs

    No cases of human poisoning recorded, however the symptoms would
    probably include headache, nausea, diarrhoea, and weakness, vomiting
    and possibly disturbances of equilibrium, tremor and convulsions.

    5.1.3  Laboratory

    Direct measurement of methoxychlor in blood and favour or its
    metabolites in urine and faeces confirms exposure.

    5.1.4  Treatment

    Rapid gastric lavage should be performed using 5% sodium bicarbonate
    if available. In case of skin contamination, the exposed area should
    be washed with soap and water. If the compound has entered the eyes
    they should be washed with isotonic saline or water.

    Treatment is mainly symptomatic and there is no specific antidote.
    Soluble barbiturates, diazepam or paraldehyde should be used if
    tremors or convulsions are evident.

    5.1 5  Prognosis

    If the acute toxic effect is survived the chances of complete
    recovery are good.

    5.1.6  References of previously reported cases

    No information of cases available.

    5.2  SURVEILLANCE TESTS

    There are no readily available field techniques to determine the
    degree of exposure.

    5.3  LABORATORY METHODS

    5.3.1  Detection and assay of compounds

    Suitable methods for the analysis of methoxychlor will be found in:
    Analytical Methods for Pesticides. Plant Growth Regulators and Food
    Additives, Zweig, vol. II, Insecticides, p. 303-312. Methoxychlor,
    W. K. Lowen et al., 1964, Academic Press, New York and London. The
    method of choice is by dehydrohalogenation and sulfonation as
    described by Fairing and Warrington, 1950, Advances in Chem. Ser.,
    1, 260. General notes on clean-up procedures and analytical
    techniques can be found in: General Analytical Information,
    Pesticide Residues, History Alternatives and Analysis J. Thomson and
    Chemistry, Lecture Series, 1966, No. 3. For analysis in the presence
    of fat see Claborn H. V and Beckman, H. F. Anal Chem., 1952, 24,
    220.

    5.3.2  Other tests in cases of poisoning

    None.

                                    * * *

See Also:
        Methoxychlor (IARC Summary & Evaluation, Volume 20, 1979)
        Methoxychlor (IARC Summary & Evaluation, Volume 5, 1974)
        Methoxychlor (ICSC)