PESTICIDE RESIDUES IN FOOD - 1979

    Sponsored jointly by FAO and WHO

    EVALUATIONS 1979

    Joint meeting of the
    FAO Panel of Experts on Pesticide Residues
    in Food and the Environment
    and the
    WHO Expert Group on Pesticide Residues
    Geneva, 3-12 December 1979

    1,2 - DICHLOROETHANE

    Explanation

    This fumigant pesticide was evaluated at the meeting in 1965 (FAO/WHO
    1965c) and reviewed in 1967 and 1971.  Prior to the 1971 meeting, it
    was listed as ethyclene dichloride.  The report of the 1978 Meeting
    made reference to problems caused in member countries of FAO and WHO
    by the use of certain fumigants and recommended re-evaluation of
    1,2-dichloroethane.

    RESIDUES IN FOOD AND THEIR EVALUATION

    The report of the 1971 Meeting to which reference should be made,
    contained a statement of general principles relating to residues of
    fumigants.

    USE PATTERN

    Post-Harvest Use

    1,2-dichloroethane (Ethylene dichloride, EDC) has been widely used as
    a grain fumigant in post-harvest storage.  Because of its
    flammability, it is always mixed with other less flammable liquids in
    grain fumigant formulations, the most common being carbon
    tetrachloride.  The latter also acts as a fumigant and carrier to aid
    downwards distribution of EDC which otherwise tends to adsorb heavily
    in the upper grain layers.  EDC has more effective insecticidal
    properties than carbon tetrachloride and until recently it has also
    been considered safer for semi-skilled or farmer application than the
    more acutely toxic grain fumigants such as methyl bromide and
    phosphine.  There has therefore been considerable application of
    liquid grain fumigants containing EDC by farmers and their employees
    and by grain storage personnel.

    Recent reports on tumour production in rats and mice (National Cancer
    Inst. 1978) due to feeding EDC, albeit at high dosage levels, have led
    to reconsideration of the use pattern of EDC in some countries, and
    for example, in the UK a decision has been taken to withdraw grain
    fumigant mixtures containing EDC from non-professional pest control
    use.  This decision is based on the promise that professional pest
    control operators are in a better position to monitor and guard
    against breathing the fumigant vapours during operations than
    unskilled personnel.  In fact the amount of vapour that could be
    ingested say in the course of a day at the present Threshold Limit
    Value (50 ppm) is considerably in excess of that which could
    conceivably be consumed as a residue of the fumigant in food.

    RESIDUES ARISING FROM SUPERVISED TRIALS

    Post-harvest use

    The 1971 Meeting noted results of work carried out in the Netherlands
    (Wit et al. 1969) showing that wheat aired for several weeks after
    fumigation with a mixture-of 1,2-dichloroethane, carbon tetrachloride,
    1-2-dibromoethane contained 10-40 mg/kg EDC and that on milling the
    amounts found in white flour ranged between 2 and 11 mg/kg with
    residues in bread generally below 0.05 mg/kg.

    Berck (1974) determined residual fumigants after treating a farm bin
    containing 27 tons of wheat with a mixture of EDC, carbon
    tetrachloride and 1,2-dibromoethane (30:63:7 w/w) at 0.661/tonne.
    Although residues of carbon tetrachloride and 1,2-dibromoethane were
    detected, Berck was unable to find any residual EDC in the wheat.  It
    is assumed that this was due to lack of analytical method sensitivity.
    Cassells, Scudamore and Heuser (1975) found that after exposing wheat
    and maize to EDC at a concentration-time product (cxt) of 1970 mg h/l
    with carbon tetrachloride at a cxt of 1250 mg h/l by application of a
    3:1 v/v EDC/carbon tetrachloride mixture, resulting EDG residue levels
    immediately after removal of the cereal grains from the chamber were
    about 450 mg/kg for wheat and 800 mg/kg for maize.  These levels
    greatly exceeded the residue levels of carbon tetrachloride found (40
    and 170 mg/kg respectively) indicating heavier sorption of EDC than
    carbon tetrachloride at equivalent dose levels.  After 28 days airing
    EDC residues were reduced to 70-150 mg/kg in wheat and 20-110 mg/kg in
    maize, indicating a more rapid loss of residual fumigant from maize.
    After 12 weeks airing, residue levels were 8-40 mg/kg for wheat and
    4-10 mg/kg for maize.  EDC aired from maize more rapidly at 25°C than
    at 10°C but with wheat the effect of temperature was less marked.

    FATE OF RESIDUES

    As indicated by trials reported above, the major route of EDC residue
    reduction in stored fumigated produce is by volatilization.  No
    reaction products in plant products have been reported so far as is
    known.

    In the rat EDC has been reported (Nachtomi et al., 1965) to react to
    give mercapturic acid and S-(ß-hydroxythyl)N-acetyl cysteine.  These
    reaction products were also found when 1,2-dibromoethane was
    administered.  Alumot et al. (1975) in 2-year feeding studies in the
    rat found only a slight increase in liver fat at very high doses and
    proposed a no-effect level of 25 mg/kg (rat) and 250 mg/kg in the
    diet.  In 2-year tests on laying hens with EDC at 250 and 500 mg/kg in
    the diet, Alumot et al (1975) reported a decrease in egg weight from
    month 4, and egg production was affected at 500 mg/kg.  A tolerance of
    100 mg/kg in feed and ADI of 5 mg per kg body weight was suggested for
    laying hens and a 250 mg/kg residue tolerance and an ADI of 25 mg per
    kg body weight for growing chicks and cocks.

    EVIDENCE OF RESIDUES IN FOOD IN COMMERCE OR AT CONSUMPTION

    Selective monitoring of cargoes of wheat and other grains imported
    into the U.K. during 1978-79 showed that all 267 wheat samples
    contained less than 5.0 mg/kg of residual 1,2-dichloroethane.  Of 323
    samples of miscellaneous other grains, two samples of imported rice
    alone contained residues between 5 and 10 mg/kg, and no samples of any
    grain exceeded this level (Fishwick and Rutter 1979).  Monitoring of
    barley, rice, rye and wheat shipments imported into the Netherlands
    (184 samples) revealed no residue levels exceeding 0.1 mg/kg (Admiral
    et al., 1979).

    METHODS OF RESIDUE ANALYSIS

    Residual 1,2-dichloroethane in cereal grains and milled products and
    other stored products can be determined by gas chromatography
    following cold extraction (Heuser and Scudamore, 1969) or following
    continuous solvent co-distillation from a suspension using toluene and
    boiling water (Beilorai and Alumot, 1966) or by microdistillation
    under vacuum (Page and Kennedy, 1975).  For the method of Heuser and
    Scudamore (1969) a limit of detection of 1-5 mg/kg was claimed and for
    the method of Beilorai and Alumot (1966) 0.1-1.0 mg/kg.  A head-space
    analytical technique (Greve and Hogendoorn 1979) has claimed a
    sensitivity of 0.1 mg/kg.

    NATIONAL MRLs REPORTED TO THE MEETING

    A number of countries including Australia, Canada and the United
    States have taken the view that no residue will be present in foods
    ready for consumption when 1,2-dichloroethane is applied to raw
    commodities and require that residues must not be present (Australia)
    or exempt foods from a tolerance (eg. USA).  An EEC draft directive in
    1976 proposed a limit of 10 mg/kg in cereals put into circulation for
    human consumption.  Netherlands' limits were reported to the meeting
    as: cereals, 40 mg/kg; flour, 10 mg/kg.

    APPRAISAL

    1,2-dichloroethane (EDC) in used as a cereal grain fumigant in a
    number of countries, generally in admixture with another liquid
    fumigant used as a flame suppressant.  It in generally most effective
    in the control of insect pests in the upper 4-6 metres of grain bulks.
    Because of its relative low acute toxicity, it has been used in
    operations by farmers and unskilled persons as well as by pest control
    operators in both technologically advanced and developing countries.
    No breakdown products in grain have been identified, and the loss of
    residue by volatilization follows a regular pattern depending on
    amount of air movement, moisture content and temperature of the grain.

    Very little if any of the residue persists through to bread baked from
    fumigated wheat.  As no ADI has been allocated, it was the opinion of
    the meeting that existing guideline levels represent a realistic

    appraisal of residue levels which need not be exceeded at the specific
    stages of sampling if normal fumigation procedures are carried out.

    There is a need for analytical methods with greater sensitivity which
    are suitable for determining residue levels below 0.1 mg/kg.  If the
    compound is to continue in use as a fumigant, some consideration must
    be given to the selection of substitute flame-suppressant additives,
    since the most common one used today, carbon tetrachloride (q.v.) has
    been the subject of many adverse toxicological findings.

    EVALUATION

    The following maximum residue levels may be found after good
    fumigation practice.  They are recorded as Guideline Levels:

    Cereal grains                           50a
    Milled cereal products
    (to be subjected to baking
    or cooking)                             10
    Bread and other cereal products          0.1b*

    FURTHER WORK OR INFORMATION

    Desirable:

    Development of residue analytical methods capable of determining <0.1
    mg/kg in prepared foods.

    REFERENCES

    Admiral, P., de Bruin, A., Cat, H., Dornseiffen, J., Greve, P.A.,
    Hogendoorn, E.A., and Mulders, E.J. - Rpt. No. 95/79, (1979) Rijts
    Instituut voor de Volkagezondheid, Bilthoven, Netherlands.

    Alumot, E., Meidler, M., Holstein, P. and Herzberg, M. - Tolerance and
    acceptable daily intake of ethylene dichloride in the chicken diet.
    Food Cosmet. Toxicol. 14, (2). 111-114.

    Beilorai, R. and Alumot, E. - Determination of residues of a fumigant
    mixture in cereal grain by electron capture GLC.  J. Agric. Fd. Chem.
    14, 622

    a  To apply at point of entry into a country, and in the case of
    cereal grains for milling, if product has been freely exposed to air
    for a period of at least 24 hours;

    b  To apply to commodity at point of retail sale or when offered for
    consumption.

    *  At or about the limit of determination.

    Berck, B. - Fumigant residues of carbon tetrachloride, ethylene
    dichloride and ethylene dibromide in wheat flour bran, middlings and
    bread. Agric. and Food Chem. 22, (6) 977.

    Cassels, D.R., Scudamore, K.A. and Heuser, S.G. - Desorption of
    1,2-dichloroethane and carbon tetrachloride from cereal grains after
    fumigation.  (1975) Unpublished report Pest Infestation Control Lab.,
    U.K.

    Fishwick, F.B. and Rutter, I.R. - U.K. Survey of pesticide residues in
    cereals. (1979) Unpublished, MAFF Agric. Science, Slough Lab., U.K.

    Heuser, S.G. and Scudamore K.A. - Determination of fumigant residues
    in cereals and other foodstuffs: a multi-detection scheme for gas
    chromatography of solvent extracts. J. Sci. Fd. Agric. 20, 566.

    Nachtomi, E. Alumat, E. and Bounty, A. - The metabolism of ethylene
    dibromide and related compounds in the rat. Israel J. Chem., 3, 119.

    National Cancer Inst. - Report: Bioassay of 1,2-Dichloroethane for
    possible carcinogenicity. Bull. Brit. Ind. Biol. Res. Assoc. 1978, 17
    (8) 445.

    Page, B.D. and Kennedy, M. - Determination of methylene chloride,
    ethylene dichloride and trichloroethylene as solvent residues in spice
    oleoresins using vacuum distillation and electron-capture gas
    chromatography., J. Ass. Off. Agr. Chem. 58, 1062.

    Wit, S.L  Bessemer, A.F.H., Das, H.A., Goedkoop, W., Loosjes, F.E. and
    Mappelink, E.R. - Results of an investigation of the regression of
    three fumigants (carbon tetrachloride, ethylene dibromide and ethylene
    dichloride) in wheat during processing to bread. Lab. Rept. 36/69.
    National Inst. Publ. Health, Utrecht, Netherlands.
    
    See Also:
       Toxicological Abbreviations
       Dichloroethane, 1,2- (EHC 176, 1995, 2nd edition)
       Dichloroethane, 1,2- (EHC 62, 1987, 1st edition)
       Dichloroethane, 1,2- (ICSC)
       Dichloroethane, 1,2- (FAO Nutrition Meetings Report Series 48a)
       Dichloroethane, 1,2- (WHO Food Additives Series 30)
       Dichloroethane, 1,2-  (WHO Pesticide Residues Series 1)
       Dichloroethane, 1,2- (CICADS 1, 1998)
       Dichloroethane, 1,2- (IARC Summary & Evaluation, Volume 71, 1999)