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naled (Dibrom) Chemical Fact Sheet 6/83

                        CHEMICAL FACT SHEET FOR:



                      1.  DESCRIPTION OF CHEMICAL

- Generic Name:  1,2-dibromo-2,2-dichloroethyl dimethyl phosphate
- Common Name:  naled
- Trade Name:  Dibrom
- EPA Shaughnessy Code:  034401
- Chemical Abstracts Service (CAS) Number:  300-76-5
- Year of Initial Registration:  1959
- Pesticide Type:  Insecticide - acaricide
- Chemical Family:  Organophosphate
- U.S. and Foreign Producers:  Chevron Chemical Co.


- Application sites:  field, vegetable, and orchard crops; livestock and
  poultry, and their surroundings; greenhouses; forest and wasteland;
  agricultural, domestic, medical, and commercial establishments; and
  urban and rural outdoor areas (mosquito control).
- Types of formulations:  dusts, impregnated materials, emulsifiable
  concentrates, soluble concentrates, liquid, and ready-to-use liquids.
- Types and methods of application:  aerial and ground as a spray or
  dust; fogging; ultra low volume (ULV).
- Application rates:  varies from .01 to 10 lbs/acre
- Usual carriers:  Confidential Business Information
- Efficacy review results:  none conducted

                        3.  SCIENCE FINDINGS

Chemical Characteristics

     Manufacturing-use naled is a light, straw-colored, oily liquid with 
a slightly pungent odor.  The pure compound is a white, low melting 
point solid.  The boiling point for pure naled is 120 degrees C at 0.5 
mm Hg, and the vapor pressure is 2 x 10-4 mm Hg at 20 degrees C.  The 
empirical formula is C4H704PBr2C12, and the molecular weight is 381.  
Naled has limited solubility in aliphatic solvents, is highly soluble in 
oxygenated solvents such as ketones and alcohols, and has a low 
solubility in water.

Toxicological Characteristics

- Current available toxicology studies on naled are as follows:
  - Acute oral LD50: rat, 222-389 mg/kg; mouse, 160 mg/kg (Toxicity
    Category II)
  - Acute dermal LD50:  rabbit, 390-1100 mg/kg; rat, 800 mg/kg
   (Toxicity Category II)
 - Primary eye irritation:  corneal opacities 7 days + (Toxicity
   Category I)
 - Primary dermal irritation:  rabbit, PIS 5.8 - 5.92; human
   volunteers, severe irritation
 - Subchronic feeding:  cholinesterase NOEL in dog, 0.25 mg/kg/day
- Additional data are needed to fully assess the toxicity of naled.
- Major routes of exposure:  Application by fog and mist sprayers, and
  aircraft increases the potential for exposure to humans and non-
  target organisms to naled.  Human exposure to naled during mixing,
  handling, application, and reentry operations would be minimized by
  the use of approved respirators and other protective clothing.
  However, data are not available to fully assess such exposures.  PR
  Notice 83-2 sets forth current Agency policy on required label
  changes for reentry and farm worker safety.  A reentry level of 24
  hours for the use of naled on crops is required.

Physiological and Biochemical Behavioral Characteristics

- Mechanism of pesticidal action:  stomach and/or contact poison
- Metabolism and persistence in plants and animals:  No naled or DDVP
  was detected in tissues or milk of two goats dosed with naled at 107
  ppm in three equal daily portions and sacrificed on day -4.  The
  limits of detection were 0.05 ppm for tissues and 0.005 ppm for
  milk.  The dose is estimated to be about twenty times that which
  would normally occur in the goats' diet.
- Residues were non-detectable (<0.01 ppm) in milk from Holstein cows
  subject to body and premise sprays for 14 days with the 7.2 lb/gal
  EC formulation.

Environmental Characteristics

- Naled degrades fairly rapidly with half-lifes of <=8 hours in soils
  and <=25 hours in aqueous solutions.  Dichlorvos (DDVP), a metabolite
  of naled, is also rapidly degraded in soil with half-lifes
  of 2.3 - 8.0 hours.  Naled exhibits low to intermediate mobility in
  soils, whereas dichlorvos is intermediately mobile to mobile.
- Limited data indicate that the rapid dissipation and relatively low
  mobility of naled and intermediate mobility of dichlorvos in soil
  will mitigate contamination of groundwater.
- Naled did not accumulate in whole body tissues of killifish exposed
  to naled in static bioassay tests.  Naled was not detected (<0.02
  ppm) in any fish tissue samples taken over the 7-day test period.
  The degradate dichlorvos was found at a maximum concentration of
  0.04 ppm, approximately twice the concentration in corresponding
  water samples, 1 hour after treatment, but was not found (<0.01 ppm)
  in tissue samples taken after 24 hours.  Naled half-life in water
  samples was <24 hours.  Dichlorvos was found in all water samples,
  at a maximum concentration of 0.02 ppm after 24 hours, but <0.01 ppm
  was found in samples taken at the end of the test period.
- In summary, naled and its degradate dichlorvos dissipate rapidly in
  aerobic soils.  Naled exhibits low to intermediate mobility in
  soils, whereas dichlorvos is intermediately mobile to mobile.
  Mobility appears to be related to soil organic matter content.
  Naled degrades rapidly in aqueous solution, with rates increasing at
  higher temperatures and pH's.  Naled also rapidly degrades in sewage
  water to dichlorvos and dichloroacetaldehyde.  Neither naled nor
  dichlorvos accumulate in fish tissues.  In conclusion, naled does
  not appear to represent an environmental hazard based on the
  aforementioned data which indicate very rapid degradation and
  extremely low bioaccumulation potential.
- However, available data are insufficient to fully assess the
  environmental fate of naled.

Ecological Characteristics

- Currently available ecological effects studies on naled are as
  - Avian oral LD50:  37-65 mg/kg
  - Avian dietary LC50:  2117-2724 ppm
  - Freshwater fish LC50:  160-900 ppb
  - Acute LC50 freshwater invertebrates:  0.3 ppb
- Based on studies available to assess hazards to wildlife and aquatic
  organisms, naled is characterized as very highly toxic to bees and
  aquatic invertebrates.  It is moderately to highly toxic to fish and
  slightly toxic to upland game birds and waterfowl.  Insufficient
  data are available to assess the toxicity of naled to estuarine and
  marine organisms.
- Label precautionary statements required by the Standard should
  reduce the hazard to fish and other wildlife.  After data gaps are
  filled, the potential hazards to terrestrial and aquatic species
  will be better defined, and additional labeling requirements may be

Tolerance Assessment

- The following tolerances are established for combined residues of
  naled and 2,2-dichlorovinyl dimethyl phosphate (DDVP), expressed as
  naled, in or on raw agricultural commodities resulting from the
  application of naled formulations to growing crops, livestock, and
  poultry (40 CFR 180.125.)

   Commodity                                      Tolerance (ppm)

   Almonds (hulls, nuts)                                0.5
   Beans (dry, succulent)                               0.5
   Broccoli                                             1.0
   Brussels sprouts                                     1.0
   Cabbage                                              1.0
   Cattle (fat, meat, meat by-products)                 0.05
   Cauliflower                                          1.0
   Celery                                               3.0
   Citrus fruits (grapefruit, lemons, oranges,          3.0
   Collards                                             3.0
   Cottonseed                                           0.5
   Cucumbers                                            0.5
   Eggplant                                             0.5
   Eggs                                                 0.05
   Goats (fat, meat, meat by-products)                  0.05
   Grapes                                               0.5
   Grasses, forage                                     10.0
   Hogs (fat, meat, meat by-products)                   0.05
   Hops                                                 0.5
   Horses (fat, meat, meat by-products)                 0.05
   Kale                                                 3.0
   Legumes, forage                                     10.0
   Lettuce                                              1.0
   Melons                                               0.5
   Milk                                                 0.05
   Mushrooms                                            0.5
   Peaches                                              0.5
   Peas (succulent only)
   Peppers                                              0.5
   Poultry (fat, meat, meat by-products)                0.05
   Pumpkins                                             0.5
   Rice                                                 0.5
   Safflower seed                                       0.5
   Sheep (fat, meat, meat by-products)                  0.05
   Spinach                                              3.0
   Squash (summer, winter)                              0.5
   Strawberries                                         1.0
   Sugar beets (roots, tops)                            0.5
   Swiss chard                                          3.0
   Tomatoes                                             0.5
   Turnips (tops)                                       3.0
   Walnuts                                              0.5
   All other raw agricultural commodities               0.5
   except those listed. (To account for area pest
   [fly and mosquito] control.)

- The components of the residue metabolism in plants which are of
  concern are naled and DDVP. and to a lesser extent, organic bromide.
  Tolerances exist for combined residues of naled and DDVP (expressed as
  naled) and should continue to reflect the concern for these two
  components. The components of the residue from the metabolism in
  animals which are of concern are the same as those in or on plants.
  However, data on the metabolism of naled in poultry are missing, and
  this constitutes a data gap. The Theoretical Maximum Residue
  Contribution (TMRC) is 1.1021 mg/day as naled, assuming a 1.5 kg diet,
  based on the tolerances and food factors for all of the commodities
  for which U.S. tolerances are established.  No Acceptable Daily Intake
  (ADI) or Maximum Permissible Intake (MPI) figures have been
  established, due to the absence of acceptable toxicological data for
  naled.  Reassessment of the established naled tolerances must await
  receipt and evaluation of the required data. Although the Agency is
  unable to complete a tolerance reassessment for naled because of a
  number of residue chemistry and toxicology data gaps, the Agency has
  concluded. based on available data, that no changes in present
  tolerances are necessary at this time.  The Agency has also considered
  the residues of inorganic bromide, resulting from the use of naled on
  crops and in meat, milk, poultry, and eggs, and does not anticipate
  these residues to be of toxicological concern, and no additional
  residue data on inorganic bromides are needed.
- However, the Agency is concerned about organic brominated
  metabolites of naled and its impurities.  Accordingly, additional
  data on this organic bromide in plants and animals are being

Summary Science Statement

- Available acute oral and dermal LD50 data place naled in Toxicity
  Category II and Toxicity Category I based on primary eye irritation
- Naled is characterized as very highly toxic to bees and aquatic
  invertebrates.  It is moderately to highly toxic to fish and
  slightly toxic to upland game birds and waterfowl.
- Naled has numerous data gaps in areas of product chemistry, residue
  chemistry, toxicity, environmental fate, and ecological effects. The
  Agency cannot conduct a full risk assessment until the data required
  in the naled Standard are submitted and evaluated.


- Use classification:  not classified
- Use restrictions:  none
- Unique warning statements required on labels:
  - The following environmental hazard statement must appear on the
    manufacturing-use product labels:
    - This product is toxic to fish, aquatic invertebrates, and
      wildlife. Do not discharge into lakes, streams, ponds, or public
      water unless in accordance with NPDES permit.  For guidance,
      contact your regional office of the Environmental Protection
      Agency .
  - Labeling changes to end-use products are not required by the
    Standard; however, based on data reviewed by the Agency, the
    following statements will be required by end-use products under the
    Agency's Label Improvement Program:
    - This product is toxic to fish, aquatic invertebrates, and
      wildlife.  Do not apply directly to water or wetlands.  Runoff
      from treated areas may be hazardous to aquatic organisms in
      neighboring areas.  Do not contaminate water by cleaning of
      equipment or disposal of wastes.
    - This product is highly toxic to bees exposed to direct treatment
      on blooming crops or weeds.  Do not apply this product or allow it
      to drift to blooming crops or weeds while bees are actively
      visiting the treatment area.
  - The following General Warnings and Limitations statements must
    appear on end-use product labels which bear directions for aquatic
    use on food or feed crops:
    - Do not use with highly alkaline materials such as lime or
      bordeaux mixture.  Shrimp and crabs may also be killed at
      application rates recommended.  Do not apply to tidal or marsh
      waters which are important shrimp-producing areas.
  - A reentry interval of 24 hours for the use of naled on crops is
    required on end-use product labels containing directions for use on
  - The absence of reported fatalities from the Pesticide Incidence
    Monitoring System (PIMS) report, taken in conjunction with the
    apparent adequacy of medical and/or emergency room treatment,
    suggests an acceptably low level of risk associated with incidental
    or accidental exposure to naled products.

- Summary of risk/benefit review:
  - Dichlorvos (DDVP), a metabolite of naled, was originally referred to
    the Rebuttable Presumption Against Registration (RPAR) process
    because scientific studies indicated that dichlorvos was mutagenic
    and might cause cancer, nerve damage and birth defects in laboratory
    animals.  The RPAR Decision Document on dichlorvos was issued
    September 30, 1982.  It was concluded that the existing evidence
    does not support the issuance of an RPAR for dichlorvos and,
    consequently, that an RPAR for naled as a precursor of dichlorvos is
    also not warranted.
  - However, the Decision Document concluded that additional data on
    carcinogenicity and mutagenicity are needed to complete the risk
    assessment for dichlorvos.  Because the data base was incomplete,
    dichlorvos was removed from the RPAR process and returned to the
    registration process.  A Data Call-in Notice under FIFRA Section
    3(c)(2)(B) was issued March 23, 1983, requesting data on potential
    mutagenic effects of dichlorvos be submitted by March 23, 1985.
    Additionally, the Agency will wait until the ongoing National Cancer
    Institute dichlorvos bioassay on carcinogenicity is completed
    (currently scheduled for completion in 1984) and evaluated prior to
    determining if additional data on the carcinogenicity of dichlorvos
    will be required.  Since dichlorvos is a metabolite of naled,
    evaluation of these studies will be necessary for the completion of
    the naled risk assessment.
  - No other human toxicological hazards of concern to the Agency have
    been identified in studies reviewed for the Standard.

                       5.  SUMMARY OF MAJOR DATA GAPS

- Product chemistry:  data on the discussion of formation of
  ingredients; preliminary analysis; certification of limits; and
  analytical methods for enforcement of limits are the major product
  chemistry data gaps.
- Residue chemistry:  Additional data are required to support the
  tolerances for beans (dry and succulent), broccoli, Brussels sprouts,
  cabbage, cauliflower, celery, collards, cottonseed, cucumbers,
  eggplant, eggs, grapefruit, hops, kale, lemons, melons, mushrooms,
  oranges, pea forage, peaches, peas, peppers, poultry (fat, meat, meat
  by-products), pumpkins, soybean forage, spinach, strawberries, Swiss
  chard, tangerines, turnip tops, and winter squash.
- Data are required on residues in the processed products of citrus (any
  member fruit), cottonseed, grapes, hops, rice, and tomatoes.  Data are
  also needed for turnip roots.  A tolerance must be established for
  this commodity.
- Toxicology:  inhalation LC50, rat; 21-day dermal, rabbit; 90-day
  inhalation, rat; chronic toxicity, 2 species; oncogenicity, 2 species;
  teratogenicity, 2 species; reproduction, 2-generation rat; gene
  mutation; chromosomal aberration.
- Reentry protection:  foliar dissipation.
- Wildlife and aquatic organisms:  freshwater fish LC50 (on typical end-
  use product); acute LC50, freshwater invertebrates (on technical grade
  of active ingredient and on typical end-use product); acute LC50,
  estuarine and marine organisms).

NOTE:  All data must be submitted by June, 1986.

                      6.  CONTACT PERSON AT EPA

William H. Miller
Product Manager (16)
Insecticide-Rodenticide Branch
Registration Division (TS-767)
Environmental Protection Agency
Washington, DC  20460
(703) 557-2600