naled (Dibrom) Chemical Fact Sheet 6/83
CHEMICAL FACT SHEET FOR:
FACT SHEET NUMBER: 04
DATE ISSUED: JUNE , 1983
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.
2. USE PATTERNS AND FORMULATIONS
- 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
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.
- Current available toxicology studies on naled are as follows:
- Acute oral LD50: rat, 222-389 mg/kg; mouse, 160 mg/kg (Toxicity
- Acute dermal LD50: rabbit, 390-1100 mg/kg; rat, 800 mg/kg
(Toxicity Category II)
- Primary eye irritation: corneal opacities 7 days + (Toxicity
- 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
- 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.
- 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
- 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
- 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
Brussels sprouts 1.0
Cattle (fat, meat, meat by-products) 0.05
Citrus fruits (grapefruit, lemons, oranges, 3.0
Goats (fat, meat, meat by-products) 0.05
Grasses, forage 10.0
Hogs (fat, meat, meat by-products) 0.05
Horses (fat, meat, meat by-products) 0.05
Legumes, forage 10.0
Peas (succulent only)
Poultry (fat, meat, meat by-products) 0.05
Safflower seed 0.5
Sheep (fat, meat, meat by-products) 0.05
Squash (summer, winter) 0.5
Sugar beets (roots, tops) 0.5
Swiss chard 3.0
Turnips (tops) 3.0
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.
4. SUMMARY OF REGULATORY POSITION AND RATIONALE
- 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
- 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
- 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)
Registration Division (TS-767)
Environmental Protection Agency
Washington, DC 20460
DISCLAIMER: THE INFORMATION PRESENTED IN THIS CHEMICAL INFORMATION FACT
SHEET IS FOR INFORMATIONAL PURPOSES ONLY AND NOT TO BE USED TO FULFILL
DATA REQUIREMENTS FOR PESTICIDE REGISTRATION AND REREGISTRATION.