phosalone (Zolone) EPA Pesticide Fact Sheet
EPA Pesticide Fact Sheet
Name of Chemical: PHOSALONE
Reason for Issuance: REGISTRATION STANDARD
Fact Sheet Number:
1. DESCRIPTION OF CHEMICAL
- Generic Name: S-6-chloro-2,3-dihydro-2-oxobenzoxazol-3-yl-methyl
(Chemical) O,O-diethyl phosphorodithioate
- Common Name: Phosalone (ANSI)
- Other Chemical Nomenclature:
- S-[(6-chloro-2-oxo-3(2H)benzoxazolyl)methyl] O,O-
- O,O-diethyl phosphorodithioate S-ester with 6-chloro-
- Trade Names: Azonfene, Benzofos, RP11974, Rubitox, and Zolone.
- EPA Shaughnessy Code: 097701
- Chemical Abstracts Service (CAS) Number: 2310-17-0
- Year of Initial Registration: 1974
- Pesticide Type: Insecticide/Acaricide
- Chemical Family: Organophosphate
- U.S. and Foreign Producers: Rhone-Poulenc, Inc.
2. USE PATTERNS AND FORMULATIONS
- Application Sites: Nut crops, citrus crops, pome fruits, stone fruits,
grapes, potatoes, artichokes, roses, and arborvitae.
- Formulation Types: Technical, Emulsifiable Concentrate and Wettable
- Application Methods: Foliar: ground and aerial application.
3. SCIENCE FINDINGS
Summary Science Statement
Phosalone may have an adverse impact on birds and aquatic organisms
resulting from all use patterns, excluding ornamentals. Aquatic and
terrestrial field studies are required to determine the potential risks
to these organisms. Laboratory data show that technical phosalone is
highly toxic to fish and aquatic invertebrates.
The toxicological profile of the end-use products places them in
Toxicity Category II for primary eye irritation, acute oral and dermal
exposures. The end-use products were only mildly irritating to the skin
when tested for dermal irritation. The products were characterized as
weak dermal sensitizers. Phosalone can cause adverse effects to persons
entering treated fields and to persons involved in the preparation and
application of this pesticide. Preliminary data show that groundwater
contamination is unlikely, but the Agency is unable to conduct a full
assessment due to data gaps.
Chemical/Physical Characteristics of the Technical Material
- Physical State: Crystalline solid
- Color: White
- Molecular weight and formula: 367.8 gms-Cl2H15ClN04P52
- Melting Point: 45-47 degrees C
- Density: 1.391 g/ml at 20 degrees C
- Vapor Pressure: less than or equal to 0.5 x 10-6 mm Hg at 24 degrees C
and 16.4 x 10-6 at 60 degrees C
- Solubility: At 20 degrees C: 1.7ppm in water; 20 g/100 ml in methanol
and ethanol, and 10g/100ml in acetone, benzene, cyclohexanone,
acetonitrile, xylene, toluene, dioxane, chloroform, and methyl
- Stability: Very stable under normal laboratory conditions for a
period of 2 years.
Toxicology Characteristics (Technical Material)
- Acute Oral: Toxicity Category II (90 and 125 mg/kg in female and male
- Acute Dermal: Toxicity Category II ( LD50 > 350 mg/kg for both males
- Acute Inhalation: Waived for technical, particles analyzed were
determined not to be within the respirable range (less than or equal
to 15 microns).
- Primary Dermal Irritation: Toxicity Category IV (PDIS-0.77, mildly
irritating to intact and abraded skin).
- Primary Eye Irritation: Data gap.
- Skin Sensitization: Data gap.
- Delayed neurotoxicity: Negative in hens.
- Subchronic Oral (non-rodent): Data gap.
- Oncogenicity: Data gap.
- Chronic Feeding: NOEL for RBC inhibition in the rat is 25 ppm.
- Metabolism: Data gap
- Teratogenicity: Data gap
- Reproduction: Data gap
- Mutagenicity: Data gap for point mutation assay in mammalian cells,
structural chromosomal aberration, and other genotoxic effects.
- Major routes of exposure: Dermal and respiratory exposure to mixers,
loaders, applicators, and fieldworkers.
Phosalone is stable at pH 5 and 7, but is hydrolyzed at a pH of 9
with a half-life of 9 days. Artificial light accelerated degradation in
buffered solution at a pH of 5 and in soil. Aerobic soil metabolism
studies demonstrate half-life values of 1-7 days. Field dissipation
studies showed half-life values of 1-9 weeks. Phosalone was essentially
immobile in a soil column test. Based upon this preliminary data
phosalone appears unlikely to contaminate ground water. It exhibited
moderate accumulation in the bluegill sunfish, with rapid dissipation in
Ecological Characteristics (Technical grade)
- Avian Oral Toxicity: Slightly toxic to waterfowl (acute oral toxicity
value: mallards > 2150 mg/kg).
- Avian Dietary Toxicity: Slightly toxic to waterfowl and upland-game
(8 Days) birds (subacute toxicity values:
mallards 1659 ppm and bobwhite quail 2033 ppm).
- Freshwater Fish Acute: Very highly toxic to warmwater fish and
Toxicity (96-Hours) and highly toxic to coldwater fish (acute
LC values: 0.05 ppm bluegill and 0.63 ppm rainbow trout).
- Freshwater Invertebrate: Very highly toxic to aquatic invertebrate
Toxicity (48-Hours) (acute EC value: 0.0012 ppm Daphnia magna)
4. TOLERANCE REASSESSMENT
Tolerances have been established for phosalone on a variety of raw
agricultural commodities, in meat, fat and meat byproducts (40 CFR
180.263) and in processed food (21 CFR 193.340) and feed (21 CFR
Tolerances for the following commodities are adequately supported:
potatoes, citrus, apples, pears, apricots, cherries, nectarines,
peaches, plums (fresh prunes), dried prunes, tree nuts, almond hulls,
grapes, raisins, artichokes, and the fat, meat, and meat byproducts of
cattle, goats, hogs, horses and sheep.
Additional data are required to assess the need for food/feed
additive tolerances for the following products processed from raw
agricultural commodities bearing measurable, weathered residues: potato
granules or flakes, chips, and wet and dry peels, raisin waste and grape
The nature of the residues in both plants and animals are not
adequately understood. If, on receipt of the required metabolism data,
the Agency determines that residues in addition to the parent require
regulation, additional methods for data collection and enforcement may
Crop group tolerances may be proposed for the Pome Fruit Group at
10 ppm and for the Stone Fruit Group at 15 ppm.
The Agency has established a Provisional Acceptable Daily Intake
(PADI) at 0.0025 mg/kg/day based on a 6-month dog feeding study in which
plasma cholinesterase activity was depressed. Because a NOEL was not
established in this study a 100 fold uncertainty factor has been used
rather than the 10 fold factor normally applied for cholinesterase
5. SUMMARY OF REGULATORY POSITIONS AND RATIONALES
- Phosalone is not being placed into Special Review at this time.
Although the Agency is concerned about the potential adverse impact of
phosalone on birds and aquatic organisms resulting from the
agricultural use patterns, aquatic and terrestrial field studies are
needed in order to evaluate the potential risks to these species.
- The Agency has sufficient data (analysis of pesticides with similar
uses were found to be in jeopardy) to indicate that the current use
patterns of phosalone may affect endangered species. Endangered
species labeling is reserved pending concurrence from the Fish and
- The Agency is classifying all Phosalone end use products as Restricted
Use Pesticides; except for products packaged and labeled solely for
use around the home. Products containing phosalone for use on
cherries and citrus are restricted due to avian hazards. All use
patterns are restricted due to aquatic toxicity. The estimated
environmental concentrations exceed the LC50 value for fish and the
EC50 value for aquatic invertebrates, and the NOEL values for avian
- The Agency is imposing a 6-month rotational crop restriction for small
grains and a 12-month rotational crop restriction for leafy vegetables
and root crops.
- No significant new tolerances or new food uses will be granted until
the Agency has received sufficient data to evaluate the dietary
exposure of phosalone.
- The Agency will retain the 24-hour reentry interval imposed in the
1981 Registration Standard. This reentry interval will be retained
until the required reentry data are received and evaluated. Data
will be reviewed on a priority basis because of reported poisoning
incidents in California.
- The Agency will require that end use products bear label statements to
protect mixers, loaders, applicators, flaggers, and fieldworkers.
- Preliminary data indicate that groundwater contamination is unlikely.
The Agency is requiring environmental fate studies to fully
characterize phosalone's fate in the environment.
6. SUMMARY OF OUTSTANDING DATA REQUIREMENTS
Toxicology Time Frame
Primary Eye Irritation 9 Months
Dermal Sensitization 9 "
Acute Inhalation 9 "
Subchronic oral toxicity--Dog (for cholinesterase 12 "
Oncogenicity--rat 50 "
Teratogenicity--(rat and rabbit) 15 "
Reproduction--(rat) 39 "
Mutagenicity 12 "
Metabolism study 12 "
Dermal Absorption (rat) 9 "
Aged leaching study 12 "
Rotational Crop (Confined) 12 "
Foliar dissipation study 15 "
Spray Drift 12 "
Soil Dissipation 27 "
Fish and Wildlife
Avian reproduction 24 Months
Actual field testing- birds and mammals (citrus) 30 "
Simulated or Actual field testing-aquatic organisms 48 "
Acute toxicity to Estuarine and Marine organisms 12 "
Fish early life stage and aquatic invertebrate
life cycle 15 "
Acute toxicity to Freshwater Invertebrate 9 "
Animal and Plant metabolism 18 Months
Storage stability 15 "
Processing studies for potatoes and grapes 24 "
Residue data (tea) 18 "
Product Chemistry 6-15 Months
7. CONTACT PERSON AT EPA
Dennis H. Edwards, Jr.
Product Manager (12)
Registration Division (TS-767C)
Office of Pesticide Programs
Environmental Protection Agency
401 M Street, S. W.
Washington, D. C. 20460
Office location and telephone number:
Room 211, Crystal Mall #2
1921 Jefferson Davis Highway
Arlington, VA 22202
DISCLAIMER: The information presented in this Chemical Information Fact
Sheet is for informational purposes only and may not be used to fulfill
data requirements for pesticide registration and reregistration.