United States	Office of Pesticides
Environmental Protection	and Toxic Substances
Agency	(H7501CI
	540/FS-91-133
Pesticide
Fact Sheet
Name of Chemical: Fenamiphos
Reason for Issuance! Registration St.-mtiird
Date Issued: June 1987
Fact Sheet Number: 222
1.	DESCRIPTION OF CHEMICAL
Common Name: Fenamiphos
Chemical Name: O-ethyl-O-(3-methy1-4-methy1-thiopheny1)•
isopropy1phosphorami date
CAS Number: 22224-92-6
OPP (Shaughnessy) Number: 100601
Trade Names: Nemacur 15G, Nemacur 3
Registrant: Mobay Chemical Co.
2.	USE PATTERNS AND FORMULATIONS
Type of Pesticide: Systemic Neraaticide/Insecticide
Pests Controlled: Nematodes, Thrips
Predominant Uses: field and vegetable crops, orchards,
vineyards, non-bearing orchards, ~
nursery stock, ornamentals
Formulation Types: enulsifiable concentrate and
granular
Method of Application: soil treatment by ground spray
equipment, by granular application equipment, or by
incorporation into irrigation water. Soil incorporation
or irrigation immediately after treatment is required.
All formulations are being restricted through this
registration standard. Applicators must be certified or
under direct supervision of a certified applicator.

-------
-2-
SCIENCE FINDINGS
Toxicology Characteristics:
Acute Oral Toxicity (rat)
Acute Dermal Toxicity (rabbit)
Acute Inhalation Toxicity
(rat)
Primary Oermal Irritation
(rabbit)
Primary Eye Irritation
(rabbit)
Dermal Sensitization
(guinea pig)
Delayed Neurotoxicity
(hen)
LD50 2.7 mg/kg (category I)
LOS0 178.8 mg/fcg (category I)
LC50 0.1 mg/L (category I)
non-1rr1tating (category IV)
silghtly 1rr1 tating
(category III)
not a sensitizer
not a delayed neurotox1 cant
Subchronic Effects
90-day Feeding (rat)
90-day reeding (dog)
• * »
21-day Dermal (rabbit)
Chronic Effects
2-year chronic feeding/
oncogenicity (rats):
2-year chronic feeding
(dogs):
NOEL for cholinesterase
inhibition 4 ppm
NOEL for cholinesterase
inhibition 1 ppm
NOEL 0.S mg/kg/day
No dose related Increase
in neoplastic and non-
neoplastic lesions was
observed. Dietary
cholinesterase NOEL is
1.0 ppm. Systemic NOEL
is 10 ppm.
No gross or histopathologica1
changes were attributed to
dietary levels of fenamiphos.
Dietary chol1nesterase NOEL
Is 1.0 ppm. Systemic NOEL
is 10 ppm.

-------
-3-
Chronic Effects (continued)
18-month oncogenicity (mice):	Fenamiphos was not shown
to be oncogenic in mice.
Multigeneration reproduction
(rats):
No adverse reproductive
effects were observed.
Mutagenicity - gene mutation:	Negative.
Chromosomal aberration:
Negat ive
Physiological and biochemical behavioral characteristics
Mechanism of pesticidal action: Organophosphate/
Metabolism in plants and animals: The nature of the
residue in plants is adequately understood. The nature
of the residue in animals is not adequately understood.
Tolerances for residues of fenamiphos in food items
derived from plants are currently expressed in terms of
the combined residues of fenamiphos and its cholin-
esterase-inhibiting metabolites, fenamiphos sulfoxide
and fenamiphos sulfone. Tolerances for resiudes of
fenamiphos in food items derived from animals are
expressed in terms of the combined residues of fenaniphos
and its sulfoxide and sulfone as well as des-isopropyl
fenamiphos, des-isopropyl fenamiphos sulfoxide and
des-isopropyl fenamiphos sulfone.
Environmental Characteristics; Available data are
insufficient to fully assess the environmental fate and
transport and potential exposure to fenamiphos. Except
for the two studies listed below, all the available
environmental fate data do not meet the guideline
standards for acceptable testing.
Hydrolysis: Fenamiphos is relatively stable in neutral
and alkaline solutions.
Photodegradation in Water: Fenamiphos degrades with a
half life of 2 to 4 hours in ph 7 buffered water
irradiated with artificial light.
Groundwater; The potential for fenamiphos to reach ground
water cannot be determined at this time. Some existing
studies, though deficient in some respects, show it does
leach to some degree. The Agency will evaluate the
cholinesterase inhibitor

-------
-4-
potential of fenamiphos to contaminate ground water after
it has received and evaluated the following required data:
photodegradation in air, aerobic and anaerobic metabolism,
mobility, and field dissipation. The sulfoxide and
sulfone metabolites of fenamiphos are included in the
National Survey for Pesticides in Drinking Water, in
lieu of parent fenamiphos, as the parent readily degrades.
Ecological Characteristics:
Avian acute oral toxicity:
Avian dietary toxicity:
Avian reproduction:
bobwhite quail
mallard duck
Field studies:
Fish acute toxicity:
LD50 1.6 mg/kg
LC50 38 ppm
NOEL 2 ppm
NOEL 8 ppm
Studies using both the
granular and emulsifiable
concentrate formulations
have shown some avian and
mammalian mortality.
LC50 9-6 PPb
Tolerance Reassessment:
Tolerances have been established for residues of
fenamiphos in a variety of raw agricultural commodities,
in meat, fat and meat byproducts (40 CFR 180.349 (a] and
lb]), and in processed food (21 CFR 193.463) and feed
(21 CFR 561.2321.
Available toxicology and residue chemistry data are
insufficient to permit the Agency to conduct a full
tolerance^reassessment.. A provisional acceptable daily
intake (PADI) has been set at 0.00025 rag/kg/day, based
on the NOEL from a 2-year dog feeding study of
0.025 mg/kg/day (1 ppm) for cholinesterase inhibition
and an uncertainty factor of 100 to account for the
lack, of an acceptable teratology study. The Theoretical
Maximum Residue Contribution (TMRC) for the U,S. population
average based on anticipated residues and percent crop
treated, is 0.00011 mg/kg/day which corresponds to 42*
of the PADI. It is possible that resolution of the
teratology data gap will allow for a lower uncertainty
factor which will result in a higher ADI and consequently
a lower percentage of the ADI occupied by the TMRC.

-------
-s-
4. SUMMARY OF REGULATORY POSITION AND RATIONALE
1. The Agency will not, at this time. Initiate a Special
Review (40 CFR Part 154 J of fenaniphos. After review and
evaluation of the required studies for fish and wildlife the
Agency will reconsider the possibility of a Special Review.
Acceptable protocols for conducting the avian, mammalian, and
fish field studies must be submitted within si* months of
the issuance of the standard and be accepted by the Agency
before the initiation of field work. Annual progress reports
must also be submitted for the duration of the study. The
application rates used in these studies must be the lowest
possible rates that are still efficacious as indicated by
the required efficacy data (refer to Regulatory Position 3).
Rat ionale: Fenamiphos is very highly toxic to birds
(LD$o 1.6 mg/kg) and mammals {LD$o 2.7 mg/kg) as well as
to cold (LC50 72.1 ppb) and warm water (LC50 9.6 ppb)
fish species.
Estimated environmental concentrations (EECs) of the granular
formulation of fenamiphos exceed the acute oral LD50 for the
most sensitive avian species tested, the bobwhite quail, and
the estimated LD50 values for S other avian species. EECs
also exceed the LD50 for the rat and the estimated LD50
values for two other mannalian species. EECs of the
emulsi f iable concentrate formulation indicate that fenamiphos
residues exceed the calculated subacute dietary LC50 for four
avian species.
Field studies using both granular and spray formulations of
fenamiphos according to label directions have shown some
avian and mammalian mortality. These studies also suggest
that soil incorporation and/or Irrigation immediately following
application reduces hazards. However, because of design
deficiencies these studies do not meet guideline requirements;
therefore, a terrestrial field study is being required to
determine if the hazards indicated by lab and field studies
are below levels of concern for mammalian and avian species
under actual use conditions.
Estimated environmental concentrations for water contaminated
by aerial application to crops and for runoff exceed the
LC50 values for bluegill sunf ish, and therefore# would cause
significant adverse effects. Thus, the following tests
are being required to fully assess the potential exposure and
toxicity of fenamiphos to aquatic environments: freshwater
fish toxicity (on EPs), freshwater invertebrate acute toxicity
(using the technical and EPs), estuarine and marine acute
toxicity, fish early life stage testing, fish life cycle,
aquatic invertebrate life cycle, aquatic organism accumulat ion,
and simulated and actual field testing of aquatic organisms.

-------
-6-
2.	The Agency is requiring restricted use classification
for all fenamiphos formulated products.
Rationale: Fenamiphos exceeds the restricted use criteria
set forth in 40 CFR 162.11(c)(2)(ii) and (iii). Use of
fenamiphos formulations has resulted in mortality to birds
and mammals. Fenamiphos is acutely toxic to laboratory
animals, Toxicity Category I, by the oral, dermal, and
inhalation routes of exposure. It is also very highly toxic
to birds as well as cold and warm water fish species. Use
of fenamiphos exceeds the restricted use criteria for
fish and wildlife; calculated residues exceed 1/5 the
acute oral LD50 for mammals, 1/5 the subacute dietary LC50 ^or
avian species, and 1/10 the acute LC50 for aquatic organisms.
In addition, use of fenamiphos has resulted in mortality
to birds and mammals. Accordingly, the Agency has determined
that the risks to humans, fish, and wildlife, associated with
the unrestricted use of fenamiphos products, constitute
unreasonable adverse effects. Restricting the use of all
fenamiphos products will reduce exposure and the potential
for acute toxicity. Field studies on birds, mammals, and
aquatic organisms, are being required to determine actual
exposure levels and potential hazard.
3.	The Agency is requiring that efficacy data be submitted
to support all currently registered application rates.
Rationale: EECs based on the maximum application rate exceed
LD50 values for birds and mammals and the LC50 value for
fish. Therefore, the Agency is requiring that efficacy data
be submitted within six months of the issuance of the standard
to support the current application rates. If such data
indicate that rates could be lowered with minimal decrease in
efficacy the Agency will require that all labels be revised
to the lowest possible rates that are still efficacious;
These labeling changes would reduce environmental concentra-
tions of the pesticide while substantive data on the effects
on fish and wildlife are being collected.
4.	The Agency is requiring that all labels be revised as
follows:
1).	Directions for broadcast spray will be deleted
for sites which currently have directions for both
band and broadcast spray.
2).	All labels will prohibit the use of mist sprayers
and will direct applicators to use only coarse sprays
directed at the soil to reduce the possibility of
spray drift.
3).	All labels will specifically prohibit aerial
applicat ion.

-------
-7-
Rationale; As stated above, EECs based on the maximum
application rate exceed LD50 values for mammalian and
avian species and the LC50 value for aquatic organisms.
The above labeling changes would reduce environmental concen-
trations of the pesticide while substantive data on the
effects of fenamiphos on fish and wildlife are being collected.
5. The Agency is requiring endangered species labeling
on fenamiphos EPs registered for use on cotton and soybeans
in accordance with Pesticide Registration (PR) Notice 87-5
(issued May 1, 1987).
Rationale: Fenamiphos was reviewed for endangered species
implications. In order to protect endangered species
from harm, endangered species labeling is required.
Use restrictions: All formulations are classified as restricted
use pesticides.
Unique label statements:
° Restricted use
0 48-hour reentry interval
0 Protective clothing
0 Aerial application prohibition
0 Endangered species

-------
SUMMARY OF MAJOR DATA GAPS
Product Chemistry: All
Residue Chemistry:
Animal Metabolism
Residue Analytical Methods (plants and animals)
Storage Stability Data
Residue Studies
Environmental Fate:
Photodegradation (soil)
Aerobic and Anaerobic Soil Metabolism
Leaching and Adsorption/Desorption
Volatility (lab)
Soil Dissipation
Rotational Crops (confined and field)
Fish Accumulation
Spray Drift Droplet Spectrum and Field Evaluation
Reentry
Toxicology:
21-Day Inhalation (rat)
Teratology (rat and rabbit)
Mutagenicity
Metabolism
Ecological Effects:
Simulated and Actual Field Testing (birds and mammals)
Freshwater Fish Toxicity
Freshwater Invertebrate Acute Toxicity
Acute Toxicity to Estuarine and Marine Organisms
Fish Early Life Stage
Aquatic Invertebrate Life Cycle
Fish Life Cycle
Aquatic Organism Accumulation
Simulated and Actual Field Testing Aquatic Organisms
CONTACT PERSON AT EPA
Lois Rossi
U.S. Environmental Protection Agency (TS-767C)
401 M Street SW.
Washington, D.C. 20460
(703) 557-1900
DISCLAIMER: The information presented in this Pesticide
Fact Sheet is for informational purposes only and may
not be used to fulfill data requirements for pesticide
"registration and reregistration.

-------