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. ------- |