Fonofos (CASRN 944-22-9)
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0158
Fonofos;
CASRN 944-22-9
Health assessment information on a chemical substance is included in IRIS
only after a comprehensive review of chronic toxicity data by U.S. EPA
health scientists from several Program Offices and the Office of Research
and Development. The summaries presented in Sections I and II represent
a consensus reached in the review process. Background information and
explanations of the methods used to derive the values given in IRIS are
provided in the Background Documents.
STATUS OF DATA FOR Fonofos
File First On-Line 03/31/1987
Category (section) |
Status |
Last Revised |
---|---|---|
Oral RfD Assessment (I.A.) | on-line | 03/01/1991 |
Inhalation RfC Assessment (I.B.) | no data | |
Carcinogenicity Assessment (II.) | no data |
_I. Chronic Health Hazard Assessments for Noncarcinogenic Effects
_I.A. Reference Dose for Chronic Oral Exposure (RfD)
Substance Name — Fonofos
CASRN — 944-22-9
Last Revised — 03/01/1991
The oral Reference Dose (RfD) is based on the assumption that thresholds
exist for certain toxic effects such as cellular necrosis. It is expressed
in units of mg/kg-day. In general, the RfD is an estimate (with uncertainty
spanning perhaps an order of magnitude) of a daily exposure to the human
population (including sensitive subgroups) that is likely to be without
an appreciable risk of deleterious effects during a lifetime. Please refer
to the Background Document for an elaboration of these concepts. RfDs
can also be derived for the noncarcinogenic health effects of substances
that are also carcinogens. Therefore, it is essential to refer to other
sources of information concerning the carcinogenicity of this substance.
If the U.S. EPA has evaluated this substance for potential human carcinogenicity,
a summary of that evaluation will be contained in Section II of this file.
__I.A.1. Oral RfD Summary
Critical Effect |
Experimental Doses* |
UF
|
MF
|
RfD
|
---|---|---|---|---|
Cholinesterase 2-Year Dog Feeding Stauffer Chemical |
NOEL: 0.2 mg/kg/day LEL: 1.5 mg/kg/day |
100
|
1
|
2E-3
mg/kg/day |
*Conversion Factors: none
__I.A.2. Principal and Supporting Studies (Oral RfD)
Stauffer Chemical Company. 1969. MRID 00082233. Available from EPA. Write
to FOI, EPA, Washington, DC 20460.
Groups of purebred beagle dogs, four males and four females/group, were fed 0,
0.2, 1.5, and 12 mg/kg/day fonofos (dyfonate) in diets for 2 years. The
following effects were observed at 1.5 mg/kg/day: moderate inhibition of red
blood cell cholinesterase, an increase in liver weight, tremors, lacrimation
and salivation. At 12 mg/kg/day, there were increases in liver weight, and
tissue reactions (microscopically) in the small intestine and liver. No
compound-related effects were observed at 0.2 mg/kg/day.
__I.A.3. Uncertainty and Modifying Factors (Oral RfD)
UF — Based on a chronic exposure study, an uncertainty factor of 100 was used
to account for the inter- and intraspecies differences.
MF — None
__I.A.4. Additional Studies/Comments (Oral RfD)
The 2-year rat feeding study was not used to derive the RfD because of the
equivocal ChE depression observed. The cholinergic and systemic effects
observed in the dog, the NOEL in this species, and the appropriate UF
provided, overall, a better basis and a more conservative level for an RfD.
Data Considered for Establishing the RfD:
1) 2-Year Feeding - dog: Principal study - see previous description; core
grade minimum
2) 2-Year Feeding (oncogenic) - rat: NOEL=0.5 mg/kg/day (equivocal brain Che
inhibition); LEL=1.58 mg/kg/day (plasma and RBC ChE inhibition); core grade
supplementary (Stauffer Chemical Co., 1968a)
3) 3-Generation Reproduction - rat: Fetotoxic NOEL=1.58 mg/kg/day (HDT); core
grade minimum (Stauffer Chemical Co., 1968b)
4) Teratology - mice: Fetotoxic NOEL=2 mg/kg/day; Fetotoxic LEL=6\mg/kg/day
(sternebrae malalignment and slight dilation of 4th cerebral ventricles); core
grade minimum (Stauffer Chemical Co., 1982)
Data Gap(s): 2-Year Feeding/Oncogenic Rat Study; Rat Teratology Study; Rabbit
Teratology Study
__I.A.5. Confidence in the Oral RfD
Study — Medium
Database — Medium
RfD — Medium
The principal study appears to be of fair quality and is given a medium confidence rating. Since the database for chronic toxicity is relatively complete, the database is given a medium confidence rating. Medium confidence in the RfD follows.
__I.A.6. EPA Documentation and Review of the Oral RfD
Pesticide Registration Standard, August 1983
Pesticide Registration Files
Agency Work Group Review — 06/24/1986
Verification Date — 06/24/1986
Screening-Level Literature Review Findings — A screening-level review conducted by an EPA contractor of the more recent toxicology literature pertinent to the RfD for Fonofos conducted in November 2001 did not identify any critical new studies. IRIS users who know of important new studies may provide that information to the IRIS Hotline at hotline.iris@epa.gov or (202)566-1676.
__I.A.7. EPA Contacts (Oral RfD)
Please contact the IRIS Hotline for all questions concerning this assessment or IRIS, in general, at (202)566-1676 (phone), (202)566-1749 (FAX) or hotline.iris@epa.gov (internet address).
_I.B. Reference Concentration for Chronic Inhalation Exposure (RfC)
Substance Name — Fonofos
CASRN — 944-22-9
Not available at this time.
_II. Carcinogenicity Assessment for Lifetime Exposure
Substance Name — Fonofos
CASRN — 944-22-9
This substance/agent has not undergone a complete evaluation and determination under US EPA's IRIS program for evidence of human carcinogenic potential.
_III.
[reserved]
_IV. [reserved]
_V. [reserved]
_VI. Bibliography
Substance Name — Fonofos
CASRN — 944-22-9
Last Revised — 03/01/1991
_VI.A. Oral RfD References
Stauffer Chemical Company. 1969. MRID 00082233. Available from EPA. Write
to FOI, EPA, Washington, DC 20460.
Stauffer Chemical Company. 1968a. MRID 00082232. Available from EPA. Write
to FOI, EPA, Washington, DC 20460.
Stauffer Chemical Company. 1968b. MRID 00082234. Available from EPA. Write
to FOI, EPA, Washington, DC 20460.
Stauffer Chemical Company. 1982. MRID 00118423. Available from EPA. Write
to FOI, EPA, Washington, DC 20460.
_VI.B. Inhalation RfC References
None
_VI.C. Carcinogenicity Assessment References
None
_VII. Revision History
Substance Name — Fonofos
CASRN — 944-22-9
Date |
Section |
Description |
---|---|---|
03/01/1991 | I.A.1. | MRID No. corrected |
03/01/1991 | I.A.4. | Citations added |
03/01/1991 | VI. | Bibliography on-line |
04/01/1991 | V.B. | Missing field added (Haz. Decomp. or Byproducts) |
01/01/1992 | IV. | Regulatory actions updated |
04/01/1997 | III., IV., V. | Drinking Water Health Advisories, EPA Regulatory Actions, and Supplementary Data were removed from IRIS on or before April 1997. IRIS users were directed to the appropriate EPA Program Offices for this information. |
12/03/2002 | I.A.6. | Screening-Level Literature Review Findings message has been added. |
_VIII. Synonyms
Substance Name — Fonofos
CASRN — 944-22-9
Last Revised — 03/31/1987
- 944-22-9
- DIFONATE
- DYFONATE
- DYPHONATE
- ENT 25,796
- Fonofos
- FONOPHOS
- N 2790
- O-AETHYL-S-PHENYL-AETHYL-DITHIOPHOSPHONAT
- O-ETHYL S-PHENYL ETHYLDI-THIOPHOSPHONATE
- O-ETHYL-S-PHENYL ETHYLPHOSPHONODITHIOATE
- PHOSPHONODITHIOIC ACID, ETHYL-, O-ETHYL S-PHENYL ESTER
- STAUFFER N 2790