Oxadiazon (CASRN 19666-30-9)
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0253
Oxadiazon;
CASRN 19666-30-9
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 Oxadiazon
File First On-Line 09/30/1987
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 — Oxadiazon
CASRN — 19666-30-9
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 |
---|---|---|---|---|
Increased levels of 2-Year Rat Feeding Rhone-Poulenc, 1981 |
NOEL: 10 ppm diet LEL: 100 ppm diet |
100
|
1
|
5E-3
mg/kg/day |
*Conversion Factors -- 1 ppm = 0.05 mg/kg/day (assumed rat food consumption)
__I.A.2. Principal and Supporting Studies (Oral RfD)
Rhone-Poulenc Company. 1981. MRID No. 00149003. Available from EPA. Write to FOI, EPA, Washington, DC 20460.
The following dose levels of oxadiazon were fed to rats in their diets for 2 years: 0, 10, 100, 1000, and 3000 ppm. At the LEL, there were increased levels of serum proteins (females, 18%) and increased liver weights (31%). At 1000 ppm the following effects were seen: hepatotoxicity, hemolytic anemia, body weight changes (in males, only slight decrease in females), decreased food consumption, increases in kidney weight, and pigment nephrosis (both sexes).
__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 inter- and intraspecies differences.
MF — None
__I.A.4. Additional Studies/Comments (Oral RfD)
The increase in liver weight is considered a biologically significant response to oxadiazon, since at higher doses there was evidence of liver pathology. Thus, the NOEL is based on the absence of any observed effect on the liver.
Data Considered for Establishing the RfD:
1) 2-Year Feeding (oncogenic) - rat: Principal study - see previous description; core grade guideline
2) 3-Generation Reproduction - rat: NOEL=100 ppm (5 mg/kg/day); LEL=200 ppm (10 mg/kg/day) (fewer and lighter pups; at 400 ppm reduction in litter size); no core grade (Rhone-Poulenc, 1977)
3) 2-Year Feeding - dog: NOEL=100 ppm (2.5 mg/kg/day); core grade minimum (Rhone-Poulenc, 1974)
4) Teratology - rabbits: Not teratogenic up to and including 500 mg/kg/day; no core grade (Rhone-Poulenc, 1972a)
5) Teratology - rat: Not teratogenic but fetotoxic at 40 mg/kg/day and above; no core grade (Rhone-Poulenc, 1972b)
Data Gap(s): None
__I.A.5. Confidence in the Oral RfD
Study — High
Database — Medium
RfD — Medium
The principal study is of good quality and is given a high confidence rating. Additional studies are supportive, but not core-graded; therefore, the data base 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 Files
Agency Work Group Review — 02/18/1987
Verification Date — 02/18/1987
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 oxadiazon conducted in August 2003 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 — Oxadiazon
CASRN — 19666-30-9
Not available at this time.
_II. Carcinogenicity Assessment for Lifetime Exposure
Substance Name — Oxadiazon
CASRN — 19666-30-9
Not available at this time.
_III.
[reserved]
_IV. [reserved]
_V. [reserved]
_VI. Bibliography
Substance Name — Oxadiazon
CASRN — 19666-30-9
Last Revised — 03/01/1991
_VI.A. Oral RfD References
Rhone-Poulenc Company. 1972a. MRID No. 00061412. Available from EPA. Write to FOI, EPA, Washington, DC 20460.
Rhone-Poulenc Company. 1972b. MRID No. 00061413. Available from EPA. Write to FOI, EPA, Washington, DC 20460.
Rhone-Poulenc Company. 1974. MRID No. 00081256. Available from EPA. Write to FOI, EPA, Washington, DC 20460.
Rhone-Poulenc Company. 1977. MRID No. 00058379. Available from EPA. Write to FOI, EPA, Washington, DC 20460.
Rhone-Poulenc Company. 1981. MRID No. 00149003. 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 — Oxadiazon
CASRN — 19666-30-9
Date |
Section |
Description |
---|---|---|
12/01/1988 | I.A.4. | Study 3) core grade corrected |
05/01/1990 | II. | Carcinogen assessment now under review |
03/01/1991 | I.A.4. | Citations added |
03/01/1991 | VI. | Bibliography on-line |
01/01/1992 | IV. | Regulatory Action section on-line |
08/01/1995 | II. | EPA's RfD/RfC and CRAVE workgroups were discontinued in May, 1995. Chemical substance reviews that were not completed by September 1995 were taken out of IRIS review. The IRIS Pilot Program replaced the workgroup functions beginning in September, 1995. |
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. |
10/28/2003 | I.A.6 | Screening-Level Literature Review Findings message has been added. |
_VIII. Synonyms
Substance Name — Oxadiazon
CASRN — 19666-30-9
Last Revised — 09/30/1987
- 19666-30-9
- O,O-DIETHYL ESTER
- Oxadiazon
- PHOSPHORODITHIOIC ACID, S-((6-CHLORO-2-OXO-3(2H)-BENZOXAZOLYL)METHYL)
- RONSTAR
- RP 17623
- 2-tert-BUTYL-4-(2,4-DICHLORO-5-ISOPROPYLOXYPHENYL)-1,3,4-OXADIAZOLIN-5-ON-