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Oxadiazon
CASRN 19666-30-9
Contents
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 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 NOEL: 10 ppm diet 100 1 5E-3
serum proteins and (0.5 mg/kg/day) mg/kg/day
increased liver
weights LEL: 100 ppm diet
(5 mg/kg/day)
2-Year Rat Feeding
Study
Rhone-Poulenc, 1981
*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 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
Data Base -- 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
___I.A.7. EPA CONTACTS (ORAL RfD)
Please contact the Risk Information Hotline for all questions concerning this
assessment or IRIS, in general, at (513)569-7254 (phone), (513)569-7159 (FAX)
or RIH.IRIS@EPAMAIL.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.
_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
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-
Last updated: 5 May 1998
URL: http://www.epa.gov/iris/SUBST/0253.HTM
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