Terbutryn (CASRN 886-50-0)
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0285
Terbutryn;
CASRN 886-50-0
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 Terbutryn
File First On-Line 09/26/1988
Category (section) |
Status |
Last Revised |
---|---|---|
Oral RfD Assessment (I.A.) | on-line | 09/26/1988 |
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 — Terbutryn
CASRN — 886-50-0
Last Revised — 09/26/1988
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 |
---|---|---|---|---|
Hematologic effects 2-Year Rat Feeding Ciba-Geigy, 1980a |
NOEL: 2 ppm LEL: 300 ppm |
100
|
1
|
1E-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)
Ciba-Geigy Corporation. 1980a. MRID No. 00035923. Available from EPA. Write to FOI, EPA, Washington, DC 20460.
Two hundred sixty male and 260 female weanling Charles River CD rats were randomly distributed into the following groups: 0, (70 animals/sex), 2 (60 animals/sex), 300 (60 animals/sex) and 3000 ppm (70 animals/sex) (0, 0.1, 15, and 150 mg/kg/day) and administered terbutryn in their diets for 2 years. Based upon a statistical reevaluation of the hematologic data from this study, a NOEL for systemic effects can be set at 2 ppm. The LEL is 300 ppm based upon a statistically significant and dose-related decrease in hemoglobin and erythrocytes in female rats at 18 months. This parameter was not measured for the mid-dose group at term. At the HDT (3000 ppm) there was also a statistically significant decrease in hematocrit in females at both 18 and 24 months.
__I.A.3. Uncertainty and Modifying Factors (Oral RfD)
UF — 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)
Data Considered for Establishing the RfD:
1) 2-Year Feeding (oncogenic) - rat: Principal study - see previous description; core grade minimum
2) 6-Month Feeding - dog: NOEL=10 mg/kg/day; LEL=25 mg/kg/day (mucosal thickening of various segments of the small intestine and submucosal lymphoid hyperplasia in the stomach); core grade minimum (Ciba-Geigy Corp., 1980b)
3) 3-Generation Reproduction - rat: NOEL=15 mg/kg/day; LEL=150 mg/kg/day (decreased body weight gain and decreased fertility indices in males and females); core grade minimum (Ciba-Geigy Corp., 1980c)
4) Teratology - rat: Maternal NOEL=50 mg/kg/day; Maternal LEL=500 mg/kg/day (reduced body weight); Developmental NOEL=50 mg/kg/day; Developmental LEL=500 mg/kg/day (weight decrease, reduced ossification - front and rear paws); core grade minimum (Ciba-Geigy Corp., 1985a)
5) Teratology - rabbit: Maternal NOEL=10 mg/kg/day; Maternal LEL=50 mg/kg/day (body weight loss); Developmental NOEL=50 mg/kg/day; Developmental LEL=75 mg/kg/day (reduced ossification of sternebrae); core grade guideline (Ciba- Geigy Corp., 1985b)
Data Gap(s): None
__I.A.5. Confidence in the Oral RfD
Study — High
Database — High
RfD — High
The critical study is of good quality and is given a high confidence rating. Additional studies are supportive; therefore, the database is given a high confidence rating. High confidence in the RfD follows.
__I.A.6. EPA Documentation and Review of the Oral RfD
Source Document — This assessment is not presented in any existing U.S. EPA document.
Other EPA Documentation — Pesticide Registration Standard, July 1986; Pesticide Registration Files
Agency Work Group Review — 07/15/1987, 08/13/1987, 07/20/1988
Verification Date — 07/20/1988
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 Terbutryn conducted in September 2002 identified one or more significant new studies. IRIS users may request the references for those studies from 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 — Terbutryn
CASRN — 886-50-0
Not available at this time.
_II. Carcinogenicity Assessment for Lifetime Exposure
Substance Name — Terbutryn
CASRN — 886-50-0
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 — Terbutryn
CASRN — 886-50-0
Last Revised — 12/01/1989
_VI.A. Oral RfD References
Ciba-Geigy Corporation. 1980a. MRID No. 00035923. Available from EPA. Write to FOI, EPA, Washington, DC 20460.
Ciba-Geigy Corporation. 1980b. MRID No. 00029152. Available from EPA. Write to FOI, EPA, Washington, DC 20460.
Ciba-Geigy Corporation. 1980c. MRID No. 00035659. Available from EPA. Write to FOI, EPA, Washington, DC 20460.
Ciba-Geigy Corporation. 1985a. MRID No. 00152764. Available from EPA. Write to FOI, EPA, Washington, DC 20460.
Ciba-Geigy Corporation. 1985b. MRID No. 00152763. Available from EPA. Write to FOI, EPA, Washington, DC 20460.
_VI.B. Inhalation RfD References
None
_VI.C. Carcinogenicity Assessment References
None
_VII. Revision History
Substance Name — Terbutryn
CASRN — 886-50-0
Date |
Section |
Description |
---|---|---|
09/26/1988 | I.A. | Oral RfD summary on-line |
12/01/1989 | VI. | Bibliography on-line |
01/01/1992 | IV. | Regulatory Action section on-line |
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 — Terbutryn
CASRN — 886-50-0
Last Revised — 09/26/1988
- 886-50-0
- 4-AETHYLAMINO-2-tert-BUTYLAMINO-6-METHYLTHIO-s-TRIAZIN
- CLAROSAN
- GS 14260
- HS-14260
- IGRAN
- IGRAN 50
- 2-METHYLTHIO-4-ETHYLAMINO-6-tert-BUTYLAMINO-s-TRIAZINE
- PREBANE
- SHORTSTOP
- SHORT-STOP E
- TERBUTREX
- Terbutryn
- TERBUTRYNE
- 2-tert.BUTYLAMINO-4-AETHYLAMINO-6-METHYLTHIO-1,3,5-TRIAZIN
- 2-tert-BUTYLAMINO-4-ETHYLAMINO-6-METHYLMERCAPTO-s-TRIAZINE
- 2-tert-BUTYLAMINO-4-ETHYLAMINO-6-METHYLTHIO-s-TRIAZINE
- s-TRIAZINE, 2-(tert-BUTYLAMINO)-4-(ETHYLAMINO)-6-(METHYLTHIO)-