Jump to main content.

Isopropalin (CASRN 33820-53-0)

List of IRIS Substances

view QuickView

Main Contents



Isopropalin; CASRN 33820-53-0

Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data, as outlined in the IRIS assessment development process. Sections I (Health Hazard Assessments for Noncarcinogenic Effects) and II (Carcinogenicity Assessment for Lifetime Exposure) present the conclusions that were reached during the assessment development process. Supporting information and explanations of the methods used to derive the values given in IRIS are provided in the guidance documents located on the IRIS website.


File First On-Line 01/31/1987

Category (section)
Last Revised
Oral RfD Assessment (I.A.) on-line 09/01/1990
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 — Substance Name — Isopropalin
CASRN — 33820-53-0
Last Revised — 09/01/1990

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*

Reduced hemoglobin
lowered hematocrits,
and altered organ

90-Day Rat Feeding

Elanco Products, 1969a

NOEL: 250 ppm
(15 mg/kg/day)

LEL: 750 ppm
*Conversion Factors -- mg/kg/day determined from actual food consumption

__I.A.2. Principal and Supporting Studies (Oral RfD)

Elanco Products Company. 1969a. MRID No. 00002472. Available from EPA. Write to FOI, EPA, Washington, DC 20460.

Male and female rats were divided into 4 groups and fed the following concentrations of isopropalin in their diets: 0, 250 ppm, 750 ppm, and 2250 ppm. Average daily intake was 32, 93, and 288 mg/kg/day at the start and decreased to 15, 48, and 192 mg/kg/day by the end of 90 days. No effects were observed at 250 mg/kg/day. Reduced hemoglobin concentrations, lowered hematocrits, and altered organ weights were observed at the higher doses.

__I.A.3. Uncertainty and Modifying Factors (Oral RfD)

UF — Based on a subchronic exposure study, an uncertainty factor of 1000 was used to account for inter- and intra-species differences and the insufficient duration of the study to fully assess chronic effects.

MF — None

__I.A.4. Additional Studies/Comments (Oral RfD)

No chronic studies are required for isopropalin because of its use on tobacco. The Agency recognizes that the use of tobacco products is detrimental to the consumer and that the use of this product is voluntary.

Data Considered for Establishing the RfD

1) 90-Day Feeding - rat: Principal study - see discussion above; no core grade)

2) 90-Day Feeding - dog: NOEL=56.25 mg/kg/day (HDT); no core grade (Elanco Products, 1969b)

3) Teratology - rat: Fetotoxic NOEL=123 mg/kg/day; Maternal LEL=123 mg/kg/day (LDT); (soft stool and decreased food consumption); core grade minimum (Elanco Products, 1983a)

4) Teratology - rabbit: Fetotoxic NOEL=270 mg/kg/day; Maternal NOEL=60 mg/kg/day; Maternal LEL=270 mg/kg/day; (decreased food consumption and body weight); core grade minimum (Elanco Products, 1983b)

Data Gap(s): 1) Rat Reproduction Study

__I.A.5. Confidence in the Oral RfD

Study — Medium
Database — Low
RfD — Low

The principal rat studyy establishing the LEL appears to be fairly comprehensive in scope. However, the minimal number of animals used and the lack of detail in general suggest a rating of medium to low. Because of the lack of chronic and reproductive data, confidence in the database is considered low to medium. Confidence in the RfD can also be considered low to medium.

__I.A.6. EPA Documentation and Review of the Oral RfD

Pesticide Registration Standard (1981)

Pesticide Registration Files

Agency Work Group Review — 11/21/1985, 02/05/1986, 05/18/1986, 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 Isopropalin 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).

Top of page

_I.B. Reference Concentration for Chronic Inhalation Exposure (RfC)

Substance Name — Isopropalin
CASRN — 33820-53-0

Not available at this time.

Top of page

_II.  Carcinogenicity Assessment for Lifetime Exposure

Substance Name — Isopropalin
CASRN — 33820-53-0

This substance/agent has not undergone a complete evaluation and determination under US EPA's IRIS program for evidence of human carcinogenic potential.

Top of page

_III.  [reserved]
_IV.  [reserved]
_V.  [reserved]

_VI.  Bibliography

Substance Name — Isopropalin
CASRN — 33820-53-0
Last Revised — 09/01/1990

_VI.A. Oral RfD References

Elanco Products Company. 1969a. MRID No. 00002472. Available from EPA. Write to FOI, EPA, Washington, DC 20460.

Elanco Products Company. 1969b. MRID No. 00134907. Available from EPA. Write to FOI, EPA, Washington, DC 20460.

Elanco Products Company. 1983a. MRID No. 00131230. Available from EPA. Write to FOI, EPA, Washington, DC 20460.

Elanco Products Company. 1983b. MRID No. 00131231. Available from EPA. Write to FOI, EPA, Washington, DC 20460.

Top of page

_VI.B. Inhalation RfC References


Top of page

_VI.C. Carcinogenicity Assessment References


Top of page

_VII.  Revision History

Substance Name — Isopropalin
CASRN — 33820-53-0

03/31/1987 IV. Regulatory Action section on-line
06/01/1989 I.A.6. Work group review dates added
09/01/1990 I.A. Principal study citation year corrected
09/01/1990 I.A.4. Citations added
09/01/1990 VI. Bibliography on-line
01/01/1992 IV. Regulatory actions updated
08/01/1995 I.A.6. 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.
12/03/2002 I.A.6. Screening-Level Literature Review Findings message has been added.

Top of page

_VIII.  Synonyms

Substance Name — Isopropalin
CASRN — 33820-53-0
Last Revised — 01/31/1987

Top of page

Recent Additions | Search IRIS | IRIS Home | NCEA Home | ORD Home

Jump to main content.