Jump to main content.


Dimethoate (CASRN 60-51-5)

IRIS
List of IRIS Substances




view QuickView

Main Contents

Go

0044

Dimethoate; CASRN 60-51-5

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.

STATUS OF DATA FOR Dimethoate

File First On-Line 01/31/1987

Category (section)
Status
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 — Dimethoate
CASRN — 60-51-5
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*
UF
MF
RfD

Brain ChE inhibition

2-Year Rat Feeding
Study

American Cyanamid
Co., 1986a

NOEL: 1 ppm diet
(0.05 mg/kg/day)

LEL: 5 ppm diet
(0.25 mg/kg/day)

300
1
2E-4
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)

American Cyanamid Company. 1986a. MRID No. 00164177, 40545501. Available from EPA. Write to FOI, EPA, Washington, DC 20460.

Groups of Wistar SPF rats, 50 males and 50 females/group, were fed 0, 1, 5, 25, and 100 ppm (0, 0.05, 0.25, 1.25, and 5.0 mg/kg/day) of dimethoate in their diets for 2 years. A 2-year satellite study (animals were used for clinical chemistry, hematology, and urinalysis), with 15 rats/sex/dose group was also conducted using the same dose levels. There was a dose dependent lowering of cholinesterase activity in the brain in both males and females receiving 5, 25, and 100 ppm. Plasma and RBC cholinesterase activity was also inhibited in males and females receiving 25 and 100 ppm. Mortality was slightly increased in females receiving 100 ppm, and growth was retarded in 100 ppm males during the first half of the study. In rats receiving 100 ppm there was a slight anemia which was predominant in males and an increase in leukocytes in both sexes during the second half of the study.

__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. An additional UF of 3 was used to account for the lack of a complete database.

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 guideline

2) Cholinesterase - human: NOEL=0.2 mg/kg/day; LEL=0.4 mg/kg/day (plasma and RBC ChE inhibition); no core grade [Fisons (Canada), Ltd., 1958)

3) 90-Day Feeding - dog: ChE NOEL=2 ppm (0.05 mg/kg/day); ChE LEL=10 ppm (0.25 mg/kg/day) (RBC ChE depression); core grade minimum (American Cyanamid Co., 1968)

4) 3-Generation Reproduction - mouse: Reproductive NOEL=50 ppm (7.5 mg/kg/day) (HDT); core grade minimum (American Cyanamid Co., 1965)

5) Teratology - rat: Maternal NOEL=6 mg/kg/day; Maternal LEL=18 mg/kg/day (hypersensitivity, tremors, and unsteady gait); core grade minimum (Khera et al., 1979)

6) Teratology - rabbit: Maternal NOEL=10 mg/kg/day; Maternal LEL=20 mg/kg/day (decreased body weight); core grade supplementary (American Cyanamid, Co., 1984

Other Data Reviewed:

1) 78-Week Feeding (oncogenic) - mouse: Systemic NOEL=none; LEL=25 ppm (3.75 mg/kg/day) (hepatocyte vacuolization in females); ChE NOEL=none; LEL=25 ppm (3.75 mg/kg/day) (RBC and plasma depressed); at 200 ppm (30 mg/kg/day) (HDT) (liver tumors in females and lung and hemolymphorecticular system tumors in males were observed); core grade minimum (American Cyanamid Co., 1986b)

2) 2-Year Feeding (oncogenic) - rat: NOEL=1 ppm (0.05 mg/kg/day); LEL=10 ppm (0.5 mg/kg/day) (plasma and brain ChE inhibition); core grade supplementary (lack of detailed data disallows for histopathological effect) (American Cyanamid Co., 1970)

Data Gap(s): Chronic Dog Feeding Study; Rabbit Teratology Study

__I.A.5. Confidence in the Oral RfD

Study — High
Database — Medium
RfD — Medium

The critical study is of good quality and is given a high confidence rating. Since a chronic feeding study in a second species is lacking, 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

Registration Standard, 1982

Registration Files

Agency Work Group Review — 07/08/1985, 07/22/1985, 09/29/1986, 03/18/1987, 03/23/1988

Verification Date — 03/23/1988

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 Dimethoate 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).

Top of page


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

Substance Name — Dimethoate
CASRN — 60-51-5

Not available at this time.

Top of page


_II.  Carcinogenicity Assessment for Lifetime Exposure

Substance Name — Dimethoate
CASRN — 60-51-5

Not available at this time.

Top of page


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


_VI.  Bibliography

Substance Name — Dimethoate
CASRN — 60-51-5
Last Revised — 09/01/1990

_VI.A. Oral RfD References

American Cyanamid Company. 1965. MRID No. 00045816. Available from EPA. Write to FOI, EPA, Washington, DC 20460.

American Cyanamid Company. 1984. MRID No. 00149126. Available from EPA. Write to FOI, EPA, Washington, DC 20460.

American Cyanamid Company. 1968. MRID No. 00075532. Available from EPA. Write to FOI, EPA, Washington, DC 20460.

American Cyanamid Company. 1986a. MRID No. 00164177, 40545501. Available from EPA. Write to FOI, EPA, Washington, DC 20460.

American Cyanamid Company. 1986b. MRID No. 00163800. Available from EPA. Write to FOI, EPA, Washington, DC 20460.

American Cyanamid Company. 1970. MRID No. 00063995. Available from EPA. Write to FOI, EPA, Washington, DC 20460.

Fisons (Canada) Ltd. 1958. MRID No. 00055394. Available from EPA. Write to FOI, EPA, Washington, DC 20460.

Khera, K.S., C. Whalen, G. Trivett and G. Angers. 1979. Teratogenicity studies on pesticidal formulations of dimethoate, diuron and lindane in rats. Bull. Environ. Contam. Toxicol. 22(4-5): 522-529.

Top of page


_VI.B. Inhalation RfC References

None

Top of page


_VI.C. Carcinogenicity Assessment References

None

Top of page


_VII.  Revision History

Substance Name — Dimethoate
CASRN — 60-51-5

Date
Section
Description
03/01/1988 I.A.4. New data entered
03/01/1988 I.A.5. Confidence levels revised
03/01/1988 I.A.6. Review dates added
03/01/1988 I.A.6. Documentation corrected
06/30/1988 I.A. RfD withdrawn
08/22/1988 I.A. Revised oral RfD summary added
09/01/1990 I.A.4. Citations added
09/01/1990 IV.F.1. EPA contact changed
09/01/1990 VI. Bibliography on-line
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.
10/28/2003 I.A.6. Screening-Level Literature Review Findings message has been added.

Top of page


_VIII.  Synonyms

Substance Name — Dimethoate
CASRN — 60-51-5
Last Revised — 01/31/1987

Top of page

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


Jump to main content.