Diquat (CASRN 85-00-7)
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0153
Diquat;
CASRN 85-00-7
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 Diquat
File First On-Line 03/31/1987
Category (section) |
Status |
Last Revised |
---|---|---|
Oral RfD Assessment (I.A.) | on-line | 01/01/1995 |
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 — Diquat
CASRN — 85-00-7
Last Revised — 01/01/1995
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.
NOTE: The Oral RfD for diquat may change in the near future pending the outcome of a further review now being conducted by the RfD/RfC Work Group.
__I.A.1. Oral RfD Summary
Critical Effect |
Experimental Doses* |
UF
|
MF
|
RfD
|
---|---|---|---|---|
Minimal lens opacity Chronic Rat Study, Chevron Chemical, |
NOEL: 0.22 mg/kg/day LEL: 0.58 mg/kg/day |
100
|
1
|
2.2E-3
mg/kg/day |
*Conversion Factors -- none
__I.A.2. Principal and Supporting Studies (Oral RfD)
Chevron Chemical Company. 1985. MRID No. 00145855, 00155474, 00160673. Available from EPA. Write to FOI, EPA, Washington, DC 20460.
Groups of 50 male and 50 female Sprague-Dawley rats were fed diets containing 0, 5, l5, 75, or 375 ppm of diquat for 2 years. Experimental doses were expressed in terms of diquat cation and reported as ppm in the diet and as mg/kg bw/day. An additional group of l0 animals/sex/dose level was used for interim (at 1 year) sacrifice. The dose levels at the NOEL (15 ppm) were 0.19 mg/kg/day for males and 0.24 mg/kg/day for females. The dose levels at the LEL (75 ppm) were 0.19 mg/kg/day for males and 0.24\mg/kg/day for females. The principal toxic effects at the 75 and 375 ppm dose levels were as follows:
75 ppm - lens opacity/cataracts in eyes with secondary effects, males and females; possible kidney effects in males.
375 ppm - lens opacity/cataracts in eyes with secondary effects, males and females; decreased body weights, males and females; decreased food consumption, males and females; possible kidney effects, males; possibly increased arthritis/periarteritis in blood vessels, males; possibly increased paracortical cell hyperplasia in lymph nodes, males.
__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 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 guideline
2) Chronic Feeding (2-4 years) - dog: NOEL=1.7 mg/kg/day; LEL=5.0 mg/kg/day (cataract formation); core grade supplementary (Chevron Chemical, 1966)
3) Teratology - rat: Teratogenic NOEL=500 ppm (25 mg/kg/day) (HDT); Systemic NOEL=125 ppm (6.25 mg/kg/day); Systemic LEL=500 ppm; Maternal toxicity and Fetotoxic effects were observed at the HDT; core grade minimum (Chevron Chemical, 1973)
4) Teratology - rabbit: Systemic NOEL=1.25 mg/kg/day; Teratogenic NOEL=5.0 mg/kg/day (HDT) (maternal weight loss occurred at this level); core grade minimum (Chevron Chemical, 1974)
5) Teratology - mouse: Teratogenic NOEL=4 mg/kg/day (HDT); Systemic LEL=1.0 mg/kg/day, this level was fetotoxic (ossification was retarded) and also caused maternal toxicity; core grade minimum (Chevron Chemical, 1978)
6) 3-Generation Reproduction - rat: NOEL=500 ppm (25 mg/kg/day) (HDT) for adverse reproductive effects; NOEL=125 ppm (6.25 mg/kg/day) (minor body weight decreases only); LEL (for definite effects)=500 ppm (cataracts observed after 91 days, weight loss); core grade minimum (Chevron Chemical, 1972)
Data Gap(s): Chronic Dog Feeding Study
__I.A.5. Confidence in the Oral RfD
Study — High
Database — Medium
RfD — Medium
The principal study appears to be of high quality and is given a high confidence rating. In addition, there are generally good toxicologic studies available on diquat which, overall, provide medium to high confidence in the database, oncogenic considerations notwithstanding. Confidence in the RfD is considered medium to high.
__I.A.6. EPA Documentation and Review of the Oral RfD
Pesticide Registration Standard
Pesticide Registration Files
Agency Work Group Review — 07/22/1986, 12/09/1994
Verification Date — 07/22/1986
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 Diquat conducted in November 2001 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 — Diquat
CASRN — 85-00-7
Not available at this time.
_II. Carcinogenicity Assessment for Lifetime Exposure
Substance Name — Diquat
CASRN — 85-00-7
Not available at this time.
_III.
[reserved]
_IV. [reserved]
_V. [reserved]
_VI. Bibliography
Substance Name — Diquat
CASRN — 85-00-7
Last Revised — 09/01/1990
_VI.A. Oral RfD References
Chevron Chemical Company. 1966. MRID No. 00140578, Available from EPA. Write to FOI, EPA, Washington, DC 20460.
Chevron Chemical Company. 1972. MRID No. 00140589. Available from EPA. Write to FOI, EPA, Washington, DC 20460.
Chevron Chemical Company. 1973. EPA Accession No. 224405. Available from EPA. Write to FOI, EPA, Washington, DC 20460.
Chevron Chemical Company. 1974. MRID No. 00161635. Available from EPA. Write to FOI, EPA, Washington, DC 20460.
Chevron Chemical Company. 1978. MRID No. 00061637. Available from EPA. Write to FOI, EPA, Washington, DC 20460.
Chevron Chemical Company. 1985. MRID No. 00145855, 00155474, 00160673. 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 — Diquat
CASRN — 85-00-7
Date |
Section |
Description |
---|---|---|
03/01/1988 | I.A.5. | Confidence levels revised |
09/01/1989 | II. | Carcinogen assessment now under review |
09/01/1990 | I.A. | Principal study clarified |
09/01/1990 | I.A.4. | Citations added |
09/01/1990 | VI. | Bibliography on-line |
01/01/1992 | IV. | Regulatory actions updated |
02/01/1994 | I.A.1. | Critical dose and NOAEL(ADJ) corrected |
01/01/1995 | I.A. | Oral RfD noted as pending change |
01/01/1995 | I.A.6. | Work group review date added |
08/01/1995 | I.A., I.A.6., 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. |
12/03/2002 | I.A.6. | Screening-Level Literature Review Findings message has been added. |
_VIII. Synonyms
Substance Name — Diquat
CASRN — 85-00-7
Last Revised — 03/31/1987
- 85-00-7
- 1,1'-AETHYLEN-2,2'-BIPYRIDINIUM-DIBROMID
- AQUACIDE
- DEIQUAT
- DEXTRONE
- 9,10-DIHYDRO-8a,10a-DIAZONIAPHENANTHRENE(1,1'-ETHYLENE-2,2'-BIPYRIDYLIUM)
- DIBROMIDE
- 9,10-DIHYDRO-8a,10,-DIAZONIAPHENANTHRENE DIBROMIDE
- 5,6-DIHYDRO-DIPYRIDO(1,2a,1c)PYRAZINIUM DIBROMIDE
- 6,7-DIHYDROPYRIDO (1,2-a',1'-c)PYRAZINEDIUM DIBROMIDE
- DIPYRIDO(1,2-a',1'-c)PYRAZINEDIIUM, 6,7-DIHYDRO-, DIBROMIDE
- Diquat
- DIQUAT DIBROMIDE
- 1,1'-ETHYLENE-2,2'-BIPYRIDYLIUM DIBROMIDE
- ETHYLENE DIPYRIDYLIUM DIBROMIDE
- 1,1-ETHYLENE 2,2-DIPYRIDYLIUM DIBROMIDE
- FB/2
- NA 2781
- PREEGLONE
- REGLON
- REGLONE
- REGLOX
- WEEDTRINE-D