Chlorpyrifos (CASRN 2921-88-2)
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0026
Chlorpyrifos; CASRN 2921-88-2
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 Chlorpyrifos
File First On-Line 01/31/1987
Category (section) |
Status |
Last Revised |
---|---|---|
Oral RfD Assessment (I.A.) | on-line | 03/01/1988 |
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 — Chlorpyrifos
CASRN — 2921-88-2
Last Revised — 03/01/1988
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
|
---|---|---|---|---|
Decreased plasma ChE activity after 9 days. 20-Day Human Cholinesterase Inhibition Study Dow Chemical, 1972 |
NOEL: 0.03 mg/kg/day LOEL: 0.10 mg/kg/day |
10
|
1
|
3E-3
mg/kg/day |
*Conversion Factors: none
__I.A.2. Principal and Supporting Studies (Oral RfD)
Dow Chemical Company. 1972. Accession No. 112118. Available from EPA. Write to FOI, EPA, Washington DC 20460.
Sixteen human male volunteers were treated (4/dose) with 0, 0.014, 0.03, or 0.10 mg/kg/day of chlorpyrifos by capsule for a total of 20 days at the low and mid dose, and for 9 days at the high dose. Treatment of the high-dose group (0.1 mg/kg/day) was discontinued after 9 days due to a runny nose and blurred vision in one individual. Mean plasma ChE in this group was inhibited by about 65% compared to the control average. No effect on RBC ChE activity was apparent at any dose.
__I.A.3. Uncertainty and Modifying Factors (Oral RfD)
UF — The UF of 10 is the standard factor allowing for the range of human sensitivity for cholinesterase inhibition.
MF — None
__I.A.4. Additional Studies/Comments (Oral RfD)
Data Considered for Establishing the RfD
1) 20-day ChE inhibition study - humans: Principal study - see previous description
2) Chronic feeding - dog: Plasma ChE NOEL=0.01 mg/kg/day (LDT); NOEL (other effects)=3.0 mg/kg/day (HDT); core grade minimum (Dow Chemical, 1971a)
3) Chronic feeding - rat: Plasma ChE NOEL=0.1 mg/kg/day; NOEL (other effects)=3.0 mg/kg/day (HDT); few animals used (Dow Chemical, 1971b)
4) Reproduction - rat: ChE NOEL=0.1 mg/kg/day; Reproductive NOEL=1.0 mg/kg/day (HDT); core grade minimum (Dow Chemical, 1971c)
5) Teratology - rat: Maternal (ChE) NOEL=0.1 mg/kg/day; Developmental NOEL=15 mg/kg/day (HDT); core grade minimum (Dow Chemical, 1983)
6) Teratology - mouse: Maternal (ChE) NOEL=0.1 mg/kg/day; Developmental NOEL=10 mg/kg/day (decreased fetal length, increased skeletal variations at 25 mg/kg/day); core grade minimum (Dow Chemical, 1979)
Data Gap(s): Chronic feeding/oncogenicity - rat.
__I.A.5. Confidence in the Oral RfD
Study — Medium
Database — Medium
RfD — Medium
The principal human
study was limited because only 4 males/dose were studied, but several
doses were used; thus, the study is given a medium to low confidence
rating. The available experimental data in rats, dogs, rabbits,
and mice appears to be similar to the NOEL for ChE inhibition in
humans; thus, confidence in the database is rated medium.
Medium confidence in the RfD follows.
__I.A.6. EPA Documentation and Review of the Oral RfD
Office of Pesticide Programs files
Agency Work Group Review — 03/11/1986
Verification Date — 03/11/1986
__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 — Chlorpyrifos
CASRN — 2921-88-2
Not available at this time.
_II. Carcinogenicity Assessment for Lifetime Exposure
Substance Name —
Chlorpyrifos
CASRN — 2921-88-2
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 — Chlorpyrifos
CASRN — 2921-88-2
Last Revised — 11/10/1989
_VI.A. Oral RfD References
Dow Chemical Company. 1972. Accession No. 112118. Available from EPA. Write to FOI, EPA, Washington DC 20460.
Dow Chemical USA. 1971a. MRID No. 00029063, 00064933, 00146519. Available from EPA. Write to FOI, EPA, Washington DC 20460.
Dow Chemical USA. 1971b. MRID No. 00081270, 00095178. Available from EPA. Write to FOI, EPA, Washington DC 20460.
Dow Chemical USA. 1971c. MRID No. 00029064, 00064934. Available from EPA. Write to FOI, EPA, Washington DC 20460.
Dow Chemical USA. 1979. MRID No. 00095268. Available from EPA. Write to FOI, EPA, Washington DC 20460.
Dow Chemical USA. 1983. MRID No. 00130400. 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 — Chlorpyrifos
CASRN — 2921-88-2
Date |
Section |
Description |
---|---|---|
03/01/1988 | I.A.5. | Core grades added |
11/01/1989 | 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. |
02/22/2001 | I.A., II. | This chemical is being reassessed under the IRIS Program. |
02/09/2004 | I.A., II. | This chemical is no longer being reassessed under the IRIS Program. See Federal Register February 9, 2004 (Volume 69, Number 26). |
_VIII. Synonyms
Substance Name — Chlorpyrifos
CASRN — 2921-88-2
Last Revised — 01/31/1987
- 2921-88-2
- BRODAN
- Chlorpyrifos
- CHLORPYRIFOS-ETHYL
- DETMOL U.A.
- DOWCO 179
- DURSBAN
- DURSBAN F
- ENT 27311
- ERADEX
- ETHION, dry
- LORSBAN
- NA 2783
- OMS-0971
- O,O-DIAETHYL-O-3,5,6-TRICHLOR-2-PYRIDYLMONOTHIOPHOSPHAT
- O,O-DIETHYL O-3,5,6-TRICHLORO-2-PYRIDYL PHOSPHOROTHIOATE
- PHOSPHOROTHIOIC ACID, O,O-DIETHYL O-(3,5,6-TRICHLORO-2-PYRIDYL)ESTER
- PYRINEX