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Chlorpyrifos
CASRN 2921-88-2
Contents
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 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 NOEL: 0.03 mg/kg/day 10 1 3E-3
activity after 9 mg/kg/day
days LEL: 0.10 mg/kg/day
20-Day Human
Cholinesterase
Inhibition Study
Dow Chemical, 1972
*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 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
Data Base -- 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 data base 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 Risk Information Hotline for all questions concerning this
assessment or IRIS, in general, at (513)569-7254 (phone), (513)569-7159 (FAX)
or RIH.IRIS@EPAMAIL.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.
_VI. BIBLIOGRAPHY
Substance Name -- Chlorpyrifos
CASRN -- 2921-88-2
Last Revised -- 11/01/1989
__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
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
Last updated: 5 May 1998
URL: http://www.epa.gov/iris/SUBST/0026.HTM
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