2-Methyl-4-chlorophenoxyacetic acid (MCPA) (CASRN 94-74-6)
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0066
2-Methyl-4-chlorophenoxyacetic acid (MCPA);
CASRN 94-74-6
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 MCPA
File First On-Line 01/31/1987
Category (section) |
Status |
Last Revised |
---|---|---|
Oral RfD Assessment (I.A.) | on-line | 01/01/1991 |
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 — 2-Methyl-4-chlorophenoxyacetic acid (MCPA)
CASRN — 94-74-6
Last Revised — 01/01/1991
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
|
---|---|---|---|---|
Kidney and liver 1-Year Dog Feeding Industry Task Force |
NOEL: 6 ppm LEL: 30 ppm |
300
|
1
|
5E-4
mg/kg/day |
*Conversion Factors -- 1 ppm = 0.025 mg/kg/day (assumed dog food consumption)
__I.A.2. Principal and Supporting Studies (Oral RfD)
Industry Task Force on MCPA Research Data. 1986a. MRID No. 00152152, 00164352. Available from EPA. Write to FOI, EPA, Washington, DC 20460.
Oral aministration of technical MCPA to male and female beagle dogs (6/sex/dose) at doses of 0, 6, 30, or 150 ppm (0, 0.15, 0.75, or 3.75 mg/kg/day) for 52 weeks resulted in kidney and liver toxicity at the mid- and/or high-dose levels, with alterations in clinical chemistries (kidneys: urea, potassium, creatinine; liver: bilirubin, GPT, GOT, triglycerides, and cholesterol) associated with concommitant organ weight changes (liver) and histopathology changes (kidney: increased kidney pigment deposition in proximal tubular epithelium; liver: change in the nature/coloration of gall fluid). Therefore, based upon kidney and liver toxicity at the 30 and 150 ppm dose levels, the LEL for systemic toxicity is 30 ppm (0.75 mg/kg/day). The NOEL for systemic toxicity is 6 ppm (0.15 mg/kg/day).
__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 on chronic toxicity (chronic rat and mouse study, and teratogenicity in two species).
MF — None
__I.A.4. Additional Studies/Comments (Oral RfD)
Data Considered for Establishing the RfD
1) 1-Year Feeding - dog: Principal study - see previous description; core grade minimum
2) 90-Day Feeding - rat: NOEL=50 ppm (2.5 mg/kg/day); LEL=150 ppm (7.5 mg/kg/day) (increased absolute and relative kidney weights in mid- and high- dose males, but not females; this was associated with a significant decrease in serum calcium in high-dose males and a significant elevation in creatinine concentrations in high-dose females. Both sexes had apparent crystaluria (oxalate, calcium phosphate, urate) in the high-dose groups. Hepatotoxicity is also suggested in high-dose males based on prolonged in clotting times and decreased cholesterol concentrations); core grade minimum (Industrial Task Force on MCPA Research Data, 1985)
3) 2-Generation Reproduction - rat: NOEL=150 ppm (7.5 mg/kg/day); LEL=450 ppm (22.5 mg/kg/day) (HDT; small but statistically significant depression in male and/or female pup weights/pup weight gains by days 14 and 21 of weaning in all littering groups [F1a, F1b, F2a, F2b], which may indicate a potential delayed postnatal growth effect); core grade minimum (Industrial Task Force on MCPA Research Data, 1986b)
Other Data Reviewed:
1) 90-Day Feeding - dog: NOEL=1 mg/kg/day; LEL=3 mg/kg/day; Severe toxicity and mortality occurred at 48 mg/kg/day (HDT). There was evidence of dose- related liver and kidney toxicity (changes in serum enzymes, decreased ability to filter dyes, bromosulphalein serum retention [BSP] and phenolsulfonphthalein retention [PSP]), in both sexes at dose levels down to 3 mg/kg/day. These effects were associated with kidney and liver histopathology changes in the 12 and 48 mg/kg/day dose groups]; core grade minimum (Industrial Task Force on MCPA Research Data, 1980)
Data Gap(s): Chronic Rat Feeding Study, Chronic Mouse Feeding Study, Rat Teratology 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 chronic studies in rats and mice are 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
Pesticide Registration Standard, June 1988
Pesticide Registration Files
Agency Work Group Review — 07/22/1985, 03/18/1987, 06/22/1988
Verification Date — 06/22/1988
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 2-Methyl-4-chlorophenoxyacetic acid conducted in September 2002 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 — 2-Methyl-4-chlorophenoxyacetic acid (MCPA)
CASRN — 94-74-6
Not available at this time.
_II. Carcinogenicity Assessment for Lifetime Exposure
Substance Name — 2-Methyl-4-chlorophenoxyacetic acid (MCPA)
CASRN — 94-74-6
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 — 2-Methyl-4-chlorophenoxyacetic acid (MCPA)
CASRN — 94-74-6
Last Revised — 03/01/1991
_VI.A. Oral RfD References
THP Committee, MCPA Task Force. 1980. MRID No. 00158842. Available from EPA. Write to FOI, EPA, Washington, DC 20460.
Industry Task Force on MCPA Research Data. 1986a. MRID No. 00152152, 00164352. Available from EPA. Write to FOI, EPA, Washington, DC 20460.
Industry Task Force on MCPA Research Data. 1985. MRID No. 00165471. Available from EPA. Write to FOI, EPA, Washington, DC 20460.
Industry Task Force on MCPA Research Data. 1986b. MRID No. 40041701. 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 — 2-Methyl-4-chlorophenoxyacetic acid (MCPA)
CASRN — 94-74-6
Date |
Section |
Description |
---|---|---|
08/28/1987 | I.A. | New study - RfD changed |
03/01/1988 | I.A.6. | Verification date changed |
09/26/1988 | I.A.1. | Citation corrected |
09/26/1988 | I.A.2. | Text revised |
09/26/1988 | I.A.3. | UF text revised |
09/26/1988 | I.A.4. | Study descriptions revised |
09/26/1988 | I.A.5. | Confidence levels revised |
01/01/1991 | I.A. | Text edited |
03/01/1991 | VI. | Bibliography on-line |
01/01/1992 | IV. | Regulatory action 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. |
12/03/2002 | I.A.6. | Screening-Level Literature Review Findings message has been added. |
_VIII. Synonyms
2-Methyl-4-chlorophenoxyacetic acid (MCPA)
CASRN — 94-74-6
Last Revised — 01/31/1987
- 2M-4C
- 2M-4CH
- 2M-4KH
- 4K-2M
- 94-74-6
- AGRITOX
- AGROXON
- AGROXONE
- ANICON KOMBI
- ANICON M
- BH MCPA
- BORDERMASTER
- BROMINAL M PLUS
- B-SELEKTONON M
- 4-CHLORO-o-CRESOXYACETIC ACID
- (4-CHLORO-2-METHYLPHENOXY)-ACETIC ACID
- 4-CHLORO-o-TOLOXYACETIC ACID
- ((4-CHLORO-o-TOLYL)OXY)ACETIC ACID
- CHWASTOX
- CORNOX-M
- DICOPUR-M
- DICOTEX
- DIKOTES
- DIKOTEX
- EMCEPAN
- EMPAL
- HEDAPUR M 52
- HEDAREX M
- HEDONAL M
- HORMOTUHO
- HORNOTUHO
- KILSEM
- KREZONE
- LEGUMEX DB
- LEUNA M
- LEYSPRAY
- LINORMONE
- M 40
- MCP
- MCPA
- 2,4-MCPA
- MEPHANAC
- METAXON
- METHOXONE
- Methyl-4-chlorophenoxyacetic acid, 2-
- 2-METHYL-4-CHLORPHENOXYESSIGSAEURE
- NETAZOL
- OKULTIN M
- PHENOXYLENE PLUS
- PHENOXYLENE SUPER
- RAPHONE
- RAZOL DOCK KILLER
- RHOMENC
- RHOMENE
- RHONOX
- SEPPIC MMD
- SHAMROX
- SOVIET TECHNICAL HERBICIDE 2M-4C
- TRASAN
- USTINEX
- VACATE
- VERDONE
- VESAKONTUHO MCPA
- WEEDONE MCPA ESTER
- WEED-RHAP