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2-(2-Methyl-4-chlorophenoxy)propionic acid (MCPP) (CASRN 93-65-2 )

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2-(2-Methyl-4-chlorophenoxy)propionic acid (MCPP); CASRN 93-65-2

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.


File First On-Line 01/31/1987

Category (section)
Last Revised
Oral RfD Assessment (I.A.) on-line 08/01/1990
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 — 2-(2-Methyl-4-chlorophenoxy)propionic acid (MCPP)
CASRN — 93-65-2
Last Revised — 08/01/1990

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*

Increased absolute and
relative kidney weights

90-Day Rat Feeding Study

BASF Aktiegesellschaft,

NOEL: 50 ppm
(3 mg/kg/day)

LEL: 150 ppm
(9 mg/kg/day)


*Conversion Factors -- Actual dose tested

__I.A.2. Principal and Supporting Studies (Oral RfD)

BASF Aktiegesellschaft. 1985. MRID No. 00158359. Available from EPA. Write to FOI, EPA, Washington, DC 20460.

Fifteen Wistar rats/sex/dose were exposed to MCPP in the diet for 90 days at levels of 0, 50, 150, or 450 ppm (0, 3, 9 or 26 mg/kg/day). At 150 ppm (9 mg/kg/day), there was increased absolute and relative kidney weights in males and increased relative kidney weights in females. At 450 ppm (26 mg/kg/day), there was an increased relative and absolute kidney weights in both sexes and increased creatinine levels in females and decreased glucose levels in males. Therefore, the NOEL for this study is 3 mg/kg/day.

__I.A.3. Uncertainty and Modifying Factors (Oral RfD)

UF — An uncertainty factor of 1000 was used to account for the inter- intraspecies and for the subchronic nature of the study. An additional UF of 3 was used to account for the lack of a second species toxicity feeding study (e.g. dog), and a reproductive study (rat).

MF — None

__I.A.4. Additional Studies/Comments (Oral RfD)

Data Considered for Establishing the RfD

1) 90-Day Feeding - rat: Principal study - see previous description; core grade minimum

2) Teratology - rat: Maternal toxic NOEL=125 mg/kg/day; Developmental NOEL=50 mg/kg/day; Developmental LEL=125 mg/kg/day (increased intra-uterine deaths, decreased crown/rump lengths, and incomplete or absent ossification of the sternebrae); core grade minimum (Boots Co., Ltd., 1980)

3) Teratology - rabbit: Maternal NOEL=30 mg/kg/day; Maternal LEL=75 mg/kg/day (reduced weight gain); Developmental NOEL=75 mg/kg/day (HDT); core grade minimum (PBI-Gordon Corp., 1980)

Other Data Reviewed:

1) 90-Day Feeding - rat: Ten (10) animals/sex/group were fed 0, 50, 400, or 3200 ppm MCPP in the diet [equivalent to 0, 2.5, 20, or 160 mg/kg bw/day for 90 days (Verschuuren et al., 1975)]. The NOAEL of 2.5 mg/kg bw/day was set upon observation of increased relative kidney weights at the higher doses. Male rats had decreased hematocrits at 2.5 and 160 but not at 20 mg/kg/day, indicating that the effect at the lowest feeding level was not dose-related.

2) 7-Month Feeding - rat (MCPP diethanolamine): Groups of 10 rats were fed MCPP diethanolamine for 7 months. Increased relative kidney weights were observed at all doses (3.4, 13.4, 33.5, and 83.8 mg/kg bw/day) (Gurd et al., 1965).

Data Gap(s): Chronic Rat Feeding Study; Chronic Dog Feeding Study; Rat Reproduction Study

__I.A.5. Confidence in the Oral RfD

Study — Medium
Database — Medium
RfD — Medium

The critical study is of adequate quality and is given a medium confidence rating. A toxicity study in another species and a reproduction study are lacking, therefore, confidence in the database can be considered medium to low. Confidence in the RfD can also be considered medium to low.

__I.A.6. EPA Documentation and Review of the Oral RfD

Source Document — This assessment is not presented in any existing U.S. EPA document.

Other EPA Documentation — Pesticide Registration Standard, August 1988; Pesticide Registration Files

Agency Work Group Review — 10/09/1985, 11/06/1985, 10/12/1988

Verification Date — 10/12/1988

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-(2-Methyl-4-chlorophenoxy)propionic acid conducted in September 2002 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).

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

Substance Name — 2-(2-Methyl-4-chlorophenoxy)propionic acid (MCPP)
CASRN — 93-65-2

Not available at this time.

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_II.  Carcinogenicity Assessment for Lifetime Exposure

Substance Name — 2-(2-Methyl-4-chlorophenoxy)propionic acid (MCPP)
CASRN — 93-65-2

This substance/agent has not undergone a complete evaluation and determination under US EPA's IRIS program for evidence of human carcinogenic potential.

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

_VI.  Bibliography

Substance Name — 2-(2-Methyl-4-chlorophenoxy)propionic acid (MCPP)
CASRN — 93-65-2
Last Revised — 12/01/1989

_VI.A. Oral RfD References

BASF, Aktiengesellschaft. 1985. MRID No. 00158359. Available from EPA. Write to FOI, EPA, Washington DC 20460.

Boots Company, Ltd. 1980. MRID No. 00164569. Available from EPA. Write to FOI, EPA, Washington DC 20460.

Gurd, M., G. Harmer and B. Lessel. 1965. Summary of toxicological data: Acute toxicity and 7-month feeding studies with mecopr nd MCPA. Food Cosmet. Toxicol. 3: 883-885.

PBI-Gordon Corporation. 1980. MRID No. 00127269. Available from EPA. Write to FOI, EPA, Washington DC 20460.

Verschuuren, H.G., R. Kores and E.M. Den Tonkelar. 1975. Short-term oral and dermal toxicity of MCPA and MCPP. The Toxicologist. 3: 349-359.

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_VI.B. Inhalation RfC References


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_VI.C. Carcinogenicity Assessment References


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_VII.  Revision History

Substance Name — 2-(2-Methyl-4-chlorophenoxy)propionic acid (MCPP)
CASRN — 93-65-2

03/01/1988 I.A.1. Dose conversion clarified
12/01/1988 I.A. Withdrawn; new RfD verified (in preparation)
01/01/1989 I.A. Oral RfD summary replaced; RfD changed
12/01/1989 VI. Bibliography on-line
08/01/1990 I.A. Text edited
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.

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_VIII.  Synonyms

Substance Name — 2-(2-Methyl-4-chlorophenoxy)propionic acid (MCPP)
CASRN — 93-65-2
Last Revised — 01/31/1987

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