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Mecoprop

Publication Date: 9/95

TRADE OR OTHER NAMES

Mecoprop is commonly called MCPP. Trade names include Kilprop, Mecopar,Triester-II, Mecomin-D, Triamine-II (with MCPA and 2.4-DP), Triplet (with 2,4-D and dicamba), TriPower (with MCPA and dicamba), Trimec (with 2,4-D and dicamba), Trimec-Encore (with MCPA and dicamba), and U46 KV Fluid (1, 2).

REGULATORY STATUS

Mecoprop is a general use pesticide (GUP).

INTRODUCTION

Mecoprop is a selective, hormone-type phenoxy herbicide. It is applied postemergence and is used on ornamentals and sports turf, for forest site preparation, and on drainage ditch banks for selective control of surface creeping broadleaf weeds such as clovers, chickweed, lambsquarters, ivy, plantain and others. It is also used on wheat, barley, and oats (1, 2). Mecoprop is absorbed by plant leaves and translocated to the roots. It affects enzyme activity and plant growth (3). It acts relatively slowly requiring three to four weeks for control (2). The U.S. EPA has classified mecoprop as toxicity class III- slightly toxic. Products containing mecoprop bear the Signal Word "Caution" (1). It is available as a liquid concentrate, granules, and is sprayed on fertilizer pellets to produce weed and feed products (6).

TOXICOLOGICAL EFFECTS

ACUTE TOXICITY

Mecoprop has a low acute toxicity to test animals. The LD50, the oral dose that kills half of the test animals, is 930 -1210 mg/kg for rats and 650 mg/kg for mice (1, 2, 5). The LD50 for rats exposed dermally is greater than 4000 mg/kg (1, 4). Mecoprop is irritating to skin and eyes. It causes redness and swelling and can cause cloudy vision (7). The concentration in air which kills half of the test animals, the LC50 (4 hours) for rats, is greater than 12.5 mg/l air (3).

CHRONIC TOXICITY

Reproductive Effects

No information is currently available.

Teratogenic Effects

Mecoprop is a teratogen in rats at moderate to high doses. Oral doses of 125 mg/kg/day of MCPP in pregnant rats from days 6 to 15 of gestation caused increased intra-uterine deaths, decreased body lengths, and an increased incidence of delayed or absent bone formation in offspring. Mecoprop is not teratogenic in rabbits (6).

Mutagenic Effects

Studies show that mecoprop may be mutagenic at very high doses. Tests of mecoprop on four strains of salmonella and on s. colelicolor showed no mutagenic effects (2). However, MCPP caused an increase in sister chromatid exchange after single oral doses of 470 and 3,800 mg/kg in Chinese hamsters (6).

Carcinogenic Effects

A study of people employed in the manufacture of phenoxy herbicides including mecoprop showed an association between these herbicides and cancer of soft tissues and non-Hodgkin's lymphoma (8). However, other data do not support this conclusion (10). Thus, it is not clear if occupational exposures to phenoxy herbicides can cause cancer.

Organ Toxicity

Oral doses of 9 mg/kg/day to female rats and 27 mg/kg/day to male rats cause kidney damage (6).

Fate in Humans and Animals

Mecoprop is eliminated unchanged in the urine of mammals (3).

ECOLOGICAL EFFECTS

Effects on Birds

Mecoprop is practically non-toxic to birds. The LC50 is greater than 5,620 ppm for mallard ducks and 5,000 ppm for bobwhite quail (6). The LD50 (oral) is 740 mg/kg for Japanese quail and 700 mg/kg for bobwhite quail (3).

Effects on Aquatic Organisms

Mecoprop is virtually non-toxic to fish. Available data indicate a low potential of mecoprop to bioaccumulate in fish (6). The LC50 (96 hours) is 124 ppm for rainbow trout and greater than 100 ppm for bluegill sunfish (3, 6).

Effects on Other Animals (Nontarget species)

Mecoprop is not toxic to bees (1).

ENVIRONMENTAL FATE

Breakdown of Chemical in Soil and Groundwater

The duration of mecoprop's residual activity in soil is about two months. Adsorption of mecoprop increases with an increase in organic matter in the soil. Unaged MCPP and its salt forms are very mobile in a variety of soils (3). Because of this high mobility, it may potentially leach into groundwater (6). However, in general, phenoxy herbicides such as MCPP are not sufficiently persistent to reach groundwater (6).

Breakdown of Chemical in Surface Water

No information is currently available.

Breakdown of Chemical in Vegetation

No information is currently available.

PHYSICAL PROPERTIES AND GUIDELINES

Mecoprop is an odorless, white to light brown crystalline solid. It exists as a mixture of two optically active isomers of which one, the R+ form, mecoprop-p is herbicidally active (3). It is stable to heat, hydrolysis, reduction, and oxidation. It is acidic. Solutions of the salts of mecoprop are stable for several years under normal storage conditions. In cooler temperatures, the salt may crystallize out of solution but will re-dissolve on warming (1, 6).

Physical Properties:

Properties are of the acid form unless otherwise noted.

CAS #: 7085-19-0 (acid)
1929-86-8 (potassium salt)
1432-14-0 (diethanolamine salt)
28473-03-2 (isooctyl ester)
Chemical Name: 2-(4-chloro-2-methyl phenoxy) propionic acid
Melting Point: 94-95 degrees C (3)
Boiling Point: Decomposes before reaching boiling (6)
Solubility in water: all forms are very soluble in water at 20 degrees C (3)
Solubility in other solvents: Soluble in acetone, alcohol, benzene, diethyl ether, and ethyl acetate (3)
Partition Coefficient Octanol/Water: 1.26 at pH 7 (3)

Exposure Guidelines:

Guidelines are for the acid form unless otherwise noted.

RfD: 1 x 10 to the minus 3 mg/kg/day (9)
NOEL: 3 mg/kg/day (rats); 15 mg/kg/day (dog) (3, 9)

BASIC MANUFACTURER

PBI/Gordon
P.O. Box 4090
1217 W. 12th Street
Kansas City, MO 64101
Telephone: 816-421-4070

Review by Basic Manufacturer:

Comments solicited: October, 1994
Comments received:

REFERENCES

  1. Meister, R.T. 1992. Farm Chemicals Handbook '92. Meister Publishing Company. Willoughby, OH.
  2. Thomson, W. T. 1982. Agricultural Chemicals Book II Herbicides Thomson Publications. Fresno, CA.
  3. The Agrochemicals Handbook, Third Edition. 1994. Royal Society of Chemistry Information Systems, Unwin Brothers Ltd., Surrey, England.
  4. Meister, R.T. 1994. Farm Chemicals Handbook '94. Meister Publishing Company. Willoughby, OH.
  5. Budavari, Susan (ed.) 1989. The Merck Index, Eleventh Edition. Merck and Company Inc. Rahway, NJ.
  6. U. S. Environmental Protection Agency Office of Pesticides and Toxic Substances. 1988. Fact Sheet No. 192: 2-(2-Methyl-4-chlorophenoxy) propionic acid and its salts and esters. U.S. EPA. Washington, DC.
  7. U.S. Environmental Protection Agency. 1986. Toxchem No. 559, MCPP Document #243675 and 246437. EPA. Washington, DC.
  8. Lynge, E.A. 1985. "Follow up study of cancer incidence among workers in manufacture of phenoxy herbicides in Denmark." British Journal of Cancer. Vol. 52. pp.259-270.
  9. U.S. Department of Health and Human Services. 1988. U.S. EPA Integrated Risk Information System (IRIS) database. HHS. Washington, DC.
  10. Buzik, S.C. 1992. Toxicology of 2,4-Dichlorophenoxyacetic Acid (2,4-D) A Review. Toxicology Research Center of University of Saskatchewan. Saskatoon, Canada.