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Chlorpropham

Publication Date: 9/93

TRADE OR OTHER NAMES

Beet-Kleen, Bud Nip, Chloro IPC, CIPC, Furloe, Sprout Nip, Spud-Nic, Taterpex, Triherbide-CIPC and Unicrop CIPC.

REGULATORY STATUS

Products containing chlorpropham must bear the signal word "Caution" (1).

INTRODUCTION

Chlorpropham is a plant growth regulator used for preemergence control of grass weeds in alfalfa, lima and snap beans, blueberries, cane berries, carrots, cranberries, ladino clover, garlic, seed grass, onions, spinach, sugar beets, tomatoes, safflower, soybeans, gladioli and woody nursery stock. It is also used to inhibit potato sprouting and for sucker control in tobacco (1). Chlorpropham is available in emulsifiable concentrate and liquid formulations.

TOXICOLOGICAL EFFECTS

ACUTE TOXICITY

Chlorpropham is moderately toxic by ingestion (2). It may cause irritation of the eyes or skin (2). Symptoms of poisoning in laboratory animals have included listlessness, incoordination, nose bleeds, protruding eyes, bloody tears, difficulty in breathing, prostration, inability to urinate, high fevers, and death. Autopsies of animals have shown inflammation of the stomach and intestinal lining, congestion of the brain, lungs and other organs, and degenerative changes in the kidneys and liver (2)

The oral LD50 for chlorpropham in rats ranges from 1,200 mg/kg to 3,800 mg/kg (1, 2), and in rabbits is 5,000 mg/kg (2). The 4-hour inhalation LC50 in rats is > 32 mg/l (4).

CHRONIC TOXICITY

Chronic exposure of laboratory animals has caused retarded growth, increased liver, kidney and spleen weights, congestion of the spleen and death (2). No deaths or micropathological abnormalities occurred in rats given diets containing 2% chlorpropham for 90 days (4).

Reproductive Effects

Long-term exposure to chlorpropham may cause adverse reproductive effects (2). Chlorpropham may cross the placenta (2). In reproductive studies with rats, 500 mg/kg, the highest dose tested, produced no adverse effects (5).

Teratogenic Effects

No birth defects occurred in a 3-generation study with rats (4).

Mutagenic Effects

EPA states that, "The single acceptable mutagenicity study (gene mutation) was negative" (5).

Carcinogenic Effects

Long-term exposure to chlorpropham may cause tumors (2). In one experiment chlorpropham initiated skin cancer in mice, but this result was not confirmed by a later study (2).

Organ Toxicity

No information was found.

Fate in Humans and Animals

No information was found.

ECOLOGICAL EFFECTS

Effects on Birds

Chlorpropham is practically non-toxic to waterfowl (5). Its LD50 in mallards is > 2,000 mg/kg (1, 4).

Effects on Aquatic Organisms

Chlorpropham is moderately toxic to cold and warm water freshwater fish (5). The LC50 for chlorpropham in rainbow trout is 3 to 6 ppm, and 6.3 to 6.8 ppm in bluegill sunfish (1).

Chlorpropham accumulated in the skinned fillet of bluegill sunfish to 100 times the levels in surrounding water (5).

Effects on Other Animals (Nontarget species)

No information was found.

ENVIRONMENTAL FATE

Breakdown of Chemical in Soil and Groundwater

Chlorpropham has some potential to contaminate groundwater because it is highly soluble in water and it has only a moderate tendency to adsorb to soil particles (3, 5). Chlorpropham adsorbs strongly to organic matter, so it is unlikely to leach through soils high in organic matter. Chlorpropham does not readily adsorb to montmorillonite or kaolinite clays (4).

Chlorpropham is subject to degradation by soil microbes. Photodegradation and volatilization do not readily occur. Increasing temperatures above 35 degrees C and increasing soil moisture capacity may increase volatilization (4). Soil half-lives from 35 days (3) to 65 days at 15 degrees C or 30 days at 29 degrees C (4) have been reported. Degradation rates are affected by microbial activity and soil moisture levels (4).

Breakdown of Chemical in Surface Water

Chlorpropham is not subject to hydrolysis in aqueous solution (5).

Breakdown of Chemical in Vegetation

Chlorpropham is absorbed by the roots of susceptible grass seedlings and transported throughout the plant. It is absorbed more slowly by leaves (4). It suppresses plant transpiration and respiration and inhibits root and epicotyl growth (5).

PHYSICAL PROPERTIES AND GUIDELINES

Technical chlorpropham is a white to light brown crystalline solid (2, 5). It is stable under normal temperatures and pressures, but poses a slight fire hazard if exposed to heat or flame, and a fire and explosion hazard in the presence of strong oxidizers. It may burn but will not readily ignite. Avoid contact with strong oxidizers, excessive heat, sparks or open flame. Thermal decomposition may release highly toxic fumes of phosgene, toxic and corrosive fumes of chlorides, and oxides of carbon (2). Workers handling chlorpropham should avoid breathing vapors, wear goggles to prevent eye contact and protective clothing to prevent prolonged skin contact (2, 3).

Exposure Guidelines:

No occupational exposure limits have been established for pendimethalin by OSHA, NIOSH or ACGIH (2).

Physical Properties:

CAS #: 101-21-3
Chemical name: isopropyl m-chlorocarbanilate, or isopropyl-N-(3-chlorophenyl) carbamate
Chemical Class/Use: carbamate herbicide and plant growth regulator
Specific gravity: 1.180 at 30 degrees C (2)
H20 solubility: 89 ppm at 25 degrees C (2)
Solubility in other solvents: soluble in butyrolactone, benzene, xylene, chloroform, ketones, acetone, methanol, ethanol, isopropyl alcohol, kerosene, esters, heavy aromatic naphtha, aromatic hydrocarbons, most organic solvents and oils (2).
Melting point: 106 degrees F (41degrees C) (2)
Boiling point: 300 degrees F (149 degrees C) at 2 mm Hg (2)
Decomposition temperature: 150 degrees C and above (4)
Vapor pressure: negligible at 25 degrees C (2)
Koc: 1150 (3)

BASIC MANUFACTURER

Atochem North America, Inc.
Three Parkway
Philadelphia, PA 19102
Emergency: 215-587-7885

Review by Basic Manufacturer:

Comments solicited: April, 1993
Comments received:

REFERENCES

  1. Meister, R.T. (ed.). 1992. Farm Chemicals Handbook '92. Meister Publishing Company, Willoughby, OH.
  2. Occupational Health Services, Inc. 1992 (Nov. 11). MSDS for Chlorpropham. OHS Inc., Secaucus, NJ.
  3. U. S. Department of Agriculture, Soil Conservation Service. 1990 (Nov.). SCS/ARS/CES Pesticide Properties Database: Version 2.0 (Summary). USDA - Soil Conservation Service, Syracuse, NY.
  4. WSSA Herbicide Handbook Committee. 1989. Herbicide Handbook of the Weed Science Society of America, 6th Ed. WSSA, Champaign, IL.
  5. U.S. Environmental Protection Agency. Dec, 1987. Pesticide Fact Sheet Number 150: Chlorpropham. US EPA, Office of Pesticide Programs, Registration Div., Washington, DC.