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Imazalil

Publication Date: 9/93

TRADE OR OTHER NAMES

Trade names for products containing imazalil include Bromazil, Deccozil, Fungaflor, Freshgard, and Fungazil. The fungicide is compatible with many other types of pesticides.

INTRODUCTION

Imazalil is a systemic imidazole fungicide used to control a wide range of fungi on fruit, vegetables and ornamentals, including powdery mildew on cucumber and black spot on roses. Imazalil is also used as a seed dressing and for postharvest treatment of citrus, banana and other fruit to control storage decay. Under natural conditions it is less likely that resistant strains of fungi will develop with imazalil than with some of the other fungicides (4).

Imazalil is a general use pesticide.

TOXICOLOGICAL EFFECTS

ACUTE TOXICITY

Imazalil is classified as a moderately toxic compound and carries the signal word WARNING on the label. Test animals have experienced symptoms, including goose flesh (or goose bumps), due to the excitation of hair folicles, muscle incoordination, reduced arterial tension, tremors, and vomiting. Contact dermatitis has been noted in some cases in sensitive individuals.

Imazalil has an oral LD50 of 227 mg/kg for females rat and 343 for males. The LC50 in dogs is greater than 640 mg/kg (8). The dermal LD50 for rats is 4,200 to 4,880 mg/kg (1) and the inhalation LC50 is greater than 16 g/m3.

CHRONIC TOXICITY

Rats fed imazalil nitrate at dietary levels of 5 to 80 mg/kg for 14 weeks were not affected in appearance, behavior, survival, food consumption, urinalysis or tissue composition. There were slight liver, body weight, and bilirubin changes at higher doses (4). Groups of rats fed 5 to 80 mg/kg for 6, 12, and 24 months did not produce compound or dose-related effects on body weight gains, food consumption, appearance, behavior, or survival.

Similar results were found in a dog study where animals received up to 20 mg/kg for two years. The liver showed some slight effects at the higher doses, but all other measured and observed parameters were within normal limits.

Reproductive Effects

In three separate three-generation rat studies at low to moderate doses (5 to 80 mg/kg), there was a trend to a lower number of live births at the highest dose level. No differences were noted in percent of pregnancies or duration of pregnancy (4). It is unlikely that, at low exposure levels, imazalil will cause reproductive problems.

Teratogenic Effects

None of the rat studies mentioned above resulted in fetal abnormalities. A mouse study at doses up to 40 mg/kg was also negative.

Mutagenic Effects

Dominant lethal mutagenic effects were not evident in male and female mice. It does not appear that imazalil causes serious mutations.

Carcinogenic Effects

In a group of rats given imazalil for 30 months at low doses (5.0 mg/kg/day), there were no increases in tumors compared to the controls (4). This suggests that imazalil is non-carcenogenic.

Organ Toxicity

Based on extensive studies of structurally similar human antifungal drugs, adverse effects on humans are improbable (4).

Fate in Humans and Animals

Imazalil is rapidly absorbed, distributed, metabolized, and excreted by rats. Following a single dose of imazalil sulfate, 90% was excreted in 96 hours. Only 3% was the unmetabolized imazalil compound, indicating almost complete absorption from the gastrointestinal tract. At least four metabolites are formed. 48 hours after administration, concentrations in the liver, lung and kidney were higher than 1 mg/kg, but accumulation in fatty tissue did not occur.

ECOLOGICAL EFFECTS

Very little data on ecological effects was found. Both the mallard duck and the Japanese quail are relatively insensitive to the fungicide. The LC50 values in these birds range from about 5,500 to 6,300 mg/kg/day. These values indicate that the compound is practically non- toxic to birds. The compound should not be toxic to bees when used properly (1).

ENVIRONMENTAL FATE

In sandy or clay soils, the half-life of imazalil was four to five months. Only 6-7% was metabolized to T824 (D-dealkylated transformation product) while about 13% was an unidentified, polar compound. In a plot where seven applications were made at 14-day intervals, residues were from 0.085 - 0.14 mg/kg in the 0 - 10 cm layer. Leaching was practically non-existent and accumulation did not appear to be a problem. Half-life was calculated at about 6.5 months.

In acid to neutral aqueous solutions, imazalil is stable for at least eight weeks at 40 degrees. Decomposition occurs at elevated temperatures and under the influence of light (4).

Under normal storage conditions, oranges dipped in 2,000 mg active ingredient/l and stored have residues (89%) present as the parent compound. Only a small amount of imazalil was present in the pulp and part of this may have resulted from handling during peeling (4). The half-life was 12 to 20 weeks. Studies with apples gave similar results.

One week after treated barley seed was sown in soil, about 76% of the imazalil was in the adjacent soil and about 29% was in the seedcoat. After three weeks only 6% was in the green plant parts.

Exposure Guidelines:

NOEL: 2.5 mg/kg/day (dog and rabbit)
ADI: 0.03 mg/kg/day (WHO)
RfD: 0.013 mg/kg/day (EPA)
LEL: 5 mg/kg/day (dog)

Physical Properties:

CAS #: 35554-44-0
Chemical name: 1-[2-(2,4-dichlorophenyl)-2-(2-propenyloxy) ethyl}-1H-imidazole
Chemical class/use: imidazole fungicide
Solubility in water: 180 mg/l
Solubility in other solvents: hexane 5.21 g/100g; methanol, toluene, benzene >50 g/100g
Melting Point: thermally stable up to 285 degrees C
Vapor Pressure: 1.6 x 10-6 mPa at 25 degrees C

BASIC MANUFACTURER

Janssen Pharmaceutica
Plant Protection Division
40 Kingsbridge Rd
Piscataway, NJ 08855-3998
Telephone: 908-524-9116

Review by Basic Manufacturer:

Comments solicited: October, 1992
Comments received: November, 1992

REFERENCES

  1. Hartley, D., and H. Kidd, Editors (1991). The Agrochemicals Handbook. The Royal Society of Chemistry, The University, Nottingham, England.
  2. Spencer, E.Y. (1981). Guide to the Chemicals Used in Crop Protection. Research Branch, Agriculture Canada, Canadian Government Publishing Centre, Ottawa, Canada.
  3. Worthing, Charles R., Editor (1983). The Pesticide Manual, A World Compendium. The British Crop Protection Council, The Ravenham Press Limited, Ravenham, Suffolk, England.
  4. Food and Agriculture Organization of the United Nations, (1977). Pesticide Residues in Food - 1977. FAO Plant Production and Protection Paper, 10 sup.
  5. National Institute for Occupational Safety and Health (1983 Supplement) Registry of Toxic Effects of Chemical Substances, U. S. Dept of Health and Human Services, Public Health Service, Centers for Disease Control, Cincinnati, OH.
  6. Food and Agriculture Organization of the United Nations, (1985). Pesticide Residues in Food - 1985. FAO Plant Production and Protection Paper 72/2.
  7. Food and Agriculture Organization of the United Nations (1986) Pesticide Residues in Food - 1986. FAO Plant Production and Protection Paper 77.
  8. Edwards, I Ralph, Donald G. Ferry, and Wayne A. Temple. 1991. Fungicides and related Compounds. in Handbook of Pesticide Toxocology, Volume 3, Classes of Pesticides. Wayland J. Hayes Jr. and Edward R. Laws, Jr. editors. Academic Press, Inc., NY.