E X T O X N E T
Extension Toxicology Network
A Pesticide Information Project of Cooperative Extension Offices of
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University of California at Davis. Major support and funding was provided
by the USDA/Extension Service/National Agricultural Pesticide Impact
Assessment Program.
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Pesticide
Information
Profile
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Propazine
Publication Date: 9/93
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TRADE OR OTHER NAMES
Some trade names include Gesamil, Milocep, Milogard, Primatol, Geigy
30028, Plantulin, Propazin, G-30028, Milo-Pro and Prozinex.
REGULATORY STATUS
Propazine is classified as a general use herbicide by the U.S.
Environmental Protection Agency (EPA). Products containing propazine must
bear the EPA signal word "Caution," indicating that it is slightly poisonous
(1).
INTRODUCTION
Propazine is an herbicide used for control of broadleaf weeds and annual
grasses in sweet sorghum (24). It is applied as a spray at the time of
planting or immediately following planting, but prior to weed or sorghum
emergence. It is also used as a postemergence selective herbicide on carrots,
celery and fennel (20, 21). Propazine is available in wettable powder, liquid
and water dispersible granular formulations (23).
TOXICOLOGICAL EFFECTS
ACUTE TOXICITY
Propazine is classified as a moderately toxic herbicide. Administration
of lethal or near lethal doses to rats has caused symptoms of lethargy,
muscular weakness, runny nose, emaciation, diarrhea, and labored breathing
(22). It is mildly irritating to the skin, eyes, and upper respiratory tract
(10). Contact dermatitis has been reported among workers manufacturing
propazine (7). No cases of poisoning from human ingestion of this herbicide
have been recorded (27). Skin and eye contact with propazine, as well as
inhalation, should be avoided (20).
The amount of a chemical that is lethal to one-half (50%) of experimental
animals fed the material is referred to as its acute oral lethal dose fifty,
or LD50. The oral LD50 for propazine in rats is 3,840 to greater than 7,000
mg/kg, in mice is 3,180 mg/kg, and in guinea pigs is 1,200 mg/kg (11, 23).
Slight irritation was noted after propazine was applied to the skin of rabbits
(1). Its dermal LD50 in rats is 10,200 mg/kg, and in rabbits is greater than
2,000 mg/kg (1, 24). Eye applications of 400 mg caused mild eye irritation in
these animals (11). Symptoms of dizziness, cramping, and labored and
irregular breathing were evident in mice given 5,000 mg/kg orally (20).
Propazine has caused convulsions or coma, as well as liver and/or kidney
damage in experimental animals (3).
CHRONIC TOXICITY
When given daily to rabbits for one to four months, oral doses of 500
mg/kg propazine were reported to cause a type of anemia (4). No gross signs
of toxicity or pathologic changes were evident in rats that received daily
doses of 250 mg/kg of propazine for 130 consecutive days. No clinical or
physical toxic symptoms were observed in beagle dogs fed 1.25, 5, or 25 mg/kg
of propazine formulation in 90-day feeding studies (20).
EPA has established a Lifetime Health Advisory (LHA) level for propazine
in drinking water at 10 ug/l. EPA believes that water containing propazine at
or below this level is acceptable for drinking every day over the course of
one's lifetime, and does not pose any health concerns. Consumption of
propazine at high levels well above the LHA level over a long period of time
has caused decreased fetal weight gain and delayed fetal bone development in
animal studies (24).
The National Academy of Science has established an Acceptable Daily
Intake (ADI) of 0.0464 mg/kg/day for propazine (12, 24).
Reproductive Effects
There was an increase in the number of deaths of newborns produced by
female rats that were given 5 mg/kg of propazine during 18 days of pregnancy
(15). Consumption of propazine at high levels well above the Lifetime Health
Advisory level over a long period of time has caused decreased fetal weight
gain and delayed fetal bone development in animal studies (24). Maternal
doses of 500 mg/kg/day resulted in maternal toxicity and developmental
toxicity expressed as increased incidence of extra ribs, incomplete bone
formation, and decreased fetal body weights (29). In a 3-generation study
with rats fed 0, 0.15, 5 or 50 mg/kg/day, no effects on fertility, length of
pregnancy, pup viability or pup survival were observed. At 50 mg/kg, pup body
weights on day 21 of lactation were reduced, and there were pathological
changes in organ weights in the 2nd and 3rd generation (29).
Teratogenic Effects
No teratogenic effects were observed in rats fed 500 mg/kg/ day, the
highest dose tested (29).
Mutagenic Effects
Propazine has shown no mutagenic effects in tests conducted on human and
rat liver cells and in live hamsters (24).
Carcinogenic Effects
No evidence of increased tumor frequency was detected in a 2-year study
in mice fed doses up to 450 mg/kg of propazine each day. When rats were fed
0. 0.15, 5, or 50 mg/kg of propazine each day for 2 years, there was an
increase in the incidence of mammary gland tumors at the highest dose level.
EPA has classified propazine as a possible human carcinogen. This category
includes substances for which there is limited evidence of carcinogenicity in
animals in the absence of human data. Because propazine in drinking water may
possibly increase the risk of cancer in humans, the Lifetime Health Advisory
for propazine includes an additional margin of safety (24).
Organ Toxicity
Liver damage is one of the suspected effects of propazine (5). The
functioning of certain liver processes was decreased in rats which were given
2,500 mg/kg propazine (4).
Fate in Humans and Animals
Triazines, the family of chemicals within which propazine is included,
may disturb the metabolism of some of the B vitamins, thiamine (B1) and
riboflavin (B2). They may also concentrate and accumulate in the fat of
humans and animals (5). Propazine is readily absorbed and metabolized in the
body (4). 72 hours after administration of single oral doses of radio-labeled
propazine to rats, 66% of the dose was excreted in the urine and 23% was
excreted in the feces. This indicates that 77% of the dose was absorbed into
the bloodstream from the gastrointestinal tract. Eight days after the dosing,
propazine or its metabolites were detected in the rats' lungs, spleen, heart,
kidneys and brain (24).
ECOLOGICAL EFFECTS
Effects on Birds
Propazine is considered slightly toxic to non-toxic to birds (21). The
eight-day dietary LC50 is greater than 10,000 ppm for both bobwhite quail and
mallard ducks (20).
Effects on Aquatic Organisms
Propazine is slightly toxic to coldwater fish (29). The 96-hour LC50 is
18 ppm for rainbow trout and greater than 100 ppm for bluegill sunfish (6, 20).
Effects on Other Animals (Nontarget species)
Propazine is practically non-toxic to bees (6, 29).
ENVIRONMENTAL FATE
Breakdown of Chemical in Soil and Groundwater
Propazine does not adsorb as strongly to soil particles as other
commercial triazine herbicides. In most soils, it binds only weakly to soil
particles (Koc = 154 g/m), and, depending on soil temperature, moisture and
pH, it can become unbound. Its movement with soil moisture is limited by
partial adsorption to soil particles, as well as its low water solubility
(20). One study found propazine to be mobile in sandy loam, loam, and clay
loam soils. It was very mobile in loamy sand (29). Propazine is persistent,
moderately mobile in most soils, and it is resistant to breakdown by
hydrolysis, photolysis or biodegradation (29). For these reasons, propazine
is one of the pesticide compounds considered by the EPA to have the greatest
potential for leaching into groundwater (18). Leaching of propazine is most
likely to occur where there is irrigation and/or high rainfall, or sandy soil
(20).
A significant portion of the herbicide may be broken down by soil
microbes. Several soil microorganisms utilize propazine as a source of energy
or nitrogen. Photolysis and volatilization are not important factors in
propazine degradation (20).
Propazine will persist longer in dry or cold conditions or other
conditions which inhibit biological and chemical activity (20). When it was
applied at 0.5 pounds/acre, propazine persisted for 11 to 24 weeks (13). Its
soil half-life is 135 days (25).
Breakdown of Chemical in Water
Propazine is resistant to breakdown by hydrolysis. After 28 days, at pH
5, 60% of applied propazine remained unhydrolyzed; at pH 7, 92% remained; and
at pH 9, 100% remained (24).
Propazine has been detected in drinking water in the United States (12).
It has been found in 33 out of 1,097 surface water samples and in 15 out of
906 groundwater samples. Contaminated groundwater samples have been collected
from eight states. The maximum concentration found in any sample was 13 ug/l
(ppb) for surface water and 300 ug/l (ppb) for groundwater (24, 29).
Breakdown of Chemical in Vegetation
Propazine is absorbed principally through plant roots. After absorption,
it is moved, or translocated, upward into the plant where it accumulates in
the growing shoots and leaves of plants (20).
The breakdown of propazine in plants is assumed to be similar to the
metabolism of two other herbicides, atrazine and simazine. Propazine
accumulates and causes death in those plants that are unable to readily
metabolize it into a nonpoisonous compound (20).
PHYSICAL PROPERTIES AND GUIDELINES
Propazine is a colorless crystalline solid (28). The technical material
is more than 95% pure (7, 9). It is stable in neutral, slightly acid, or
alkaline media, but it is hydrolyzed by stronger acids and alkalis (7). It is
nonflammable and noncorrosive under normal use conditions, but may burn if
exposed to heat or flame. Thermal decomposition may produce toxic oxides of
carbon and nitrogen, and toxic and corrosive fumes of chlorides (20, 26).
Occupational Exposure Guidelines:
Occupational exposure limits for propazine have not been established by
OSHA, ACGIH, or NIOSH (26).
Physical Properties:
| CAS #: | 139-40-2 |
| Specific gravity: | 1.162 (26) |
| H20 solubility: | 8.6 ppm at 20 degrees C (1, 9, 20) |
| Solubility in other solvents: | Difficult to dissolve in organic solvents (20, 22); 6.2 g/kg at 22 degrees C in benzene and toluene (21); 2.5 g/kg in carbon tetrachloride (21); 0.5 g/100 ml at 20 degrees C in diethyl ether (6) |
| Melting point: | 212-214 degrees C (1, 7) |
| Vapor pressure: | 2.9 x 10 to the minus 8 mm Hg at 20 degrees C (7); 3.4 x 10 to the minus 6 mm Hg at 50 degrees C (20) |
| Log Kow: | 2.94 (16); 785 (8) |
| Chemical Class/Use: | selective triazine herbicide |
BASIC MANUFACTURER
Ciba-Geigy Corp.
Agricultural Division
P.O. Box 18300
Greensboro, NC 27419
Review by Basic Manufacturer:
Comments solicited: January, 1992
Comments received: April, 1992
REFERENCES
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Meister Publishing Company.
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hygiene and toxicology. Third edition. Vol. 2: Toxicology. NY: John Wiley
and Sons.
Dreisbach, R. H. 1983. Handbook of poisoning: Prevention, diagnosis
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Gosselin, R. E., et al. 1984. Clinical toxicology of commercial
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Hallenbeck, W. H. and K. M. Cunningham-Burns. 1985. Pesticides and
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Hartley, D. and H. Kidd, eds. 1983. The Agrochemicals Handbook.
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Hayes, W. J. 1982. Pesticides studied in man. Baltimore, MD:
Williams and Wilkins.
Kenaga, E. E. and C. A. I. Goring. 1980. Relationship between water
solubility, soil sorption, octanol-water partitioning and concentration of
chemicals in biota. In J. G. Eaton, P. R. Parrish, and A. C. Hendriks (eds),
Aquatic Toxicology. ASTM STP 707, pp 78. Philadelphia: Amer. Soc. Testing
and Materials.
Melnikov, N. N. 1971. Chemistry of pesticides. N.Y.: Springer-
Verlag, Inc.
Morgan, D. P. 1982 (Jan.). Recognition and management of pesticide
poisonings. Third edition. U.S. Environmental Protection Agency. Washington,
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Shepard, T. H. 1980. Catalogue of teratogenic agents. Third
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Environmental News. Office of Public Affairs (A-107). Washington, DC.
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Worthing, C. R., ed. 1983. The pesticide manual: A world
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Publishing Company, Willoughby, OH.
U.S. Environmental Protection Agency. 1988 (Aug.). Propazine:
Health Advisory. Office of Drinking Water, US EPA, Washington, DC.
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Syracuse, NY.
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propazine. OHS Inc., Secaucus, NJ.
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U.S. Environmental Protection Agency. 1988 (Dec. 20 ). Pesticide
Fact Sheet #189: Propazine. Office of Pesticides and Toxic Substances, Office
of Pesticide Programs, USEPA, Washington, DC.
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Reregistration of Pesticide Products Containing Propazine as the Active
Ingredient. Office of Pesticides and Toxic Substances, USEPA, Washington, DC.
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site is not a substitute for a pesticide label. Trade names used herein
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criticism of unnamed products implied. Most of this information is historical
in nature and may no longer be applicable.
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