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National Library of Medicine, Bethesda, MD.
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FLUROXYPYR
CASRN: 69377-81-7
For other data, click on the Table of Contents
Human Health Effects:
Human Toxicity Excerpts:
The usual symptoms include headache, giddiness, nervousness, blurred vision, weakness,
nausea, cramps, diarrhea, and discomfort in the chest. Signs include sweating, miosis,
tearing, salivation and other excessive respiratory tract secretion, vomiting, cyanosis,
papilledema, uncontrollable muscle twitches followed by muscular weakness,
convulsions, coma, loss of reflexes, and loss of sphincter control. The last four signs are
seen only in severe cases but do not preclude a favorable outcome if treatment is prompt
and energetic. Cardiac arrhythmias, various degrees of heart block, and cardiac arrest
may occur ... /Organic phosphorus pesticides/
[Hayes, W.J., Jr., E.R. Laws, Jr., (eds.). Handbook of Pesticide Toxicology. Volume 2.
Classes of Pesticides. New York, NY: Academic Press, Inc., 1991. 938]**PEER
REVIEWED**
Probable Routes of Human Exposure:
Occupational exposure to fluroxypyr may occur through inhalation and dermal contact
with this compound at workplaces where fluroxypyr is produced or used. The general
population may be exposed to fluroxypyr via inhalation of ambient air, ingestion of food
and drinking water, and dermal contact with this compound. (SRC)
**PEER REVIEWED**
Emergency Medical Treatment:
Animal Toxicity Studies:
Non-Human Toxicity Excerpts:
Mild eye irritant ... (rabbits).
[Tomlin, C.D.S. (ed.). The Pesticide Manual - World Compendium. 10th ed. Surrey, UK:
The British Crop Protection Council, 1994. 506]**PEER REVIEWED**
Non-Human Toxicity Values:
LD50 Rat oral 2405 mg/kg
[Tomlin, C.D.S. (ed.). The Pesticide Manual - World Compendium. 10th ed. Surrey, UK:
The British Crop Protection Council, 1994. 506]**PEER REVIEWED**
LD50 Rabbit percutaneous > 5000 mg/kg
[Tomlin, C.D.S. (ed.). The Pesticide Manual - World Compendium. 10th ed. Surrey, UK:
The British Crop Protection Council, 1994. 506]**PEER REVIEWED**
LC50 Rat ihl >0.296 mg/l/4 hr
[Tomlin, C.D.S. (ed.). The Pesticide Manual - World Compendium. 10th ed. Surrey, UK:
The British Crop Protection Council, 1994. 506]**PEER REVIEWED**
Metabolism/Pharmacokinetics:
Absorption, Distribution & Excretion:
In rats, following oral administration, fluroxypyr is not metabolized, but is rapidly
excreted unchanged, principally in the urine.
[Tomlin, C.D.S. (ed.). The Pesticide Manual - World Compendium. 10th ed. Surrey, UK:
The British Crop Protection Council, 1994. 507]**PEER REVIEWED**
Mechanism of Action:
Fluroxypyr is applied as fluroxypyr-meptyl. After predominantly foliar uptake, the ester
is hydrolyzed to the parent acid, which is the herbicidally active form, and translocated
rapidly to other parts of the plants. Acts by inducing characteristic auxin-type responses,
e.g. leaf curling.
[Tomlin, C.D.S. (ed.). The Pesticide Manual - World Compendium. 10th ed. Surrey, UK:
The British Crop Protection Council, 1994. 506]**PEER REVIEWED**
Pharmacology:
Environmental Fate & Exposure:
Environmental Fate/Exposure Summary:
Fluroxypyr is not regestered for use in the United States however it's production and use
as a systemic herbicide is expected to result in its release to the environment through
various waste streams. If fluroxypyr is released to air, a vapor pressure of 9.42X10-7
mm Hg at 25 deg C indicates fluroxypyr will exist in both the vapor and particulate
phases in the ambient atmosphere. Vapor-phase fluroxypyr will be degraded in the
atmosphere by reaction with photochemically-produced hydroxyl radicals; the half-life
for this reaction in air is estimated to be 13 hours. Particulate-phase fluroxypyr will be
removed from the atmosphere by wet and dry deposition. Photolysis studies of
fluroxypyr have indicated that fluroxypyr does not undergo photolysis under typical
environmental conditions. If released to soil, fluroxypyr is expected to have a high
mobility based upon a measured Koc of 74. Volatilization from moist soil surfaces is not
expected to be an important fate process based upon an estimated Henry's Law constant
of 4.5X10-14 atm-cu m/mole. Fluroxypyr is not expected to volatilize from dry soil
surfaces based upon its vapor pressure. If released to soil or water, fluroxypyr is rapidly
degraded. Biodegradation of fluroxypyr in soil is rapid with half-lives ranging from 1 to
3 weeks, yielding a dichloropyridinol and a methoxypyridine metabolite as major
products. Biodegradation is also rapid in sediments/water solutions, and yields the
dichloropyridinol and two monochloropyridinol metabolites. In water, fluroxypyr is not
expected to adsorb to suspended solids and sediment in water based upon the measured
Koc value. Volatilization of fluroxypyr from water surfaces is not expected to be an
important fate process based upon the estimated Henry's Law constant. A pKa of 2.94
indicates fluroxypyr will exist almost entirely in the ionized form at pH values of 5 to 9,
pH values typically found in the environment, and therefore volatilization from water
surfaces is not expected to be an important fate process. An estimated BCF of 3.2
suggests the potential for bioconcentration of fluroxypyr in aquatic organisms is low.
Occupational exposure to fluroxypyr may occur through inhalation and dermal contact at
workplaces where fluroxypyr is produced or used. Those living near fields treated with
fluroxypyr formulations may also be exposed through inhalation or dermal contact.
(SRC)
**PEER REVIEWED**
Probable Routes of Human Exposure:
Occupational exposure to fluroxypyr may occur through inhalation and dermal contact
with this compound at workplaces where fluroxypyr is produced or used. The general
population may be exposed to fluroxypyr via inhalation of ambient air, ingestion of food
and drinking water, and dermal contact with this compound. (SRC)
**PEER REVIEWED**
Artificial Pollution Sources:
Fluroxypyr is not registered for use in the United States(1). However, the production and
use of fluroxypyr as a systemic herbicide, typically present in herbicide formulations as
the fluroxypyr-methylheptyl ester(2), is expected to result in the release of fluroxypyr to
the environment through various waste streams(SRC).
[(1) Farm Chemicals Handbook 1999. Willoughby, OH: Meister Publishing Co., p. C 190
(1999) (2) Tomlin CDS ed; The Pesticide Manual World Compendium. 11th ed., Surrey,
England: British Crop Protection Council p. 597 (1997)]**PEER REVIEWED**
Environmental Fate:
TERRESTRIAL FATE: Based on a classification scheme(1), a measured Koc value of
74(2) indicates that fluroxypyr is expected to have high mobility in soil. Volatilization of
fluroxypyr from moist soil surfaces is not expected to be an important fate process(SRC)
given an estimated Henry's Law constant of 4.5X10-14 atm-cu m/mole(SRC), using a
fragment constant estimation method(3). Fluroxypyr is not expected to volatilize from
dry soil based upon a vapor pressure of 9.42X10-7 mm Hg(4). Biodegradation is
expected to be an important fate process in soil with half-lives ranging from 1 to 3
weeks(5).
[(1) Swann RL et al; Res Rev 85: 17-28 (1983) (2) Lehmann RG, Miller JR, Laskowski
DA; Weed Res 30: 383-8 (1990) (3) Meylan WM, Howard PH; Environ Toxicol Chem
10: 1283-93 (1991) (4) Budavari S, ed; The Merck Index. 12th ed. Whitehouse Station,
NJ: Merck and Co., Inc., p. 712 (1996) (5) Lehmann RG et al; Weed Res 30: 375-82
(1990)]**PEER REVIEWED**
AQUATIC FATE: Based on a classification scheme(1), a measured Koc value of 74(2)
indicates that fluroxypyr is not expected to adsorb to suspended solids and sediment in
water. Volatilization from water surfaces is not expected based upon an estimated
Henry's Law constant of 4.54X10-14 atm-cu m/mole(SRC), developed using a fragment
constant estimation method(3). A pKa of 2.94 indicates fluroxypyr will exist almost
entirely in the ionized form at pH values of 5 to 9, and therefore volatilization from water
surfaces is not expected to be an important fate process. According to a classification
scheme(4), an estimated BCF of 3.2(SRC), from an estimated log Kow of 1.2(5) and a
regression derived equation(6) suggests the potential for bioconcentration in aquatic
organisms is low. Biodegradation in water is likely to be an important fate process as
rapid degradation of fluroxypyr was observed in soil/water solutions(7).
[(1) Swann RL et al; Res Rev 85: 17-28 (1983) (2) Lehmann RG et al; Weed Res 30:
383-8 (1990) (3) Meylan WM, Howard PH; Environ Toxicol Chem 10: 1283-93 (1991)
(4) Franke C et al; Chemosphere 29: 1501-14 (1994) (5) Meylan WM, Howard PH; J
Pharm Sci 84: 83-92 (1995) (6) Meylan WM et al; Environ Toxicol Chem 18: 664-72
(1999) (7) Lehmann RG et al; Weed Res 33: 197-204 (1993)]**PEER REVIEWED**
ATMOSPHERIC FATE: According to a model of gas/particle partitioning of
semivolatile organic compounds in the atmosphere(1), fluroxypyr, which has a vapor
pressure of 9.42X10-7 mm Hg at 25 deg C(2), is expected to exist in both the vapor and
particulate phases in the ambient atmosphere. Vapor-phase fluroxypyr is expected to be
degraded in the atmosphere by reaction with photochemically-produced hydroxyl
radicals(SRC). The half-life for this reaction in air is estimated to be 13 hours(SRC),
from a rate constant of 2.9X10-11 cu cm/molecule-sec at 25 deg C(SRC) determined
using a structure estimation method(3). Particulate-phase fluroxypyr may be removed
from the air by wet and dry deposition(SRC).
[(1) Bidleman TF; Environ Sci Technol 22: 361-367 (1988) (2) Budavari S, ed; The
Merck Index. 12th ed. Whitehouse Station, NJ: Merck and Co., Inc., p. 712 (1996) (3)
Meylan WM, Howard PH; Chemosphere 26: 2293-99 (1993)]**PEER REVIEWED**
Environmental Biodegradation:
In soil, fluroxypyr is rapidly degraded by microorganisms to 4-amino-3,5-dichloro-6fluoropyrid-2-ol,4-amino-3,5-dichloro-2-methoxypyridine, and carbon dioxide. Half-lives
ranged from 1 to 3 weeks(1). In sediment/soil solutions, under aerobic and anaerobic
conditions, 4-amino-3,5-dichloro-6-fluoropyrid-2-ol,4-amino-3-chloro-6-fluoropyrid-2ol, and carbon dioxide were formed. Additionally, under anaerobic conditions, 4-amino5-chloro-6-fluoropyrid-2-ol was formed. Degradation half-lives of 0.5-2 weeks were
observed(2). In a two-year study of the metabolism of C14-radiolabeled fluroxypyr on
two types of soil in lysimeters, fluroxypyr was rapidly metabolized and by the end of 3
months, only 1% of the applied parent was detected(3). In a study of C14-radiolabeled
fluroxypyr-methylheptyl ester on four types of soils, the ester rapidly hydrolyzed to
fluroxypyr, and fluroxypyr was then found to degrade with half-lives from 7 to 23 days,
depending on soil type(4).
[(1) Lehmann RG et al; Weed Res 31: 347-55 (1991) (2) Lehmann RG et al; Weed Res
33: 197-204 (1993) (3) Brumhard B, Fuhr F; Lysimeter Studies of Pesticides in the Soil.
Brit Crop Prot Council Monograph No. 53 (1992) (4) Lehmann RG et al; Weed Res 30:
375-82 (1990)]**PEER REVIEWED**
Environmental Abiotic Degradation:
The rate constant for the vapor-phase reaction of fluroxypyr with photochemicallyproduced hydroxyl radicals has been estimated as 2.9X10-11 cu cm/molecule-sec at 25
deg C(SRC) using a structure estimation method(1). This corresponds to an atmospheric
half-life of about 13 hours(SRC) at an atmospheric concentration of 5X10+5 hydroxyl
radicals per cu cm(1). Fluroxypyr is not expected to undergo hydrolysis in the
environment due to the lack of hydrolyzable functional groups(3) nor photolyze due to
the lack of absorption in the environmental UV spectrum (>290 nm). Particulate-phase
fluroxypyr may be removed from the air by wet and dry deposition(SRC).
[(1) Meylan WM, Howard PH; Chemosphere 26: 2293-99 (1993) (2) Mill T et al;
Environmental Fate and Exposure Studies Development of a PC-SAR for Hydrolysis:
Esters, Alkyl Halides and Epoxides. EPA Contract No. 68-02-4254. Menlo Park, CA:
SRI International (1987) (3) Lyman WJ et al; Handbook of Chemical Property Estimation
Methods. Washington, DC: Amer Chem Soc pp. 7-4, 7-5 (1990)]**PEER REVIEWED**
Environmental Bioconcentration:
An estimated BCF of 3.2 was calculated for fluroxypyr(SRC), using an estimated log
Kow of 1.2(1) and a regression-derived equation(2). According to a classification
scheme(3), this BCF suggests the potential for bioconcentration in aquatic organisms is
low.
[(1) Meylan WM, Howard PH; J Pharm Sci 84: 83-92 (1995) (2) Lyman WJ et al;
Handbook of Chemical Property Estimation Methods. Washington, DC: Amer Chem Soc
pp. 5-4, 5-10 (1990) (3) Franke C et al; Chemosphere 29: 1501-14 (1994)]**PEER
REVIEWED**
Soil Adsorption/Mobility:
A batch adsorption Koc value for fluroxypyr was experimentally determined to be 74(2).
According to the classification scheme(1), this measured Koc value suggests that
fluroypyr is expected to have a high mobility in soil.
[(1) Swann RL et al; Res Rev 85: 23 (1983) (2) Lehmann RG et al; Weed Res 30: 383388 (1990)]**PEER REVIEWED**
Volatilization from Water/Soil:
The Henry's Law constant for fluroxypyr is estimated as 4.54X10-14 atm-cu
m/mole(SRC) using a fragment constant estimation method(1). This Henry's Law
constant indicates that fluroxypyr is expected to be essentially nonvolatile from water
surfaces(2), and that volatilization of fluroxypyr from moist soil surfaces in not expected
to occur(SRC). Fluroxypyr is not expected to volatilize from dry soil surfaces(SRC)
based upon a vapor pressure of 9.42X10-7 mm Hg(3).
[(1) Meylan WM, Howard PH; Environ Toxicol Chem 10: 1283-93 (1991) (2) Lyman WJ
et al; Handbook of Chemical Property Estimation Methods. Washington, DC: Amer
Chem Soc pp. 15-1 to 15-29 (1990) (3) Budavari S, ed; The Merck Index. 12th ed.
Whitehouse Station, NJ: Merck and Co., Inc., p. 712 (1996)]**PEER REVIEWED**
Plant Concentrations:
In a study to determine C-14 uptake in rotational crops 1, 4 and 12 months after
application of the formulation, fluroxypyr dissipated too rapidly to be taken up by most
of the rotational crops. Wheat plants absorbed only small quantities through the roots,
and these residues were not deposited in the grain, but in the straw/chaff fraction, which
is recycled back to the field(1).
[(1) Lehmann RG et al; Weed Res 31: 347-55 (1991)]**PEER REVIEWED**
Environmental Standards & Regulations:
Chemical/Physical Properties:
Molecular Formula:
C7H5Cl2FN2O3
[Tomlin, C.D.S. (ed.). The Pesticide Manual - World Compendium. 10th ed. Surrey, UK:
The British Crop Protection Council, 1994. 506]**PEER REVIEWED**
Molecular Weight:
255.03
[Budavari, S. (ed.). The Merck Index - An Encyclopedia of Chemicals, Drugs, and
Biologicals. Whitehouse Station, NJ: Merck and Co., Inc., 1996. 712]**PEER
REVIEWED**
Color/Form:
White crystalline solid
[Budavari, S. (ed.). The Merck Index - An Encyclopedia of Chemicals, Drugs, and
Biologicals. Whitehouse Station, NJ: Merck and Co., Inc., 1996. 712]**PEER
REVIEWED**
Odor:
Odorless
[Budavari, S. (ed.). The Merck Index - An Encyclopedia of Chemicals, Drugs, and
Biologicals. Whitehouse Station, NJ: Merck and Co., Inc., 1996. 712]**PEER
REVIEWED**
Melting Point:
232 deg C
[Lide, D.R. (ed.). CRC Handbook of Chemistry and Physics. 79th ed. Boca Raton, FL:
CRC Press Inc., 1998-1999. ,p. 3-166]**PEER REVIEWED**
Density/Specific Gravity:
1.09 at 24 deg C
[Tomlin, C.D.S. (ed.). The Pesticide Manual - World Compendium, 11 th ed., British
Crop Protection Council, Surrey, England 1997 597]**PEER REVIEWED**
Dissociation Constants:
pKa = 2.94
[Tomlin, C.D.S. (ed.). The Pesticide Manual - World Compendium, 11 th ed., British
Crop Protection Council, Surrey, England 1997 597]**PEER REVIEWED**
Solubilities:
In water, 91 mg/l (20 deg C). In acetone 51.0, methanol 34.6, ethyl acetate 10.6,
isopropanol 9.2, dichloromethane 0.1, toluene 0.8, xylene 0.3 (all in g/l, 20 deg C).
[Tomlin, C.D.S. (ed.). The Pesticide Manual - World Compendium, 11 th ed., British
Crop Protection Council, Surrey, England 1997 597]**PEER REVIEWED**
Vapor Pressure:
9.42X10-7 mm Hg @ 25 deg C
[Budavari, S. (ed.). The Merck Index - An Encyclopedia of Chemicals, Drugs, and
Biologicals. Whitehouse Station, NJ: Merck and Co., Inc., 1996. 712]**PEER
REVIEWED**
Chemical Safety & Handling:
Stability/Shelf Life:
Stable in acidic media. ... Stable at temperatures up to melting point. Stable in visible
light.
[Tomlin, C.D.S. (ed.). The Pesticide Manual - World Compendium. 10th ed. Surrey, UK:
The British Crop Protection Council, 1994. 505]**PEER REVIEWED**
Disposal Methods:
SRP: At the time of review, criteria for land treatment or burial (sanitary landfill)
disposal practices are subject to significant revision. Prior to implementing land disposal
of waste residue (including waste sludge), consult with environmental regulatory
agencies for guidance on acceptable disposal practices.
**PEER REVIEWED**
Occupational Exposure Standards:
Manufacturing/Use Information:
Major Uses:
Herbicide
[Tomlin, C.D.S. (ed.). The Pesticide Manual - World Compendium, 11 th ed., British
Crop Protection Council, Surrey, England 1997 597]**PEER REVIEWED**
Manufacturers:
DowElanco
[Tomlin, C.D.S. (ed.). The Pesticide Manual - World Compendium, 11 th ed., British
Crop Protection Council, Surrey, England 1997 598]**PEER REVIEWED**
General Manufacturing Information:
Not registered for use in US /Fluroxypyr-meptyl/
[Farm Chemicals Handbook 1999. Willoughby, OH: Meister Publishing Co., 1999.,p. C
190]**PEER REVIEWED**
Formulations/Preparations:
Fluroxypyr ... /can be/ applied as fluroxypyr-meptyl.
[Tomlin, C.D.S. (ed.). The Pesticide Manual - World Compendium, 11 th ed., British
Crop Protection Council, Surrey, England 1997 598]**PEER REVIEWED**
Formulation type: emulsifiable concentrate
[Tomlin, C.D.S. (ed.). The Pesticide Manual - World Compendium, 11 th ed., British
Crop Protection Council, Surrey, England 1997 598]**PEER REVIEWED**
Mixtures: (fluroxypyr-meptyl +) bromoxynil; isoproturon; bromoxynil + ioxynil;
clopyralid + MCPA; dichlorprop + MCPA; clopyralid + ioxynil; glyphosate; bromoxynil
+ ioxynil + clopyralid; metosulam.
[Tomlin, C.D.S. (ed.). The Pesticide Manual - World Compendium, 11 th ed., British
Crop Protection Council, Surrey, England 1997 598]**PEER REVIEWED**
Laboratory Methods:
Analytic Laboratory Methods:
Product analysis by hplc. Residues of fluroxypyr and fluroxypyr-meptyl determined by
hplc.
[Tomlin, C.D.S. (ed.). The Pesticide Manual - World Compendium, 11 th ed., British
Crop Protection Council, Surrey, England 1997 597]**PEER REVIEWED**
Special References:
Synonyms and Identifiers:
Synonyms:
4-Amino-3,5-dichloro-6-fluoro-2-pyridyloxyacetic acid
**PEER REVIEWED**
Associated Chemicals:
fluroxypyr-methyl;81406-37-3
Formulations/Preparations:
Fluroxypyr ... /can be/ applied as fluroxypyr-meptyl.
[Tomlin, C.D.S. (ed.). The Pesticide Manual - World Compendium, 11 th ed., British
Crop Protection Council, Surrey, England 1997 598]**PEER REVIEWED**
Formulation type: emulsifiable concentrate
[Tomlin, C.D.S. (ed.). The Pesticide Manual - World Compendium, 11 th ed., British
Crop Protection Council, Surrey, England 1997 598]**PEER REVIEWED**
Mixtures: (fluroxypyr-meptyl +) bromoxynil; isoproturon; bromoxynil + ioxynil;
clopyralid + MCPA; dichlorprop + MCPA; clopyralid + ioxynil; glyphosate; bromoxynil
+ ioxynil + clopyralid; metosulam.
[Tomlin, C.D.S. (ed.). The Pesticide Manual - World Compendium, 11 th ed., British
Crop Protection Council, Surrey, England 1997 598]**PEER REVIEWED**
Administrative Information:
Hazardous Substances Databank Number: 6655
Last Revision Date: 20000929
Last Review Date: Reviewed by SRP on 9/23/1999
Update History:
Complete Update on 03/03/2000, 40 fields added/edited/deleted.