3,6-Dichlorpyridin-2-carbonsure

Agrochemicals -> Pesticide active substances

Active substance -> EU Pesticides database: Approved

Pesticides -> Herbicides, Other

Herbicides

Pesticide (Clopyralid) -> USDA PDB

Pesticide

log Kow = 1.06

1.06

White crystalline solid

Colorless crystals

In water, 7.85X10+3 mg/L (distilled water); 188 g/L at pH 5, 143 g/L ay pH 7; 157 g/L at pH 9, all at 20 °C

Approximately 1000 ppm in water at 25 °C

Solubility at 25 °C: > 25% w/w in methanol, acetone, xylene

Solubility (g/kg, 20 °C): acetonitrile 121, n-hexane 6, methanol 104

Solubility at 25 °C: acetone > 25 g/100 mL; methanol > 15 g/100 mL; xylene < 0.65 g/100 mL

Solubility in water at 20 °C: poor

151-152 °C

151-152 °C

0.000012 [mmHg]

9.98X10-6 mm Hg at 25 °C

Vapor pressure, Pa at 25 °C: 0.002

White odorless solid; [Merck Index] Colorless or white odorless solid; [ICSC] White powder; [MSDSonline]

ODOURLESS WHITE OR COLOURLESS CRYSTALS.

Store above 28 °F or warm to 40 °F and agitate before use.

Stable in acidic media. Stable in UV irradiation.

Storage stability: stable, excess of 2 yr.

2.32

pKa = 2.32

Danger

H318: Causes serious eye damage [Danger Serious eye damage/eye irritation]

P264+P265, P280, P305+P354+P338, and P317 (click each P-code to see the statement)

Danger

H318 (99.7%): Causes serious eye damage [Danger Serious eye damage/eye irritation]

P264+P265, P273, P280, P305+P354+P338, P317, P391, and P501 (click each P-code to see the statement)

Regulation (EC) No 396/2005 (amended)

06/64/EC, Reg. (EU) 2018/524, Reg. (EU) 2019/168, Reg. (EU) 2020/421, Reg. (EU) 2021/1191, Reg. (EU) 2021/566, Reg. (EU) No 540/2011, Reg. (EU) No 678/2014

Clopyralid: HSNO Approval: HSR007876 Approved with controls

Tolerances are established for residues of the herbicide clopyralid, including its metabolites and degradates, in or on the commodities in the table below from its application in the acid form or in the form of its salts. Compliance with the tolerance levels specified below is to be determined by measuring only clopyralid, (3,6-dichloro-2-pyridinecarboxylic acid), in or on the following commodities:[Table#6081]

New Active Ingredients ... includes chemicals not previously registered as pesticides, as well as pesticide active ingredients initially registered after November 1, 1984 and that currently have active product registrations. By law, these pesticides must meet new safety standards, such as those described in the Food Quality Protection Act of 1996 and, if new safety standards are met, will be reviewed again on a 15-year cycle. Clopyralid is designated by EPA as a New Pesticide Active Ingredient. Active Ingredient Number: 117403; Type of Pesticide: conventional-herbicide; Use Site: food use and non-food use (residential turf); Year: 1987.

Eye Dam. 1 (99.7%)

Eye damage - category 1

Eye Dam. 1

Fresh air, rest.

First rinse with plenty of water for several minutes (remove contact lenses if easily possible), then refer for medical attention.

Rinse mouth.

Do not store or transport in containers made from aluminium.

Do not contaminate water, food, or feed by storage ... Store above 28 °F or warm to 40 °F and agitate before use. /Lontrel Turf and Ornamental/

SRP: The most favorable course of action is to use an alternative chemical product with less inherent propensity for occupational harm/injury/toxicity or environmental contamination. Recycle any unused portion of the material for its approved use or return it to the manufacturer or supplier. Ultimate disposal of the chemical must consider: the material's impact on air quality; potential migration in soil or water; effects on animal and plant life; and conformance with environmental and public health regulations.

Personal protection: particulate filter respirator adapted to the airborne concentration of the substance. Sweep spilled substance into covered containers. If appropriate, moisten first to prevent dusting. Carefully collect remainder. Then store and dispose of according to local regulations.

Nonrefillable containers 5 gallons or less: Container Reuse: Non refillable container. Do not reuse or refill this container. Offer for recycling if available. Triple rinse or pressure rinse container (or equivalent) promptly after emptying. /Lontrel Turf and Ornamental/

Refillable containers 5 gallons or larger: Container Reuse: Refillable container. Refill this container with pesticide only. Do not reuse this container for any other purpose. Cleaning the container before final disposal is the responsibility of the person disposing of the container. Cleaning before refilling is the responsibility of the refiller. /Lontrel Turf and Ornamental/

Personal protection: particulate filter respirator adapted to the airborne concentration of the substance. Sweep spilled substance into covered containers. If appropriate, moisten first to prevent dusting. Carefully collect remainder. Then store and dispose of according to local regulations.

SRP: The scientific literature for the use of contact lenses in industry is conflicting. The benefit or detrimental effects of wearing contact lenses depend not only upon the substance, but also on factors including the form of the substance, characteristics and duration of the exposure, the uses of other eye protection equipment, and the hygiene of the lenses. However, there may be individual substances whose irritating or corrosive properties are such that the wearing of contact lenses would be harmful to the eye. In those specific cases, contact lenses should not be worn. In any event, the usual eye protection equipment should be worn even when contact lenses are in place.

Do not eat, drink, or smoke during work.

Use this product only in accordance with its labeling and with the Worker Protection Standard, 40 CFR Part 170. /Lontrel Turf and Ornamental/

Do not apply this product in a way that will contact workers or other persons, either directly or through drift. Only protected handlers may be in the area during application. /Lontrel Turf and Ornamental/

For more Preventive Measures (Complete) data for CLOPYRALID (8 total), please visit the HSDB record page.

LD50; Species: Apis mellifera (Bee) oral >100 ug/bee for 48 hr /Conditions of bioassay not specified/

LC50; Species: Oncorhynchus mykiss (Rainbow trout); Concentration: 103.5 mg/L for 96 hr /Conditions of bioassay not specified/

LC50; Species: Lepomis macrochirus (Bluegill sunfish); Concentration: 125.4 mg/L for 96 hr /Conditions of bioassay not specified/

LC50; Species: Oncorhynchus mykiss (Rainbow Trout) juvenile, weight 0.55 g, length 42 mm; Conditions: freshwater, static, 7.6 °C, pH 8.02, hardness 289 mg/L CaCO3, alkalinity 250 mg/L CaCO3, dissolved oxygen 8.40 mg/L; Concentration: 700000 ug/L for 96 hr (95% confidence interval: 630000-780000 ug/L) /95% purity/

LC50; Species: Salvelinus confluentus (Bull Trout) juvenile, weight 0.59 g, length 41 mm; Conditions: freshwater, static, 7.6 °C, pH 2.0-7.5, hardness 289 mg/L CaCO3, alkalinity 250 mg/L CaCO3, dissolved oxygen 8.40 mg/L; Concentration: 802000 ug/L for 96 hr (95% confidence interval: 674000-955000 ug/L) /95% purity/

TERRESTRIAL FATE: Based on a classification scheme(1), Koc values of 0.4 to 12.9(2), indicate that clopyralid is expected to have very high mobility in soil(SRC). However, many leachate studies have reported little or no clopyralid detected in the leachate(3-5). The pKa of clopyralid is 2.32(6), indicating that this compound will exist almost entirely in anion form in the environment and anions generally do not adsorb more strongly to soils containing organic carbon and clay than their neutral counterparts(7). Volatilization of clopyralid from moist soil surfaces is not expected to be an important fate process(SRC) given its pKa(6). Clopyralid is not expected to volatilize from dry soil surfaces(SRC) based upon a vapor pressure of 9.98X10-6 mm Hg at 24 °C(8). Aerobic biodegradation half-lives of clopyralid have been reported to range from 1 to >200 days depending on the soil used, moisture content, temperature and initial concentration of clopyralid applied(9).

TERRESTRIAL FATE: In wind tunnel field simulated conditions, radio-labeled clopyralid, applied at a rate of 118 g/ha, had residual radio-label amounts of 0.5% volatilized, 53.4% found in leaves, <0.1% found in leachate, 44.1% found in soil(1).

TERRESTRIAL FATE: Radio-labeled clopyralid was applied to sugar beet and oilseed rape in undisturbed soil lysimeter studies(1). Percent residual radioactivity after 26, 25, and 25 months were measured(1).[Table#6080]

AQUATIC FATE: Based on a classification scheme(1), Koc values of 0.4 to 12.9(2), indicate that clopyralid is not expected to adsorb to suspended solids and sediment(SRC). A pKa of 2.32(3) indicates clopyralid will exist almost entirely in the anion form at pH values of 5 to 9 and therefore volatilization from water surfaces is not expected to be an important fate process(SRC). According to a classification scheme(4), a reported BCF of 19(5), suggests bioconcentration in aquatic organisms is low(SRC). Clopyralid is not expected to undergo hydrolysis in the environment due to the lack of functional groups that hydrolyze under environmental conditions(6). Clopyralid may biodegrade in aquatic environments based upon aerobic biodegradation half-lives of 1 to >200 days in soil studies(7).

ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), clopyralid, which has a vapor pressure of 9.98X10-6 mm Hg at 24 °C(2), will exist in both the vapor and particulate phases in the ambient atmosphere. Vapor-phase clopyralid is degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals(SRC); the half-life for this reaction in air is estimated to be 29 days(SRC), calculated from its rate constant of 5.5X10-11 cu cm/molecule-sec at 25 °C(SRC) that was derived using a structure estimation method(3). Particulate-phase clopyralid may be removed from the air by wet or dry deposition(SRC). Clopyralid contains chromophores that absorb at wavelengths >290 nm(4) and, therefore, may be susceptible to direct photolysis by sunlight(SRC).

/AQUATIC SPECIES/ Clopyralid (3,6-dichloro-2-pyridinecarboxylic acid) exhibits low acute toxicity to fish, including the rainbow trout (Oncorhynchus mykiss) and the threatened bull trout (Salvelinus confluentus). However, there are no published chronic toxicity data for clopyralid and fish that can be used in ecological risk assessments. We conducted 30-day chronic toxicity studies with juvenile rainbow trout exposed to the acid form of clopyralid. The 30-day maximum acceptable toxicant concentration (MATC) for growth, calculated as the geometric mean of the no observable effect concentration (68 mg/L) and the lowest observable effect concentration (136 mg/L), was 96 mg/L. No mortality was measured at the highest chronic concentration tested (273 mg/L). The acute:chronic ratio, calculated by dividing the previously published 96-hr acutely lethal concentration (96-hr ALC(50); 700 mg/L) by the MATC was 7.3. Toxicity values were compared to a four-tiered exposure assessment profile assuming an application rate of 1.12 kg/ha. The Tier 1 exposure estimation, based on direct overspray of a 2-m deep pond, was 0.055 mg/L. The Tier 2 maximum exposure estimate, based on the Generic Exposure Estimate Concentration model (GEENEC), was 0.057 mg/L. The Tier 3 maximum exposure estimate, based on previously published results of the Groundwater Loading Effects of Agricultural Management Systems model (GLEAMS), was 0.073 mg/L. The Tier 4 exposure estimate, based on published edge-of-field monitoring data, was estimated at 0.008 mg/L. Comparison of toxicity data to estimated environmental concentrations of clopyralid indicates that the safety factor for rainbow trout exposed to clopyralid at labeled use rates exceeds 1000. Therefore, the herbicide presents little to no risk to rainbow trout or other salmonids such as the threatened bull trout.

/AQUATIC SPECIES/ ...96-hr static acute toxicity studies /were conducted/ to evaluate the relative sensitivity of juveniles of the threatened bull trout (Salvelinus confluentus) and the standard cold-water surrogate rainbow trout (Onchorhyncus mykiss) to three rangeland herbicides commonly used for controlling invasive weeds in the northwestern United States. Relative species sensitivity was compared using three procedures: standard acute toxicity testing, fractional estimates of lethal concentrations, and accelerated life testing chronic estimation procedures. The acutely lethal concentrations (ALC) resulting in 50% mortality at 96 hr (96-hr ALC50s) were determined using linear regression and indicated that the three herbicides were toxic in the order of picloram acid > 2,4-D acid > clopyralid acid. The 96-hr ALC50 values for rainbow trout were as follows: picloram, 41 mg/L; 2.4-D, 707 mg/L; and clopyralid, 700 mg/L. The 96-hr ALC50 values for bull trout were as follows: picloram, 24 mg/L; 2.4-D, 398 mg/L; and clopyralid, 802 mg/L. Fractional estimates of safe concentrations, based on 5% of the 96-hr ALC50, were conservative (overestimated toxicity) of regression-derived 96-hr ALC5 values by an order of magnitude. Accelerated life testing procedures were used to estimate chronic lethal concentrations (CLC) resulting in 1% mortality at 30 days (30-day CLC1) for the three herbicides: picloram (1 mg/L rainbow trout, 5 mg/L bull trout), 2,4-D (56 mg/L rainbow trout, 84 mg/L bull trout), and clopyralid (477 mg/L rainbow trout; 552 mg/L bull trout). Collectively, the results indicated that the standard surrogate rainbow trout is similar in sensitivity to bull trout. Accelerated life testing procedures provided cost-effective, statistically defensible methods for estimating safe chronic concentrations (30-day CLC1s) of herbicides from acute toxicity data because they use statistical models based on the entire mortality:concentration:time data matrix.

/FIELD STUDIES/ In this study, a curtained wetland approach was used to investigate the effects of a herbicide mixture (2,4-D, MCPA, clopyralid, dicamba, dichlorprop, mecoprop, bromoxynil, and glyphosate) on the structure and function of microbial communities in an ephemeral wetland and a semi-permanent wetland. In the two studied wetlands, located in Manitoba Zero Till Research Association Farm, Brandon, Manitoba, Canada, herbicide treatment based on maximum-exposure scenarios had a significant effect on pelagic and biofilm phytoplankton productivity over relatively short time periods. The stimulation of phytoplankton productivity in the ephemeral wetland appeared to be the result of a hormonal effect of the auxin-type herbicides present in the mixture, similar to naturally occurring auxins. Herbicidal effects of auxin-type herbicides were also noticed in the semi-permanent wetland where phytoplankton productivity was suppressed during the first week as a result of the concentration addition effect of the auxin-type herbicides present in the mixture. BIOLOG and pigment profiles of the biofilm community suggested a change in the community structure in both wetlands.

Cough. Sore throat.

Redness.

Redness. Pain.

Clopyralid was applied to a roadside study site on highway 37 that drains into Tolay Creek, CA at a rate of 1.05 ug/sq cm(2). Clopyralid concentrations in surface runoff samples collected over study period (Nov 27, 2001 to Jan 27, 2002) were 3.03 to 7.11 ug/L(2).

Koc values of 2(1), 4.6(2) and 0.4 to 12.9(3) have been reported. According to a classification scheme(4), these Koc values suggest that clopyralid is expected to have very high mobility in soil. However, many leachate studies have reported little or no clopyralid detected in the leachate(2,5-6). The pKa of clopyralid is 2.32(7), indicating that this compound will exist almost entirely in anion form in the environment and anions generally do not adsorb more strongly to soils containing organic carbon and clay than their neutral counterparts(8).

Koc values of clopyralid were reported for soil with reported characteristics(1,2).[Table#6082]

Clopyralid, applied on a seep study area at Riesel, TX at 0.56 kg/ha, migration thru the soil was studied(1). Clopyralid was also detected 15 days after application at the depth of 46-61 cm and 61-76 cm at concentrations of 4 and 2 mg/cu m, respectively. It was also detected 48 days after application at a depth of 46-61 cm at a concentration of 2 mg/cu m. Clopyralid was never detected at the 76-91 cm depth(1).[Table#6083]

RURAL/REMOTE: Weekly atmospheric samples (May 4 to June 29, 2004) taken in St Damase, Yamaska basin area of Quebec, Canada had clopyralid concentrations of <4 to 235 pg/cu m, monthly samples taken June 29 to Sept 21 were reported as <4 pg/cu m(1).

AEROBIC: While some investigators found clopyralid to be biodegradable in field soils(1-2), others found that the herbicide was relatively persistent in field soil(3). Thus the biodegradation of clopyralid appears to be soil dependent and the rate of biodegradation in soil may be enhanced both by higher temperature and higher number of organisms that are capable of degrading the herbicide(4). The half-lives of clopyralid in a clay, clay loam and sandy loam soil at 20 °C and 85% field moisture capacity were estimated to be 38 days, 13 days and 36 days, respectively(4).

AEROBIC: The aerobic biodegradation half-lives of clopyralid was investigated in three agricultural soils with varying environmental conditions (temperature, moisture holding capacity (MHC)) and varied clopyralid concentrations(1).[Table#6079]

Tolerances are established for residues of the herbicide clopyralid, including its metabolites and degradates, in or on the commodities in the table below from its application in the acid form or in the form of its salts. Compliance with the tolerance levels specified below is to be determined by measuring only clopyralid, (3,6-dichloro-2-pyridinecarboxylic acid), in or on the following commodities:[Table#6081]

New Active Ingredients ... includes chemicals not previously registered as pesticides, as well as pesticide active ingredients initially registered after November 1, 1984 and that currently have active product registrations. By law, these pesticides must meet new safety standards, such as those described in the Food Quality Protection Act of 1996 and, if new safety standards are met, will be reviewed again on a 15-year cycle. Clopyralid is designated by EPA as a New Pesticide Active Ingredient. Active Ingredient Number: 117403; Type of Pesticide: conventional-herbicide; Use Site: food use and non-food use (residential turf); Year: 1987.

Groups of 5 Crl:CD (F-344) BR rats/sex were dosed with single iv treatments of (14)C-labeled clopyralid, either 5 mg/kg in saline, by single gavage doses of 5 or 150 mg/kg (14)C-clopyralid. An additional 5 rats/sex were dosed daily with 5 mg/kg/day unlabeled clopyralid for 14 days, followed by a single treatment with 5 mg/kg/day of (14)C-clopyralid. No label was found in expired air. Tissue levels at 72 hour sacrifices were either very low (carcass or stomach) or non-detectable for the several treatment regiments. Generally, over 90% of label was found in urine collected within 24 hr, regardless of administration method. Small amounts of label (1-5%) were found in feces. An analysis of the only detectable urinary labeled fraction found this to be unaltered clopyralid.

The patterns of absorption and translocation of 14(C) clopyralid commercially formulated as the acid, monoethanolamine salt, potassium salt, 2-ethylhexyl ester and 1-decyl ester were compared in Cirsium arvense and Polygonum convolvulus grown under three environmental regimes. Plants were grown under a 35% or 65% RH regime in silica sand maintained at 33% w/w moisture or under a water stress regime at 65% RH. Approximately 26, 39, 86, 93 and 100% of the applied 14(C)-activity from the 2-ethylhexyl ester, acid, monoethanolamine salt, 1-decyl ester and potassium salt, respectively, were recovered 72 h after application to glass cover slips placed in the growth room. However, loss of applied 14(C)-activity after application of the five formulations to both plant species was significant only for the 2-ethylhexyl ester. Regardless of environmental regime, the acid was the most readily absorbed formulation. In contrast to the acid, the salts and esters were less readily absorbed. When the data were expressed as a percentage of absorbed radioactivity, there was no significant difference in translocation when the acid, monoethanolamine salt and potassium salt were compared. However, significantly smaller quantities of the absorbed 2-ethylhexyl and 1-decyl ester were exported from the treated leaf. These results indicate that once absorbed, the esters do not readily partition out of the cuticle, whereas the acid and two salts move into the symplast for subsequent translocation. When the results of the three environmental regimes were compared, the absorption of the monoethanolamine and potassium salts were greatly reduced under low humidity or water stress, whereas the acid and esters were not affected.

Groups of 5 Crl:CD (F-344) BR rats/sex were dosed with single iv treatments of (14)C-labeled clopyralid, either 5 mg/kg in saline, by single gavage doses of 5 or 150 mg/kg (14)C-clopyralid. An additional 5 rats/sex were dosed daily with 5 mg/kg/day unlabeled clopyralid for 14 days, followed by a single treatment with 5 mg/kg/day of (14)C-clopyralid. No label was found in expired air. Tissue levels at 72 hour sacrifices were either very low (carcass or stomach) or non-detectable for the several treatment regiments. Generally, over 90% of label was found in urine collected within 24 hr, regardless of administration method. Small amounts of label (1-5%) were found in feces. An analysis of the only detectable urinary labeled fraction found this to be unaltered clopyralid.

Used as post-emergence herbicide for control of annual and perennial broad-leaved weeds in beets, maize, onions, strawberries, flax, and grassland; [HSDB] Used as a herbicide and food additive; [Hawley]

Farming (Pesticides) [Category: Industry]

For clopyralid (USEPA/OPP Pesticide Code: 117403) ACTIVE products with label matches. /SRP: Registered for use in the U.S. but approved pesticide uses may change periodically and so federal, state and local authorities must be consulted for currently approved uses./

Herbicide

Post-emergence control of many annual and perennial broad-leaved weeds of the families Polygonaceae, Compositae, Leguminosae, and Umbelliferae ... Provides particularly good control of creeping thistle (Cirsium arvense), perennial sow-thistle, coltsfoot, mayweeds, and Polygonum species.

Food additive

2-Pyridinecarboxylic acid, 3,6-dichloro- is listed as a High Production Volume (HPV) chemical (65FR81686). Chemicals listed as HPV were produced in or imported into the U.S. in >1 million pounds in 1990 and/or 1994. The HPV list is based on the 1990 Inventory Update Rule. (IUR) (40 CFR part 710 subpart B; 51FR21438).

Production volumes for non-confidential chemicals reported under the Inventory Update Rule.[Table#6086]

Premix Partners: Acetochlor; Benazolin; Bensulfuron-methyl; 2,4,-D; Dicamba; Flumetsulam; Fluroxypyr; MCPA; Triclopyr.

Soluble concentrate

Wettable powder

Water soluble granule

For more Formulations/Preparations (Complete) data for CLOPYRALID (37 total), please visit the HSDB record page.

2-Pyridinecarboxylic acid, 3,6-dichloro-: ACTIVE

The WHO Recommended Classification of Pesticides by Hazard identifies clopyralid (technical grade) as Class III: slightly hazardous; Main Use: herbicide.

Application by ground or aerial foliage sprays. Rates: 1/16 lb to 4 lb/acre. Usual carrier: water.