SPECTRUM

Chemical Fact Sheet

Chemical Abstract Number (CAS #) 1918021
CASRN 1918-02-1
SynonymsPicloram
4-Amino-3,5,6-trichloro-2-pyridinecarboxylic acid
Analytical Methods EPA Method 515.3
EPA Method 555
EPA Method 644
EPA Method 8151
Molecular FormulaC6H3Cl3N2O2

Link to the National Library of Medicine's Hazardous Substances
Database for more details on this compound.

Use SYSTEMIC HERBICIDE PICLORAM & ITS SALTS ARE HERBICIDES MOST BROADLEAVED CROPS, EXCEPT CRUCIFERS, ARE SENSITIVE; MOST GRASSES ARE RESISTANT. EFFECTIVE IN CONTROLLING ANNUAL WEEDS; USED ALONE OR IN COMBINATION WITH 2,4-D AGAINST DEEP-ROOTED PERENNIALS ON NON-CROP LAND; AS PELLETS OR IN COMBINATION WITH 2.4-D OR 2,4,5-T BRUSH CONTROL. AT EXTREMELY LOW DOSAGES, ACTS AS A GROWTH REGULATOR ON APRICOTS, FIGS, CHERRIES, ETC. Picloram is used to control bitterweed, knapweed, leafy spurge, locoweed, larkspur, mesquite, prickly pear, and snakeweed on rangeland in the western states.
Apparent Color COLORLESS POWDER ; CRYSTALS
Odor CHLORINE-LIKE
Melting Point 218-219 DEG C
Molecular Weight 241.48
Sensitivity Data SKIN--MILD IRRITANT, NOT A SKIN SENSITIZER TO HUMANS. EYES--MODERATE IRRITATION WHICH HEALS READILY. INHALATION--DUSTS MAY BE SOMEWHAT IRRITATING
Environmental Impact Picloram is released to the environment primarily from its application as a herbicide and its use is restricted in the U.S. If released to land it will not adsorb to the soil, hydrolyze, or evaporate from soils or surfaces. It will be subject to leaching to groundwater and may be subject to significant biodegradation in soils and groundwater. If released to water it will not be expected to adsorb to sediments, to bioconcentrate in aquatic organisms, to evaporate, or to appreciably hydrolyze. It will be subject to significant near surface photolysis with reported half-lives ranging from 2.3-41.3 days. Based on biodegradation in soils and groundwater, it may be subject to degradation in surface waters. As an aromatic amine, its rate of degradation in water and soil may be increased due to oxidation by free radicals, adsorption to humic materials followed by oxidation, and catalytic oxidation by cations, although no experimental data specific to picloram were found. If released to the atmosphere it will be subject to significant deposition and washout due to its low vapor pressure (will adsorb to particulate matter) and significant water solubility. It may also be subject to significant direct photolysis. The estimated vapor phase half-life in the atmosphere is 12.21 days as a result of reaction with photochemically produced hydroxyl radicals. General human exposure will occur mainly through its manufacture and use as a herbicide.
Environmental Fate TERRESTRIAL FATE: SORPTION OF PICLORAM BY ORGANIC MATTER & CERTAIN CLAYS HAS BEEN DEMONSTRATED. HOWEVER, PICLORAM SALT FORMULATIONS ARE WATER SOLUBLE & LEACHING MAY OCCUR IN SANDY SOILS LOW IN ORGANIC MATTER. /TERRESTRIAL FATE: DEGRADATION STUDIES OF PICLORAM IN SOIL WAS CONDUCTED. T/2= 0.693/K. IN REGINA HEAVY CLAY, AT 25 DEG C & AT MOISTURE HOLDING CAPACITY T/2= 68 - 10 DAYS. /Aquatic Fate: it is decomposed in water to negligible levels within 180 days. In a study a standing pond was sprayed at a rate of 4 lb/acre, which resulted in 2400 ppb at time 0, 700 ppb at day 1, & 6 ppb at 180 days. TERRESTRIAL FATE: PICLORAM IS THE MOST PERSISTANT HERBICIDE OF THE GROUP CHLOROBENZOIC ACIDS/. TERRESTRIAL FATE: If picloram is released to soil it will not be expected to adsorb to the soil and may leach to groundwater, a conclusion supported by the detection of picloram in some groundwater samples. However, picloram is an aromatic amine, and some aromatic amines have been shown to bind to humic materials which may be present in some moist soils; this binding may decrease leaching processes (see also ABIO). It will not be expected to hydrolyze or evaporate from soils or surfaces. It may be subject to significant biodegradation with reported half-lives in soils ranging from 55-100 days or more. AQUATIC FATE: If picloram is released to water it will not be expected to adsorb to sediments, to bioconcentrate in aquatic organisms, to evaporate, or to appreciably hydrolyze. As an aromatic amine, however, it may bind to humic materials (see also ABIO and KOC). It will be subject to significant near-surface direct photolysis with reported half-lives for irradiation by sunlight under various conditions ranging from 2.3-41.3 days. No information concerning the biodegradation in surface waters was found; however, degradation reported in lab tests with groundwater samples and soils suggest that biodegradation in water may occur. ATMOSPHERIC FATE: If picloram is released to the atmosphere it will probably be subject to significant deposition and washout due to its very low vapor pressure and significant water solubility. It may also be subject to direct photolysis based on its ready photolysis in aqueous solutions. The estimated vapor-phase half-life in the atmosphere is 12.21 days as a result of reaction with photochemically produced hydroxyl radicals. /Terrestrial Fate: Studies on the persistence, metabolism, and toxicity of heterocyclic pesticides are reviewed. Picloram is highly persistent in soil, but is rapidly degraded by UV light in aqueous solutions. It does not suppress soil microorganisms, and has low toxicity in aquatic organisms. The herbicide picloram was applied to control spotted knapweed in the northern Rockies to determine persistence in soils and vegetation, losses by photodegradation, rainfall induced migration, and potential contamination of surface and groundwater. Two sites were selected to represent best case and worst case conditions for on site retention of picloram. A valley bottom terrace was treated with 0.28 kg/ha of picloram in the spring of 1985, and sampled over the following 445 days. In the spring of 1986, 1.12 kg/ha of picloram was applied to both sides of a minimal construction logging road extending 4 km along a stream draining a granitic upper mountain watershed. Of the 17.1 sq km watershed, 0.15% was sprayed. Vegetation, soils, surface water, and groundwater near the road were sampled during the 90 days following application. At the valley bottom site, 36, 13, and 10.5% of the picloram applied persisted after 90, 365, and 445 days. At the mountain watershed site, 78% persisted after 90 days. Picloram was not detected in the surface or groundwater during the 90 days after application. Loss by photodegradation during the first 7 days after treatment was important at both sites.
Drinking Water Impact GROUNDWATER: Riesel, TX, 1971-73, subsurface water after treatment of 1:1 mixture of picloram and 2,4,5-T, 90 samples, 13% pos, not detected (nd)-trace; well water, 8 wells, 10 samples, 30% pos, nd-trace; drainage lysimeter water, 126 samples, 86% pos, nd-4 ppb . Picloram was aerially applied to a longleaf pine (Pinus palustris L) site in the upper coastal plain of Alabama to control kudzu. Pellets (10% ai) were spread at the rate of 56 kg/ha on loamy sand Typic Kanhapludult soils. Movement of the herbicide was monitored with mineral soil samples, tension-cup lysimeters, flow-proportional streamflow samplers, and discrete samplers. Picloram levels in the upper 15 cm of mineral soil peaked at 0.96 to 2.25 mg/kg 225 days after application, depending on slope position, and declined to 0.13 to 0.29 mg/kg one year later. In soil solution, picloram was detected at a depth of 0.4 m between 26 and 273 days after application. Only 4 of 15 lysimeters consistently contained detectable residues. Maximum picloram levels in soil solution were 130, 450, and 191 mg/cu m for ridge, midslope, and toe-slope positions, respectively. Downstream monitoring began 4 days after the herbicide application, and an initial concentration of 68 mg/cu m of picloram was detected. The maximum downstream concentration of 77 mg/cu m occurred 18 days after the application, immediately after the second storm event. Downstream levels dropped to <10 mg/cu m after 90 days and to <2 mg/cu m after 200 days. Following localized retreatment along the stream more than a year after the initial treatment, levels climbed again into the 20 to 30 mg/cu range. Most of the initial off-site movement came from a perennial stream that had been inadvertently treated, but subsequently storm runoff was the largest contributor to stream contamination. Picloram residues in this stream were similar to those observed downstream, but they were higher (up to 241 mg/cu m) and dropped faster to below 2 mg/cu m after day 150. EFFL: Reisel, TX, 1970-72, runoff water from fields treated with 1:1 mixture of picloram and 2,4,5-T, 13 day period after spraying, 21 samples, 100% pos, 15-830 ppb, avg 464 ppb; 40-110 days after spraying, 22 samples, 91% pos, not detected-3 ppb .

DISCLAIMER - Please Read

Florida-Spectrum List of Services
Florida-Spectrum Homepage