Technical Factsheet on: PICLORAM
List of Contaminants
As part of the Drinking Water and Health pages, this fact sheet is part of a larger publication:
National Primary Drinking Water Regulations
Drinking Water Standards
MCLG: 0.5 mg/L
MCL: 0.5 mg/L
HAL(child): 1- to 10- day: 20 mg/L; Longer-term: 0.7 mg/L
Health Effects Summary
Acute: EPA has found picloram to potentially cause the following
health effects from acute exposures at levels above the MCL:
damage to central nervous system, weakness, diarrhea, weight
loss.
Drinking water levels which are considered "safe" for short-term
exposures: For a 10-kg (22 lb.) child consuming 1 liter of water
per day, a one- to ten-day exposure to 20 mg/L or up to a 7-year
exposure to 0.7 mg/L.
Chronic: Picloram has the potential to cause the following
health effects from long-term exposures at levels above the MCL:
liver damage.
Cancer: There is inadequate evidence to state whether or not
picloram has the potential to cause cancer from a lifetime
exposure in drinking water.
Usage Patterns
Picloram is a systemic herbicide used in salt form for
controlling annual weeds on crops, and in combination with 2,4-D
or 2,4,5-T against perennials on non-croplands for brush control.
Picloram is used to control bitterweed, knapweed, leafy spurge,
locoweed, larkspur, mesquite, prickly pear, and snakeweed on
rangeland in the western states.
EPA estimates that 300,000 lbs. of picloram were produced in the
US in 1982.
Release Patterns
Picloram is released to the environment primarily from its
application as a herbicide, and also during its production and
handling. Since picloram is not a listed chemical in the Toxics
Release Inventory, data on releases during its manufacture and
handling are not available.
Environmental Fate
Picloram is the most persistent of the chlorobenzoic acid
herbicides.
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. It will not be expected to hydrolyze or evaporate from
soils or surfaces. It may be subject to significant
biodegradation in soils and ground water, with reported
half-lives in soils ranging from 55-100 days or more.
If released to water it will not be expected to adsorb to
sediments, 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.
Picloram is not expected to bioconcentrate in aquatic organisms
based on a reported BCF of 31 in fish and estimated BCFs of 1 to
20.
General human exposure will occur mainly through its manufacture
and use as a herbicide.
Chemical/ Physical Properties
CAS Number: 1918-02-1
Color/ Form/Odor: Colorless crystals or powder with a
chlorine-like odor; forms water soluble salts
M.P.: 218-219 C B.P.: _ C
Vapor Pressure: 6.2x10-7 mm Hg, 25 C
Octanol/Water Partition (Kow): N/A
Density/Spec. Grav.: N/A
Solubility: 430 mg/L of water at 25 C; Soluble in water
Soil sorption coefficient: Koc average= 13; moderate mobility in
soil
Odor/Taste Thresholds: N/A
Bioconcentration Factor: BCF=31 in fish; not expected to
bioconcentrate in aquatic organisms.
Henry's Law Coefficient: N/A; negligible volatilization
Trade Names/Synonyms: 4-amino-3,5,6-trichloropicolinic acid;
"Agent White"; Tordon
Other Regulatory Information
Monitoring For Ground/Surface Water Sources:
- Initial Frequency- 4 quarterly samples every 3 years
- Repeat Frequency- If no detections during initial round:
- 2 quarterly per year if serving >3300 persons;
- 1 sample per 3 years for smaller systems
- Triggers - Return to Initial Freq. if detect at > 0.0001 mg/L
Analysis:
| Reference Source |
Method Numbers |
| EPA 600/4-88-039 |
515.1; 515.2; 555 |
Treatment- Best Available Technologies:
Granular Activated Charcoal
For Additional Information:
EPA can provide further regulatory and other general information:
EPA Safe Drinking Water Hotline - 800/426-4791
Other sources of toxicological and environmental fate data include:
Toxic Substance Control Act Information Line - 202/554-1404
Toxics Release Inventory, National Library of Medicine - 301/496-6531
Agency for Toxic Substances and Disease Registry - 404/639-6000
National Pesticide Hotline - 800/858-7378
List of Contaminants
|
