arsenic acid Chemical Fact Sheet 9/86
CHEMICAL FACT SHEET FOR:
FACT SHEET NUMBER: 91
DATE ISSUED: SEPTEMBER, 1986
1. DESCRIPTION OF CHEMICAL
- Chemical Names: Arsenic acid, Orthoarsenic acid
- Common Name: Arsenic Acid
- Trade Names: Desiccant L-10 to the minus R, Hi Yield to the minus R,
H-10, Poly Brand Desiccant, Hi Yield to the minus R, Synergized H-1O
to the minus R
- EPA Shaughnessy Code: 006801
- Chemical Abstracts Service (CAS) Number: 7778-39-4
- Pesticide Types: Dessicant, wood preservative
- Chemical Family: Inorganic arsenicals
- U.S. and Foreign Producers: Penwalt Corporation
Voluntary Purchasing Corporation
2. USE PATTERNS AND FORMULATIONS
- Application Sites: Terrestrial crop use on machine and stripper
harvested cotton as a desiccant; Non-food use on seed crop okra
(Arizona only) as a desiccant.
- Types of Formulations: 75% soluble concentrate formulation
intermediate, also used as end-use product.
- Types and Methods of Application: Foliar spray (single application at
least 4 and 10 days prior to harvest of cotton and okra,
- Application Rates: Cotton -- 2.94 to 4.42 pounds active per acre
Okra -- 4.42 pounds active per acre
(Note: 1 quart of 75% liquid = about 2.94 pounds active ingredient).
- Usual Carriers: Water
3. SCIENCE FINDINGS
- Physical state: Aqueous solution
- Oxidation state: Pentavalent Arsenic
- Color: Pale yellow to pale green
- Odor: None
- Boiling point: Not available
- Specific gravity: 1.884 at 20 degrees C
- Solubility: Readily soluble in water, forming various As salts
- Stability: Most stable under conditions favoring oxidation and at
high pH; under reduction conditions or low pH,
pentavalent form may convert to trivalent arsenic.
- Unusual handing characteristics: Reacts with fabric, galvanized
metals, black iron and certain other metals resulting in
deterioration, corrosion, or liberation of toxic gases
(e.g., hydrogen, arsine).
Forms of inorganic arsenic referended in the Registration Standard
- Arsenic acid: H3AsO4, containing arsenic in a +5 oxidation form
- Sodium arsenate (Na3AsO4): The sodium salt of arsenic acid, also +5
- Arsenic trioxide (As203): An oxide of arsenic, containing arsenic
in a +3 oxidation form
- Sodium arsenite (NaAsO2): A sodium compound related to arsenic
trioxide, also +3
- Acute toxicity: Although arsenic is known to be highly toxic by
ingestion, few animal studies are available on the active ingredient,
or on the formulated products of arsenic acid. Moreover, the toxicity
of arsenic compounds may vary widely depending in the type of
formulation and the form of inorganic arsenic in the product.
- Oral (rat) - 40-100 mg/kg. Rats are not a good test species,
however, since, alone among animal test species, they retain
arsenic in their bodies without significant excretion. Humans are
known to be more sensitive to acute arsenic effects than rats.
- Dermal - Undetermined.
- Inhalation - Undetermined.
- Eye and Skin Irritation - Undetermined.
- Dermal Sensitization - Undetermined.
- Chronic toxicity
- Arsenic compounds, including arsenic acid, have been classified
as Class A oncogens. Epidermiological studies on workers in
copper smelting and pesticide manufacturing, and on populations
exposed to excess levels of arsenic in well water in Taiwan are
the basis for this classification. Inhalation exposure leads to
lung cancers, and ingestion exposure has shown a correlation
with development of skin cancers.
- The lifetime inhalation oncogenic risks to workers from the
cotton use have been estimated at negligible for applicators,
and 10 to the minus (-4) to 10 to the minus (-5) for mixer/
- Dermal and oral oncogenic risks have not been calculated
because the risk models are still undergoing Agency review.
Completion of this review is expected in late 1986 or early
- The sodium salt of arsenic acid (sodium arsenate) and the sodium
salt of arsenous acid (a related form of arsenic) have been
found to be mutagenic, that is, to interact with DNA to cause
heritable effects. Numerous assays have been conducted on cells
in vitro. Other observed effects include interference with DNA
repair mechanisms, direct toxicity to mammalian gonads, and
positive effects in microbial systems. Other evidence suggests
that similar effects may occur in vivo. Sodium arsenite is a
more potent mutagen than sodium arsenate.
- Sodium arsenate has been shown to produce teratogenic or
fetotoxic effects in hamsters (15-25 mg/kg intravenously); mice
(40-45 mg/kg intraperitoneally); and rats (20-50 mg/kg
interperitoneally). Similar results have been obtained with
sodium arsenite at lower dosages. These results have not been
demonstrated using an oral route of exposure, or have been found
only at dosages that also cause significant maternal mortality.
Because the effects have been shown only using routes of
exposure that are not likely to occur with pesticide use, and
because the studies were not adequate to establish no-observed
effect levels (NOELs) the Agency will require an oral
teratogenicity study in two species other than the rat.
- Reproductive effects:
- No data that meet Agency standards are available. A
reproduction study on a species other than the rat will be
- Subchronic and chronic exposure to arsenic compounds causes
peripheral and central nervous system neuropathy, the effects of
which vary from slight to severe depending on the level and
duration of exposure.
- Other subchronic and chronic effects:
- Inorganic arsenic compounds have been observed to cause
cardiovascular, skin, blood, and liver and kidney effects in
humans. The same effects have been observed in experimental
animals. The NOEL for blood effects in dogs is 50 ppm (1.25
mg/kg). The NOEL for liver effects in rats of arsenites is 62.5
ppm and of arsenates is 125 ppm.
- The metabolism of inorganic arsenic compounds in animals is well
known. The pentavalent form, such as arsenic acid, is
metabolized by reduction into the trivalent form, followed by
transformation into organic forms which are excreted within
several days via the urine. All mammals exhibit this metabolism
except rats, which retain arsenic in their bodies for up to 90
Physiological and Biochemical Behavioral Characteristics
- Mechanism of Pesticide Action - Protein denaturation and enzyme
inactivation, resulting in desiccation of plant foliage and stems.
- Few data are available on the environmental fate of arsenic acid.
Arsenic is a naturally occurring compound that is ubiquitous and
exists in different forms (species) depending on environmental
conditions. Arsenic acid rapidly dissolves in water. The arsenic
moiety of the residue cannot be distinguished from natural arsenic
in the soil. Special environmental fate data are required to be
submitted. Studies on environmental fate of arsenic acid must be
designed to differentiate between natural and pesticide sources of
- Groundwater concerns: Arsenic has been detected in groundwater
underlying areas of arsenic acid use. However, the source of this
contamination cannot be determined. Limited information currently
available suggests that arsenic acid will not leach significantly.
Additional data are required to further evaluate leaching potential.
- Avian acute toxicity: No data available
- Avian dietary toxicity: Mallard duck - 1606 ppm
Bobwhite quail - 168 ppm
- Freshwater fish toxicity: Bluegill sunfish - 66.8 ppm
Rainbow trout - 53.1 ppm
- Aquatic invertebrates: Daphnia magna - 6.5 ppm
- Based on limited data, the Agency characterizes arsenic acid as
moderately toxic to birds by ingestion in the diet. Arsenic acid is
slightly toxic to fish and moderately toxic to aquatic invertebrates.
- Endangered Species: Cotton desiccant use may pose a potential
hazard to the Attwater's Greater Prairie Chicken in three Texas
counties (Victoria, Refugio, and Fort Bend). The Agency has
referred arsenic acid to the Office of Endangered Species, U.S.
Department of Interior, for review as part of a group of cotton
pesticides, and will require labeling to protect this endangered
- A tolerance of 4.0 ppm in cottonseed oil has been established for
arsenic acid, expressed as arsenic trioxide (As203) (40 CFR 180.180).
The use on okra seed crop is a non-food use for which no tolerance is
- Because the metabolism and chronic effects of inorganic arsenic in
humans are well-known, the Agency is not requiring the submission of
chronic feeding studies on arsenic acid per se. For regulatory
purposes, and until teratogenicity and reproduction studies are
submitted, the Agency has calculated a provisional acceptable daily
intake (PADI) based upon studies using sodium arsenate.
- Based upon a dog study having a NOEL of 50 ppm (1.25 mg/kg of actual
arsenic) and a safety factor of 100, the PADI is 0.0165 mg/kg/day of
As203, and the maximum permissible intake for a 60 kg person is 0.99
- Available residue data indicate that the maximum residue that will
theoretically occur in cottonseed from use of arsenic acid is 0.009
mg/day. The maximum residue therefore uses 0.009/0.99 of the
maximum permissible intake, or 0.9%.
Reported Pesticide Incidents
- In the period from 1966-1981, 8 incidents were reported to the
Agency concerning arsenic acid related to its cotton use. Among
these, one involved one human fatality and two persons hospitalized,
three involved cattle, and four involved crop damage from spray
drift of arsenic acid from nearby farms.
Summary Science Statement
- Arsenic acid is a form of inorganic arsenic. Such compounds are
acutely toxic to humans by ingestion. Inorganic arsenical compounds
have been classified as Class A oncogens, demonstrating positive
oncogenic effects based on sufficient human epidermiological
evidence. The weight of evidence indicates that inorganical
arsenical compounds are also mutagens. Although there is
teratogenic and fetotoxic potential based on intravenous and
intraperitoneal routes of exposure, there is insufficient evidence
by the oral route to confirm arsenic acid's teratogenic or fetotoxic
effects. Neurotoxic effects have been demonstrated after acute,
subchronic and chronic exposures. The metabolism of arsenical
compounds in humans is well-documented, but animal studies are not
adequate to determine no observed effect levels (NOELs) and
acceptable daily intakes (ADIs).
- The environmental fate of arsenic acid is not well documented.
Studies to demonstrate its fate must take into account the fact that
inorganic arsenicals are natural constituents of the soil, and that
the forms of inorganic arsenic may change depending on environmental
conditions. Based on very limited data, arsenic acid is not
predicted to leach significantly. Although elevated levels of
arsenic have been found in groundwater in Texas, the source of the
arsenic cannot be determined; non-pesticide sources may have been
- Arsenic acid is moderately toxic to birds, slightly toxic to fish
and moderately toxic to aquatic invertebrate species.
4. SUMMARY OF REGULATORY POSITION AND RATIONALE
- Arsenic acid is currently undergoing Agency Special Review, based upon
its oncogenic and teratogenic effects. Products will remain
registered until the conclusion of this review. New uses, however,
will not be accepted.
- Arsenic acid products will be restricted to use by certified
applicators, because of its acute toxicity and oncogenicity.
- Use restrictions based upon groundwater concerns are not warranted at
the present time.
- Reentry intervals are not required because use as a desiccant does not
lead to significant exposure to field workers.
- Protective clothing is specified for mixer/loaders and applicators,
because of the acidic properties of arsenic acid, and its potential
oncogenic risks to mixer/loaders and applicators.
- Endangered species labeling statements are required because of
potential hazard to the Attwater's Greater Prairie Chicken in Texas.
An avian residue monitoring study is required to determine actual
levels of arsenic acid in avian feed items.
- Tolerances will be reassessed based upon residue and metabolism
studies to be submitted. A rotational crop restriction may be needed
if follow up crops take up arsenic acid residues from the soil.
5. SUMMARY OF MAJOR DATA GAPS
- Product chemistry data - arsenic acid Feb. 1987
- Residue chemistry data - arsenic acid Feb. 1988
- Plant and animal metabolism
- Analytical methodology for residues
- Magnitude of residues in cotton
- Environmental fate studies
- Metabolism in soil Dec. 1988
- Leaching Aug. 1987
- Laboratory volatility Aug. 1987
- Soil dissipation Dec. 1988
- Rotational crop studies Dec. 1989
- Toxicology studies
- Acute toxicity Feb. 1987
- Teratology (rabbit and mouse or hamster) Dec. 1987
- Reproduction (rodent other than rat) Dec. 1989
- Dermal penetration Aug. 1987
- Glove permeability Feb. 1987
- Ecological effects studies
- Avian acute toxicity May 1987
- Residue monitoring study on avian food items Dec. 1987
- Aquatic invertebrate early life stage Dec. 1987
6. CONTACT PERSON AT EPA
Richard F. Mountfort
Product Manager No. 23
U.S. Environmental Protection Agency
401 M St., SW
Washington, D.C 20460
THE INFORMATION PRESENTED IN THIS CHEMICAL INFORMATION FACT SHEET
IS FOR INFORMATIONAL PURPOSES ONLY AND NOT TO BE USED TO FULFILL
DATA REQUIREMENTS FOR PESTICIDE REGISTRATION AND REREGISTRATION.