lead arsenate EPA Pesticide Fact Sheet 12/86
EPA Pesticide Fact Sheet
Name of Chemical: Lead arsenate
Reason for Issuance: Special review
Date Issued: December 1986
Fact Sheet Number: 112
1. DESCRIPTION OF CHEMICAL
- Common Name: Lead Arsenate
- Chemical Name: Acid Orthoarsenate - PbHAsO4
Basic Orthoarsenate - Pb4(PbOH) (AsO4)3
- Trade Name: Lead Arsenate, Gypsine, Security, Talbot
- EPA Shaughnessy Code: Standard (Acid) 013502
- Chemical Abstracts Service (CAS) Number: 7778-40-9
- Year of Initial Registration:
- Pesticide Type: Growth Regulator, Insecticide, Herbicide, and
- Chemical Family: Inorganic Arsenicals
- U.S. and Foreign Producers: Mechema Chemicals Ltd.
2 USE PATTERNS AND FORMULATIONS
Lead arsenate is currently used as a growth regulator on 17% of the
U.S. grapefruit crop. 10,000 pounds of lead arsenate are also used
annually to control cockroaches, silverfish and crickets. The Agency is
unaware of any current use as a foliar insecticide or as a herbicide.
- Types and Methods of Application: Airblast sprayer, foliar aerial
dust, bait box.
- Application Rates: Growth Regulator - 1.3 lbs arsenic/A; Foliar
Insecticide - 1.7 lbs arsenic/A
- Types of Formulations: Dust, flowable liquid, wettable powder,
granular, impregnated, wettable powder/dust
3. SCIENCE FINDINGS
- Lead arsenate is a pentavalent form of inorganic arsenic. It normally
exists as white crystals with no discernible odor. Lead arsenate
contains 22% arsenic and is very slightly soluble in cold water. The
melting point of lead arsenate is 1042 degrees C, the density is 7.80
and the molecular weight is 347.12. Technical lead arsenate consists
of 95-98% lead arsenate. Under most conditions basic lead arsenate is
more stable than acid lead arsenate.
- Inorganic arsenical compounds have been classified as Class A
oncogens, demonstrating positive oncogenic effects based on sufficient
human epidemiological evidence.
- Inorganic arsenicals have been assayed for mutagenic activity in a
variety of test systems ranging from bacterial cells to peripheral
lymphocytes from humans exposed to arsenic. The weight of evidence
indicates that inorganic arsenical compounds are mutagenic.
- Evidence exists indicating that there is teratogenic and fetotoxic
potential based on intravenous and intraperitoneal routes of exposure;
however, evidence by the oral route is insufficient to confirm lead
arsenate's teratogenic and fetotoxic effects.
- Inorganic arsenicals are known to be acutely toxic. The symptoms which
follow oral exposure include severe gastrointestinal damage resulting
in vomiting and diarrhea, and general vascular collapse leading to
shock, coma and death. Muscular cramps, facial edema, and cardio-
vascular reactions are also known to occur following oral exposure to
- The environmental fate of lead arsenate 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
forms of inorganic arsenic may change depending on environmental
conditions. Based on very limited data lead arsenate is not predicted
to leach significantly.
- Lead arsenate is moderately toxic to birds, slightly toxic to fish and
moderately toxic to aquatic invertebrate species.
- Metabolism: The metabolism of inorganic arsenic compounds
in animals is well known. The pentavalent form, such as lead
arsenate, is metabolized by reduction into the trivalent form,
followed by transformation into organic forms which are excreted
within several days via the urine. All animals exhibit this
metabolism except rats, which retain arsenic in their bodies for up to
- Tolerance Assessment: Tolerances were established in 40 CFR 180.194
for residues of lead arsenate.
- Reported Pesticide Incidents: The Agency's Pesticide Incident
Monitoring System (PIMS) has many recorded incidents of accidental
poisonings from the use of lead arsenate baits. Nine of these
incidents involved hospitalizations and 16 involved child poisonings
from "roach hive" products.
4. SUMMARY OF REGULATORY POSITION AND RATIONALE
The Agency is proposing to cancel all existing nonwood registrations
of lead arsenate, with the exception of the growth regulator use on
grapefruit. Measures to mitigate the inhalation risks including dust
masks, respirators, which would be expected to reduce inhalation
exposure by 80 and 90 percent, respectively, and restricting the use to
certified applicators were considered by the Agency during the Special
Review. The Agency has determined that these protective measures would
not reduce risks to an acceptable level in light of the limited
benefits. The Agency has further determined that the toxicological
risks from all nonwood uses of lead arsenate, except the grapefruit
use, outweigh the limited benefits. The growth regulator use on
grapefruit is being deferred pending further evaluation by EPA's Risk
Assessment Forum of the carcinogenic potency of inorganic arsenic from
dermal and dietary exposures
- Benefits Analysis: The economic impact from cancellation of the lead
arsenate insecticide baits could range from $.84 to $6.7 million, the
actual amount depending on whether the alternative chemical is applied
by homeowners or professionals. No economic impact is expected as a
result of cancellation of the herbicide and foliar insecticide uses of
lead arsenate. Viable alternatives are available.
5. CONTACT PERSON
Special Review Branch, Registration Division
Office of Pesticide Programs (TS-767C)
401 M Street, S.W.
Washington, D.C. 20460
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