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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
                         Basic             013503
- Chemical Abstracts Service (CAS) Number:  7778-40-9
- Year of Initial Registration:
- Pesticide Type:  Growth Regulator, Insecticide, Herbicide, and
  Fungicide
- Chemical Family:  Inorganic Arsenicals
- U.S. and Foreign Producers:  Mechema Chemicals Ltd.
                               (Great Britain),


                    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

Chemical Characteristics

- 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.


Toxicological Characteristics

- 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
  arsenic.


Environmental Characteristics

- 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.


Ecological Characteristics

- 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
  90 days.
- 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

Douglas McKinney
Special Review Branch, Registration Division
Office of Pesticide Programs  (TS-767C)
401 M Street, S.W.
Washington, D.C.  20460
(703) 557-5488


DISCLAIMER:  The information presented in this Pesticide Fact Sheet is 
for informational purpose only and may not be used to fulfill data 
requirements for pesticide registration or reregistration.