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Magnesium Phosphide - Chemical Fact Sheet 4/86

                        CHEMICAL FACT SHEET FOR:
                          MAGNESIUM PHOSPHIDE



                       1. DESCRIPTION OF CHEMICAL

- Generic Name:  Magnesium Phosphide
- Trade Name:  Magtoxin
- EPA Shaughnessy Code:  066504
- Chemical Abstract (CAS) Number:  12057-74-8
- Year of Initial Registration:  1979
- Pesticide Type:  Solid fumigant
- Chemical Family:  Inorganic Phosphides
- U.S. and Foreign Producers:  Degesch America, Inc.; Research Products
  Company; PestCon Systems, Inc.; Bernardo Chemicals.

                     2. USE PATTERNS AND FORMULATIONS

- Application Sites:  Indoor fumigation of agricultural commodities,
  animal feeds, processed food commodities, and non-food commodities
  (tobacco).  Outdoor fumigation for burrowing rodent and mole control.
- Formulations:  Tablets and pellets; powders in bags, envelopes and
  other containers.
- Application Rates:  30 tablets or 75 pellets per square feet; 1-4
  tablets or 5-20 pellets for rodent burrows.

                           3. SCIENCE FINDINGS

Chemical Characteristics

- Solid, dark gray material (granules, or powder); molecular weight
  134.70; material must be protected from moisture in the atmosphere
  in air-tight containers; contact of the solid material with moisture
  in the air, or with water, or acids release phosphine, a highly
  toxic gas.

Toxicology Characteristics

- Requirements for acute toxicity data have been waived because of
  the well known extreme inhalation toxicity of phosphine gas which it
  generates.  Accordingly, magnesium phosphide has been placed in
  toxicity category I, the highest toxicity category.
- No chronic toxicology studies are required with respect to dietary
  exposure because there is not a potential for dietary exposure
  (tolerances are set at limit of detection).
- Toxicology studies on phosphine gas are required to assess the
  margins of safety for exposed workers and applicators because the
  Agency does not have adequate data to determine whether phosphine
  may cause any long term adverse effects to humans.

Physiological and Biochemical Behavioral Characteristics

- N/A

Environmental Characteristics

- Magnesium phosphide reacts with moisture or water to release
  phosphine gas, which eventually dissipates into the atmosphere.  The
  resulting material from the reaction is magnesium hydroxide, a
  relatively inert and innocuous material, which is a constituent of
- Exposure (monitoring data) and related information are required to
  help assess the margins of safety for applicators and workers
  exposed to phosphine gas.

Ecological Characteristics

- Phosphine is a highly toxic gas to a wide range of living organisms.
  Indoor uses pose no risk to non-target organisms outside of the site
  to be treated.  Outdoor end use products (1.e.  rodent and mole
  control) must bear special precautionary labeling to protect
  endangered species.  Manufacturing use products must bear
  environmental hazard statements for wildlife.

Tolerance Assessment

- Tolerances have been established for raw agricultural commodities at
  a level of 0.1 ppm (40 CFR 180.377); processed foods 0.01 ppm (21
  CFR 193.225); and animal feeds 0.1 ppm (40 CFR 561.268).  Finished
  food and feed must be held 48 hours prior to being offered to the
  consumer; tobacco fumigated in hogsheads must be aerated 72 hours.

Problems Known to Have Occurred with Use of the Chemical

- None

Summary Science Statement

- The Agency has determined that the registered uses of this chemical
  will not generally cause unreasonable adverse effects to humans or
  the environment if used in accordance with the approved use
  directions and revised precautionary statements prescribed by this


- Magnesium phosphide will remain a Restricted Use Pesticide due to
  the extreme acute toxicity of phosphine gas which is released from
  the pesticide when it is exposed to moisture in the air.  Therefore,
  it may be used only by certified applicators or persons under their
- This amended standard adds several new regulatory requirements to
  the label:
- For retail sale to and used only by a certified applicator or by
  persons trained in accordance with the product manual working
  under the direct supervision and in the physical presence of the
  certified applicator.
- Respiratory protection is not required if the fumigant is applied
  from outside of a site such as a railroad car or to fill an
  automatic dispenser located outside of a structure.  However, if
  the applicator enters a confined space to apply the fumigant,
  respiratory protection is required.  Exposure during application
  within a confined space may not exceed 0.3 ppm phosphine as an 8
  hour time weighted average (TWA).  Engineering controls such as
  forced air ventilation are recommended as the primary means of
  meeting the exposure standard.  Otherwise, an approved respirator
  must be worn.
- Monitoring must be conducted with a low level detector device to
  assure that the exposure standard is not exceeded.  If monitoring
  shows that exposure is less than the standard, no respirator is
  required.  If more than 0.3 ppm TWA is encountered, a full face
  NIOSH/MSHA approved canister respirator is required up to 15 ppm
  phosphine.  This type of respirator must be available during
  fumigation within a confined space.  If more than 15 ppm or
  unknown levels of phosphine are present, a NIOSH/MSHA approved
  self contained breathing apparatus (SCBA) is required.  SCBA must
  be available at the site or locally such as at a fire department
  or rescue squad.
- After application, no person may be exposed to more than 0.3 ppm
  phosphine (maximum concentration).  Exposures may occur if the
  fumigated site leaks into an adjacent indoor area, during transfer
  of treated commodity, or during reentry into an incompletely
  aerated space.
- All entrances to a fumigated site must be placarded (except for
  railroad hopper cars which must be placarded on both sides near
  the ladders and on the top hatch where fumigant was applied).  A
  placard may only be removed after the commodity is completely
  aerated.  Each fumigated site must be monitored and shown to
  contain 0.3 ppm or less phosphine in the air space around and in
  the mass of the commodity.  If more than 0.3 ppm is detected, the
  placard must be transferred with the treated commodity.  Persons
  must be informed of the presence of phosphine and adequate
  measures taken to prevent exposure to more than 0.3 ppm.
- When fumigating from within a confined space or when reentering an
  incompletely aerated space, two trained persons must be present.

                     5.  SUMMARY OF MAJOR DATA GAPS:

- 90 day inhalation study in rats
- Teratogenicity study in one species
- Mutagenicity battery
- Exposure (monitoring data and related information for major sites)

                       6.  CONTACT PERSON AT EPA

Jeff Kempter,
Product Manager 21
Disinfectants Branch
Registration Division (TS-767C)
401 M Street, S.W.
Washington, D.C. 20460
(703) 557-7470