2 • Honeybee inhalation toxicity (non

- guideline, phosphine)

Additionally, there are uncertain ties about the characteristics of the treatment facilities in which phosphine is used. Examples include building size (dimensions) , aeration methods, air exchange exhaust rates, emission control devices (if any), and the number, size, and relative locatio n of stacks and vents that serve as the release points during phosphine aeration operations. Collectively t hese factors will directly influence emission rates

, the magnitude of downwind dispersion from treated structures

, and therefore affect outdoor air concentrations. Submission of

this information will aid the Agency in estimating realistic, high

- end exposure scenarios and will reduce the potential of the Agency producing overly protective restrictions on the use of this pesticide.3 

# Problem Formulation for the Environmental Fate, Ecological Risk, Endangered Species, and Drinking Water Exposure Assessments in Support of the

Registration Review of Al uminum Phosphide

, M a g nesium Phosphide , and Phosphine

P h osphine (PH 3 

### ) 1



### CAS: 7803

- 51

- 2, 20859

- 73

- 8, 12057

- 74

- 8

PC Code: 066500, 066501, 066504

Environmental Fate and Effects Division Prepared by: Michael Lowit, Ph.D., Ecologist Stephen Wente , Ph.D., Biologist U.S. Environmental Protection Agency Office of Pesticide Programs Environmental Fate and Effects Division

Environmental Risk Branch I 1200 Pennsylvania Ave., NW

Mail Code 7507P Washington, DC 20460 Reviewed by: Faruque Khan, Ph.D., Senior Fate Scientist Robin Sternberg, Ph.D., Wildlife Biologist

1 Al phosphide (a crystalline solid) and Mg phosphide (an amorphous solid) are difficult to represent structurally; therefore, only the active ingredient of all three pesticides, phosphine, is depicted. 

## P H

H H4 Table of Contents

1. Purpose

................................ ................................ ................................ ................................ ........ 5

2. Problem Formulation

................................ ................................ ................................ .................. 5 2.1. Nature of Regulatory Action

................................ ................................ ................................ 5

2.2. Previous Assessments

................................ ................................ ................................ .......... 5 2.2.1. Ecological Risk Assessments

................................ ................................ ........................ 5 2.2.2. Drinking Water Assessments

................................ ................................ ........................ 6

3. Stressor Source and Distribution

................................ ................................ ................................ 6

3.1. Mechanism of Action

................................ ................................ ................................ .......... 6

3.2. Overview of Pesticide Use and Usage

................................ ................................ ................ 6

3.3. Environmental Fate and Transport

................................ ................................ ...................... 9

3.4. Clean Water Act

................................ ................................ ................................ ................ 11 4. Receptors

................................ ................................ ................................ ................................ .. 11

4.1. Incident Databases Review

................................ ................................ ............................... 12

5. Risk Hypotheses

................................ ................................ ................................ ....................... 12 6. Analysis Plan

................................ ................................ ................................ ........................... 13

6.1. Stressors of Concern

................................ ................................ ................................ .......... 13 6.2. Measures of Exposure

................................ ................................ ................................ ........ 13 6.2.1. Aquatic Exposure

................................ ................................ ................................ ........ 14

6.2.2. Terrestrial Exposure

................................ ................................ ................................ .... 14

6.3. Measures of Effect

................................ ................................ ................................ ............. 16 6.4. Integration of Exposure and Effects

................................ ................................ .................. 16 6.5. Endangered Species Assessments

................................ ................................ ...................... 16 6.6. Endocrine Disruptor Screening

................................ ................................ .......................... 16 6.7. Drinking Water Assessment

................................ ................................ .............................. 16

6. 8. Preliminary Identification of Data Gaps

................................ ................................ ............ 17

6.8.1. Environmental Fate Data

................................ ................................ ............................ 17 6.8.2. Ecological Effects Data

................................ ................................ ............................... 18

7. References

................................ ................................ ................................ ................................ 21 Appendix A. Atmos pheric Modeling

................................ ................................ ........................... 23 Appendix B. Data Call

- In Tables

................................ ................................ ................................ . 275 1. Purpose

The purpose of this problem formulation is to provide an understanding of what is known about the environmental fate, ecological effects, and currently registered uses of Al uminum (Al) phosphide, M a g nesium (Mg) phosphide

, and phosphine 2

. This document provides a plan for analyzing data relevant to Al phosphide, Mg phosphide , and phosphine and for conducting environmental fate, ecological risk, endangered species, and drinking water exposure assessments for registered uses. Additionally, this problem formulation identifies data gaps, uncertainties, and potential assumptions used to address those uncertainties relative to characterizing the potential ecological risk associated with the registered uses of Al phosphide, Mg pho sphide , and phosphine.

2. Problem Formulation

2.1. Nature of Regulatory Action

As part of the implementation of the new Registration Review program 3 pursuant to Section 3(g) of the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), the Agency is beginning its

evaluation of Al phosphide, Mg phosphide , and phosphine to determine whether they continue to meet the FIFRA standard for registration . This problem formulation in support of the registration review of Al phosphide, Mg phosphide , and phosphine will be posted in the initial docket which will open the public phase of the review process.

2.2. Previous Assessments

2.2.1. Ecological Risk Ass essments

Previous assessments identified a risk concern for non

- target species using or inhabiting burrows treated with Al phosphide or Mg phosphide. There was no ecological risk concern for indoor

uses.

• In 2010, EFED conducted an assessment on the risk to several federally threatened and endangered species from use of Al phosphide and Mg phosphide ( US EPA , 2010). A “no effect” determination was made for indoor uses due to an incomplete exposure pathway. For outdoor uses (burrow treatment), a “may affect and likely to adversely affect” determination was made for all evaluated species: Alameda whipsnake ( Masticophis lateralis euryxanthus ), California Tiger Salamander ( Ambystoma californiense )

– Central

Cali fornia, Sonoma County, and Santa Barbara County distinct population segments, San Francisco garter snake ( Thamnophis sirtalis ), and San Joaquin Kit Fox ( Vulpes macrotis

mutica ). Additionally, the assessment concluded that “...there is the potential for

modi fication of designated critical habitat for the Alameda whipsnake and the California Tiger Salamander by virtue of sealing and rendering toxic treated small mammal burrows, and the elimination of small mammals that construct such burrows.”

• EFED completed the Al phosphide and Mg phosphide Reregistration Eligibility Document (RED) in 1998 (DP 236730). The RED cited endangered species consultations ( see below ) regarding risk to listed species ; risk to non

- listed species was

2 Zinc phosphide, although similar in many respects to the pesticides assessed in this document, is not us ed as a structural fumigant, and therefore, will be addressed in the future in a separate document.

3 http://www.epa.gov/oppsrrd1/registration_review/6 not addressed . The document concl uded that “no ecological or fate data have been required in the past .... and none are needed at this time.” The potential for exposure was summarized as “Al phosphide and Mg phosphide are expected to degrade rapidly in the environment to aluminum hydroxide and magnesium hydroxide and phosphine, the toxicant of these pesticides. It appears that phosphine will degrade in days and is at low risk for contaminating ground or surface waters. Phosphine near the soil surface is expected to diffuse into the atmosph ere and be removed via photodegradation. Phosphine trapped beneath the soil surface will bind to soil, inhibiting movement, and be oxidized to phosphates.”

• In 1981, The United States Department of the Interior’s Fish and Wildlife Service completed a B iological O pinion on the use of Mg phosphide for rodent and mole pest control (FWS/OES EPA

- 81

- 6). The Biological Opinion stated: “Analysis of the chemical action of magnesium phosphide, the areas of intended use, the life history and ecological

data of lis ted and proposed species indicate that any species using or inhabiting burrow systems could be impacted by the use of this pesticide.” The document continues with the finding of jeopardy for the following species: black footed ferret ( Mustela nigripes ),

ea stern indigo snake ( Drymarchon corais couperi ), San Joaquin kit fox ( Vulpes macrotis

mutica ), Utah prairie dog ( Cynomys parvidens ), blunt

- nosed leopard lizard ( Gamelia

silus ), and desert tortoise ( Gopherus agassizii ). A follow

- up consultation (FWS/OES

EPA

- 81

- 9) indicated that conclusions from the B iological O pinion on the use of Mg phosphide apply to the same uses of Al phosphide.

2.2.2. Drinking Water Assessments

A drinking water assessment (DWA) has not been conducted on Al phosphide, Mg phosphide, or phosphine.

3. Stressor Source and Distribution

Al phosphide, Mg phosphide, and phosphine are considered to be three different pesticides for regulatory purposes. However, Al phosphide and Mg phosphide breakdown in the presence of

moisture to produce phos phine gas , which is the active ingredient (ai) of all three pesticides.

Indoor uses of Al phosphide, Mg phosphide , and phosphine include treatment of food/feed, agricultural commodities, food preparation sites, storage sites, and beehives. Al phosphide and Mg phosphide are also labeled for outdoor use in sealed burrows.

3.1. Mechanism of Action

The mechanism of phosphine toxicity is not completely understood. Phosphine is a strong reducing agent that likely inhibits mitochondrial respiration b y reacting with enzymes such as cytochrome c oxidase.

3.2. Overview of Pesticide Use and Usage

Al phosphide was first registered for use in the US in 1958, followed by Mg phosphide in 1979, and phosphine in 2002. Al phosphide and Mg phosphide are registered f or use in burrows for rodent control. Phosphine is registered for indoor use on numerous food (post

- harvest) and non

food items as an insecticide and rodenticide. In recent years phosphine usage increased sharply7 in California ( Screening Level Usage Anal ysis, 8/6 /2012) due to new phosphine products and reduced availability of methyl

- bromide according to the Biological and Economic Analysis Division (BEAD)

.

Uses and application rates are based on the most recent L abel U se I nformation S ystem report ( LUIS report) provided by BEAD ( 4/29/2013

– Al phosphide; 3/13 /201 3

– Mg phosphide ; and

3/5/2013

- p hosphine ). The m aximum application rates and application methods are list ed in

Table 1 and 2 . The registration review ecological risk assessment will be based on current label

information at the time of assessment.

Table 1 . Maxi mum Rates for Registered Outdoor Uses of Al Phosphide and Mg Phosphide 1

Use Site Method of Application Single Maximum Application Rate

(lb ai/ burrow ) Maximum Number of Applications per Year Annual Maximum (lb ai/ burrow )

Al Phosphide

Various 2 Animal Burrow

Treatment 0.0158 Not specified Not specified

Mg Phosphide

Various 2 Animal Burrow

Treatment 0.0174 Not specified Not specified

1 There is no registered outdoor use of phosphine.

2 A gricultural crops/soils (unspecified ), agricultural fallow/idleland/ conservation reserve (Mg phosphide only)

, agricultural rights

- of

- way/fencerows/hedgerows (Mg phosphide only) , airports/landing fields,

commercial/institutional/industrial premises/equipment (outdoor), golf course turf, nonagricultural rights

- of

way/fencerows/hedgerows, nonagricultural uncultivated areas/soils, orchards (unspecified), pastures, rangeland,

recreational areas , and residential lawns (Al phosphide only)

Table 2 . Maximum Rates for Registered Indoor Uses of Al Phosphide, Mg Phosphide, and Phosphine

Use Site Method of Application Single Maximum Application Rate (lb ai / ft 3 ) Maximum Number of Applications per

Year Annual Maximum (lb ai / ft 3 )

Al Phosphide

Various 1 Fumigant 0 .0006 Not specified Not specified

Mg Phosphide

Various 1 Fumigant 0 .00064313 Not specified Not specified

Phosphine

Various 1 Fumigant 0.000 3 2 Not specified Not specified

1 See the following text for descriptions of specific indoor uses.

I ndoor uses of Al Phosphide include: airtight storage (flat)

- empty, airtight storage (flat)

- full, airtight storage (small)

- empty, airtight storage (small)

- full, almond, automobiles, taxis, limousines, recreational vehicles, & tires, barges (empty), barges (full), barley, beehives/bee colony (diseased/nuisance), brazil nut, candy (processed), cashew, cereal flour/bakery mixes (processed), cereal foods (pasta/crackers) (processed), cereals (processed), cheese/cheese byproducts (processed), chocolate/ch ocolate products (processed), cocoa, coffee, coffee (processed), commercial shipping containers

- feed/food

- empty, commercial shipping containers

feed/food

- full, commercial storages/warehouses premises, commercial transportation facilities

feed/food

- empty, c ommercial transportation facilities

- feed/food

- full, commercial transportation8 facilities (non

- feed/non

- food), corn (processed/ground), corn (unspecified), corn, pop, cotton, cotton (unspecified), cottonseed (animal feed) (processed), date, egg yolk solids (dried) (processed), feed mills/feed processing plants, feed/food commodities (bagged/temporary storage), fig, filbert (hazelnut), fish (unspecified)(meat), food and feed products (processed), food processing plant premises (nonfood contact), fruits (dried /dehydrated) (processed), furs/feathers/hair (stored processed products), grain/cereal/flour bins

- empty, grain/cereal/flour

bins

- full, grasses grown for seed, herbs and spices (processed), human clothing (insect and mold/mildew control), leather/leather hi des (stored processed products), legume vegetables, livestock feed (processed), malt/malt beverage (processed), meat products (cured) (processed), meat products (processed), milk (dried)/nondairy creamers (processed), non

- feed/non

- food commodities (tempora ry storage), non

- grass forage/fodder/straw/hay, nut meats (processed), oats, oats (processed), ornamental herbaceous plants, paper/paper products, peanuts, pecan, pet animal/bird feed (processed), pistachio, plantago ovata (medicinal), proso millet, rice, rice (processed/milled/enriched/polished/brewers grits), rice, wild, rye, safflower, seeds (unspecified), sesame, ships and boats, silos, sorghum, soybean flour/milled fractions (processed), soybeans (unspecified), sugar (processed), sunflower, tea (proces sed), textiles/fabrics/fibers (stored), tobacco, triticale, vegetables (dried/dehydrated) (processed), walnut (English/black), wheat, wood pressure treatment to forest products, and yeast (processed).

Indoor uses of Mg Phosphide include: airtight storage (flat)

- full, airtight storage (small)

- empty, airtight storage (small)

- full, almond, automobiles, taxis, limousines, recreational vehicles, & tires, barges (full), barley, beans, beehives/bee colony (diseased/nuisance), brazil nut, breweries, candy (process ed), cashew, cereal flour/bakery mixes (processed), cereal foods (pasta/crackers) (processed), cereals (processed), cheese/cheese byproducts (processed), chocolate/chocolate products (processed), coffee (processed), commercial shipping containers

- feed/food

- full, commercial storages/warehouses premises, commercial transportation facilities

- feed/food

- full, corn (unspecified), corn, pop, cotton (unspecified), cottonseed (animal feed) (processed), dairy animal feed (processed), date, egg yolk solids (dried) (pr ocessed), empty containers to be used for processed feed/food, feed mills/feed processing plants, feed/food commodities (bagged/temporary storage), feed/food containers

- full, felt/furs/feathers/felt products, fig, filbert (hazelnut), fish (unspecified)(mea t), food and feed products (processed), food processing plant equipment (food contact), food processing plant premises (nonfood contact), fruits (dried/dehydrated) (processed), furs/feathers/hair (stored processed products), grain/cereal/flour

bins

- empty, grain/cereal/flour bins

- full, grain/cereal/flour elevators

- empty, herbs and spices (processed), leather/leather hides (stored processed products), legume vegetables, livestock feed (processed), malt/malt beverage (processed), meat products (cured) (process ed), milk (dried)/nondairy creamers (processed), non

- feed/non

- food commodities (temporary storage),

non

- feed/non

- food containers

- full, nut meats (processed), oats, oats (processed), paper/paper products, peanuts (unspecified), pecan, pet animal/bird feed ( processed), pistachio, plantago ovata (medicinal), proso millet, rice, rice (processed/milled/enriched/polished/brewers grits), rice, wild, rye, seeds (unspecified), ships and boats, silos, sorghum (unspecified), soybean flour/milled fractions (processed), soybeans (unspecified), storage areas

- full, sugar (processed), tea (processed), textiles/fabrics/fibers (stored), tobacco/tobacco products (processed), triticale, vegetables (dried/dehydrated) (processed), vegetables (processed), vegetables (unspecified), walnut ( English /black), wheat, yeast (processed)

Indoor u ses of phosphine include: airtight storage (flat)

- full, alfalfa, almond, automobiles, taxis, limousines, recreational vehicles, & tires, avocado, banana, barley, brazil nut, breweries,9 cabbage, chinese, candy (processed), cashew, cereal flour/bakery mixes (processed), cereal foods (pasta/crackers) (processed), cereals (processed), cheese/cheese byproducts (processed), chocolate/chocolate products (processed), citron (citrus), cocoa, coffee, coffe e (processed), commercial storages/warehouses premises, commercial transportation facilities (all or unspecified), comme rcial transportation facilities ( non

- feed/non

- food ) , corn (processed/ground), corn (unspecified), corn, pop, cottonseed (animal feed) (p rocessed), date, dill, egg yolk solids (dried) (processed), eggplant, endive (escarole), feed mills/feed processing plants, feed/food

treatment

- storage/processing/handling equipment, fig, filbert (hazelnut), fish (unspecified)(meat), food and feed products (processed), food processing plant equipment (food contact), food processing plant premises (nonfood contact), fruits (dried/dehydrated) (processed), furs/feathers/hair (stored processed products), grapefruit, grasses grown for seed, herbs and spices (pro cessed), human clothing (insect and mold/mildew control), kumquat, leather/leather hides (stored processed products), leather/leather products, legume vegetables, lemon, lettuce, lime, malt/malt beverage (processed), mango, meat products (cured) (processed ), milk (dried)/nondairy creamers (processed), millet (proso), non

- feed/nonfood commodities (temporary storage), non

- feed/nonfood commodities temporary storage (tents/tarps), non

feed/nonfood treatments

- storage/processing/handling equip, non

- grass animal f eeds, non

- grass forage/fodder/straw/hay, nut meats (processed), oats, oats (processed), okra, orange, ornamental herbaceous plants, papaya, paper/paper products, peanuts, pecan, pepper, persimmon, pimento, pistachio, plantago ovata (medicinal), plantain, r ice, rice (processed/milled/enriched/polished/brewers grits), rice, wild, rye, safflower, salsify, seeds (unspecified), sesame, ships and boats, silos, sorghum, soybean flour/milled fractions (processed), soybeans (unspecified), starch (processed), sugar ( processed), sunflower, sweet potato, tangelo, tangerines, tea (processed), textiles/fabrics/fibers (stored), tobacco, tobacco/tobacco products (processed), tomato, triticale, vegetables (dried/dehydrated) (processed), walnut ( English /black), wheat, wood pr otection treatment to forest products (unseasoned), and yeast (processed)

.

T here are u ncertainties in the usage of phosphine i n treatment facilities (maximum chamber or building s izes ), aeration methods, air exchange exhaust rates, and the use of emission control

devi c e s . These factors will directly influence emission rates and affect outdoor air concentrations. In addition, there is a lack of information related to the design of buildings used for fumigation treatments , including the dimensions of build ings, different size s of buildings, as

well as the number , sizes, and relative locations of stack s and vents that serve as the release points during phosphine aeration operations. These variables all impact the magnitude of downwind dispe rsion from treate d structures.

3.3. Environmental Fate and Transport

The physical and chemical properties of Al phosphide, Mg phosphide, and phosphine are

summarized in Table 3

.10 Table 3 . Phy sical, Chemical, and Environmental Fate Properties of Al Phosphide, Mg Phosphide, and Phosphine
Physical Chemical Property Al Phosphide M g Phosphide Phosphine

Chemical Structure Crystalline solid Amorphous solid

Molecular Formula AlP Mg 3 P 2 PH 3 Molecular Weight 57.96 g/mol 134.86 g/mol 34 g/mol Solubility at 20oC 260 mg/L No data 371 mg/L Flammability Limit NA NA 18,000 ppm

Melting Point 2530oC Decomposes before melting - 134oC

Vapor Pressure (mmHg) NA NA 2.93 × 10 4 (25  ̊ C)

The following discussion summarizes the properties and fate assessment of Al phosphide, Mg phosphide, and phosphine as described in the 1998 Al phosphide and Mg phosphide RED ( DP

236730 )

.

Phosphine Gas

Under normal environmental conditions

, phosphine (PH 3 ) exists as a gas. The solubility of phosphine in water at normal atmospheric pressure is approximately 340 ppm (WHO

, 1988). Because of its high vapor pressure ( 2.93 × 10 4 mm Hg at 25  ̊ C ; Daubert and Danner , 1989 ) and Henry's Law Constant (0.1 atm m 3 /mol), phosphine is expected to mainly remain in the atmosphere (WHO

, 19 88).

Phosphine in the atmosphere is rapidly degraded (WHO

, 1988). Gas

- phase phosphine will be degraded in the atmosphere by reaction with photochemically

- produced hydroxyl radicals; and has a reported atmospheric half

- life of less than 1 day. Phosphine does not contain chromophores that absorb at wavelengths >290 nm and therefore is not expected to be susceptible to direct photolysis by sunlight ( Lyman et al , 1990 )

. The expected reaction products of phosphine in air with photochemically

- produced hydroxy l radicals are oxyacids of phosphorus and inorganic phosphate.

Al phosphide and M g Phosphide

Al phosphide (AlP) and Mg phosphide (Mg 3 P 2 ) appear to be non

- persistent under most

environmental conditions and are non

- mobile in soil because of their instability at atmospheric

moisture con dition s

. Al phosphide and Mg phosphide react with water or moisture in air to

generate the gas phosphine w hich is the active ingredient of these pesticides (Cotton and

Wilkerson

, 1988 ; Fluck

, 1973 ; G reenwood and Earnshaw

, 1984 ; and WHO

, 1988). Other products of hydrolysis are aluminum and magnesium hydroxides. The reactions can be written

as follows: P H

H H11 (1) Al P + 3H 2 0 → Al(OH) 3 + PH 3 or

(2) Mg 3 P 2 + 6H 2 0 → 3Mg(OH) 2 + 2PH 3

The aluminum and magnesium hydroxide residues can further react to produce mineral phases that are known to occur naturally in the environment (Lindsay

, 1979). Inorganic phosphate and

other phosphorus oxyacids are expected to be products formed from the oxidation of phosphine in soils (WHO

, 1988 ; H i lton and Robinson

, 1972 ).

Several published laboratory studies suggest that phosphine below the soil surface is quickly adsorbed and degraded. Gaseous phosphine added to soil headspace at 1000 mg/kg dry soil in closed containers degrades 50% after approximately 5 days with air dried soil and 11 days in water saturated soil (Hilton and Robinson

, 1972). Smaller quantities of phosphine may be

remov ed by soil through a faster mechanism because phosphine added at a lower concentration (0.35 μg/kg) was undetectable in 50 minutes (Eiseman et al.

, 1997). Diffusion through the soil environment is expected to be slow as phosphine is sorbed in seconds when pushed through several types of soil in a nitrogen carrier (Berck and Gunther

, 1970).

It should be noted that the labels for burrow uses of Al phosphide and Mg phosphide require insertion of the pellets far enough below the soil surface to prevent smothe ring of the pellets by the seal closing off the burrow. This suggests that release of phosphine gas will not occur at the soil surface where it might dissipate to the atmosphere. The combination of heavier than air density (vapor density 1.17 ; WHO

, 1988) , insertion well below the soil surface, and the reactivity and bin d ing of phosphine to soil all suggest that exposures to phosphine gas from

burrow uses are isolated within the burrow chamber.

3.4. Clean Water Act

Al phosphide, Mg phosphide , and phosphine are not identified as a cause of impairment for any water bodies listed as impaired under section 303(d) of the Clean Water Act 4 . In addition, no Total Maximum Daily Loads (TMDL) related to these chemicals has been developed 5 . The Impaired Waters and Total Maximum Daily Loads website can be consulted for more

information 6 . The Agency invites submission of water quality data for Al phosphide, Mg phosphide , and phosphine , if any such data exist . To the extent possible, data should conform to the quality stand ards in the OPP Standard Operating Procedure: Inclusion of Impaired Water Body and Other Water Quality Data in OPP’s Registration Review Risk Assessment and Management Process 7 , in order to ensure they can be used quantitatively or qualitatively in pestici de risk assessments.

4. Receptors

Consistent with the process described in the Overview Document (USEPA

, 2004 ), the risk assessment will rely on a surrogate species approach. Toxicological data generated from surrogate test species, which are intended to be representative of broad taxonomic groups, are

4 http://iaspub.epa.gov/tmdl_waters10/attains_nation_cy.cause_detail_303d?p_cause_group_id=885

5 http://iaspub.epa.gov/tmdl_waters10/attains_nation.tmdl_pollutant_detail?p_pollutant_group_id=885&p_pollutant_ group_name=PESTICIDES

6 http://www.epa.gov/owow/tmd l/

7 http://www.epa.gov/oppfead1/cb/ppdc/2006/november06/session1

- sop.pdf12 used to extrapolate the potential effects on a variety of species (receptors) included under these taxonomic groupings.

T oxicity data from studies submitted by pesticide registrants along with available op en literature will be used to evaluate the potential direct and indirect effects of Al phosphide, Mg phosphide, and phosphine to terrestrial receptors. This includes toxicity on the technical grade active ingredient, degradates, and when available, formul ated products ( e.g. , “Six

- Pack” studies). Open literature studies will be identified through EPA’s ECOTOXicology (ECOTOX) database 8

, which use s a literature search engine for lo cating chemical toxicity data.

Guideline toxicity data are not available for Al phosphide, Mg phosphide, or phosphine except
for limited mammalian data. The phosphine 4

- hour inhalation LC 50 = 0.117 mg/L for rats ( MRID 46290604). The ECOTOX database will be searched when the risk assessment is prepared. At that time, open literatu re studies with endpoints more sensitive than those from guideline studies will be reviewed.

4.1. Incident Databases Review

R eview s w ere conducted of the Ecological Incident Information System ( EIIS, v 2.1.1 ), the Aggregate Incident Data System , and the Avian Incident Monitoring System (AIMS) 9 on 2/2/2013

.

There were four incidents associated with Al phosphide involving birds, two involving mammals, and one involving terrestrial plants. No incidents were reported for Mg phosphide.

Details of these incidents were reported in the last risk assessment ( US EPA , 2010). Reported vertebrate incidents for Al phosphide were not likely associated with labeled uses of the pesticide; reports of phosphine detected in dead animals w ere probably associated with ingestion

of Al phosphide or Zn (Zinc) phosphide. The one minor plant incident associated with Al phosphide contained too little information to reach a definitive conclusion regarding plant

effects.

The total number of actual incidents associated with the use of Al phosphide, Mg phosphide, and phosphine may be higher than what is reported to the Agency. Incidents may go unreported since effects may not be immediately apparent or readily attributed to the use of a chemical. As such, the absence of incident reports c annot be construed as the absence of incidents.

5. Risk Hypothes e s

Al phosphide and Mg phosphide , when used in sealed burrows in accordance with current labels, are expected to quickly degrade to phosphine gas. All three compounds are expected to

remain in the sealed burrow until degraded

. When used in accordance with the labels, u se of Al phosphide and Mg phosphide will be lethal to all non

- target terrestrial animals within the sealed

burrow and will adverse ly a ffect the survival, growth, and reproducti on of terrestrial plants possessing root systems that penetrate a treated burrow. N on

- target organisms include federally

- listed threatened and endangered species.

8 http://cfpub.epa.gov/ecotox/

9 http://www.abcbirds.org/abcprograms/policy/ toxins /aims/aims/index.cfm13 Al phosphide, Mg phosphide, and p hosphine, when used for indoor treatment in accordance with current labels, will result in offsite movement of phosphine via emission to the atmosphere from treated structures, leading to exposure of non

- target terrestrial organisms (Al phosphide and Mg phosphide are expected to quickly and compl etely degrade to phosphine). There is no expectation of a complete exposure pathway for aquatic organisms. Phosphine emissions from treated structures may serve as a source of phosphine exposure to terrestrial wildlife. When

used in accordance with the labels, phosphine will adverse ly a ffect the survival, growth, and reproduction of non

- target terrestrial organisms. N on

- target organisms include federally

- listed threatened and endangered species.

6. Analysis Plan

In order to address the risk hypothes e s, the potential for adverse effects on the environment is estimated. The use, environmental fate, and ecological effects of Al phosphide, Mg phosphide, and phosphine will be characterized and integrated to assess risk. This will be accomplished using a ri sk quotient (ratio of exposure concentration to effects concentration) approach. Although risk is often defined as the likelihood and magnitude of adverse ecological effects, the risk quotient

- based approach does not provide a quantitative estimate of lik elihood or magnitude of an adverse effect. However, as outlined in the Overview Document (USEPA, 2004), the likelihood of effects to individual organisms from particular uses of Al phosphide, Mg phosphide, and phosphine will be estimated using the probit dose

- response slope and either the

level of concern (LOC) or actual calculated risk quotient value.

This analysis plan will be revisited and may be revised depending upon a full review of the data available in the open literature and the information submi tted by the public in response to the opening of the r egistration r eview docket.

6.1. Stressors of Concern

The stressors of concern will be Al phosphide, Mg phosphide, and phosphine. Phosphine is a registered active ingredient and the major degradation product of Al phosphide and Mg phosphide , which are effectively delivery agents for phosphine. Other degradates are Al hydroxide, Mg hydroxide, and phosphate ; all of which occur naturally in the environment.

Phosphine released from structures or within burrows are the primary exposure pathways of concern for terrestrial organisms. Terrestrial and aquatic exposure to Al phosphide and Mg phosphide is not expected

. A quatic exposure to phosphine is assu med minimal (see Section 6.2).

6.2. Measures of Exposure

Exposure from structural fumigant uses will be modeled using high

- end exposure scenarios

based on the ma ximum labeled

- allowed concentrations in the structure to be fumigated and release rates designed to produce a realistic

, high

- end exposure. As stated previously, t here are

u ncertainties in the usage of phosphine in treatment facilities (maximum chamber or building

s izes ), aeration methods, air exchange exhaust rates, and the use of emission control devi c e s

. These factors will directly influence emission rates and affect outdoor air concentrations. In addition, there is a lack of information related to the design of buildings used for fumigation

treatments , including the dimensions of buildings, different size s of buildings, as well as the

number , sizes, and relative locations of stack s and vents that serve as the release points during phosphine aeration operations. These variables all impact the magnitude of downwind14 dispe rsion from treated structures. S ubmission of information that aids the Agency in designing realistic, high

- end exposure scenarios will reduce the potential of the Agency producing overly protective restrictions to the use of th is pesticide

. Burrow uses are expected to produce sufficient exposures to kill organisms within the burrow, but negligible exposure outside the burrow.

6.2.1

. Aquatic Exposure

Limited exposure is expected based on the labeled uses and the fate properties of Al phosphide, Mg phosphide, and phosphine

. As described previously, burrow applications are expected to

remain in the burrow and are not considered to have a complete exposure pathway to aquatic

environments outside of the burrow. Structural release s of phosphine are expected to result in minimal aquatic expos ure given its rapid atmospheric degradation and that it will not tend to partition to water given its high vapor pressure ( 2.93 × 10 4 at 25  ̊ C ) and Henry's Law Constant (0.1 atm m 3 /mol).

If available, monitoring data will be evaluated and used for characterization

.

6.2.2

. Terrestrial Exposure

No above

- ground exposure modeling will be conducted for burrow applications

. Al phosphide and Mg phosphide are expected to react fully in a sealed burrow, producing lethal concentrations of phosphine gas. E xp osure will be assumed lethal to all animals within a sealed burrow. Phosphine is expected to remain in the sealed burrow until degraded given that it is heavier than air, reacts quickly with water, and binds to soil particles. Phosphine exposure within a treated

burrow will be characterized because p lants will be exposed if their root systems penetrate the

burro w

.

6.2.2.1

. Phosphine, Al Phosphide, and Mg Phosphide Release Scenarios Specified on Labels

Phosphine c oncentration s in air near treated facilities w ere initially estimated by a Tier

- I screening model, AERSCREEN ( http://www.epa.gov/scram001/dispersion_screening.htm )

. The

Tier

- I model will produce estimates of "worst

- case" 1

- hour concentrations for a single source, without the need for hourly meteorological data . Air EECs may be refined by the Tier II Probabilistic Exposure and Risk Model for Fumigants (PERFUM). PERFUM is capable of producing a di stribution of air EECs from a range of different meteorological conditions.

Al phosphide, Mg phosphide , and phosphine are used to treat a wide variety of stored food products and post

- harvested commodities. Treatments are permissible for a wide variety of structures including grain mills, grain bins, industrial facilities, warehouses, cargo holds with fumigation chambers, and other storage facilities. Labels also allow mechanical and passive

aeration of treated structures. Mechanical aeration releases the fumigant outdoors from the treated structure using a forced airflow through a stack or vent. Passive aeration involves the ventilation of treated structures via natural means such as opening of windows and doors to

allow air to circulate around the b uilding.

Labels specify maximum application rates, or indoor concentrations, which are maintained over periods of time for treatments inside the structures. Phosphine gas is applied at a maximum application rate of 0.320 lb/1,000 ft 3

. The maximum phosph ine

- equivalent application rates15 from Al phosphide and Mg phosphide products are also at 0.320 lb/1,000 ft 3 . The maximum application rates identified from product labels for each formulation for the phosphides are specified in Table 4

.

Table 4

. Maximum P hosphine

- E quivalent Indoor A pplication R ates for V arious Al

P hosphide and Mg P hosphide F ormulations.

Mg Phosphide Formulation Phosphine Equivalent Application Rate (lb/1,000 ft 3 )

Tablets 0.320 Bag 0.146

Fumi Cell 0.317 Fumi Strip 0.316

Pellets 0.220

Granules 0.320 Al Phosphide Formulation Phosphine Equivalent Application Rate (lb/1,000 ft 3 )

Tablets 0.320

Pellets 0.320 Bags 0.315

Granules 0.316 Rope 0.316 *Bold values indicate maximum application rate

In this screening

- level approach, EFED will develop upper

- bound atmospheric release scenarios

for th ese use pattern s

. The Health Effects Division (HED) has conducted an air exposure assessment with methyl bromide which possesses a similar broad use pattern (USEPA, 2008)

. The H ED assessment identified the largest building size for a grain mill or warehouse of up to 10,000,000 cubic feet. In addition, HED assumed a 12

- hour minimum release from these large structures. Furthermore, HED assumed that emissions over the 12

- hour peri od declined at an exponential rate. This is based on indoor air monitoring shown for passive aeration and mechanical aeration of methyl bromide in treated buildings. Therefore, since phosphine releases are similar to methyl bromide, EFED’s approach for d eveloping release scenarios will be consistent with HED’s approach for methyl bromide.

Based on this parameterization and the mechanical release scenario, AERSCREEN produces a

maximum 1

- hour concentration estimate of 8.4 × 10 8 μg/m 3 ( Appendix A )

. This estimate is obviously overly conservative (too high) in that it exceeds the flam ma bility limit of phosphine gas ( 18,000 ppm 10 ) by a factor of

~ 3 4 :

8

. 423 × 10 8 μg/m 3 = 8.423 × 10 5 mg/m 3

24.45 L/mol * 8.423 × 10 5 mg/m 3 ÷ 34 g/mol = 605,712. 8 ppm 11

605,712. 8 ppm ÷ 18,000 ppm = 33.6

Where, the m olecular volume of one mole of ideal gas is 24.465 L/mol at 25 °C at 1 atm.

10 http://www.cdc.gov/niosh/ershdb/EmergencyResponseCard_29750035.html

11 http://www.ccohs.ca/oshanswers/chemicals/convert.html16 Therefore EFED has elected to use the intended application concentration ( 3,625 ppm) as stated

on the ECO 2 FUMETM (Reg. # 68387

- 7 ) and VAPORPH3O5TM (Reg. # 68387

- 8) labels as a more reasonable screening level maximum 1

- hour air concentration. This would approximate a scenario in which a catastrophic release ( e.g. , structural failure of some sort) occurs rather than a

controlled relea se. Again, the Agency welcomes the submission of additional information that might help the Agency arrive at a more reasonable maximum screening level.

6.3. Measures of Effect

Toxicity effects data will be used as measures of direct and indirect effects t o biological receptors (USEPA, 2004). As discussed previously, data will be obtained from registrant

submitted studies and from literature studies identified in ECOTOX.

Quantitative assessment of risks will be based on study endpoints that can be directl y linked to the Agency’s assessment endpoints of impaired survival, growth, and reproduction. Sub

- lethal effects ( e.g. , lethargy and changes in coloration) will be evaluated qualitatively. Available

incident data will be used to further characterize risk

.

6.4. Integration of Exposure and Effects

The exposure and effects data will be integrated in order to evaluate potential adverse ecological

effects on non

- target species. The risk quotient (RQ) method will be used to compare exposure

and measured toxic ity values. EECs will be divided by toxicity values. The resulting RQs will be compared to the Agency’s LOC s (USEPA, 2004).

6.5. Endangered Species Assessments

Consistent with the Agency’s responsibility under the Endangered Species Act (ESA), the Agen cy will evaluate risks to f ederally

- listed threatened and endangered (listed) species from registered uses of Al phosphide, Mg phosphide, and phosphine . This assessment will be

conducted i n accordance with the Overview Document (USEPA, 2004), provisions of the ESA,

and the Services’ Endangered Species Consultation Handbook (USFWS and NMFS, 1998).

6.6. Endocrine Disruptor Screening

As required by Federal Food, Drug and Cosmetic Act (FFDCA) s ection 408(p), Al phosphide, Mg phosphide, and phosphine are subject to the endocrine screening part of the Endocrine Disruptor Screening Program (EDSP) 12

. Al phosphide, Mg phosphide , and phosphine are not in

the first or second group of pesticide active ingredients to be screened under the EDSP.

6.7. Drinking Water Assessment

A d rinking w ater a ssessment will not be conducted for Al phosphide, Mg phosphide, or phosphine because e xposure via drinking water is expected to be minimal. Again, l imited exposure is expected based on the labeled uses and the fate properties of Al phosphide, Mg phosphide, and phosphine . As described previously

, burrow applications are expected to remain

in the burrow and are not considered to have a complete exposure pathw ay to aquatic

environments outside of the burrow. Structural release s of phosphine are expected to result in minimal aquatic exposure given its rapid atmospheric degradation and that it will not tend to

12 http://www.epa.gov/endo/17 partition to water given its high vapor pressure ( 2. 93 × 10 4 at 25  ̊ C ) and Henry's Law Constant (0.1 atm m 3 /mol).

6.8. Preliminary Identification of Data Gaps

6.8.1. Environmental Fate Data

No fate data have been submitted for Al phosphide, Mg phosphide, or phosphine ( Table 5 ).

Table 5. Environmental Fa te Data for Al Phosphide, Mg Phosphide, and Phosphine

Guideline Description MRID Classification Data Gap Comments

835.2120 Hydrolysis None Not applicable No Typically, data is not required for highly reactive solids (Al phosphide and Mg phosphide) or gases (phosphine). Furthermore, limited aquatic exposure is expected based on the

labeled uses and the fate properties of these compounds. 835.2240 Photodegradation in Water None Not applicable No

835.2410 Soil Photolysis None Not applicable No

835.2370 Photodegradation in Air None Not applicable No

835.4100 Aerobic Soil Metabolism None Not applicable No

835.4200 Anaerobic Soil Metabolism None Not applicable No

835.4300 Aerobic Aquatic Metabolism None Not applicable No

835.4400 Anaerobic Aquatic Metabolism None Not applicable No

835.1230

835.1240 Leaching
Adsorption/Desorption None Not applicable No

835.1410 Laboratory Volatility None Not applicable No

835.8100 Field Volatility None Not applicable No

835.6100 Terrestrial Field Dissipation None Not applicable No

835.6200 Aquatic Field Dissipation None Not applicable No

850.6100 ECM/ILV (Water) None Not applicable No

850.6100 ECM/ILV (Soil) None Not applicable No

850.1730 Bioaccumulation in Fish None Not applicable No

Exposure to phosphine is expected to occur through air and will be modeled using atmospheric transport models

. Typically such modeling estimates the air concentration over time ( exposure duration) assuming gaseous emissions dissipate with time due to dispe rsion with air movement

and degradation over time . It is anticipated that dispersion will reduce air concentrations much

faster than de gradation. Therefore at this time, EFED is not requesting additional fate data for Al phosphide, Mg phosphide , or phosphine to support its atmospheric transport modeling efforts

.

T here are u ncertainties in the usage of phosphine i n treatment facilities (maximum chamber or building s izes ), aeration methods, air exchange exhaust rates, and the use of emission control

d evi c e s . These factors will directly influence emission rates and affect outdoor air concentrations. In addition, there is a lack of information related to the design of buildings for the fumigation, including the dimensions of buildings, different size s of buildings, as well as the

number , sizes, and relative locations of stack s and vents that serve as the release points during phosphine aeration operations. These variables all impact the magnitude of downwind18 dispersion from treated structures. Submissi on of information that refines these uncertainties is expected to have a high potential to add value to the ecological risk assessment.

6.8.2. Ecological Effects Data

No toxicity data have been submitted for Al phosphide, Mg phosphide, or phosphine ( Table s 6, 7, and 8 ).

Aquatic studies are not requested for Al phosphide, Mg phosphide, or phosphine because exposure is expected to be minimal

.

Terrestrial studies are not requested f or Al phosphide or Mg phosphide because exposure will be

assumed lethal to all animals within a sealed burrow (via formation of phosphine gas). There is not a complete exposure pathway for organisms outside the sealed burrow because Al phosphide and Mg phosphide are expected to react fully (inside the burrow) to produce phosphin e gas. Additionally, there is not a complete exposure pathway for indoor uses of Al phosphide and Mg phosphide.

The following studies are requested for phosphine due to potential exposure after release from

treated structures:

• Terrestrial plant toxici ty ( non

- guideline vegetative vigor )

• Avian i nhalation toxicity (non

- guideline)

• Honeybee inhalation toxicity (non

- guideline)

Terrestrial Plants

- Vegetative Vigor (phosphine)

A non

- guideline terrestrial plant study (vegetative vigor , exposure to phosphine gas ) is recommended to reduce uncertainty in risk conclusions because of potential exposure and

adverse effects to non

- target plants. Phosphine exposure is expected via atmospheric emission from treated structures; once released, phosphine is expected to move to ground

- level given that it is heavier than air. Plants will also be exposed to phosphine in treated burrows if their root systems penetrate the burrow. There is some evidence to suggest that plants may be adversely affected if exposed to phosphi ne; according to a WHO report (1998)

, phosphine produced harmful effects on growing lettuce at concentrations between 3 and 8 mg/m 3 . Given the potential for effects and exposure, risk to plants will be presumed in the absence of data.

Avian acute inhalation toxicity (phosphine)

An avian inhalation study is recommended to reduce uncertainty in risk conclusions because of potential exposure and the known inhalation toxicity of phosphine to vertebrates. According to a WHO report (1998), 100% mortali ty was observed in hens and turkeys exposed to 211

- 224 mg/m 3 for roughly 1 hour, although the study results may have been confounded by the presence of compounds other than phosphine (repor ted in Pepelko et al., 2004). Given the potential for

effects and exposure, risk to bird s will be presumed in the absence of data.19 Honeybee acute inhalation toxicity (phosphine)

A honeybee inhalation study is recommended to reduce uncertainty in risk conclusions because of potential exposure and effects. Adverse eff ects are expected for insects given that the proposed mode

- of

- action of phosphine is related to the inhibition of mitochondrial respiration. Furthermore, phosphine is used to control insects in structures; therefore, there is a reasonable expectation that phosphine would pose a direct risk to non

- target invertebrates, including insects. Given the potential for effects and exposure, risk to terrestrial invertebrates will be presumed in

the absence of data.

Table 6. Ecological Effects Data for Aquatic Ani mals Exposed to Al Phosphide, Mg Phosphide, and Phosphine

Guideline Description MRID Classification Data Gap? Comments

850.1075 Acute freshwater fish toxicity (cold water species) None Not applicable No Typically, data is not required for highly reactive solids ( Al phosphide and Mg phosphide) or gases (phosphine). Furthermore, limited aquatic exposure is expected based on the labeled uses and the fate properties of these compounds. Acute freshwater fish toxicity (warm water species) None Not applicable No

Acute estuarine/ marine fish toxicity None Not applicable No

850.1010 Acute toxicity to

freshwater

invertebrates None Not applicable No

850.1025 Acute estuarine/

marine mollusk toxicity None Not applicable No

850.1035 Acute estuarine/

marine invertebrate toxicity None Not applicable No

850.1300 Freshwater invertebrate life cycle None Not applicable No

850.1400 Freshwater fish early life stage None Not applicable No20 Table 7. Ecological Effects Data for Terrestrial Animals Exposed to Al Phosphide, Mg Phosphide, and Phosphine

Guideline Description MRID Classification Data Gap? Comments

850.2100 Avian acute oral toxicity (upland game or waterfowl species) None Not applicable No 1 1 Acute inhalation is the primary route of exposure; thus, acute oral/dietary/contact toxicity studies are not

recommended.

2 Birds and insects could potentially be exposed to phosphine released from

treated structures. Data have high value in reducing uncertainty of risk. A study protocol should be submitted to the Agency prior to conducting each study. Bobwhite quail is the recommended test species for the bird study

.

3 Inhalation is the primary route of exposure. Continual

inhalation exposure to phosphine is unlikely; however, acute inhalation exposure could cause reproductive effects depending on the timing of the exposure. Although reproductive risk is uncertain without data, data

are not recommended because of logistical constraint s on study design. It is impractical to conduct long term

inhalation exposure experiments with phosphine or

to detect reproductive effects from acute exposure because it is unknown when exposure may elicit and effect. In lieu of data, a weight of evidenc e approach will be used to

characterize risk on a qualitative basis. Avian acute oral toxicity (passerine species) None Not applicable No 1

Non

guideline Avian acute inhalation toxicity None Not applicable Yes 2

850.2200 Avian dietary toxicity (upland game species) None Not applicable No 1

Avian dietary toxicity

(waterfowl species) None Not applicable No 1

850.2300 Avian reproduction (upland game species) None Not applicable No 1

Avian reproduction (waterfowl species) None Not applicable No 1

Non

guideline Avian reproduction ( inhalation toxicity ) None Not applicable Yes 3

850.3020 Honeybee acute contact toxicity None Not applicable No 1

Non

guideline Honeybee inhalation toxicity None Not applicable Yes 221 Table 8. Ecological Effects Data for Plants Exposed to Al Phosphide, Mg Phosphide, and Phosphine

Guideline Description MRID Classification Data Gap? Comments

850.4100 A Terrestrial plant toxicity (Tier I&II seedling emergence) None Not applicable No 1 1 Limited exposure is anticipated for seeds.

2 Exposure is anticipated in the form of phosphine gas (the exposure regime of standard plant testing does not apply)

. Data on phosphine toxicity have high value in reducing uncertainty. A study protocol should be

submitted to the Agency prior to conducting the study.

3 Limited aquatic exposure is expected based on the labeled uses and the fate properties of these compounds. 850.4150 B Terrestrial plant toxicity (Tier I&II vegetative vigor) None Not applicable No 2

Non

guideline Terrestrial plant toxicity (Tier I&II vegetative vigor)

- vapor phase None Not applicable Yes 2

850. 45 00 C Aquatic plant growth (freshwater green alga) None Not applicable No 3

Aquatic plant growth (freshwater diatom) None Not applicable No 3

Aquatic plant growth

(saltwater diatom) None Not applicable No 3

850.45 5 0 C Aquatic plant growth (Cyanobacteria) None Not applicable No 3

850.4400 Aquatic plant growth (vascular plants) None Not applicable No 3

A As of July 2012 the Final Guideline 850.4100 contains both Tier I and Tier II test guidance (formerly 850.4100 and

850.4225, respectively).

B As of July 2012 the Final Guideline 850.4150 contains both Tier I and Tier II test guidance (formerly 850.4150 an d

850.4250, respectively).

C As of July 2012 (formerly 850. 54 00)

7. References

Berck, B. and F.A. Gunther. 1970. Rapid determination of sorption affinity of phosphine by fumigation within a gas chromatographic column. J. Agric. Food Chem . 18(1): 148

- 153.

Cotton, F.A. and G. Wilkerson. 1988. Advanced Inorganic Chemistry. Fifth Edition. John Wiley and Sons, New York.

Daubert, T.E. and R.P. Danner. Physical and Thermodynamic Properties of Pure Chemicals Data Compilation. Washington, D.C.: Taylo r and Francis, 1989 , p. 458

.

Eiseman, F., Glindemann, D., Bergman, A., and P. Kuschk. 1997. Soils as a source and sink of phosphine. Chemosphere 35(3): 523

- 533.

Fluck, E. The Chemistry of Phosphine. 1973. in Topics in Current Chemistry. 35:1

- 64.

Greenwood, N.N. and A. Earnshaw. 1984. Chemistry of the Elements. Pergamon Press, Oxford,

U.K.22 Hilton, H.W. and W.H. Robinson. 1972. Fate of zinc phosphide and phosphine in the soil

water environment. J. Agric. Food Chem . 20(6): 1209

- 1213.

Lindsa y, W.L. 1979. Chemical Equilibria in soils. John Wiley and Sons, New York.

Lyman WJ et al . 1990. Handbook of Chemical Property Estimation Methods. Washington, D C: Amer Chem Soc pp. 8

- 12.

Pepelko, B., J. Seckar, P.R. Harp, J.H. Kim, D. Gray, and E.L. Anderson. 2004. Worker Exposure Standard for Phosphine Gas. Risk Analysis. Vol. 24, No. 5, pg 1201

- 1213.

US EPA

. 2010. Risks of Aluminum and Magnesium Phosphides Uses to the Federally Threatened Alameda Whipsnake ( Masticophis lateralis euryxanthus) an d California Tiger Salamander ( Ambystoma californiense ), Central California Distinct Population Segment and Federally Endangered California Tiger Salamander ( Ambystoma californiense ) Sonoma County Distinct Population Segment and Santa Barbara County Distin ct Population Segment, San Francisco Garter Snake ( Thamnophis sirtalis tetrataenia ), and San Joaquin Kit Fox ( Vulpes macrotis mutica). U.S. Environmental Protection Agency, Office of Pesticide Programs, Washington DC.

USEPA. 2008. Second Addenda to the 2006 (DP Barcode 304623) Phase 5 Human Health Risk Assessment for Commodity Uses. Office of Pesticide Programs. Washington, DC. (November 26, 2008) (DP 304612). USEPA. 2004. Overview of the Ecological Risk Assessment Proc ess in the Office of Pesticide Programs. U.S. Environmental Protection Agency, Office of Prevention, Pesticides and Toxic Substances, Office of Pesticide Programs, Washington DC.

USFWS and NMFS. 1998. Endangered Species Consultation Handbook: Procedures for Conducting Consultation and Conference Activities Under Section 7 of the Endangered Species Act. Final Draft.

WHO (World Health Organization). 1998. Phosphine and Selected Metal Phosphides. WHO,

Geneva.23 

### Appendix A . Atmospheric Modeling

AERSCREEN Description

The Agency’s recommended screening dispersion model for the near field, the American Meteorological Society/EPA Regulatory Screening Model (AERSCREEN) 13 , will be used to generate screening estimated environmental concentrations (EECs) for the various release scenarios. The Tier I analysis will consider the emission rates and release flow rates and stack parameters for the various mechanical release scenarios for phosphine. Worst

- case meteorological conditions (light winds and stagnan t conditions) and downwash 14 parameters are assumed to calculate peak air EECs, representing one

- hour average concentrations.

A schematic of release scenarios from fumigated structures and the related conceptual model for ground

- level exposure is shown i n Figure A1 . For purposes of this screening

- level analysis, all ecological receptors of concern will be assumed to be present directly downwind from the building at ground level.

Figure A1

. Schematic illustrating fumigation releases from treated stru ctures and conceptual model for ground

- level exposure.

AERSCREEN Release Scenarios

Each release scenario for phosphine will be based on the maximum application rate of 0.320 lb/1,000 ft 3 inside a 10,000,000 ft 3 structure. Scenario 1 of the AERSCREEN evaluation represents the mechanical release of phosphine. Scenario 2 represents the passive aeration release scenario. Each modeled release scenarios assumes that the aeration is complete after twelve hours. However, peak air concentra tions will only consider the mode of the exponential emissions curve which results in maximized peak (one

- hour) air concentrations.

The input parameter values used in AERSCREEN for the screening analysis of phosphine air exposure for Mechanical Scenario ( Scenario 1 ) is shown in Table A1 . The AERSCREEN input parameter values for Passive Scenario (Scenario 2 ) is shown in Table A2

. The AERSCREEN modeling captures the upper

- bound air exposure from release scenarios consolidated above from information on the phosphine product label.

13 http://www.epa.gov/scram001/dispersion_screening.htm

14 Downwash is defined as the downward flow often observed on the leeside of buildings induced by wake turbulence. Pollutants released from buildings can often become embedded in downwash flows and wake cavities.24 Table A1

. AESCREEN I nput P arameter V alues for the M echanical R elease S cenario (Scenario 1) of P hosph ine, Al P hosphide, and Mg P hosphide L abels

Input Parameter Option/Value Notes Scenario 1 English or Metric Units E (English) Source Type P (Point) Stack releases required for all uses Emission Rate (lb/hr) 253.97 Mode of exponential emissions trend curve 1

Stack or Release Height Above Ground (ft) 100 Default for 10,000,000 ft. 3 building size based on methyl bromide HED assessment 2

Stack Diameter (in) 590.55 Default for 10,000,000 ft. 3 building size based on

m ethyl bromide HED assessment 2

Stack Temperature (°F) Equivalent to Ambient Temperature (input = 0) No stack temperatures specified, conservative assumption is non

- buoyant source Option for Flow Rate or Flow Velocity 3 (Flow Rate ACFM)

Stack Exit Stream

Flow Rate (f t 3 /min) 13,889 Based on 12

- hour exchange of volume (air exchange rate = 0.083 air exchanges per hour) 3

Urban or Rural? R (Rural) Conservative default

Minimum Distance to Ambient Air (ft) 3.3 Conservative default

NO 2 Chemistry 1 (No chemistry/pollutant is

not NO 2 ) Tracer gas

- NO

x emissions not modeled

Include Building Downwash? Y (Yes) Downwash is feasible downward transport mechanism for plume in release scenarios

Use Pre

- Existing BPIPPRM File? N (No) Downwash parameters to be input manually Building Height (ft) 100 Equivalent to stack height Maximum Horizontal Building Dimension (ft) 316.23 Square building footprint consistent with building heights specified above Minimum Horizontal Building Dimension (ft) 316.23 Square building footprint consistent with building heights specified above Maximum Building Dimension Angle to True North (degrees) 0 Conservative parameterization of building

downwash

– stack located on the leeward edge of the building Direction of Stack from Building Center (degrees) 0

Distance Between Stack and Building Center (ft) 158.1

Terrain Heights? N (No) Only flat terrain considered Maximum Distance to Probe (m) 5,000 Default

- maximum feasible distance for screen

Include Discrete Receptors N (No) Automated receptors sufficient Flagpole Receptors N (No) Ground

- level concentrations assumed Source Elevation (ft) 0 Stack base from ground release assumed Minimum Temperature (°F)

- 10 Default

– typical national temperature range Maximum Temperature (°F) 100 Default

– typical national temperature range Minimum Wind Speed (m/s) 0.5 Minimum in model: conservative default

Anemometer Height (ft) 33 Typical boundary layer reference height (10 meters)

Surface Characteristics Option 1 (Single User Specified Values)

Albedo 0.6 Bare surface assumed around source 4

Bowen Ratio 3.0 Bare surface assumed around source 4

Surface Roughness Length (m) 0.001 Bare surface assumed around source 4

1 Emission Rate (lb/hr) = 

### ( ) 

### [ ]

. sec/ 600

, 3 exp 1 0
hr AXR V C

− − × × where C

o is the application rate = 0.321 lb/1,000 ft 3 , V is the

building volume = 10,000,000 ft 3 , and AXR is the air exchange rate = 0.083 air exchanges per hour.25 2 Methyl bromide HED risk assessment citation:

Dawson, J. 2008. Second Addenda to the 2006 (DP Barcode 304623) Phase 5 Human Health Risk Assessment for Commodity Uses. Office of Pesticide Programs. Washington, DC. (November 26, 2008) (DP 304612).

3 Flow rate (ft. 3 /min) = Air exchange rate (air exchanges/hr) x Structure Size (ft 3 ) x hr

60 min

4 Default values for bare soil assumed. Please refer to “User’s Guide for the AERMOD Meteorological

Preprocessor (AERMET)” ( http://www.epa.gov/scram001/7thconf/aermod /aermetugb.pdf ) for further details.

Table A2

. AESCREEN I nput P arameter V alues for the P assive R elease S cenario (Scenario 2) of Al P hosphide, Mg P hosphide , and Phosphine L abels

Input Parameter Option/Value Notes Scenario 2 English or Metric Units M (Metric) Source Type A (Area)

Emission Rate (g/s) 32.11 Mode of exponential flux rate trend curve 1

Emission rate input is based on resulting flux rate (3.456 x 10 - 3 g/m 2

- s) x Area of Building Footprint (9,290 m 2 )

Area of building footprint for 10,000,000 ft. 3

building based on methyl bromide HED

assessment 2

Release Height Above Ground (m) 15.24 Release height of half the building size

assumed based on HED assessment 2

Height of building for 10,000,000 ft. 3 based on methyl bromide HED assessment 2

Minimum Horizontal Building Dimension (m) 96.4 Square building footprint consistent with building heights specified above Maximum Horizontal Building Dimension (m) 96.4 Square building footprint consistent with building heights specified above

Initial Vertical Dimension (m) 15.24 Equivalence to release height assumed

Urban or Rural? R (Rural) Conservative default

Minimum Distance to Ambient Air (m) 1 Conservative default

NO 2 Chemistry 1 (No chemistry/pollutant

is not NO 2 ) Tracer gas

- NO

x emissions not modeled

Maximum Distance to Probe (m) 5,000 Default

- maximum feasible distance for screen Include Discrete Receptors N (No) Automated receptors sufficient Flagpole Receptors N (No) Ground

- level concentrations assumed Source Elevation (m) 0 Stack base from ground release assumed Minimum Temperature (K) 250 (Default) Default

– typical national temperature range Maximum Temperature (K) 310 (Default) Default

– typical national temperature range Minimum Wind Speed (m/s) 0.5 Minimum in model: conservative default

Anemometer Height (m) 10 Typical boundary layer reference height

Surface Characteristics Option 1 (Single User Specified Values)

Albedo 0.6 Bare surface assumed around source 3

Bowen Ratio 3.0 Bare surface assumed around source 3

Surface Roughness Length (m) 0.001 Bare surface assumed around source 3

1 Flux rate (g/m 2

- s) 

### ( ) 

### [ ]

A hr AXR V C

× − − × ×

=

. sec/ 600

, 3 exp 1 0 where C

o is the application rate = 0.321 lbs./1,000 ft 3 (5.13 g/ft 3 ), V

is the building volume = 10,000,000 ft 3 (283,168.5 m 3 ), A is the area = 100,000 ft 2 (9,290 m 2 ), and AXR is the air exchange rate = 0.083 air exchanges per hour.

2 Methyl bromide HED risk assessment citation:26 Dawson, J. 2008. Second Addenda to the 2006 (DP Barcode 304623) Phase 5 Human Health Risk Assessment

f or Commodity Uses. Office of Pesticide Programs. Washington, DC. (November 26, 2008) (DP 304612).

3 Default values for bare soil assumed. Please refer to “User’s Guide for the AERMOD Meteorological

Preprocessor (AERMET)” ( http://www.epa.gov/scram001/7thconf/aermod/aermetugb.pdf ) for further details.27 

### Appendix B. Data Call

- In Tables

Guideline Number: Non

- guideline Study Title: Acute Honey bee Vapor Exposure Study

Rationale for Requiring the Data A honeybee inhalation (vapor exposure) study is recommended to reduce uncertainty in risk conclusions because of potential exposure and effects. I t is expected that honey bees and other insect pollinators will be exposed to phosphine primarily in the vapor phase. Adverse effects are expected for insects given that the proposed mode

- of

- action of phosphine is related to the inhibition of mitochondrial respiration. Furthermore, phosphine is used to control insects in structures; therefo re, there is a reasonable expectation that phosphine would pose a direct ri sk to

non

- target invertebrates once it is vented outside of the structure . Given the potential for effects and exposure, risk to terrestrial invertebrates will be presumed in the a bsence of data. Practical Utility of the Data

How will the data be used? Data from an acute honey bee vapor exposure stud y will be used to assess risk to non

- target
terrestrial invertebrates exposed to phosphine near release points

.

How could the data impact the Agency’s future decision

- making? If future ecological risk assessments are performed without these data, the Agency would have to presume risk to non

- ta rget terrestrial invertebrates from exposure to phosphine

. Therefore,

use of phosphine, Al phosphide, and Mg phosphide would be potentially restricted in areas where honey bees, other pollinator insects, or listed insects could be exposed. The lack of these data will limit the flexibility the Agency and registrants have in mitigating potential r isks and

could result in restrictions for use of phosphine, Al phosphide, and Mg phosphide that are unnecessarily severe.

Guideline Number: Non

- guideline Study Title: Avian Inhalation Rationale for Requiring the Data An avian inhalation study is recommended to reduce uncertainty in risk conclusions because of potential exposure and the known inhalation toxicity of phosphine to vertebrates. According to a WHO report (1998), 100% mortality was observed in hens and turkeys exposed to 211

- 224 mg/m 3 f or roughly 1 hour, although the study results may have been confounded by the presence of compounds other than phosphine (repor ted in Pepelko et al., 2004). Given the potential for effects and exposure, risk to bird s will be presumed in the absence of dat a. Practical Utility of the Data

How will the data be used? Data from an avian inhalation study will be used to assess risk to avian species exposed to phosphine near release points.

How could the data impact the Agency’s future decision

- making? If future endangered species risk assessments are performed without these data, the Agency

would assume risk to birds from exposure to phosphine

. Therefore, use of phosphine, Al phosphide, and Mg phosphide would be potentially restricted in areas where lis ted species could be exposed. The lack of these data will limit the flexibility the Agency and registrants have in mitigating potenti al risks and could result in restrictions for use of phosphine, Al phosphide, and Mg phosphide that are unnecessarily seve re.28 Guideline Number: Non

- guideline Study Title: Terrestrial Plant Vapor Phase Study Rationale for Requiring the Data

A non

- guideline terrestrial plant study (vegetative vigor, vapor exposure) is recommended to reduce uncertainty in risk conclusions because of potential exposure and adverse effects to terrestrial plants. Phosphine exposure is expected via atmospheric emission from treated structures; once released, phosphine is expected to move to ground

- level given that it is heavier

tha n air. Plants will also be exposed to phosphine in treated burrows if their root systems penetrate the burrow. There is some evidence to suggest that plants may be adversely affected if exposed to phosphine; according to a WHO report (1998), phosphine pr oduced harmful effects on growing lettuce at concentrations between 3 and 8 mg/m 3 . Given the potential for effects and exposure, risk to plants will be presumed in the absence of data. Practical Utility of the Data

How will the data be used?

Data from a terrestrial plant study (vegetative vigor, vapor exposure) will be used to assess risk to terrestrial plants exposed to phosphine near release points.

How could the data impact the Agency’s future decision

- making? If future endangered species risk ass essments are performed without these data, the Agency would assume risk to terrestrial plants from exposure to phosphine. Therefore, use of phosphine, Al phosphide, and Mg phosphide would be potentially restricted in areas where listed species could be exposed. The lack of these data will limit the flexibility the Agency and registrants have in mitigating potenti al risks and could result in restrictions for use of phosphine, Al phosphide, and Mg phosphide that are unnecess arily severe.