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INTRODUCTION

This is the Environmental Protection Agency’s (EPA or the Agency) Final Work Plan (FWP) for

the registration review of aluminum phosphide and magnesium phosphide (hereafter referred to 

as “metal phosphides”) and phosphine. This work plan addresses public comments received 

concerning the Preliminary Work Plan (PWP), which was posted in the metal phosphide and 

phosphine registration review docket (EPA-HQ-OPP-2013-0081). Phosphine is a colorless gas 

registered for use against stored-product insect pests and vertebrate pests, mainly rodents. It is 

formulated as a pressurized gas and it is also the active ingredient for the metal phosphides. The 

metal phophides are formulated as impregnated materials, pellets/tablets, and granules which 

release phosphine gas upon exposure to atmospheric moisture. 

The Agency is implementing the registration review program pursuant to Section 3(g) of the 

Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), and will review each registered 

pesticide every 15 years to determine whether it continues to meet the FIFRA standard for 

registration. Changes in science, public policy, and pesticide use practices occur over time. The 

registration review program is intended to make sure that, as the ability to assess risk evolves and 

as policies and practices change, all registered pesticides continue to meet the statutory standard. 

The public phase of registration review begins when the initial docket is opened for each case. 

Information on this program is provided on the Agency’s website.

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The FWP begins with any updates since the PWP was issued. Next is a summary of substantive 

comments received during the public comment period for the PWP concerning anticipated data 

needs, expected risk assessments, or the estimated timeline identified in the PWP, and a 

summary of the Agency’s responses to those comments. This section is followed by registration 

review planned data needs, risk assessments expected to be conducted, and the projected

registration review timeline for the metal phosphides and phosphine. Lastly, there is a discussion

of next steps.

UPDATES SINCE THE PWP WAS ISSUED

There are no updates on the metal phosphides and phosphine since the PWP.

SUMMARY OF COMMENTS AND AGENCY RESPONSES

During the 60-day public comment period on the Aluminum Phosphide, Magnesium Phosphide, 

and Phosphine Preliminary Work Plan, which opened on September 25, 2013 and closed on 

November 25, 2013, the Agency received 17 public comments. Comments were submitted by a 

registrant, fumigant applicators, and non-profit organizations. The Agency considered the issues 

and concerns raised by each of the seven unique comments submitted. The registration review 

timeline, data-requirements, and anticipated risk assessment needs did not change as a result of 

these comments as outlined in the final work plan. In the PWP, EPA also solicited comments on 

the specific topics of environmental justice, water quality concerns, and trade irritants, but no 

comments or information were received on those issues.

 1 http://www.epa.gov/oppsrrd1/registration_review/
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The comments address the registration review process and utility of fumigants in commodity and 

structural fumigation. Public comments and EPA responses in their entirety are located in the 

docket, EPA-HQ-OPP-2013-0081. 

• Summarized public comments and Agency responses of a broad regulatory nature are in 

the Responses to Public Comments on the Aluminum Phosphide, Magnesium Phosphide 

and Phosphine Preliminary Work Plan. 

• Comments and responses related to the anticipated ecological risk assessment or data 

needs are in the Responses to Public Comments on the Aluminum Phosphide, Magnesium 

Phosphide and Phosphine Problem Formulation.

• Comments relevant to the anticipated human health risk assessment or data needs are in 

the Response to Public Comments on the Preliminary Work Plan (PWP) for Aluminum 

Phosphide, Magnesium Phosphide, and Phosphine. 

PLANNED DATA NEEDS

Table 1 below summarizes the planned data needs for the metal phosphides and phosphine based 

on the Registration Review: Preliminary Problem Formulation for Environmental Fate, 

Ecological Risk, Endangered Species, and Drinking Water Exposure Assessments for Aluminum 

Phosphide, Magnesium Phosphide, and Phosphine; Phosphide (Al, Mg) and Phosphine: 

Human-Health Assessment Scoping Document Supporting Registration Review, and the 

Agency’s response to comments documents discussed in the previous section of this document. 

The planned data needs have not changed from what was included in the PWP.

Table 1: Planned Data Needs for the Aluminum Phosphide, Magnesium Phosphide, and 

Phosphine Registration Review

Guideline 

Number2 Study Title2

Test Material

Estimated 

Timeframe

(Months from 

receipt of DCI)

Anticipated Data Needs for the Parent Aluminum Phosphide, Magnesium Phosphide, and 

Phosphine

875.1700 Product use information TEP 12

875.1400 Inhalation exposure for applicators TEP 24

875.2500 Post-application inhalation exposure 3 TEP 24

NonGuidelineExtended one-generation reproduction study via 

inhalation route TGAI 36

 2 On June 27, 2012, EPA announced certain revisions in harmonized guideline series 850 – Ecological Effects Tests 

– including renumbering and other designations or changes for some guideline studies. See “Final Test 

Guidelines; OCSPP 850 Series; Notice of Availability” 77 FR 38282, June 27, 2012. 

http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPPT-2009-0154-0028 3 This study is needed to assess post-application exposures for workers within and near structural fumigation 

facilities/operations or who work with treated commodities/materials.
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Table 1: Planned Data Needs for the Aluminum Phosphide, Magnesium Phosphide, and 

Phosphine Registration Review

Guideline 

Number2 Study Title2

Test Material

Estimated 

Timeframe

(Months from 

receipt of DCI)

NonGuideline Special acute inhalation study TGAI 12

NonGuideline Ambient air monitoring study TEP 36

NonGuideline Monitoring data on fumigated commodities TEP 24

NonGuidelineTerrestrial plant toxicity (vegetative vigor; vapor 

exposure) TGAI 12

NonGuideline Avian acute inhalation toxicity TGAI 24

NonGuideline Honeybee acute vapor exposure study TGAI 24

TGAI = technical grade active ingredient; TEP = typical end-use product;
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RISK ASSESSMENTS FOR REGISTRATION REVIEW

During registration review, the Agency will conduct a comprehensive ecological risk assessment, 

including an endangered species assessment, for all uses of the metal phosphides and phosphine.

For human health, EPA will conduct revised dietary, residential, and occupational risk 

assessments during registration review. If toxicological endpoints or points of departure are 

revised based on the data that are required for registration review, they will be considered in the 

new assessments, as well as any changes to the standard operating procedures or default 

exposure assumptions.

Table 2 below summarizes the planned registration review risk assessments based on the EFED 

Problem Formulation and HED Scoping Document. The planned assessments have not changed 

from what was included in the PWP.

Table 2: Planned Risk Assessments for the Aluminum Phosphide, Magnesium Phosphide, and 

Phosphine Registration Review

Type of Risk Assessment Conduct? Notes

Ecological and Environmental Fate

Comprehensive ecological 

(species to be assessed 

include terrestrial and aquatic 

organisms), including 

endangered species 

Y The stressors of concern will be the metal phosphides 

and phosphine. Phosphine released from structures or 

within burrows comprise the primary exposure 

pathways of concern for terrestrial organisms. 

Aquatic exposure to phosphine is assumed to be 

minimal. Terrestrial (above ground) and aquatic 

exposure to the metal phosphides is not expected. 

Incidents Will check for 

updates

For a discussion of reported ecological incidents for 

the metal phosphides and phosphine, see page 12 of 

the Problem Formulation.

Human Health

Dietary

Food Y A new dietary exposure and risk assessment may be 

required during Registration Review to incorporate 

potential changes to the phosphine toxicological 

points of departure (PODs). 

Drinking water N Given the use pattern and the physical/chemical 

properties of the metal phosphides and phosphine, 

there is a low exposure potential for ground and 

surface water.

Occupational

Handlers (mixers, loaders, 

applicators)

Y A new occupational handler risk reassessment will

incorporate new data, updated PODs, and, to the 

extent that they are available, policies currently under 

development regarding assessment of fumigant 

chemicals. 
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Post-application Y A new occupational post-application risk 

reassessment will be undertaken using new data,

updated PODs, and to the extent that they are 

available, policies currently under development 

regarding assessment of fumigant chemicals. 

Residential

Handlers N The metal phosphides and phosphine are restricted 

use pesticides, so residential handlers are prohibited 

from applying these products.

Post-application N Metal phosphide and phosphine exposure to 

occupants of fumigated structures is expected to be 

negligible given proper aeration procedures. 

Bystander Y Bystander risk (anyone not part of the fumigation) 

from phosphine emissions from treated commodities 

and structures will need to be evaluated based on 

label prescribed use conditions, and if the PODs or 

uncertainty factors (UFs) change based on acute 

toxicological data identified. 

Other

Aggregate Y Evaluates the combined risk from dietary and 

residential exposures.

Cumulative N The metal phosphides and phosphine are not members 

of a cumulative group, so no cumulative risk 

assessment is planned.

Tolerances Y Tolerances are established for residues of the 

fumigants aluminum phosphide, magnesium 

phosphide and phosphine gas in 40 CFR §180.225. 

Incidents Will check for 

updates

For a discussion of reported human incidents for the 

metal phosphides and phosphine see page 12 of the 

Scoping Document and the Aluminum Phosphide, 

Magnesium Phosphide and Phosphine: Review of 

Human Incidents. 

TIMELINE

EPA has created the following estimated timeline for the completion of the metal phosphides and 

phosphine registration review in Table 3 below. The projected timeline has been updated since 

the PWP to reflect the lengthening of the timeframe between posting of the draft risk assessment 

and the proposed decision by one quarter.

Table 3: Registration Review for Phosphide, Magnesium Phosphide, and Phosphine –

Projected Registration Review Timeline

Activities Estimated Date

Opening the Docket

Open Docket and 60-day Public Comment Period September 2013 –

Completed

Close Public Comment November 2013 –
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Table 3: Registration Review for Phosphide, Magnesium Phosphide, and Phosphine –

Projected Registration Review Timeline

Activities Estimated Date

Completed

Case Development

Final Work Plan March 2014 –

Completed

Issue DCI 2014 April - June 

Data Submission 2017 April - June

60-day Public Comment Period for Draft Risk Assessments4 2018 Oct. – Dec.

Registration Review Decision

60-day Public Comment Period for Proposed Registration Review 

Decision

2019 –July – Sept. 

Registration Review Decision and Begin Post-Decision Follow-up 2020

Total (years) 7

NEXT STEPS

As noted previously, the Agency plans to require several environmental fate, ecological effects, 

and human health studies for the metal phosphides and phosphine through a Data Call-In Notice, 

expected to be issued in June 2014. 

 4 The regulations governing Registration Review generally require the Agency to provide a public comment period 

of at least 30 calendar days for draft risk assessments; see 40 CFR Part 155.53(c). For conventional pesticides, the 

Agency plans to provide a 60 calendar day public comment period generally for draft risk assessments.