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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 propylene oxide (PPO). This work plan addresses public comments 

received concerning the Preliminary Work Plan (PWP), which was posted in the PPO 

registration review docket (EPA-HQ-OPP-2013-0156). PPO is registered for use as an 

insecticidal fumigant on several foods such as processed spices, dried garlic and onion, cocoa 

(beans and powder), in-shell and processed nutmeats (except peanuts), figs, raisins, and prunes. 

Nonfood uses include those on cosmetics, non-edible gums, ores, packaging, pigments, 

pharmaceutical materials, and discarded nut shells prior to disposal. In addition, there is a label 

claim that PPO aids in the control of microbiological spoilage and it is used as a sterilant on food 

and nonfood products for this purpose. 

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.1

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 PPO. Lastly, there is a discussion of next steps. 

UPDATES SINCE THE PWP WAS ISSUED

There are no additional updates on PPO since the PWP. 

SUMMARY OF COMMENTS AND AGENCY RESPONSES

During the 60-day public comment period on the PPO Preliminary Work Plan, which opened on 

September 25, 2013 and closed on November 25, 2013, the Agency received public comments 

from seven submitters. Comments were submitted by the registrant ABERCO, the American 

Spice Trade Association, the Minor Crop Farmer’s Alliance, the American Farm Bureau, the 

California Almond Board, the Physicians Committee for Responsible Medicine, and the Citrus 

Research and Education Center at the Institute of Food and Agricultural Sciences, University of 

Florida. The comments do not address the timeline described in the PWP, but they do address 

the data requirements and generally address the planned ecological and human health risk 

assessments. In the PWP, EPA also solicited comments on the specific topics of environmental 

justice, water quality concerns, and trade irritants. The comment from the registrant ABERCO 

 

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 http://www.epa.gov/oppsrrd1/registration_review/ 
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indicated that they have no information on the former two topics, but with regard to trade 

irritants they indicated that they are working with EPA towards CODEX acceptance of current 

MRLs. 

Public comments did not result in changes to the anticipated registration review data needs, risk 

assessments, or timeline. Public comments and the EPA response to comments document are 

located in the docket at EPA-HQ-OPP-2013-0156. 

PLANNED DATA NEEDS

Table 1 below summarizes the planned data needs for PPO based on the Registration Review: 

Preliminary Problem Formulation for Environmental Fate and Ecological Risk, Endangered 

Species, and Drinking Water Assessments for Propylene Oxide (PPO) and the Propylene Oxide: 

Human Health Assessment Scoping Document in Support of Registration Review. The planned 

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

Table 1: Planned Data Needs for the PPO Registration Review 

Guideline 

Number2 Study Title2 

Test Material 

Estimated 

Timeframe 

(Months from 

receipt of DCI) 

Anticipated Data Needs for the Parent PPO 

NonGuideline Avian acute inhalation toxicity TGAI 24 

NonGuideline Honeybee acute vapor exposure toxicity TGAI 24 

NonGuideline Terrestrial plant toxicity TEP 12 

875.1400 Inhalation indoor exposure TEP 24 

875.1700 Product use information TEP 12 

875.2500 Inhalation exposure study3 TEP 24 

NonGuideline Acute inhalation toxicity study - rodent TGAI 12 

NonGuideline Monitoring data on fumigated commodities TEP 24 

NonGuideline Ambient air monitoring TEP 36 

 

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 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 PPO Registration Review 

Guideline 

Number2 Study Title2 

Test Material 

Estimated 

Timeframe 

(Months from 

receipt of DCI) 

Anticipated Data Needs for Propylene Chlorohydrin (PCH), Reaction Product 

870.6200 Acute neurotoxicity - rat Reaction 

Product 12 

870.3700 Prenatal developmental toxicity – rat and rabbit Reaction 

Product 24 

Outstanding Data Requirements from GDCI-042501-266274

860.1650 Submittal of analytical reference standards PAI, residue of 

concern 

Due August 

2008 

TGAI = technical grade active ingredient; TEP = typical end-use product; PAI = pure active ingredient 

 

 

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 The study listed in this section was previously required through a generic data call-in issued in August 2006 and is 

still outstanding. The study will not be included in the anticipated Registration Review DCI because it is already 

required through the earlier DCI. The Agency is working with the registrant to follow up on the overdue study. 
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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 PPO. For human health, EPA will 

conduct revised dietary, residential, aggregate 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 and the planned assessments have not 

changed from what was included in the PWP. 

Table 2: Planned Risk Assessments for the PPO 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 Only the parent PPO will be assessed. There is no 

evidence that degradates will form substantially in air 

for terrestrial non-target exposure. Aquatic non-target 

exposure will not be assessed because of PPO’s 

volatility and short retention time in water. 

Incidents Will check for 

updates 

There are no reported incidents. For a discussion of 

reported ecological incidents for PPO, see page 13 of 

the Problem Formulation. 

Human Health 

Dietary 

Food Y A new dietary exposure risk assessment may be 

required during Registration Review to incorporate 

potential changes to the PPO and PCH toxicological 

points of departure (PODs), updated consumption 

information, and utilization of the newest version of 

DEEM-FCID. 

Drinking water N PPO is unlikely to have detectable residues for both 

parent and degradates in surface water and ground 

water.

Occupational 

Handlers (mixers, loaders, 

applicators) 

Y A new occupational handler risk reassessment may be 

completed during registration review to incorporate 

the most recent exposure data, Agency policies, or if 

toxicological reevaluation of PPO results in changes 

to endpoints. 
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Post-application Y Tasks for workers near fumigation 

facilities/operations need to be defined in order to 

assess post-application activities. Potential exposures 

due to off-gassing will also be assessed for workers 

conducting post-application activities near treatment 

operations. 

Residential 

Handlers N There are no residential uses of PPO. 

Post-application N There are no residential uses of PPO. 

Bystander Y Additional or revised residential bystander risk 

assessments may be necessary based on the most 

recent exposure data, Agency policies, or if the 

toxicological reevaluation results in changes to the 

endpoints. Additional use information requested 

above under the Use and Usage Information – 

Guidance for Commenters section would refine this 

analysis. 

Other 

Aggregate Y Evaluates the combined risk from dietary and 

residential exposures. Aggregate risk assessments 

may be required during registration review because 

residential bystander exposure may be assessed. 

Cumulative N EPA has not made a common mechanism of toxicity 

finding as to PPO and any other substance, and has 

also not assumed that PPO has a common mechanism 

of toxicity with other substances. 

Tolerances Y The tolerance expression for propylene oxide will be 

reviewed during registration review to ensure that it 

appropriately covers metabolites and degradates and 

that it specifies the residues to be measured for each 

commodity; modifications will be made as needed. 

Incidents Will check for 

updates 

No cases involving PPO were identified. For a 

discussion of reported human incidents for PPO see 

page 10 of the Scoping Document and Propylene 

Oxide: Review of Human Incidents. 

TIMELINE

EPA has created the following estimated timeline for the completion of the PPO 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. 
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Table 3: Registration Review for PPO – Projected Registration Review Timeline

Activities Estimated Date

Opening the Docket

Open Docket and 60-day Public Comment Period Sept. 2013 – Completed

Close Public Comment Nov. 2013 – 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 Assessments5[1] 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 PPO through a Data Call-In Notice, expected to be issued in 2014. 

 

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 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.